Snakebite: Difference between revisions
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{{short description|Injury caused by bite from snakes}} |
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{{Other uses2|Snakebite}} |
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{{other uses}} |
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{{Use dmy dates|date=January 2014}} |
{{Use dmy dates|date=January 2014}} |
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{{Infobox medical condition (new) |
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{{pp-semi-sock|small=yes}} |
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| name = Snakebite |
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{{Infobox disease |
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| image = Cobra bite in Thailand (image, 2023).jpg |
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| caption = A [[cobra]] bite on the foot of a girl in [[Thailand]] |
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| Image = Mossegada de serp verda.JPG |
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| field = [[Emergency medicine]] |
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| symptoms = Two [[puncture wound]]s, [[redness]], [[Edema|swelling]], severe pain at the area<ref name=CDC2012/><ref name=Gold2002/> |
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| DiseasesDB = 29733 |
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| complications = [[hemorrhage|Bleeding]], [[kidney failure]], [[anaphylaxis|severe allergic reaction]], [[necrosis|tissue death]] around the bite, breathing problems, [[amputation]], [[envenomation]]<ref name=CDC2012/><ref name=WHO2015/> |
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| ICD10 = {{ICD10|T|63|0|t|51}}, T14.1, W59 (nonvenomous), X20 (venomous) |
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| onset = |
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| ICD9 = {{ICD9|989.5}}, {{ICD9|E905.0}}, {{ICD9|E906.2}} |
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| duration = |
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| types = |
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| causes = [[Snakes]]<ref name=CDC2012/> |
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| MedlinePlus = 000031 |
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| risks = Working outside with one's hands ([[farming]], [[forestry]], construction);<ref name=CDC2012/><ref name=WHO2015/> harassment;<ref>{{cite web|url=https://www.fs.usda.gov/detail/eldorado/learning/safety-ethics/?cid=STELPRDB5259659|title=Eldorado - Outdoor Safety & Ethics}}</ref><ref>{{cite web | url=https://wildlife.utah.gov/news/utah-wildlife-news/1202-rattlesnake-encounter-what-to-do.html | title=What to do if you encounter a rattlesnake}}</ref> [[drunkenness]]<ref>{{cite web | url=https://reptilesmagazine.com/alcohol-and-snake-bites/ |title=Alcohol and Snake Bites – Reptiles Magazine | date=December 2011}}</ref> |
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| eMedicineSubj = med |
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| diagnosis = |
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| eMedicineTopic = 2143 |
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| differential = |
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| MeshID = D012909 |
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| prevention = [[Protective footwear]], avoiding areas where snakes live, not handling snakes<ref name=CDC2012/> |
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| treatment = Washing the wound with soap and water, [[antivenom]]<ref name=CDC2012/><ref name=WHONeg/> |
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| medication = |
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| prognosis = Depends on type of snake<ref name=Marx2010/> |
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| frequency = Up to 5 million a year<ref name=WHO2015/> |
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| deaths = 94,000–125,000 per year<ref name=WHO2015/> |
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}} |
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<!-- Definition and symptoms --> |
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A '''snakebite''' is an injury caused by a bite from a [[snake]], often resulting in [[puncture wound]]s inflicted by the animal's [[fang]]s and sometimes resulting in [[envenomation]]. Although the majority of snake species are non-venomous and typically kill their prey with [[constriction]] rather than [[snake venom|venom]], [[venomous snakes]] can be found on every continent except [[Antarctica]].<ref name="Kasturiratne" /> Snakes often bite their prey as a method of hunting, but also for defensive purposes against predators. Since the physical appearance of snakes may differ, there is often no practical way to identify a species and professional medical attention should be sought.<ref name="SVDK">{{Cite journal|year=2007 |title=Snake Venom Detection Kit: Detection and Identification of Snake Venom |publisher=CSL Limited|url=http://www.csl.com.au/docs/92/398/SVDK_Product_Leaflet,0.pdf|accessdate=2009-11-24 |quote=The physical identification of Australian and Papua New Guinean snakes is notoriously unreliable. There is often marked colour variation between juvenile and adult snakes and wide size, shape and colour variation between snakes of the same species. Reliable snake identification requires expert knowledge of snake anatomy, a snake key and the physical handling of the snake}}</ref><ref name="White2006">{{Cite journal|last1=White |first1=Julian|year=2006 |title=Snakebite & Spiderbite: Management Guidelines |publisher=Department of Health, Government of South Australia |location=Adelaide |pages=1–71 |url=http://www.sahealth.sa.gov.au/wps/wcm/connect/public+content/sa+health+internet/resources/snakebitespiderbiteguidelinessa-sahealth08|isbn=0-7308-9551-3 |accessdate=2009-11-24 |quote=The colour of brown snakes is very variable and misleading for identification purposes. They may be brown, red brown, grey, very dark brown and may be plain in color, have speckling, stripes or bands, or have a dark or black head}}</ref> |
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A '''snakebite''' is an injury caused by the bite of a snake, especially a [[venomous snake]].<ref>{{cite web |title=Definition of Snakebite |url=https://www.merriam-webster.com/dictionary/snakebite |website=www.merriam-webster.com |access-date=17 June 2019 |language=en}}</ref> A common sign of a bite from a venomous snake is the presence of two [[puncture wound]]s from the animal's [[fang]]s.<ref name=CDC2012/> Sometimes [[envenomation|venom injection from the bite]] may occur.<ref name=WHO2015>{{cite web |title=Animal bites: Fact sheet N°373 |url=https://www.who.int/mediacentre/factsheets/fs373/en/ |publisher=[[World Health Organization]] |access-date=19 May 2015 |date=February 2015 |url-status=live |archive-url=https://web.archive.org/web/20150504100257/http://www.who.int/mediacentre/factsheets/fs373/en/ |archive-date=4 May 2015}}</ref> This may result in redness, swelling, and severe pain at the area, which may take up to an hour to appear.<ref name=CDC2012/><ref name=Gold2002/> [[Vomiting]], blurred vision, tingling of the limbs, and sweating may result.<ref name=CDC2012/><ref name=Gold2002/> Most bites are on the hands, arms, or legs.<ref name=Gold2002>{{cite journal | vauthors = Gold BS, Dart RC, Barish RA | title = Bites of venomous snakes | journal = The New England Journal of Medicine | volume = 347 | issue = 5 | pages = 347–356 | date = August 2002 | pmid = 12151473 | doi = 10.1056/NEJMra013477}}</ref><ref>{{cite journal | vauthors = Daley BJ, Torres J | title = Venomous snakebites | journal = Journal of Emergency Medical Services| volume = 39 | issue = 6 | pages = 58–62 | date = June 2014 | pmid = 25109149}}</ref> [[Fear]] following a bite is common with symptoms of a [[Tachycardia|racing heart]] and [[Dizziness|feeling faint]].<ref name=Gold2002/> The [[venom]] may cause [[hemorrhage|bleeding]], [[kidney failure]], a [[anaphylaxis|severe allergic reaction]], [[necrosis|tissue death]] around the bite, or breathing problems.<ref name=CDC2012>{{cite web|title=Venomous Snakes|url=https://www.cdc.gov/niosh/topics/snakes/|publisher=[[U.S. National Institute for Occupational Safety and Health]]|access-date=19 May 2015|date=24 February 2012|url-status=live|archive-url= https://web.archive.org/web/20150429051901/http://www.cdc.gov/niosh/topics/snakes/|archive-date=29 April 2015}}</ref><ref name=WHO2015/> Bites may result in the [[amputation|loss of a limb]] or other [[Chronic condition|chronic problems]] or even death.<ref name="Healthline Media UK Ltd">{{cite web |last1=Eske |first1=Jamie |last2=Biggers |first2=Alana |title=How to identify and treat snake bites |url=https://www.medicalnewstoday.com/articles/324007 |website=Medical News Today |publisher=Healthline Media UK Ltd |access-date=4 May 2022 |language=English |date=14 December 2018}}</ref><ref name=WHO2015/> |
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The outcome depends on the type of snake, the area of the body bitten, the amount of [[snake venom]] injected, the general health of the person bitten, and whether or not anti-venom serum has been administered by a doctor in a timely manner.<ref name="Healthline Media UK Ltd"/><ref name=Marx2010>{{cite book| vauthors = Marx JA |title=Rosen's emergency medicine: concepts and clinical practice |date=2010 |publisher=Mosby/Elsevier |location=Philadelphia |isbn=978-0-323-05472-0|page=746|edition=7|url=https://books.google.com/books?id=u7TNcpCeqx8C&pg=PA746|url-status=live|archive-url= https://web.archive.org/web/20150521114649/https://books.google.com/books?id=u7TNcpCeqx8C&pg=PA746|archive-date=21 May 2015}}</ref> Problems are often more severe in children than adults, due to their smaller size.<ref name=WHO2015/><ref>{{cite book| vauthors = Peden MM |title=World Report on Child Injury Prevention|date=2008|publisher=[[World Health Organization]]|isbn=978-92-4-156357-4|page=128|url=https://books.google.com/books?id=UeXwoNh8sbwC&pg=PA128|language=en|url-status=live|archive-url=https://web.archive.org/web/20170202050637/https://books.google.com/books?id=UeXwoNh8sbwC&pg=PA128|archive-date=2 February 2017}}</ref><ref name=WHOantivenoms/> Allergic reactions to snake venom can further complicate outcomes and can include [[anaphylaxis]], requiring additional treatment and in some cases resulting in death.<ref name="Healthline Media UK Ltd"/> |
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The outcome of snake bites depends on numerous factors, including the species of snake, the area of the body bitten, the amount of venom injected, and the health conditions of the person. Feelings of terror and panic are common after a snakebite and can produce a characteristic set of symptoms mediated by the [[autonomic nervous system]], such as a [[Tachycardia|racing heart]] and [[nausea]].<ref name="Gold2002" /><ref name="Kitchens1987" /> Bites from non-venomous snakes can also cause injury, often due to [[laceration]]s caused by the snake's teeth, or from a resulting infection. A bite may also trigger an [[anaphylactic]] reaction, which is potentially fatal. First aid recommendations for bites depend on the snakes inhabiting the region, as effective treatments for bites inflicted by some species can be ineffective for others. |
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<!-- Cause --> |
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The number of fatalities attributed to snake bites varies greatly by geographical area. Although deaths are relatively rare in [[Australia]], [[Europe]] and [[North America]],<ref name="Kasturiratne" /><ref name="Chippaux 1998">{{Cite journal |last=Chippaux |first=J.P. |year=1998 |title=Snake-bites: appraisal of the global situation |journal=Bulletin of the World Health Organization |volume=76 |issue=5 |pages=515–24 |url=http://www.kingsnake.com/aho/pdf/menu6/chippaux1998.pdf |accessdate=2009-07-03|pmid=9868843|pmc=2305789}}</ref><ref name="Gutierrez2007" /> the morbidity and mortality associated with snake bites is a serious public health problem in many regions of the world, particularly in rural areas lacking medical facilities. Further, while [[South Asia]], [[Southeast Asia]], and [[sub-Saharan Africa]] report the highest number of bites, there is also a high incidence in the [[Neotropics]] and other equatorial and [[subtropical]] regions.<ref name="Kasturiratne" /><ref name="Chippaux 1998" /><ref name="Gutierrez2007" /> Each year tens of thousands of people die from snake bites,<ref name="Kasturiratne" /> yet the risk of being bitten can be lowered with preventive measures, such as wearing protective footwear and avoiding areas known to be inhabited by dangerous snakes. |
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Snakes bite both as a method of hunting and as a means of protection.<ref name=Kast2008/> [[Risk factor]]s for bites include working outside with one's hands such as in [[farming]], [[forestry]], and construction.<ref name="CDC2012" /><ref name="WHO2015" /> Snakes commonly involved in envenomations include [[elapid]]s (such as [[krait]]s, [[cobra]]s and [[mamba]]s), [[viper]]s, and [[sea snake]]s.<ref name=WHONeg>{{cite web|publisher=[[World Health Organization]] |title=Neglected tropical diseases: Snakebite|url=https://www.who.int/neglected_diseases/diseases/snakebites/en/|access-date=19 May 2015|archive-url=https://web.archive.org/web/20150930063057/http://www.who.int/neglected_diseases/diseases/snakebites/en/|archive-date=30 September 2015}}</ref> The majority of snake species do not have venom and kill their prey by [[constriction]] (squeezing them).<ref name=Gold2002/> Venomous snakes can be found on every continent except [[Antarctica]].<ref name=Kast2008/> Determining the type of snake that caused a bite is often not possible.<ref name=WHONeg/> The [[World Health Organization]] says snakebites are a "neglected [[public health issue]] in many tropical and subtropical countries",<ref name=WHOantivenoms>{{cite web |publisher=[[World Health Organization]] |title=Snake antivenoms: Fact sheet N°337 |url=https://www.who.int/mediacentre/factsheets/fs337/en/ |date=February 2015 |access-date=16 May 2017 |url-status=live |archive-url=https://web.archive.org/web/20170418105431/http://www.who.int/mediacentre/factsheets/fs337/en/ |archive-date=18 April 2017}}</ref> and in 2017, the WHO categorized snakebite envenomation as a [[Neglected Tropical Disease]] (Category A). The WHO also estimates that between 4.5 and 5.4 million people are bitten each year, and of those figures, 40–50% develop some kind of clinical illness as a result.<ref name=Langley2020>{{cite journal |last1=Langley |first1=Ricky |last2=Haskell |first2=Marilyn Goss |last3=Hareza |first3=Dariusz |last4=King |first4=Katherine |title=Fatal and Nonfatal Snakebite Injuries Reported in the United States |journal=Southern Medical Journal |date=October 2020 |volume=113 |issue=10 |pages=514–519 |doi=10.14423/SMJ.0000000000001156|pmid=33005969 |s2cid=222070778}}</ref> Furthermore, the death toll from such an injury could range between 80,000 and 130,000 people per year.<ref>World Health Organization. Prevalence of snakebite envenoming. <nowiki>[https://web.archive.org/web/20170922113845/http://www.who.int/snakebites/epidemiology/en/ ]</nowiki>. Accessed April 15, 2019</ref><ref name=Langley2020/> The purpose was to encourage research, expand the accessibility of antivenoms, and improve snakebite management in "[[Developing country|developing countries]]".<ref>{{cite web|url=https://www.who.int/snakebites/resources/s40409-017-0127-6/en/|archive-url=https://web.archive.org/web/20170922115522/http://www.who.int/snakebites/resources/s40409-017-0127-6/en/|archive-date=22 September 2017|title=WHO | Snakebite envenomation turns again into a neglected tropical disease!|website=WHO}}</ref> |
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<!-- Prevention and treatment --> |
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Prevention of snake bites can involve wearing protective footwear, avoiding areas where snakes live, and not handling snakes.<ref name=CDC2012/> Treatment partly depends on the type of snake.<ref name=CDC2012/> Washing the wound with soap and water and holding the limb still is recommended.<ref name=CDC2012/><ref name=WHONeg/> Trying to suck out the venom, cutting the wound with a knife, or using a [[tourniquet]] is not recommended.<ref name=CDC2012/> [[Antivenom]] is effective at preventing death from bites; however, antivenoms frequently have [[side effect]]s.<ref name=WHO2015/><ref name=Gutierrez2007/> The type of antivenom needed depends on the type of snake involved.<ref name=WHONeg/> When the type of snake is unknown, antivenom is often given based on the types known to be in the area.<ref name=WHONeg/> In some areas of the world, getting the right type of antivenom is difficult and this partly contributes to why they sometimes do not work.<ref name=WHO2015/> An additional issue is the cost of these medications.<ref name=WHO2015/> Antivenom has little effect on the area around the bite itself.<ref name=WHONeg/> [[Mechanical ventilation|Supporting the person's breathing]] is sometimes also required.<ref name=WHONeg/> |
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<!-- Epidemiology --> |
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The number of venomous snakebites that occur each year may be as high as five million.<ref name=WHO2015 /> They result in about 2.5 million envenomations and 20,000 to 125,000 deaths.<ref name=WHO2015/><ref name=Kast2008/> The frequency and severity of bites vary greatly among different parts of the world.<ref name=Kast2008>{{cite journal | vauthors = Kasturiratne A, Wickremasinghe AR, de Silva N, Gunawardena NK, Pathmeswaran A, Premaratna R, Savioli L, Lalloo DG, de Silva HJ | display-authors = 6 | title = The global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths | journal = PLOS Medicine | volume = 5 | issue = 11 | pages = e218 | date = November 2008 | pmid = 18986210 | pmc = 2577696 | doi = 10.1371/journal.pmed.0050218 | doi-access = free}}</ref> They occur most commonly in [[Africa]], [[Asia]], and [[Latin America]],<ref name=WHO2015/> with rural areas more greatly affected.<ref name=WHO2015/><ref name=WHOantivenoms/> Deaths are relatively rare in [[Australia]], [[Europe]] and [[North America]].<ref name=Kast2008/><ref name=Gutierrez2007>{{cite journal | vauthors = Gutiérrez JM, Lomonte B, León G, Rucavado A, Chaves F, Angulo Y | title = Trends in snakebite envenomation therapy: scientific, technological and public health considerations | journal = Current Pharmaceutical Design | volume = 13 | issue = 28 | pages = 2935–2950 | year = 2007 | pmid = 17979738 | doi = 10.2174/138161207782023784}}</ref><ref name=Chippaux1998>{{cite journal | vauthors = Chippaux JP | title = Snake-bites: appraisal of the global situation | journal = Bulletin of the World Health Organization | volume = 76 | issue = 5 | pages = 515–524 | year = 1998 | pmid = 9868843 | pmc = 2305789}}</ref> For example, in the United States, about seven to eight thousand people per year are bitten by venomous snakes (about one in 40 thousand people) and about five people die (about one death per 65 million people).<ref name=CDC2012 /> |
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== Signs and symptoms == |
== Signs and symptoms == |
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[[File:Snake bite symptoms.png|thumb| |
[[File:Snake bite symptoms.png|thumb|upright=1.4|The most common symptoms of any kind of snake envenomation.<ref name=MedlinePlus/><ref>[http://www.health-care-clinic.org/diseases/snakebite.html Health-care-clinic.org – Snake Bite First Aid – Snakebite] {{webarchive|url=https://web.archive.org/web/20160116034305/http://www.health-care-clinic.org/diseases/snakebite.html |date=16 January 2016}} Retrieved on 21 mars, 2009</ref><ref>Snake bite image example at [http://www.mdconsult.com/das/patient/body/127551351-2/0/10041/8928_en.jpg MDconsult – Patient Education – Wounds, Cuts and Punctures, First Aid for] {{webarchive|url=https://web.archive.org/web/20160107214703/http://www.mdconsult.com/das/patient/body/127551351-2/0/10041/8928_en.jpg |date=7 January 2016}}</ref> However, there is vast variation in symptoms between bites from different types of snakes.<ref name="MedlinePlus">[https://www.nlm.nih.gov/MEDLINEPLUS/ency/article/000031.htm MedlinePlus – Snake bites] {{webarchive|url=https://web.archive.org/web/20101204102457/http://www.nlm.nih.gov/medlineplus/ency/article/000031.htm |date=4 December 2010}} From Tintinalli JE, Kelen GD, Stapcynski JS, eds. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw Hill; 2004. Update date: 27 February 2008. Updated by: Stephen C. Acosta, MD, Department of Emergency Medicine, Portland VA Medical Center, Portland, OR. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. Retrieved on 19 mars, 2009</ref>]] |
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The most common first symptom of all snakebites is an overwhelming fear, which may contribute to other symptoms, and may include [[nausea]] and [[vomiting]], [[diarrhea]], [[vertigo (medical)|vertigo]], [[fainting]], [[tachycardia]], and cold, clammy skin.<ref name="Gold2002" /><ref name="Kitchens1987">{{cite journal | vauthors = Kitchens CS, Van Mierop LH | title = Envenomation by the Eastern coral snake (Micrurus fulvius fulvius). A study of 39 victims | journal = JAMA | volume = 258 | issue = 12 | pages = 1615–1618 | date = September 1987 | pmid = 3625968 | doi = 10.1001/jama.258.12.1615}}</ref> Snake bites can have a variety of different signs and symptoms depending on their species.<ref name="Healthline Media UK Ltd" /> |
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[[Dry bite|Dry snakebites]] and those inflicted by a non-venomous species may still cause severe injury. The bite may become infected from the snake's saliva. The fangs sometimes harbor pathogenic microbial organisms, including ''[[Clostridium tetani]]'', and may require an updated tetanus immunization.<ref>Otten E, Blomkalns A. Venomous animal injuries. In: Marx J, Hockberger R,Walls R, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. St Louis: Mosby; 2002</ref><ref name=Langley2020 /> |
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The most common symptoms of all snakebites are overwhelming fear, panic, and emotional instability, which may cause symptoms such as [[nausea]] and [[vomiting]], [[diarrhea]], [[vertigo (medical)|vertigo]], [[fainting]], [[tachycardia]], and cold, clammy skin.<ref name="Gold2002" /><ref name="Kitchens1987">{{Cite journal| author=Kitchens C, Van Mierop L|title=Envenomation by the Eastern coral snake (Micrurus fulvius fulvius). A study of 39 victims|journal=JAMA|volume=258|issue=12|pages=1615–18|year=1987|pmid=3625968|doi=10.1001/jama.258.12.1615}}</ref> Television, literature, and folklore are in part responsible for the hype surrounding snakebites, and people may have unwarranted thoughts of imminent death. |
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Most snakebites, from either a venomous or a non-venomous snake, will have some type of local effect.<ref name="Online Khabar">{{cite web | vauthors = Lamsal S |title=Snakebites in Nepal are a medical emergency. Here are things you should know about them |url=https://english.onlinekhabar.com/snakebites-in-nepal-know-everything.html |date=3 June 2023 |website=[[Online Khabar]] |access-date=21 June 2023}}</ref> Minor pain and [[Erythema|redness]] occur in over 90 percent of cases, although this varies depending on the site.<ref name="Gold2002" /> Bites by [[Viper (animal)|vipers]] and some [[cobra]]s may be extremely painful, with the local tissue sometimes becoming tender and severely [[Edema|swollen]] within five minutes.<ref name=Gutierrez2007/> This area may also bleed and blister and may lead to tissue [[necrosis]]. Other common initial symptoms of [[pit viper]] and [[Viper (animal)|viper]] bites include lethargy, bleeding, weakness, nausea, and vomiting.<ref name="Gold2002" /><ref name=Gutierrez2007/> Symptoms may become more life-threatening over time, developing into [[hypotension]], [[tachypnea]], severe tachycardia, severe internal bleeding, altered [[sensorium]], [[kidney failure]], and [[respiratory failure]].<ref name="Gold2002" /><ref name=Gutierrez2007/> |
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[[Dry bite|Dry snakebites]], and those inflicted by a non-venomous species, can still cause severe injury. There are several reasons for this: a snakebite may become infected with the snake's saliva and fangs sometimes harboring pathogenic microbial organisms, including ''[[Clostridium tetani]]''. Infection is often reported with viper bites whose fangs are capable of deep puncture wounds. Bites may cause [[anaphylaxis]] in certain people. |
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Bites by some snakes, such as the [[kraits]], [[coral snake]], [[Mojave rattlesnake]], and the [[Crotalus mitchellii|speckled rattlesnake]], may cause little or no pain, despite their serious and potentially life-threatening venom.<ref name="Gold2002" /> Some people report experiencing a "rubbery", "minty", or "metallic" taste after being bitten by certain species of rattlesnake.<ref name="Gold2002" /> [[Spitting cobra]]s and [[rinkhals]]es can spit venom in a person's eyes. This results in immediate pain, [[ophthalmoparesis]], and sometimes [[blindness]].<ref name="Warrell1976">{{cite journal | vauthors = Warrell DA, Ormerod LD | title = Snake venom ophthalmia and blindness caused by the spitting cobra (Naja nigricollis) in Nigeria | journal = The American Journal of Tropical Medicine and Hygiene | volume = 25 | issue = 3 | pages = 525–529 | date = May 1976 | pmid = 1084700 | doi = 10.4269/ajtmh.1976.25.525}}</ref><ref name="Ismail1993">{{cite journal | vauthors = Ismail M, al-Bekairi AM, el-Bedaiwy AM, Abd-el Salam MA | title = The ocular effects of spitting cobras: I. The ringhals cobra (Hemachatus haemachatus) venom-induced corneal opacification syndrome | journal = Journal of Toxicology. Clinical Toxicology | volume = 31 | issue = 1 | pages = 31–41 | year = 1993 | pmid = 8433414 | doi = 10.3109/15563659309000372}}</ref> |
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Most snakebites, whether by a venomous snake or not, will have some type of local effect. There is minor pain and [[Erythema|redness]] in over 90% of cases, although this varies depending on the site.<ref name="Gold2002" /> Bites by [[Viper (animal)|vipers]] and some [[cobra]]s may be extremely painful, with the local tissue sometimes becoming tender and severely [[Edema|swollen]] within 5 minutes.<ref name="Gutierrez2007" /> This area may also bleed and blister and can eventually lead to tissue [[necrosis]]. Other common initial symptoms of [[pitviper]] and [[Viper (animal)|viper]] bites include lethargy, bleeding, weakness, nausea, and vomiting.<ref name="Gold2002" /><ref name="Gutierrez2007" /> Symptoms may become more life-threatening over time, developing into [[hypotension]], [[tachypnea]], severe tachycardia, severe internal bleeding, altered [[sensorium]], [[kidney failure]], and [[respiratory failure]].<ref name="Gold2002" /><ref name="Gutierrez2007" /> |
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[[File:Tissue necrosis following bite from Bothrops asper PLoS Medicine.jpg|thumb|left|upright|Severe [[tissue necrosis]] following ''[[Bothrops asper]]'' envenomation that required [[amputation]] above the knee. The person was an 11-year-old boy, bitten two weeks earlier in [[Ecuador]], but treated only with [[antibiotic]]s.<ref name="Gutierrez2006">{{cite journal | vauthors = Gutiérrez JM, Theakston RD, Warrell DA | title = Confronting the neglected problem of snake bite envenoming: the need for a global partnership | journal = PLOS Medicine | volume = 3 | issue = 6 | pages = e150 | date = June 2006 | pmid = 16729843 | pmc = 1472552 | doi = 10.1371/journal.pmed.0030150 | doi-access = free}}</ref>]] |
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Some Australian elapids and most viper envenomations will cause [[coagulopathy]], sometimes so severe that a person may bleed spontaneously from the mouth, nose, and even old, seemingly healed wounds.<ref name="Gutierrez2007" /> Internal organs may bleed, including the brain and intestines,<ref name="Cunha2021">{{cite web | url = https://www.emedicinehealth.com/snakebite/symptom.htm | title = Symptoms and Signs of Snakebite (Snake Bite) | last = Cuhna | first = John P. | publisher = [[WebMD]] | date= August 6, 2021 | website = [[eMedicine]]Health | access-date = July 26, 2022}}</ref> and [[ecchymosis]] (bruising) of the skin is often seen.<ref name="SmallAnimalToxicology">{{cite journal | last1 = Peterson | first1 = Michael E. | last2 = Talcott | first2 = Patricia A. | year = 2013 | title = Snake Bite: North American Pit Vipers | url = https://www.sciencedirect.com/science/article/pii/B9781455707171000752 | journal = Small Animal Toxicology | edition = 3rd | pages = 783–797 | doi = 10.1016/B978-1-4557-0717-1.00075-2 | isbn = 978-1-4557-0717-1}}</ref> |
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The venom of elapids, including [[sea snakes]], [[Bungarus|kraits]], [[Naja|cobras]], [[Ophiophagus hannah|king cobra]], [[Dendroaspis|mambas]], and many Australian species, contains toxins which attack the nervous system, causing [[neurotoxicity]].<ref name="Gold2002" /><ref name=Gutierrez2007/><ref name="Phillips2002">{{cite journal | vauthors = Phillips CM |year=2002 |title=Sea snake envenomation |journal=Dermatologic Therapy |volume=15 |issue=1 |pages=58–61(4) |doi=10.1046/j.1529-8019.2002.01504.x |s2cid=73275266 |url=http://www.kingsnake.com/aho/pdf/menu6/phillips2002.pdf |access-date=24 July 2009 |url-status=live |archive-url=https://web.archive.org/web/20110428095839/http://www.kingsnake.com/aho/pdf/menu6/phillips2002.pdf |archive-date=28 April 2011}}</ref> The person may present with strange disturbances to their vision, including blurriness. [[Paresthesia]] throughout the body, as well as difficulty in speaking and breathing, may be reported.<ref name="Gold2002" /> Nervous system problems will cause a huge array of symptoms, and those provided here are not exhaustive. If not treated immediately they may die from [[respiratory failure]].<ref name="ManagementofRespiratoryFailure">{{cite journal |last1 = Sabirin |first1 = Mira R |last2 = Sudjud |first2 = Reza W |last3 = Suwarman |first3 = Suwarman |last4 = Pradian |first4 = Erwin |date = August 18, 2020 |title = Management of Respiratory Failure Following Snake Bite |journal = Journal of Health and Medical Sciences |volume = 3 |issue = 3 |pages = 338–349 |doi = 10.31014/aior.1994.03.03.129 |s2cid = 224885423 |url = https://ssrn.com/abstract=3676254 |issn = 2622-7258 |access-date=July 27, 2022 |url-status = live |archive-url = https://web.archive.org/web/20220727124831/https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3676254 |archive-date = July 27, 2022}}</ref> |
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Interestingly, bites caused by the [[Mojave Rattlesnake|Mojave rattlesnake]], [[kraits]], [[coral snake]], and the [[Crotalus mitchellii|speckled rattlesnake]] reportedly cause little or no pain despite being serious injuries.<ref name="Gold2002" /> Those bitten may also describe a "rubbery," "minty," or "metallic" taste if bitten by certain species of rattlesnake.<ref name="Gold2002" /> [[Spitting cobra]]s and [[rinkhals]]es can spit venom in a persons eyes. This results in immediate pain, [[ophthalmoparesis]], and sometimes [[blindness]].<ref name="Warrell1976">{{Cite journal|last=Warrell |first=David A. |coauthors=L. David Ormerod |year=1976|title=Snake Venom Ophthalmia and Blindness Caused by the Spitting Cobra (Naja Nigricollis) in Nigeria |journal=The American Society of Tropical Medicine and Hygiene |volume=25 |issue=3 |pages=525–9 |url=http://www.ajtmh.org/cgi/content/abstract/25/3/525 |accessdate=2009-09-05 |pmid=1084700}}</ref><ref name="Ismail1993">{{Cite journal|last=Ismail |first=Mohammad |coauthors=Abdullah M. Al-Bekairi, Ayman M. El-Bedaiwy, Mohammad A. Abd-El Salam |year=1993 |title=The ocular effects of spitting cobras: I. The ringhals cobra (Hemachatus haemachatus) Venom-Induced corneal opacification syndrome |journal=Clinical Toxicology |volume=31 |issue=1 |pages=31–41 |doi=10.3109/15563659309000372 |pmid=8433414}}</ref> |
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[[File:Tissue necrosis following bite from Bothrops asper PLoS Medicine.jpg|thumb|left|Severe [[tissue necrosis]] following ''[[Bothrops asper]]'' envenomation that needed [[amputation]] above the knee. The person was an 11-year-old boy, bitten two weeks earlier in [[Ecuador]], but treated only with [[antibiotic]]s.<ref name="plosmedecine">{{cite web|url=http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0030150 |title=Confronting the Neglected Problem of Snake Bite Envenoming: The Need for a Global Partnership |publisher=PLoS Medicine |date=|accessdate=2012-06-06}}</ref>]] |
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Some Australian elapids and most viper envenomations will cause [[coagulopathy]], sometimes so severe that a person may bleed spontaneously from the mouth, nose, and even old, seemingly healed wounds.<ref name="Gutierrez2007" /> Internal organs may bleed, including the brain and intestines and will cause [[ecchymosis]] (bruising) of the skin. |
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Venom emitted from some types of cobras, almost all vipers, and some sea snakes cause [[necrosis]] of muscle tissue.<ref name="Gutierrez2007" /> Muscle tissue will begin to die throughout the body, a condition known as [[rhabdomyolysis]]. Rhabdomyolysis can result in damage to the kidneys as a result of myoglobin accumulation in the renal tubules. This, coupled with [[hypotension]], can lead to [[acute kidney injury]], and, if left untreated, eventually death.<ref name="Gutierrez2007" /> |
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Venom emitted from elapids, including [[sea snakes]], [[Bungarus|kraits]], [[Naja|cobras]], [[Ophiophagus hannah|king cobra]], [[Dendroaspis|mambas]], and many Australian species, contain toxins which attack the nervous system, causing [[neurotoxicity]].<ref name="Gold2002" /><ref name="Gutierrez2007">{{Cite journal|last=Gutiérrez |first=José María |coauthors=Bruno Lomonte, Guillermo León, Alexandra Rucavado, Fernando Chaves, Yamileth Angulo |year=2007|title=Trends in Snakebite Envenomation Therapy: Scientific, Technological and Public Health Considerations |journal=Current Pharmaceutical Design |volume=13 |issue=28 |pages=2935–50 |doi=10.2174/138161207782023784 |pmid=17979738}}</ref><ref name="Phillips2002">{{Cite journal |last=Phillips |first=Charles M. |year=2002|title=Sea snake envenomation |journal=Dermatologic Therapy |volume=15|issue=1 |pages=58–61(4)|doi=10.1046/j.1529-8019.2002.01504.x |url=http://www.kingsnake.com/aho/pdf/menu6/phillips2002.pdf|accessdate=2009-07-24}}</ref> The person may present with strange disturbances to their vision, including blurriness. [[Paresthesia]] throughout the body, as well as difficulty in speaking and breathing, may be reported.<ref name="Gold2002" /> Nervous system problems will cause a huge array of symptoms, and those provided here are not exhaustive. If not treated immediately they may die from [[respiratory failure]]. |
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Snakebite is also known to cause depression and post-traumatic stress disorder in a high proportion of people who survive.<ref>{{cite journal | vauthors = Bhaumik S, Kallakuri S, Kaur A, Devarapalli S, Daniel M | title = Mental health conditions after snakebite: a scoping review | journal = BMJ Global Health | volume = 5 | issue = 11 | pages = e004131 | date = November 2020 | pmid = 33257419 | pmc = 7705584 | doi = 10.1136/bmjgh-2020-004131}}</ref> |
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Venom emitted from some types of cobras, almost all vipers, some Australian elapids and some sea snakes causes [[necrosis]] of muscle tissue.<ref name="Gutierrez2007" /> Muscle tissue will begin to die throughout the body, a condition known as [[rhabdomyolysis]]. Rhabdomyolysis can result in damage to the kidneys as a result of myoglobin accumulation in the renal tubules. This, coupled with [[hypotension]], can lead to [[acute renal failure]], and, if left untreated, eventually death.<ref name="Gutierrez2007" /> |
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== Cause == |
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{{See also|List of dangerous snakes}} |
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In the developing world most snakebites occur in those who work outside such as farmers, hunters, and fishermen.<!-- <ref name=Brut2013/> --> They often happen when a person steps on the snake or approaches it too closely.<!-- <ref name=Brut2013/> --> In the United States and Europe snakebites most commonly occur in those who keep them as pets.<ref name=Brut2013>{{cite book | veditors = Garcia HH, Tanowitz HB, Del Brutto OH |title=Neuroparasitology and tropical neurology|date=2013|isbn=978-0-444-53499-6|page=351|url=https://books.google.com/books?id=bJx3g30aDhIC&pg=PA351|url-status=live|archive-url=https://web.archive.org/web/20170908174306/https://books.google.com/books?id=bJx3g30aDhIC&pg=PA351|archive-date=8 September 2017|last1=Garcia|first1=Hector H.|last2=Tanowitz|first2=Herbert|last3=Del Brutto|first3=Oscar H.|publisher=Newnes}}</ref> |
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The type of snake that most often delivers serious bites depends on the region of the world.<!-- <ref name=Brut2013/> --> In Africa, it is [[mamba]]s, [[Egyptian cobra]]s, [[Bitis arietans|puff adders]], and [[carpet viper]]s.<!-- <ref name=Brut2013/> --> In the Middle East, it is carpet vipers and [[elapid]]s.<!-- <ref name=Brut2013/> --> In [[Latin America]], it is snakes of the ''[[Bothrops]]'' and ''[[Crotalus]]'' types,<!-- <ref name=Brut2013/> --> the latter including [[rattlesnake]]s.<ref name=Brut2013/> In North America, rattlesnakes are the primary concern, and up to 95% of all snakebite-related deaths in the United States are attributed to the [[Crotalus atrox|western]] and [[Crotalus adamanteus|eastern diamondback]] rattlesnakes.<ref name="Gold2002"/><!-- Bothrops aren't in North America. Copperheads and water moccasins are less venomous (and mostly found only in Southeastern U.S.), and bites from coral snakes are rare. --> The greatest number of bites are inflicted on the hands.{{Citation needed|date=April 2024}} People get bitten by handling snakes or in the outdoors by putting their hands on the wrong places. The next largest number of bites occur on the ankles, as snakes are often hidden or camouflaged extremely well to fend off predators. Most bite victims are bitten by surprise, and it is a comfortable fiction that rattlesnakes always forewarn their bite victims - often the bite is the first indication a snake is near. Since most venomous snakes move about during the dawn dusk or night, one may expect more encounters during the early morning or late afternoon, though many species such as the Western Diamondback may be encountered at any time of day and in fact most bites occur during the month of April when both snakes and humans are out and about and encounter one another hiking, in yards, or on pathways. Children playing within short distances of their homes crawl under porches, jump into bushes, pull boards of wood from a pile and are bitten. Most however occur when people handle rattlesnakes.<ref>{{cite book|last1=Campbell|first1=Sheldon|last2=Shaw|first2=Charles E.|title=Snakes of The American West|year=1974|publisher=[[Alfred A. Knopf]]|location=New York|isbn=978-0-394-48882-0}}</ref> In South Asia, it was previously believed that [[Indian cobra]]s, [[common krait]]s, [[Russell's viper]], and carpet vipers were the most dangerous;<!-- <ref name=Brut2013/> --> other snakes, however, may also cause significant problems in this area of the world.<ref name=Brut2013/> |
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== Pathophysiology == |
== Pathophysiology == |
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Since [[envenomation]] is completely voluntary, all venomous snakes are capable of biting without injecting venom into a person. Snakes may deliver such a "[[dry bite]]" rather than waste their venom on a creature too large for them to eat, a behaviour called [[venom metering]].<ref name="Young2002">{{ |
Since [[envenomation]] is completely voluntary, all venomous snakes are capable of biting without injecting venom into a person. Snakes may deliver such a "[[dry bite]]" rather than waste their venom on a creature too large for them to eat, a behaviour called [[venom metering]].<ref name="Young2002">{{cite journal | vauthors = Young BA, Lee CE, Daley KM |year=2002 |title=Do Snakes Meter Venom? |journal=BioScience |volume=52 |issue=12 |pages=1121–26 |doi=10.1641/0006-3568(2002)052[1121:DSMV]2.0.CO;2 |quote=The second major assumption that underlies venom metering is the snake's ability to accurately assess the target |doi-access=free}}</ref> However, the percentage of dry bites varies among species: 80 percent of bites inflicted by [[sea snakes]], which are normally timid, do not result in envenomation,<ref name="Phillips2002" /> whereas for [[pit viper]] bites the number is closer to 25 percent.<ref name="Gold2002" /> Furthermore, some snake [[genera]], such as [[rattlesnake]]s, can internally regulate the amount of venom they inject.<ref name="Young2001">{{cite journal | vauthors = Young BA, Zahn K | title = Venom flow in rattlesnakes: mechanics and metering | journal = The Journal of Experimental Biology | volume = 204 | issue = Pt 24 | pages = 4345–4351 | date = December 2001 | pmid = 11815658 | doi = 10.1242/jeb.204.24.4345 | url = http://jeb.biologists.org/cgi/reprint/204/24/4345.pdf | url-status = live | quote = With the species and size of target held constant, the duration of venom flow, maximum venom flow rate and total venom volume were all significantly lower in predatory than in defensive strikes | archive-url = https://web.archive.org/web/20090109013518/http://jeb.biologists.org/cgi/reprint/204/24/4345.pdf | archive-date = 9 January 2009}}</ref> There is a wide variance in the composition of venoms from one species of venomous snake to another. Some venoms may have their greatest effect on a victim's respiration or circulatory system. Others may damage or destroy tissues. This variance has imparted to the venom of each species a distinct chemistry. Sometimes antivenins have to be developed for individual species. For this reason, standard therapeutic measures will not work in all cases. |
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Some dry bites may also be the result of imprecise timing on the snake's part, as venom may be prematurely released before the fangs have penetrated the person.<ref name="Young2002" /> Even without venom, some snakes, particularly large constrictors such as those belonging to the [[Boidae]] and [[Pythonidae]] families, can deliver damaging bites; large specimens often cause severe [[laceration]]s, or the snake itself pulls away, causing the flesh to be torn by the needle-sharp recurved teeth embedded in the person. While not as life-threatening as a bite from a venomous species, the bite can be at least temporarily debilitating and could lead to dangerous infections if improperly dealt with. |
Some dry bites may also be the result of imprecise timing on the snake's part, as venom may be prematurely released before the fangs have penetrated the person.<ref name="Young2002" /> Even without venom, some snakes, particularly large constrictors such as those belonging to the [[Boidae]] and [[Pythonidae]] families, can deliver damaging bites; large specimens often cause severe [[laceration]]s, or the snake itself pulls away, causing the flesh to be torn by the needle-sharp recurved teeth embedded in the person. While not as life-threatening as a bite from a venomous species, the bite can be at least temporarily debilitating and could lead to dangerous infections if improperly dealt with.{{citation needed|date=May 2021}} |
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While most snakes must open their mouths before biting, African and Middle Eastern snakes belonging to the family [[Atractaspididae]] |
While most snakes must open their mouths before biting, African and Middle Eastern snakes belonging to the family [[Atractaspididae]] can fold their fangs to the side of their head without opening their mouth and jab a person.<ref name="Deufel2003">{{cite journal | vauthors = Deufel A, Cundall D | title = Feeding in Atractaspis (Serpentes: Atractaspididae): a study in conflicting functional constraints | journal = Zoology | volume = 106 | issue = 1 | pages = 43–61 | year = 2003 | pmid = 16351890 | doi = 10.1078/0944-2006-00088 | bibcode = 2003Zool..106...43D | url = https://www.academia.edu/7083466 | access-date = 19 May 2014 | url-status = live | archive-url = https://web.archive.org/web/20160107214703/http://www.academia.edu/7083466/Feeding_in_Atractaspis_-_for_analysis | archive-date = 7 January 2016}}</ref> |
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=== Snake venom === |
=== Snake venom === |
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{{Main|Snake venom}} |
{{Main|Snake venom|Venom-induced consumption coagulopathy}} |
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It has been suggested that snakes evolved the mechanisms necessary for venom formation and delivery sometime during the [[Miocene]] epoch.<ref name="Jackson2003">{{ |
It has been suggested that snakes evolved the mechanisms necessary for venom formation and delivery sometime during the [[Miocene]] epoch.<ref name="Jackson2003">{{cite journal | vauthors = Jackson K |year=2003 |title=The evolution of venom-delivery systems in snakes |journal=[[Zoological Journal of the Linnean Society]] |volume=137 |issue=3 |pages=337–354 |doi=10.1046/j.1096-3642.2003.00052.x |url=http://www.kingsnake.com/aho/pdf/menu2/jackson2002.pdf |access-date=25 July 2009 |url-status=live |archive-url=https://web.archive.org/web/20121010135351/http://www.kingsnake.com/aho/pdf/menu2/jackson2002.pdf |archive-date=10 October 2012 |doi-access=free}}</ref> During the mid-[[Tertiary]], most snakes were large [[ambush predator]]s belonging to the superfamily [[Henophidia]], which use constriction to kill their prey. As open grasslands replaced forested areas in parts of the world, some snake families evolved to become smaller and thus more agile. However, subduing and killing prey became more difficult for the smaller snakes, leading to the evolution of snake venom. The most likely hypothesis holds that venom glands evolved from specialized salivary glands. The venom itself evolved through the process of natural selection; it retained and emphasized the qualities that made it useful in killing or subduing prey. Today we can find various snake species in stages of this hypothesized development. There are the highly efficient envenoming machines - like the rattlesnakes - with large capacity venom storage, hollow fangs that swing into position immediately before the snake bites, and spare fangs ready to replace those damaged or lost.<ref>{{cite book|last1=Campbell|first1=Sheldon|last2=Shaw|first2=Charles E.|title=Snakes of The American West|year=1974|page=181|publisher=[[Alfred A. Knopf]]|location=New York|isbn=978-0-394-48882-0}}</ref><ref name="Jackson2003" /> Other research on [[Toxicofera]], a hypothetical [[clade]] thought to be ancestral to most living reptiles, suggests an earlier time frame for the evolution of snake venom, possibly to the order of tens of millions of years, during the [[Late Cretaceous]].<ref name="Fry2006">{{cite journal | vauthors = Fry BG, Vidal N, Norman JA, Vonk FJ, Scheib H, Ramjan SF, Kuruppu S, Fung K, Hedges SB, Richardson MK, Hodgson WC, Ignjatovic V, Summerhayes R, Kochva E | display-authors = 6 | title = Early evolution of the venom system in lizards and snakes | journal = Nature | volume = 439 | issue = 7076 | pages = 584–588 | date = February 2006 | pmid = 16292255 | doi = 10.1038/nature04328 | url = http://www.venomdoc.com/downloads/2005_BGF_Nature_squamate_venom.pdf | access-date = 18 September 2009 | s2cid = 4386245 | bibcode = 2006Natur.439..584F | archive-url = https://web.archive.org/web/20090530032125/http://www.venomdoc.com/downloads/2005_BGF_Nature_squamate_venom.pdf | archive-date = 30 May 2009}}</ref> |
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Snake venom is produced in modified [[parotid gland]]s normally responsible for secreting saliva. It is stored in structures called [[wikt:alveolus|alveoli]] behind the animal's eyes and ejected voluntarily through its hollow tubular [[fangs]].{{citation needed|date=March 2023}} |
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Venom in many snakes, such as pit vipers, affects virtually every organ system in the human body and can be a combination of many toxins, including [[cytotoxins]], [[hemotoxins]], [[neurotoxins]], and [[myotoxin]]s, allowing for an enormous variety of symptoms.<ref name="Gold2002" /><ref name="Russell1980a">{{cite journal | vauthors = Russell FE | title = Snake venom poisoning in the United States | journal = Annual Review of Medicine | volume = 31 | pages = 247–259 | year = 1980 | pmid = 6994610 | doi = 10.1146/annurev.me.31.020180.001335 | s2cid = 1322336}}</ref> Snake venom may cause [[cytotoxicity]] as various enzymes including [[hyaluronidase]]s, [[collagenase]]s, [[proteinase]]s and [[phospholipase]]s lead to breakdown (dermonecrosis) and injury of local tissue and inflammation which leads to pain, edema and blister formation.<ref name="Seifert">{{cite journal |last1=Seifert |first1=Steven A. |last2=Armitage |first2=James O. |last3=Sanchez |first3=Elda E. |title=Snake Envenomation |journal=New England Journal of Medicine |date=6 January 2022 |volume=386 |issue=1 |pages=68–78 |doi=10.1056/NEJMra2105228|pmid=34986287 |pmc=9854269 |s2cid=245771267}}</ref> [[Metalloproteinase]]s further lead to breakdown of the extracellular matrix (releasing inflammatory mediators) and cause microvascular damage, leading to hemorrhage, skeletal muscle damage (necrosis), blistering and further dermonecrosis.<ref name="Seifert" /> The metalloproteinase release of the inflammatory mediators leads to pain, swelling, and white blood cell ([[leukocyte]]) infiltration. The lymphatic system may be damaged by the various enzymes contained in the venom leading to edema; or the lymphatic system may also allow the venom to be carried systemically.<ref name="Seifert" /> Snake venom may cause muscle damage or [[myotoxin|myotoxicity]] via the enzyme [[phospholipase A2]] which disrupts the plasma membrane of muscle cells. This damage to muscle cells may cause [[rhabdomyolysis]], respiratory muscle compromise, or both.<ref name="Seifert" /> Other enzymes such as bradykinin potentiating peptides, natriuretic peptides, [[vascular endothelial growth factor]]s, [[proteases]] can also cause [[hypotension]] or low blood pressure.<ref name="Seifert" /> Toxins in snake venom can also cause kidney damage (nephrotoxicity) via the same inflammatory cytokines. The toxins cause direct damage to the [[Glomerulus (kidney)|glomeruli]] in the kidneys as well as causing protein deposits in [[Bowman's capsule]]. Or the kidneys may be indirectly damaged by envenomation due to shock, clearance of toxic substances such as immune complexes, blood degradation products, or products of muscle breakdown (rhabdomyolysis).<ref name="Seifert" /> |
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Snake venom is produced in modified [[parotid gland]]s normally responsible for secreting saliva. It is stored in structures called [[wikt:alveolus|alveoli]] behind the animal's eyes, and ejected voluntarily through its hollow tubular [[fangs]]. Venom is composed of hundreds to thousands of different [[protein]]s and [[enzymes]], all serving a variety of purposes, such as interfering with a prey's cardiac system or increasing tissue permeability so that venom is absorbed faster. |
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In [[venom-induced consumption coagulopathy]], toxins in snake venom promote hemorrhage via activation, consumption, and subsequent depletion of clotting factors in the blood.<ref name="Seifert" /> These clotting factors normally work as part of the [[coagulation cascade]] in the blood to form blood clots and prevent hemorrhage. Toxins in snake venom (especially the venom of New World pit vipers (the family [[crotalina]])) may also cause low platelets ([[thrombocytopenia]]) or altered platelet function also leading to bleeding.<ref name="Seifert" /> |
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Venom in many snakes, such as pitvipers, affects virtually every organ system in the human body and can be a combination of many toxins, including [[cytotoxins]], [[hemotoxins]], [[neurotoxins]], and [[myotoxin]]s, allowing for an enormous variety of symptoms.<ref name="Gold2002" /><ref name="Russell1980a">{{Cite journal |last=Russell |first=Findlay E. |year=1980 |title=Snake Venom Poisoning in the United States |journal=Annual Review of Medicine |volume=31 |pages=247–59|doi=10.1146/annurev.me.31.020180.001335|pmid=6994610}}</ref> Earlier, the venom of a particular snake was considered to be one kind only i.e. either hemotoxic or neurotoxic, and this erroneous belief may still persist wherever the updated literature is hard to access. Although there is much known about the protein compositions of venoms from Asian and American snakes, comparatively little is known of Australian snakes. |
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Snake venom is known to cause neuromuscular paralysis, usually as a flaccid paralysis that is descending; starting at the facial muscles, causing [[Ptosis (eyelid)|ptosis]] or drooping eyelids and [[dysarthria]] or poor articulation of speech, and descending to the respiratory muscles causing respiratory compromise.<ref name="Seifert" /> The neurotoxins can either bind to and block membrane receptors at the post-synaptic neurons or they can be taken up into the pre-synaptic neuron cells and impair neurotransmitter release.<ref name="Seifert" /> Venom toxins that are taken up intra-cellularly, into the cells of the pre-synaptic neurons are much more difficult to reverse using anti-venom as they are inaccessible to the anti-venom when they are intracellular.<ref name="Seifert" /> |
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The strength of venom differs markedly between species and even more so between families, as measured by [[median lethal dose]] (LD<sub>50</sub>) in mice. Subcutaneous LD<sub>50</sub> varies by over 140-fold within elapids and by more than 100-fold in vipers. The amount of venom produced also differs among species, with the [[Gaboon viper]] able to potentially deliver from 450–600 milligrams of venom in a single bite, the most of any snake.<ref name="Spawls">{{Cite book |title=The Dangerous Snakes of Africa |last=Spawls |first=Stephen |coauthors=Bill Branch |year=1997 |publisher=Southern Book Publishers |location=Johannesburg |isbn=1-86812-575-0 |page=192}}</ref> [[Opisthoglyphous]] colubrids have venom ranging from life-threatening (in the case of the boomslang) to barely noticeable (as in ''[[Tantilla]]''). |
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The strength of venom differs markedly between species and even more so between families, as measured by [[median lethal dose]] (LD<sub>50</sub>) in mice. Subcutaneous LD<sub>50</sub> varies by over 140-fold within elapids and by more than 100-fold in vipers. The amount of venom produced also differs among species, with the [[Gaboon viper]] able to potentially deliver from 450 to 600 milligrams of venom in a single bite, the most of any snake.<ref name="Spawls">{{cite book |title=The Dangerous Snakes of Africa | vauthors = Spawls S, Branch B |year=1997 |publisher=Southern Book Publishers |location=Johannesburg |isbn=978-1-86812-575-3 |page=192}}</ref> [[Opisthoglyphous]] colubrids have venom ranging from life-threatening (in the case of the [[boomslang]]) to barely noticeable (as in ''[[Tantilla]]'').{{citation needed|date=May 2021}} |
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== Prevention == |
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[[File:RodriguezParkHoustonSnakes.JPG|thumb|right|Sign at Sylvan Rodriguez Park in [[Houston, Texas]] warning of the presence of snakes.]] |
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== Prevention == |
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Snakes are most likely to bite when they feel threatened, are startled, are provoked, or have no means of escape when cornered. Encountering a snake is potentially dangerous and it is recommended to leave the vicinity. It is difficult to safely identify many snake species as appearances may vary dramatically. |
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[[File:RodriguezParkHoustonSnakes.JPG|thumb|right|Sign at Sylvan Rodriguez Park in [[Houston, Texas]], warning of the presence of snakes.]] |
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Snakes are likely to approach residential areas when attracted by prey, such as [[rodents]]. |
Snakes are most likely to bite when they feel threatened, are startled, are provoked, or when they have been cornered. Snakes are likely to approach residential areas when attracted by prey, such as [[rodents]]. Regular [[pest control]] can reduce the threat of snakes considerably. It is beneficial to know the species of snake that are common in local areas, or while travelling or hiking. [[Africa]], [[Australia]], the [[Neotropics]], and [[South Asia]] in particular are populated by many dangerous species of snake. Being aware of—and ultimately avoiding—areas known to be heavily populated by dangerous snakes is strongly recommended.{{citation needed|date=July 2020}} |
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When in the wilderness, treading heavily creates ground vibrations and noise, which will often cause snakes to flee from the area. However, this generally only applies to vipers as some larger and more aggressive snakes in other parts of the world, such as |
When in the wilderness, treading heavily creates ground vibrations and noise, which will often cause snakes to flee from the area. However, this generally only applies to vipers, as some larger and more aggressive snakes in other parts of the world, such as [[mamba]]s and [[cobra]]s,<ref name="Haji">{{cite web| vauthors = Haji R |title=Venomous snakes and snake bites|url=http://www.zoocheck.com/Reportpdfs/Venomous%20snakes.pdf|website=Zoocheck Canada|access-date=25 October 2013|archive-url=https://web.archive.org/web/20120425231856/http://www.zoocheck.com/Reportpdfs/Venomous%20snakes.pdf|archive-date=25 April 2012}}</ref> will respond more aggressively. If presented with a direct encounter, it is best to remain silent and motionless. If the snake has not yet fled, it is important to step away slowly and cautiously.{{citation needed|date=May 2021}} |
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The use of a flashlight when engaged in camping activities, such as gathering firewood at night, can be helpful. Snakes may also be unusually active during especially warm nights when ambient temperatures exceed {{convert|21|°C|°F|abbr=on}}. It is advised not to reach blindly into hollow logs, flip over large rocks, and enter old [[Log cabin|cabins]] or other potential snake hiding |
The use of a flashlight when engaged in camping activities, such as gathering firewood at night, can be helpful. Snakes may also be unusually active during especially warm nights when ambient temperatures exceed {{convert|21|°C|°F|abbr=on}}. It is advised not to reach blindly into hollow logs, flip over large rocks, and enter old [[Log cabin|cabins]] or other potential snake hiding places. When [[climbing|rock climbing]], it is not safe to grab ledges or crevices without examining them first, as snakes are [[Ectotherm|cold-blooded]] and often sunbathe atop rock ledges.{{citation needed|date=May 2021}} |
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In the United States more than 40 |
In the United States, more than 40 percent of people bitten by snakes intentionally put themselves in harm's way by attempting to capture wild snakes or by carelessly handling their dangerous pets—40 percent of that number had a [[blood alcohol level]] of 0.1 percent or more.<ref>{{cite journal | vauthors = Kurecki BA, Brownlee HJ | title = Venomous snakebites in the United States | journal = The Journal of Family Practice | volume = 25 | issue = 4 | pages = 386–392 | date = October 1987 | pmid = 3655676}}</ref> |
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It is also important to avoid snakes that [[apparent death|appear to be dead]], as some species will |
It is also important to avoid snakes that [[apparent death|appear to be dead]], as some species will roll over on their backs and stick out their tongue to fool potential threats. A snake's detached head can immediately act by [[reflex action|reflex]] and potentially bite. The induced bite can be just as severe as that of a live snake.<ref name="Gold2002" /><ref>{{cite journal | vauthors = Gold BS, Barish RA | title = Venomous snakebites. Current concepts in diagnosis, treatment, and management | journal = Emergency Medicine Clinics of North America | volume = 10 | issue = 2 | pages = 249–267 | date = May 1992 | pmid = 1559468 | doi = 10.1016/S0733-8627(20)30712-4}}</ref> |
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As a dead snake is incapable of regulating the venom injected, a bite from a dead snake can often contain large amounts of venom.<ref name="Suchard1999">{{cite journal | vauthors = Suchard JR, LoVecchio F | title = Envenomations by rattlesnakes thought to be dead | journal = The New England Journal of Medicine | volume = 340 | issue = 24 | page = 1930 | date = June 1999 | pmid = 10375322 | doi = 10.1056/NEJM199906173402420 | doi-access = free}}</ref> |
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== Treatment == |
== Treatment == |
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It |
It may be difficult to determine if a bite by any species of snake is life-threatening. A bite by a North American [[Agkistrodon contortrix|copperhead]] on the ankle is usually a moderate injury to a healthy adult, but a bite to a child's abdomen or face by the same snake may be fatal. The outcome of all snakebites depends on a multitude of factors: the type of snake, the size, physical condition, and temperature of the snake, the age and physical condition of the person, the area and tissue bitten (e.g., foot, torso, vein or muscle), the amount of venom injected, the time it takes for the person to find treatment, and finally the quality of that treatment.<ref name="Gold2002" /><ref name="Gold1994" /> An overview of systematic reviews on different aspects of snakebite management found that the evidence base from majority of treatment modalities is low quality.<ref name="Interventions for the management of">{{cite journal | vauthors = Bhaumik S, Beri D, Lassi ZS, Jagnoor J | title = Interventions for the management of snakebite envenoming: An overview of systematic reviews | journal = PLOS Neglected Tropical Diseases | volume = 14 | issue = 10 | pages = e0008727 | date = October 2020 | pmid = 33048936 | pmc = 7584233 | doi = 10.1371/journal.pntd.0008727 | doi-access = free}}</ref> An analysis of World Health Organization guidelines found that they are of low quality, with inadequate stakeholder involvement and poor methodological rigour.<ref>{{cite journal | vauthors = Bhaumik S, Jagadesh S, Lassi Z | title = Quality of WHO guidelines on snakebite: the neglect continues | journal = BMJ Global Health | volume = 3 | issue = 2 | pages = e000783 | date = 2018-04-01 | pmid = 29662699 | pmc = 5898301 | doi = 10.1136/bmjgh-2018-000783}}</ref> In addition, access to effective treatment modalities is a major challenge in some regions, particularly in most African countries.<ref name=":0">{{Cite journal |last=Berg |first=Philipp |last2=Theart |first2=Francois |last3=van Driel |first3=Marcel |last4=Saaiman |first4=Esta L. |last5=Mavoungou |first5=Lise-Bethy |date=2024-11-06 |title=Snakebite envenoming in Africa remains widely neglected and demands multidisciplinary attention |url=https://www.nature.com/articles/s41467-024-54070-y |journal=Nature Communications |language=en |volume=15 |issue=1 |pages=9598 |doi=10.1038/s41467-024-54070-y |issn=2041-1723|pmc=11541957 }}</ref> |
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=== Snake identification === |
=== Snake identification === |
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Identification of the snake is important in planning treatment in certain areas of the world |
Identification of the snake is important in planning treatment in certain areas of the world but is not always possible. Ideally, the dead snake would be brought in with the person, but in areas where snake bite is more common, local knowledge may be sufficient to recognize the snake. However, in regions where polyvalent [[antivenom]]s are available, such as North America, identification of snakes is not a high-priority item. Attempting to catch or kill the offending snake also puts one at risk for re-envenomation or creating a second person bitten, and generally is not recommended.<ref name="auto">{{cite journal |last1=Knudsen |first1=Cecilie |last2=Jürgensen |first2=Jonas A. |last3=Føns |first3=Sofie |last4=Haack |first4=Aleksander M. |last5=Friis |first5=Rasmus U. W. |last6=Dam |first6=Søren H. |last7=Bush |first7=Sean P. |last8=White |first8=Julian |last9=Laustsen |first9=Andreas H. |date=2021 |title=Snakebite Envenoming Diagnosis and Diagnostics |journal=Frontiers in Immunology |volume=12 |page=661457 |doi=10.3389/fimmu.2021.661457 |pmid=33995385 |pmc=8113877 |issn=1664-3224|doi-access=free}}</ref> |
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The three types of venomous snakes that cause the majority of major clinical problems are [[Viper (animal)|vipers]], [[Bungarus|kraits]], and [[Naja|cobras]]. Knowledge of what species are present locally can be crucial, as is knowledge of typical signs and symptoms of envenomation by each type of snake. A scoring system can be used to try to determine the biting snake based on clinical features,<ref>{{ |
The three types of venomous snakes that cause the majority of major clinical problems are [[Viper (animal)|vipers]], [[Bungarus|kraits]], and [[Naja|cobras]]. Knowledge of what species are present locally can be crucial, as is knowledge of typical signs and symptoms of envenomation by each type of snake. A scoring system can be used to try to determine the biting snake based on clinical features,<ref>{{cite journal | vauthors = Pathmeswaran A, Kasturiratne A, Fonseka M, Nandasena S, Lalloo DG, de Silva HJ | title = Identifying the biting species in snakebite by clinical features: an epidemiological tool for community surveys | journal = Transactions of the Royal Society of Tropical Medicine and Hygiene | volume = 100 | issue = 9 | pages = 874–878 | date = September 2006 | pmid = 16412486 | doi = 10.1016/j.trstmh.2005.10.003}}</ref> but these scoring systems are extremely specific to particular geographical areas and might be compromised by the presence of escaped or released non-native species.<ref name="auto"/> |
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=== First aid === |
=== First aid === |
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Snakebite [[first aid]] recommendations vary, in part because different snakes have different types of venom. Some have little local effect, but life-threatening systemic effects, in which case containing the venom in the region of the bite by pressure immobilization is desirable. Other venoms instigate localized tissue damage around the bitten area, and immobilization may increase the severity of the damage in this area, but also reduce the total area affected; whether this trade-off is desirable remains a point of controversy. Because snakes vary from one country to another, first aid methods also vary. |
Snakebite [[first aid]] recommendations vary, in part because different snakes have different types of venom. Some have little local effect, but life-threatening systemic effects, in which case containing the venom in the region of the bite by pressure immobilization is desirable. Other venoms instigate localized tissue damage around the bitten area, and immobilization may increase the severity of the damage in this area, but also reduce the total area affected; whether this trade-off is desirable remains a point of controversy. Because snakes vary from one country to another, first aid methods also vary.{{citation needed|date=March 2023}} |
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Many organizations, including the [[American Medical Association]] and [[American Red Cross]], recommend washing the bite with soap and water. Australian recommendations for snake bite treatment are against cleaning the wound. Traces of venom left on the skin/bandages from the strike can be used in combination with a snake bite identification kit to identify the species of snake. This speeds the determination of which antivenom to administer in the emergency room.<ref>{{cite web|url=http://www.usyd.edu.au/anaes/venom/snakebite.html |title=Treatment of Australian Snake Bites |author=Chris Thompson |website=Australian anaesthetists' website |archive-url=https://web.archive.org/web/20070323132545/http://www.usyd.edu.au/anaes/venom/snakebite.html |archive-date=23 March 2007}}</ref> |
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However, most first aid guidelines agree on the following: |
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#Protect the person and others from further bites. While identifying the species is desirable in certain regions, risking further bites or delaying proper medical treatment by attempting to capture or kill the snake is not recommended. |
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#Keep the person calm. [[Acute stress reaction]] increases blood flow and endangers the person. |
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#[[Call for help]] to arrange for transport to the nearest hospital [[emergency room]], where [[antivenom]] for snakes common to the area will often be available. |
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#Make sure to keep the bitten limb in a functional position and below the person's heart level so as to minimize blood returning to the heart and other organs of the body. |
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#Do not give the person anything to eat or drink. This is especially important with consumable alcohol, a known [[vasodilator]] which will speed up the absorption of venom. Do not administer [[stimulant]]s or [[Analgesics|pain medications]], unless specifically directed to do so by a physician. |
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#Remove any items or clothing which may constrict the bitten limb if it swells (rings, bracelets, watches, footwear, etc.) |
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#Keep the person as still as possible. |
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#Do not [[Incision|incise]] the bitten site. |
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Many organizations, including the [[American Medical Association]] and [[American Red Cross]], recommend washing the bite with soap and water. Australian recommendations for snake bite treatment recommend against cleaning the wound. Traces of venom left on the skin/bandages from the strike can be used in combination with a snake bite identification kit to identify the species of snake. This speeds determination of which antivenom to administer in the emergency room.<ref>{{cite web |url=http://www.usyd.edu.au/anaes/venom/snakebite.html |title=Treatment of Australian Snake Bites |author=Chris Thompson |work=Australian anaesthetists' website}}{{dead link|date=June 2012}}</ref> |
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India developed a national snake-bite protocol in 2007 which includes advice to:<ref name="Indian NationalProtocol2007">{{cite web|url=http://www.whoindia.org/LinkFiles/Chemical_Safety_Snakebite_Protocols_2007.pdf |title=Indian National Snakebite Protocols 2007|publisher=Indian National Snakebite Protocol Consultation Meeting, 2 August 2007, Delhi|accessdate=31 May 2012}}</ref> |
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*Reassure the patient. 70% of all snakebites are from non-venomous species. Only 50% of bites from vemomous species actually envenomate the patient |
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*Immobilise in the same way as a fractured limb. Use bandages or cloth to hold the splints, with care taken not to apply pressure or block the blood supply (such as with ligatures). |
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*Get to Hospital Immediately. Traditional remedies have '''no''' proven benefit in treating snakebite. |
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*Tell the doctor of any systemic symptoms, such as droopiness of a body part, that manifest on the way to hospital. |
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=== Pressure immobilization === |
=== Pressure immobilization === |
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{{ |
{{Further|Pressure immobilization technique}} |
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[[File:Bundesarchiv Bild 135-KA-01-019, Tibetexpedition, Melken einer Schlange.jpg|thumb|right|A [[Russell's viper]] is being "milked". Laboratories use extracted snake venom to produce [[antivenom]], which is often the only effective treatment for potentially fatal snakebites.]] |
[[File:Bundesarchiv Bild 135-KA-01-019, Tibetexpedition, Melken einer Schlange.jpg|thumb|right|A [[Russell's viper]] is being "milked". Laboratories use extracted snake venom to produce [[antivenom]], which is often the only effective treatment for potentially fatal snakebites.]] |
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As of 2008, clinical evidence for [[pressure immobilization]] via the use of an [[elastic bandage]] is limited.<ref name="Currie2008">{{ |
As of 2008, clinical evidence for [[pressure immobilization]] via the use of an [[elastic bandage]] is limited.<ref name="Currie2008">{{cite journal | vauthors = Currie BJ, Canale E, Isbister GK | title = Effectiveness of pressure-immobilization first aid for snakebite requires further study | journal = Emergency Medicine Australasia | volume = 20 | issue = 3 | pages = 267–270 | date = June 2008 | pmid = 18549384 | doi = 10.1111/j.1742-6723.2008.01093.x | s2cid = 40768561}}</ref> It is recommended for snakebites that have occurred in Australia (due to [[elapids]] which are neurotoxic).<ref name="Walker2013">{{cite journal | vauthors = Patrick Walker J, Morrison R, Stewart R, Gore D | title = Venomous bites and stings | journal = Current Problems in Surgery | volume = 50 | issue = 1 | pages = 9–44 | date = January 2013 | pmid = 23244230 | doi = 10.1067/j.cpsurg.2012.09.003}}</ref> It is not recommended for bites from non-neurotoxic snakes such as those found in North America and other regions of the world.<ref name="Walker2013" /><ref name="ACM2011" /> The British military recommends pressure immobilization in all cases where the type of snake is unknown.<ref>{{cite journal | vauthors = Wall C | title = British Military snake-bite guidelines: pressure immobilisation | journal = Journal of the Royal Army Medical Corps | volume = 158 | issue = 3 | pages = 194–198 | date = September 2012 | pmid = 23472565 | doi = 10.1136/jramc-158-03-09 | s2cid = 22415445}}</ref> |
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The object of pressure immobilization is to contain venom within a bitten limb and prevent it from moving through the [[lymphatic system]] to the vital organs. This therapy has two components: pressure to prevent lymphatic drainage, and immobilization of the bitten limb to prevent the pumping action of the [[skeletal muscle]]s. |
The object of pressure immobilization is to contain venom within a bitten limb and prevent it from moving through the [[lymphatic system]] to the vital organs. This therapy has two components: pressure to prevent lymphatic drainage, and immobilization of the bitten limb to prevent the pumping action of the [[skeletal muscle]]s.{{citation needed|date=March 2023}} |
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=== Antivenom === |
=== Antivenom === |
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Until the advent of [[antivenom]], bites from some species of snake were almost universally fatal.<ref name="INCHEM">{{cite web | |
Until the advent of [[antivenom]], bites from some species of snake were almost universally fatal.<ref name="INCHEM">{{cite web | vauthors = White J |title=Oxyuranus microlepidotus |url=http://www.inchem.org/documents/pims/animal/taipan.htm |date=November 1991 |publisher=Chemical Safety Information from Intergovernmental Organizations |quote=Without appropriate antivenom treatment up to 75% of taipan bites will be fatal. Indeed, in the era before specific antivenom therapy, virtually no survivors of taipan bite were recorded. |access-date=24 July 2009 |url-status=live |archive-url=https://web.archive.org/web/20090803070213/http://www.inchem.org/documents/pims/animal/taipan.htm |archive-date=3 August 2009}}</ref> Despite huge advances in emergency therapy, antivenom is often still the only effective treatment for envenomation. The first antivenom was developed in 1895 by French physician [[Albert Calmette]] for the treatment of [[Indian cobra]] bites. Antivenom is made by injecting a small amount of venom into an animal (usually a horse or sheep) to initiate an immune system response. The resulting [[antibodies]] are then harvested from the animal's blood.{{citation needed|date=March 2023}} |
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Antivenom is injected into the person [[Intravenous therapy|intravenously]], and works by binding to and neutralizing venom enzymes. It cannot undo damage already caused by venom, so antivenom treatment should be sought as soon as possible. Modern antivenoms are usually polyvalent, making them effective against the venom of numerous snake species. Pharmaceutical companies |
Antivenom is injected into the person [[Intravenous therapy|intravenously]], and works by binding to and neutralizing venom enzymes. It cannot undo the damage already caused by venom, so antivenom treatment should be sought as soon as possible. Modern antivenoms are usually polyvalent, making them effective against the venom of numerous snake species. Pharmaceutical companies that produce antivenom target their products against the species native to a particular area. The availability of antivenom is a major concern in some areas, including most of Africa, due to economic reasons (antivenom crisis).<ref name=":0" /> In Sub-Saharan Africa, the efficacy of antivenom is often poorly characterised and some of the few available products have even been found to lack effectiveness.<ref>{{Cite journal |last=Potet |first=Julien |last2=Smith |first2=James |last3=McIver |first3=Lachlan |date=2019-06-24 |title=Reviewing evidence of the clinical effectiveness of commercially available antivenoms in sub-Saharan Africa identifies the need for a multi-centre, multi-antivenom clinical trial |url=https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0007551 |journal=PLOS Neglected Tropical Diseases |language=en |volume=13 |issue=6 |pages=e0007551 |doi=10.1371/journal.pntd.0007551 |issn=1935-2735 |pmc=6615628 |pmid=31233536 |doi-access=free}}</ref> |
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Although some people may develop serious adverse reactions to antivenom, such as [[anaphylaxis]], in emergency situations this is usually treatable in a hospital setting and hence the benefit outweighs the potential consequences of not using antivenom. Giving [[adrenaline]] (epinephrine) to prevent adverse reactions to antivenom before they occur might be reasonable in cases where they occur commonly.<ref name="Nuch2000" /> Antihistamines do not appear to provide any benefit in preventing adverse reactions.<ref name="Nuch2000">{{cite journal | vauthors = Nuchpraryoon I, Garner P | title = Interventions for preventing reactions to snake antivenom | journal = The Cochrane Database of Systematic Reviews | issue = 2 | pages = CD002153 | year = 2000 | volume = 1999 | pmid = 10796682 | pmc = 7017854 | doi = 10.1002/14651858.CD002153}}</ref> |
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=== Outmoded === |
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[[File:Snakebite kit.jpg|thumb|right|Old style snake bite kit that should not be used.]] |
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The following treatments while once recommended are considered of no use or harmful including: tourniquets, incisions, suction, application of cold, and application of electricity.<ref name="ACM2011">{{cite journal|last=American College of Medical|first=Toxicology|coauthors=American Academy of Clinical, Toxicology; American Association of Poison Control, Centers; European Association of Poison Control, Centres; International Society of, Toxinology; Asia Pacific Association of Medical, Toxicology|title=Pressure immobilization after North American Crotalinae snake envenomation|journal=Journal of Medical Toxicology|date=December 2011|volume=7|issue=4|pages=322–3|pmid=22065370|doi=10.1007/s13181-011-0174-2|pmc=3550191}}</ref> Cases in which these treatments appear to work may be the result of [[dry bite]]s. |
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=== Chronic Complications === |
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* Application of a [[tourniquet]] to the bitten limb is generally not recommended. There is no convincing evidence that it is an effective first aid tool as ordinarily applied.<ref name="theak">{{Cite journal |author=Theakston RD |title=An objective approach to antivenom therapy and assessment of first-aid measures in snake bite |journal=Ann. Trop. Med. Parasitol. |volume=91 |issue=7 |pages=857–65 |year=1997|pmid=9625943 |doi= 10.1080/00034989760626 |url=http://www.kingsnake.com/aho/pdf/menu6/theakston1997.pdf|format=PDF}}</ref> Tourniquets have been found to be completely ineffective in the treatment of ''[[Crotalus durissus]]'' bites,<ref>{{Cite journal |author=Amaral CF, Campolina D, Dias MB, Bueno CM, Rezende NA |title=Tourniquet ineffectiveness to reduce the severity of envenoming after Crotalus durissus snake bite in Belo Horizonte, Minas Gerais, Brazil |journal=Toxicon |volume=36 |issue=5 |pages=805–8 |year=1998 |pmid=9655642 |doi= 10.1016/S0041-0101(97)00132-3|url=http://linkinghub.elsevier.com/retrieve/pii/S0041-0101(97)00132-3}}</ref> but some positive results have been seen with properly applied tourniquets for cobra venom in the [[Philippines]].<ref>{{Cite journal |author=Watt G, Padre L, Tuazon ML, Theakston RD, Laughlin LW |title=Tourniquet application after cobra bite: delay in the onset of neurotoxicity and the dangers of sudden release |journal=Am. J. Trop. Med. Hyg. |volume=38 |issue=3 |pages=618–22 |year=1988 |pmid=3275141 }}</ref> Uninformed tourniquet use is dangerous, since reducing or cutting off circulation can lead to [[gangrene]], which can be fatal.<ref name="theak" /> The use of a compression bandage is generally as effective, and much safer. |
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Chronic health effects of snakebite include but are not limited to non-healing and chronic ulcers, musculoskeletal disorders, amputations, chronic kidney disease, and other neurological and endocrine complications.<ref>{{cite journal | vauthors = Kasturiratne A, Lalloo DG, Janaka de Silva H | title = Chronic health effects and cost of snakebite | journal = Toxicon | volume = 9-10 | page = 100074 | date = July 2021 | pmid = 34355162 | pmc = 8321925 | doi = 10.1016/j.toxcx.2021.100074| bibcode = 2021TxcnX...900074K }}</ref><ref>{{cite journal | vauthors = Bhaumik S, Gopalakrishnan M, Meena P | title = Mitigating the chronic burden of snakebite: turning the tide for survivors | journal = Lancet | volume = 398 | issue = 10309 | pages = 1389–1390 | date = October 2021 | pmid = 34537105 | doi = 10.1016/S0140-6736(21)01905-X | issn=0140-6736 | s2cid = 237541103}}</ref> The treatment of chronic complications of snakebite has not been well researched and there a systems approach consisting of a multi-component intervention.<ref>{{cite journal | vauthors = Bhaumik S, Gopalakrishnan M, Meena P | title = Mitigating the chronic burden of snakebite: turning the tide for survivors | journal = Lancet | volume = 398 | issue = 10309 | pages = 1389–1390 | date = October 2021 | pmid = 34537105 | doi = 10.1016/S0140-6736(21)01905-X| issn=0140-6736 | s2cid = 237541103}}</ref><ref name="Interventions for the management of" /> |
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* Cutting open the bitten area, an action often taken prior to suction, is not recommended since it causes further damage and increases the risk of infection. |
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* Sucking out venom, either by mouth or with a pump, does not work and may harm the affected area directly.<ref name="pmid16781926">{{Cite journal |author=Holstege CP, Singletary EM |title=Images in emergency medicine. Skin damage following application of suction device for snakebite |journal=Annals of Emergency Medicine |volume=48 |issue=1 |pages=105, 113 |year=2006 |pmid=16781926 |doi=10.1016/j.annemergmed.2005.12.019}}</ref> Suction started after 3 minutes removes a clinically insignificant quantity—less than one thousandth of the venom injected—as shown in a human study.<ref>{{Cite journal|author=Alberts M, Shalit M, LoGalbo F|title=Suction for venomous snakebite: a study of "mock venom" extraction in a human model|journal=Annals of Emergency Medicine|volume=43|issue=2|pages=181–6|year=2004|pmid=14747805|doi=10.1016/S0196-0644(03)00813-8}}</ref> In a study with pigs, suction not only caused no improvement but led to [[necrosis]] in the suctioned area.<ref name="pmid11055564">{{Cite journal |author=Bush SP, Hegewald KG, Green SM, Cardwell MD, Hayes WK |title=Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model |journal=Wilderness & environmental medicine |volume=11 |issue=3 |pages=180–8 |year=2000 |pmid=11055564 |doi=10.1580/1080-6032(2000)011[0180:EOANPV]2.3.CO;2 }}</ref> Suctioning by mouth presents a risk of further poisoning through the mouth's [[oral mucosa|mucous tissues]].<ref>Riggs BS, Smilkstein MJ, Kulig KW, ''et al.'' Rattlesnake envenomation with massive oropharyngeal edema following incision and suction (Abstract). Presented at the AACT/AAPCC/ABMT/CAPCC Annual Scientific Meeting, Vancouver, Canada, September 27 October 2, 1987.</ref> The well-meaning family member or friend may also release bacteria into the persons wound, leading to infection. |
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=== Outmoded === |
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[[File:Snakebite kit.jpg|thumb|right|Old-style snake bite kit that should not be used.]] |
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The following treatments, while once recommended, are considered of no use or harmful, including tourniquets, incisions, suction, application of cold, and application of electricity.<ref name="ACM2011">{{cite journal | title = Pressure immobilization after North American Crotalinae snake envenomation | journal = Journal of Medical Toxicology | volume = 7 | issue = 4 | pages = 322–323 | date = December 2011 | pmid = 22065370 | pmc = 3550191 | doi = 10.1007/s13181-011-0174-2 | author1 = American College of Medical Toxicology | author2 = American Academy of Clinical Toxicology | author3 = American Association of Poison Control Centers | author4 = European Association of Poison Control Centres | author5 = International Society of Toxinology | author6 = Asia Pacific Association of Medical Toxicology}}</ref> Cases in which these treatments appear to work may be the result of [[dry bite]]s. |
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* Application of a [[tourniquet]] to the bitten limb is generally not recommended. There is no convincing evidence that it is an effective first-aid tool as ordinarily applied.<ref name="theak">{{cite journal | vauthors = Theakston RD | title = An objective approach to antivenom therapy and assessment of first-aid measures in snake bite | journal = Annals of Tropical Medicine and Parasitology | volume = 91 | issue = 7 | pages = 857–865 | date = October 1997 | pmid = 9625943 | doi = 10.1080/00034989760626 | url = http://www.kingsnake.com/aho/pdf/menu6/theakston1997.pdf | url-status = live | archive-url = https://web.archive.org/web/20081230093058/http://www.kingsnake.com/aho/pdf/menu6/theakston1997.pdf | archive-date = 30 December 2008}}</ref> Tourniquets have been found to be completely ineffective in the treatment of ''[[Crotalus durissus]]'' bites,<ref>{{cite journal | vauthors = Amaral CF, Campolina D, Dias MB, Bueno CM, Rezende NA | title = Tourniquet ineffectiveness to reduce the severity of envenoming after Crotalus durissus snake bite in Belo Horizonte, Minas Gerais, Brazil | journal = Toxicon | volume = 36 | issue = 5 | pages = 805–808 | date = May 1998 | pmid = 9655642 | doi = 10.1016/S0041-0101(97)00132-3| bibcode = 1998Txcn...36..805A }}</ref> but some positive results have been seen with properly applied tourniquets for cobra venom in the [[Philippines]].<ref>{{cite journal | vauthors = Watt G, Padre L, Tuazon ML, Theakston RD, Laughlin LW | title = Tourniquet application after cobra bite: delay in the onset of neurotoxicity and the dangers of sudden release | journal = The American Journal of Tropical Medicine and Hygiene | volume = 38 | issue = 3 | pages = 618–622 | date = May 1988 | pmid = 3275141 | doi = 10.4269/ajtmh.1988.38.618 | s2cid = 29451180}}</ref> Uninformed tourniquet use is dangerous since reducing or cutting off circulation can lead to [[gangrene]], which can be fatal.<ref name="theak" /> The use of a compression bandage is generally as effective, and much safer. |
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* Cutting open the bitten area, an action often taken before suction, is not recommended since it causes further damage and increases the risk of infection; the subsequent cauterization of the area with fire or silver nitrate (also known as ''infernal stone'') is also potentially threatening.<ref name="peola">{{cite book | vauthors = Lupano G, Peola P |date=1915 |title=Corso di Scienze Naturali a uso delle Scuole Complementari |trans-title=A Course of Natural Sciences for the Complementary Institutes |language=it |publisher=G.B. Paravia |page=68}}</ref> |
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* Sucking out venom, either by mouth or with a pump, does not work and may harm the affected area directly.<ref name="pmid16781926">{{cite journal | vauthors = Holstege CP, Singletary EM | title = Images in emergency medicine. Skin damage following application of suction device for snakebite | journal = Annals of Emergency Medicine | volume = 48 | issue = 1 | pages = 105, 113 | date = July 2006 | pmid = 16781926 | doi = 10.1016/j.annemergmed.2005.12.019 | doi-access = free}}</ref> Suction started after three minutes removes a clinically insignificant quantity—less than one-thousandth of the venom injected—as shown in a human study.<ref>{{cite journal | vauthors = Alberts MB, Shalit M, LoGalbo F | title = Suction for venomous snakebite: a study of "mock venom" extraction in a human model | journal = Annals of Emergency Medicine | volume = 43 | issue = 2 | pages = 181–186 | date = February 2004 | pmid = 14747805 | doi = 10.1016/S0196-0644(03)00813-8}}</ref> In a study with pigs, suction not only caused no improvement but led to [[necrosis]] in the suctioned area.<ref name="pmid11055564">{{cite journal | vauthors = Bush SP, Hegewald KG, Green SM, Cardwell MD, Hayes WK | title = Effects of a negative pressure venom extraction device (Extractor) on local tissue injury after artificial rattlesnake envenomation in a porcine model | journal = Wilderness & Environmental Medicine | volume = 11 | issue = 3 | pages = 180–188 | year = 2000 | pmid = 11055564 | doi = 10.1580/1080-6032(2000)011[0180:EOANPV]2.3.CO;2 | doi-access = free}}</ref> Suctioning by mouth presents a risk of further poisoning through the mouth's [[oral mucosa|mucous tissues]].<ref>Riggs BS, Smilkstein MJ, Kulig KW, ''et al.'' Rattlesnake envenomation with massive oropharyngeal edema following incision and suction (Abstract). Presented at the AACT/AAPCC/ABMT/CAPCC Annual Scientific Meeting, Vancouver, Canada, September 27 October 2, 1987.</ref> The helper may also release bacteria into the person's wound, leading to infection. |
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* Immersion in warm water or sour milk, followed by the application of [[snake-stones]] (also known as ''la Pierre Noire''), which are believed to draw off the poison in much the way a sponge soaks up water. |
* Immersion in warm water or sour milk, followed by the application of [[snake-stones]] (also known as ''la Pierre Noire''), which are believed to draw off the poison in much the way a sponge soaks up water. |
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* Application of [[potassium permanganate]]. |
* Application of a one-percent solution of [[potassium permanganate]] or [[chromic acid]] to the cut, exposed area.<ref name="peola"/> The latter substance is notably toxic and carcinogenic. |
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* Drinking abundant quantities of alcohol following the cauterization or disinfection of the wound area.<ref name="peola"/> |
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* Use of electroshock therapy in animal tests has shown this treatment to be useless and potentially dangerous.<ref>{{Cite journal|author=Russell F|title=Another warning about electric shock for snakebite|journal=Postgrad Med|volume=82|issue=5|page=32|year=1987|pmid=3671201}}</ref><ref>{{Cite journal|author=Ryan A|title=Don't use electric shock for snakebite|journal=Postgrad Med|volume=82|issue=2|page=42|year=1987|pmid=3497394}}</ref><ref>{{Cite journal|author=Howe N, Meisenheimer J|title=Electric shock does not save snakebitten rats|journal=Annals of Emergency Medicine|volume=17|issue=3|pages=254–6|year=1988|pmid=3257850|doi=10.1016/S0196-0644(88)80118-5}}</ref><ref>{{Cite journal|author=Johnson E, Kardong K, Mackessy S|title=Electric shocks are ineffective in treatment of lethal effects of rattlesnake envenomation in mice|journal=Toxicon|volume=25|issue=12|pages=1347–9|year=1987|pmid=3438923|doi=10.1016/0041-0101(87)90013-4}}</ref> |
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* Use of electroshock therapy in animal tests has shown this treatment to be useless and potentially dangerous.<ref>{{cite journal | vauthors = Russell FE | title = Another warning about electric shock for snakebite | journal = Postgraduate Medicine | volume = 82 | issue = 5 | page = 32 | date = October 1987 | pmid = 3671201 | doi = 10.1080/00325481.1987.11699990}}</ref><ref>{{cite journal | vauthors = Ryan AJ | title = Don't use electric shock for snakebite | journal = Postgraduate Medicine | volume = 82 | issue = 2 | page = 42 | date = August 1987 | pmid = 3497394 | doi = 10.1080/00325481.1987.11699922 | s2cid = 222260195}}</ref><ref>{{cite journal | vauthors = Howe NR, Meisenheimer JL | title = Electric shock does not save snakebitten rats | journal = Annals of Emergency Medicine | volume = 17 | issue = 3 | pages = 254–256 | date = March 1988 | pmid = 3257850 | doi = 10.1016/S0196-0644(88)80118-5}}</ref><ref>{{cite journal | vauthors = Johnson EK, Kardong KV, Mackessy SP | title = Electric shocks are ineffective in treatment of lethal effects of rattlesnake envenomation in mice | journal = Toxicon | volume = 25 | issue = 12 | pages = 1347–1349 | year = 1987 | pmid = 3438923 | doi = 10.1016/0041-0101(87)90013-4| bibcode = 1987Txcn...25.1347J }}</ref> |
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In extreme cases, in remote areas, all of these misguided attempts at treatment have resulted in injuries far worse than an otherwise mild to moderate snakebite. In worst-case scenarios, thoroughly constricting tourniquets have been applied to bitten limbs, completely shutting off blood flow to the area. By the time the person finally reached appropriate medical facilities, their limbs had to be [[amputated]].{{citation needed|date=March 2023}} |
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=== In development === |
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In extreme cases, in remote areas, all of these misguided attempts at treatment have resulted in injuries far worse than an otherwise mild to moderate snakebite. In worst case scenarios, thoroughly constricting tourniquets have been applied to bitten limbs, completely shutting off blood flow to the area. By the time the person finally reached appropriate medical facilities their limbs had to be [[amputated]]. |
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Several new drugs and treatments are under development for snakebite. For instance, the metal chelator [[dimercaprol]] has recently been shown to potently antagonize the activity of Zn<sup>2+</sup>-dependent snake venom [[metalloproteinase]]s ''in vitro''.<ref>{{cite journal | vauthors = Albulescu LO, Hale MS, Ainsworth S, Alsolaiss J, Crittenden E, Calvete JJ, Evans C, Wilkinson MC, Harrison RA, Kool J, Casewell NR | display-authors = 6 | title = Preclinical validation of a repurposed metal chelator as an early-intervention therapeutic for hemotoxic snakebite | journal = Science Translational Medicine | volume = 12 | issue = 542 | pages = eaay8314 | date = May 2020 | pmid = 32376771 | pmc = 7116364 | doi = 10.1126/scitranslmed.aay8314}}</ref> New [[Monoclonal antibody|monoclonal antibodies]], polymer gels and a small molecule inhibitor called [[Varespladib]] are in development.<ref>{{cite web|title=The search for better antivenoms heats up as snakebites get renewed attention|url=https://cen.acs.org/biological-chemistry/biotechnology/search-better-antivenoms-heats-snakebites/97/i4|access-date=2020-10-15|website=Chemical & Engineering News|language=en}}</ref> A core outcome set (minimal list of consensus outcomes that should be used in future intervention research) for snakebite in South Asia is being developed.<ref>{{cite journal |last1=Bhaumik |first1=Soumyadeep |last2=Beri |first2=Deepti |last3=Tyagi |first3=Jyoti |last4=Clarke |first4=Mike |last5=Sharma |first5=Sanjib Kumar |last6=Williamson |first6=Paula R. |last7=Jagnoor |first7=Jagnoor |date=2022-06-08 |title=Outcomes in intervention research on snakebite envenomation: a systematic review |journal=F1000Research |volume=11 |page=628 |doi=10.12688/f1000research.122116.1 |pmid=36300033 |pmc=9579743 |language=en |doi-access=free}}</ref> |
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== Epidemiology == |
== Epidemiology == |
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{{Main|Epidemiology of snakebites}} |
{{Main|Epidemiology of snakebites}} |
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{{multiple image |direction=vertical |width= |
{{see also|List of fatal snake bites in the United States|List of fatal snake bites in Australia}} |
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{{multiple image |direction=vertical |width=350 |align=right |image1=World distribution of snakes.svg |image2=Number of snake envenomings (2007).svg |caption1=Map showing the approximate world distribution of snakes. |caption2=Map showing the global distribution of snakebite morbidity.}} |
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Earlier estimates for snakebite vary from 1.2 to 5.5 million, with 421,000 to 2.5 million being envenomings, and causing 20,000 to 125,000 deaths.<ref name=WHO2015/><ref name=Kast2008/> More recent modelling estimates that in 2019, about 63,400 people died globally from snakebite, with 51,100 of these deaths happening in India.<ref>{{cite journal |last1=Roberts |first1=Nicholas L. S. |last2=Johnson |first2=Emily K. |last3=Zeng |first3=Scott M. |last4=Hamilton |first4=Erin B. |last5=Abdoli |first5=Amir |last6=Alahdab |first6=Fares |last7=Alipour |first7=Vahid |last8=Ancuceanu |first8=Robert |last9=Andrei |first9=Catalina Liliana |last10=Anvari |first10=Davood |last11=Arabloo |first11=Jalal |last12=Ausloos |first12=Marcel |last13=Awedew |first13=Atalel Fentahun |last14=Badiye |first14=Ashish D. |last15=Bakkannavar |first15=Shankar M. |date=2022-10-25 |title=Global mortality of snakebite envenoming between 1990 and 2019 |journal=Nature Communications |language=en |volume=13 |issue=1 |page=6160 |doi=10.1038/s41467-022-33627-9 |pmid=36284094 |pmc=9596405 |bibcode=2022NatCo..13.6160G |s2cid=253111038 |issn=2041-1723}}</ref> Since reporting is not mandatory in much of the world, the data on the frequency of snakebites is not precise.<ref name=Kast2008/> Many people who survive bites have permanent tissue damage caused by venom, leading to disability.<ref name="Gutierrez2007" /> Most snake envenomings and fatalities occur in [[South Asia]], [[Southeast Asia]], and [[sub-Saharan Africa]], with [[India]] reporting the most snakebite deaths of any country.<ref name=Kast2008/> Available evidence on the effect of climate change on the epidemiology of snakebite is limited but it is expected that there will be a geographic shift in the risk of snakebite: northwards in North America and southwards in South America and Mozambique, and increase in the incidence of bite in Sri Lanka.<ref>{{cite journal |last1=Bhaumik |first1=Soumyadeep |last2=Beri |first2=Deepti |last3=Jagnoor |first3=Jagnoor |date=October 2022 |title=The impact of climate change on the burden of snakebite: Evidence synthesis and implications for primary healthcare |journal=Journal of Family Medicine and Primary Care |language=en-US |volume=11 |issue=10 |pages=6147–6158 |doi=10.4103/jfmpc.jfmpc_677_22 |pmid=36618235 |pmc=9810950 |s2cid=253452433 |issn=2249-4863 |doi-access=free}}</ref> |
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Most snakebites are caused by non-venomous snakes. Of the roughly 3,000 known species of snake found worldwide, only 15% are considered dangerous to humans.<ref name="Kasturiratne">{{Cite journal |last=Kasturiratne |first=A. |year=2008|title=The Global Burden of Snakebite: A Literature Analysis and Modelling Based on Regional Estimates of Envenoming and Deaths |journal=PloS Medicine |pmid=18986210 |volume=5 |issue=11 |pmc=2577696 |pages= e218|doi=10.1371/journal.pmed.0050218 |url=http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.0050218;jsessionid=66B81B3E56F5DABADB52D86E51BE334F |accessdate=2009-06-24 |editor1-last=Winkel |editor1-first=Ken |author-separator=, |author2=Wickremasinghe A. R. |author3=de Silva N. |author4=Gunawardena N. K. |author5=Pathmeswaran A. |display-authors=4 |last6=Premaratna |first6=R |last7=Savioli |first7=L |last8=Lalloo |first8=DG |last9=De Silva |first9=HJ}}</ref><ref name="Gold2002">{{Cite journal |last=Gold |first=Barry S. |coauthors=Richard C. Dart, Robert A. Barish |date=1 April 2002|title=Bites of venomous snakes |journal=The New England Journal of Medicine |volume=347 |issue=5 |pages=347–56|doi=10.1056/NEJMra013477 |pmid=12151473}}</ref><ref>{{Cite journal |last=Russell |first=F. E. |title=When a snake strikes |journal=Emerg Med |volume=22 |issue=12 |pages=33–4, 37–40, 43 |year=1990}}</ref> Snakes are found on every continent except [[Antarctica]].<ref name="Kasturiratne" /> The most diverse and widely distributed snake family, the [[colubrid]]s, has approximately 700 venomous species,<ref name="Mackessy2002">{{Cite journal |last=Mackessy |first=Stephen P. |year=2002 |title=Biochemistry and pharmacology of colubrid snake venoms |journal=Journal of Toxicology: Toxin Reviews |volume=21 |issue=1–2 |pages=43–83 |doi=10.1081/TXR-120004741 |url=http://www.unco.edu/nhs/biology/faculty_staff/mackessy/colubrid.pdf |accessdate=2009-09-26 |quote=Estimates of the number of venomous colubrids approach 700 species. Most may not produce a venom capable of causing serious damage to humans, but at least five species (''Dispholidus typus'', ''Thelotornis capensis'', ''Rhabdophis tigrinus'', ''Philodryas olfersii'' and ''Tachymenis peruviana'') have caused human fatalities}}</ref> but only five [[genera]]—[[Dispholidus|boomslang]]s, [[Thelotornis|twig snake]]s, [[Rhabdophis|keelback snake]]s, [[Philodryas|green snake]]s, and [[Tachymenis|slender snake]]s—have caused human fatalities.<ref name="Mackessy2002" /> |
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Most snakebites are caused by non-venomous snakes. Of the roughly 3,000 known species of snake found worldwide, only 15% are considered dangerous to humans.<ref name="Gold2002"/><ref name=Kast2008/> Snakes are found on every continent except [[Antarctica]].<ref name=Kast2008/> The most diverse and widely distributed snake family, the [[colubrid]]s, has approximately 700 venomous species,<ref name="Mackessy2002">{{cite journal | vauthors = Mackessy SP |s2cid=86568032 |year=2002 |title=Biochemistry and pharmacology of colubrid snake venoms |journal=Journal of Toxicology: Toxin Reviews |volume=21 |issue=1–2 |pages=43–83 |doi=10.1081/TXR-120004741 |url=http://www.unco.edu/nhs/biology/faculty_staff/mackessy/colubrid.pdf |access-date=26 September 2009 |quote=Estimates of the number of venomous colubrids approach 700 species. Most may not produce a venom capable of causing serious damage to humans, but at least five species (''Dispholidus typus'', ''Thelotornis capensis'', ''Rhabdophis tigrinus'', ''Philodryas olfersii'' and ''Tachymenis peruviana'') have caused human fatalities |archive-url=https://web.archive.org/web/20100602041516/http://www.unco.edu/nhs/biology/faculty_staff/mackessy/colubrid.pdf |archive-date=2 June 2010 |citeseerx=10.1.1.596.5081}}</ref> but only five [[genera]]—[[boomslang]]s, [[Thelotornis|twig snakes]], [[Rhabdophis|keelback snakes]], [[Philodryas|green snakes]], and [[Tachymenis|slender snakes]]—have caused human fatalities.<ref name="Mackessy2002" /> |
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Since reporting is not mandatory in many regions of the world,<ref name="Kasturiratne" /> snakebites often go unreported. Consequently, no accurate study has ever been conducted to determine the frequency of snakebites on the international level. However, some estimates put the number at 5.4 million snakebites, 2.5 million envenomings, resulting in perhaps 125,000 deaths.<ref name="Kasturiratne" /> Others estimate 1.2 to 5.5 million snakebites, 421,000 to 1.8 million envenomings, and 20,000 to 94,000 deaths.<ref name="Kasturiratne" /> Many people who survive bites nevertheless suffer from permanent tissue damage caused by venom, leading to disability.<ref name="Gutierrez2007" /> Most snake envenomings and fatalities occur in [[South Asia]], [[Southeast Asia]], and [[sub-Saharan Africa]], with [[India]] reporting the most snakebite deaths of any country.<ref name="Kasturiratne" /> |
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Worldwide, snakebites occur most frequently in the summer season when snakes are active and humans are outdoors.<ref name= |
Worldwide, snakebites occur most frequently in the summer season when snakes are active and humans are outdoors.<ref name=Kast2008/><ref name="WingertChan1988">{{cite journal | vauthors = Wingert WA, Chan L | title = Rattlesnake bites in southern California and rationale for recommended treatment | journal = The Western Journal of Medicine | volume = 148 | issue = 1 | pages = 37–44 | date = January 1988 | pmid = 3277335 | pmc = 1026007}}</ref> Agricultural and tropical regions report more snakebites than anywhere else.<ref name=Kast2008/><ref name="Gutierrez2006"/> In the United States, those bitten are typically male and between 17 and 27 years of age.<ref name="Gold2002" /><ref name="WingertChan1988" /><ref>{{cite journal | vauthors = Parrish HM | title = Incidence of treated snakebites in the United States | journal = Public Health Reports | volume = 81 | issue = 3 | pages = 269–276 | date = March 1966 | pmid = 4956000 | pmc = 1919692 | doi = 10.2307/4592691 | jstor = 4592691}}</ref> Children and the elderly are the most likely to die.<ref name="Gold2002" /><ref name="Gold1994">{{cite journal | vauthors = Gold BS, Wingert WA | title = Snake venom poisoning in the United States: a review of therapeutic practice | journal = Southern Medical Journal | volume = 87 | issue = 6 | pages = 579–589 | date = June 1994 | pmid = 8202764 | doi = 10.1097/00007611-199406000-00001 | s2cid = 37771848}}</ref> |
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== Mechanics == |
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{{see also|Envenomation}} |
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[[File:Snake Venom Delivery System Diagram.jpg|thumb|Basic diagram of a snake's venom delivery system]] |
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When venomous snakes bite a target, they secrete [[venom]] through their venom delivery system. The venom delivery system generally consists of two venom glands, a compressor muscle, venom ducts, a fang sheath, and [[fang]]s. The primary and accessory venom glands store the venom quantities required during [[envenomation]]. The compressor muscle contracts during bites to increase the pressure throughout the venom delivery system. The pressurized venom travels through the primary venom duct to the secondary venom duct that leads down through the fang sheath and fang. The venom is then expelled through the exit [[Body orifice|orifice]] of the fang. The total volume and flow rate of venom administered into a target varies widely, sometimes as much as an order of magnitude. One of the largest factors is snake species and size, larger snakes have been shown to administer larger quantities of venom.<ref name="Hayes et al. 2002"/> |
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=== Predatory vs. defensive bites === |
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===Most venomous=== |
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Snake bites are classified as either predatory or defensive. During defensive strikes, the rate of venom expulsion and total volume of venom expelled is much greater than during predatory strikes. Defensive strikes can have 10 times as much venom volume expelled at 8.5 times the flow rate.<ref>{{cite journal | vauthors = Young BA, Zahn K | title = Venom flow in rattlesnakes: mechanics and metering | journal = The Journal of Experimental Biology | volume = 204 | issue = Pt 24 | pages = 4345–4351 | date = December 2001 | pmid = 11815658 | doi = 10.1242/jeb.204.24.4345}}</ref> This can be explained by the snake's need to quickly subdue a threat. While employing similar venom expulsion mechanics, predatory strikes are quite different from defensive strikes. Snakes usually release the prey shortly after the envenomation allowing the prey to run away and die. Releasing prey prevents retaliatory damage to the snake. The venom scent allows the snake to relocate the prey once it is deceased.<ref name="Hayes et al. 2002">{{cite book |chapter=Factors that influence venom expenditure in viperids and other snake species during predatory and defensive contexts | vauthors = Hayes WK, Herbert SS, Rehling GC, Gennaro JF |year=2002 |url= http://eaglemountainpublishing.s3.amazonaws.com/PDF/Biology%20of%20the%20Vipers/CH%2013_hayes_.pdf |title=Biology of the Vipers |pages=207–233 |publisher=Eagle Mountain Publishing}}</ref> The amount of venom injected has been shown to increase with the mass of the prey animal.<ref>{{cite journal | vauthors = Hayes WK |title=Venom metering by juvenile prairie rattlesnakes, ''Crotalus v. viridis'': effects of prey size and experience |journal=Animal Behaviour |date=1995 |volume=50 |issue=1 |pages=33–40 |doi=10.1006/anbe.1995.0218|s2cid=53160144}}</ref> Larger venom volumes allow snakes to effectively euthanize larger prey while remaining economical during strikes against smaller prey. This is an important skill as venom is a metabolically expensive resource.{{citation needed|date=May 2021}} |
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{|class="wikitable" border="1" style="margin:0 1em 0.5em 1em;" |
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|+ Most venomous snakes of the world (Ernst and Zug ''et al.'' 1996)<ref name="ErZug">{{cite book|last= Zug|first= George R.|title= Snakes in Question: The Smithsonian Answer Book |year= 1996|publisher= Smithsonian Institution Scholarly Press |location= Washington D.C., USA|isbn= 1-56098-648-4}}</ref> |
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|'''Rank''' || '''Snake''' || '''Region''' || '''[[subcutaneous injection|SC]] {{LD50}}''' |
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| 1 || [[Inland taipan]] || Australia || 0.01 mg/kg |
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| 2 || [[Pseudonaja textilis|Eastern brown snake]] || Australia, Papua New Guinea, Indonesia || 0.0365 mg/kg |
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| 3 || [[Dubois' seasnake]] || Coral Sea, Arafura Sea, Timor Sea and Indian Ocean || 0.044 mg/kg |
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| 4 || [[Black mamba]] || Sub-Saharan Africa || 0.05 mg/kg |
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| 5 || [[Pelamis platura|Yellow bellied sea snake]] || Tropical oceanic waters || 0.067 mg/kg |
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| 6 || [[Acalyptophis peronii|Peron's sea snake]] || Gulf of Siam, Strait of Taiwan, Coral sea islands, and other places || 0.079 mg/kg |
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| 7 || [[Many-banded krait]] || Mainland China, Taiwan, Vietnam, Laos, Burma || 0.09 mg/kg |
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| 8 || [[Coastal Taipan]] || Australia || 0.106 mg/kg |
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| 9 || [[Black-banded sea krait]] || eastern coast of the Malay Peninsula and Brunei, and in Halmahera, Indonesia.. || 0.111 mg/kg |
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| 10 || [[Beaked sea snake]] || Tropical Indo-Pacific || 0.1125 mg/kg |
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=== Venom Metering === |
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Venom metering is the ability of a snake to have neurological control over the amount of venom released into a target during a strike based on situational cues. This ability would prove useful as venom is a limited resource, larger animals are less susceptible to the effects of venom, and various situations require different levels of force. There is a lot of evidence to support the venom metering hypothesis. For example, snakes frequently use more venom during defensive strikes, administer more venom to larger prey, and are capable of dry biting. A dry bite is a bite from a venomous snake that results in very little or no venom expulsion, leaving the target asymptomatic.<ref>{{cite journal | vauthors = Naik BS | title = "Dry bite" in venomous snakes: A review | journal = Toxicon | volume = 133 | pages = 63–67 | date = July 2017 | pmid = 28456535 | doi = 10.1016/j.toxicon.2017.04.015 | bibcode = 2017Txcn..133...63N | s2cid = 36838996}}</ref> However, there is debate among many academics about venom metering in snakes. The alternative to venom metering is the pressure balance hypothesis.{{citation needed|date=March 2023}} |
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[[File:Dendroaspis polylepis by Bill Love.jpg|right|thumb|Black mamba]] |
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Mortality rate (often determined by measured toxicity on mice) is a commonly used indicator to determine the danger of any given venomous snake, but important too are its efficiency of venom delivery, its venom yield and its behavior when it encounters humans.<ref name="World's Deadliest Snakes">Venomous Snakes. [http://www.reptilegardens.com/reptiles/snakes/venomous/worlds-deadliest-snakes.php World's Deadliest Snakes – Ranking scale]. [[Reptile Gardens]]. Retrieved October 18, 2013.</ref><ref name="What are the world's most deadly venomous snakes?">Walls, Jerry G. . [http://www.reptilesmagazine.com/Snakes/Wild-Snakes/The-Worlds-Deadliest-Snakes/ Deadly Snakes: What are the world's most deadly venomous snakes?]. [[Reptiles (magazine)]]. Retrieved November 5, 2013.</ref> Experts invariably name the black mamba and coastal taipan as the deadliest venomous snake species in the world. Of all the venomous snake species in the world, the black mamba and the coastal taipan are considered to be the biggest threats to humans in case of a bite. Both species are [[elapid]]s and they're very similar to each other. In fact, in several aspects of morphology, ecology and behaviour, the coastal taipan is strongly convergent with the black mamba.<ref name="TaipanMamba">{{cite journal|authors=Shine, Richard; Covacevich, Jeanette.|title=A Ecology of Highly Venomous Snakes: the Australian Genus ''Oxyuranus'' (Elapidae)|url=http://links.jstor.org/sici?sici=0022-1511(198303)17:1%3C60:EOHVST%3E2.0.CO;2|journal= Journal of Herpetology | volume= 17 | issue= 1 |date = March 1983 |pages= 60–69}}</ref> Black mamba and coastal taipan bites require very rapid and vigorous antivenom therapy as they are almost always fatal. The venoms of both species are exceptionally quick acting and both can cause human fatality in as little as 30 minutes. Black mambas in particular have been known to cause death in as little as 20 minutes post-envenomation.<ref name="NG" /><ref name="NW" /> Many snake experts have cited the black mamba and the coastal taipan as the world's most dangerous snakes (Hunter, 1998).<ref name="Haji">{{cite web|last=Haji|first=R.|title=Venomous snakes and snake bites|url=http://www.zoocheck.com/Reportpdfs/Venomous%20snakes.pdf|work=Zoocheck Canada|accessdate=25 October 2013}}</ref><ref name="Pitman74">{{cite book|last=Pitman|first=Charles R.S.|authorlink=Charles Pitman (scientist)|title=A Guide to the Snakes of Uganda|year=1974|publisher=Wheldon & Wesley|location=United Kingdom|isbn=0-85486-020-7|page=290}}</ref><ref name="QM">{{cite web|title=Coastal Taipan|url=http://www.qm.qld.gov.au/Find+out+about/Animals+of+Queensland/Reptiles/Snakes/Common+and+dangerous+species/Coastal+Taipan|work=Queensland Museum|publisher=Queensland Government|accessdate=21 October 2013}}</ref> |
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The pressure balance hypothesis cites the retraction of the fang sheath as the many mechanisms for producing outward venom flow from the venom delivery system. When isolated, fang sheath retraction has experimentally been shown to induce very high pressures in the venom delivery system.<ref>{{cite journal | vauthors = Young BA, Kardong KV | title = Mechanisms controlling venom expulsion in the western diamondback rattlesnake, Crotalus atrox | journal = Journal of Experimental Zoology Part A: Ecological Genetics and Physiology | volume = 307 | issue = 1 | pages = 18–27 | date = January 2007 | pmid = 17094108 | doi = 10.1002/jez.a.341 | doi-access = free | bibcode = 2007JEZA..307...18Y}}</ref> A similar method was used to stimulate the compressor musculature, the main muscle responsible for the contraction and squeezing of the venom gland, and then measuring the induced pressures. It was determined that the pressure created from the fang sheath retraction was at times an order of magnitude greater than those created by the compressor musculature. Snakes do not have direct neurological control of the fang sheath, it can only be retracted as the fangs enter a target and the target's skin and body provide substantial resistance to retract the sheath. For these reasons, the pressure balance hypothesis concludes that external factors, mainly the bite and physical mechanics, are responsible for the quantity of venom expelled.{{citation needed|date=March 2023}} |
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====Black mamba==== |
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{| class="wikitable sortable floatright" border="1" |
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|+ Various species' mice and human fatality count based on maximum venom dose (by Zug, George R, 1996) |
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|- |
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! scope="col" class="unsortable" | Species |
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! scope="col" | LD<sub>50</sub> [[Subcutis|SC]] |
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! scope="col" | Dose |
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! scope="col" | Mice |
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! scope="col" | Humans |
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|- |
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| Inland taipan (''O. microlepidotus'') || 0.01 mg/kg<ref name="ErZug" /> || 110 mg<ref name="inchem1" /> || 1,085,000 || 289 |
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|- |
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| Black mamba (''D. polylepis'') || 0.05 mg/kg<ref name="ErZug" /> || 400 mg<ref name="Chippaux" /> || 400,000 || 107 |
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|- |
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| Forest cobra (''N. melanoleuca'') || 0.225 mg/kg<ref name="ErZug" /><ref name=M67/> || 1102 mg<ref name="Mir06" /> || 244,889 || 65 |
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|- |
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| Eastern brown snake (''P. textilis'') || 0.03 mg/kg<ref name="ErZug" /> || 155 mg<ref name="Mir06" /> || 212,329 || 58 |
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|- |
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| Coastal taipan (''O. s. scutellatus'') || 0.106 mg/kg<ref name="ErZug" /> || 400 mg<ref name="inchem1" />|| 208,019 || 56 |
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|- |
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| Caspian cobra (''N. oxiana'') || 0.18 mg/kg<ref name=IJEB/> || 590 mg<ref name="Latifi84" />|| 162,165 || 42 |
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|- |
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| Russell's viper (''D. russelli'') || 0.162 mg/kg<ref name="ErZug" /> || 268 mg<ref name="Mal03" />|| 88,211 || 22 |
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| King cobra (''O. hannah'') || 1.09 mg/kg<ref name="ErZug" /> || 1000 mg<ref name="OHVY">{{cite journal|last=Pung|first=Yuh Fen|coauthors=Peter T. H. Wong, Prakash P. Kumar, Wayne C. Hodgson, R. Manjunatha Kini|title=Ohanin, a Novel Protein from King Cobra Venom, Induces Hypolocomotion and Hyperalgesia in Mice|journal=Journal of Biological Chemistry|date=24 January 2005|volume=280|issue=13|pages=13137–13147|doi=10.1074/jbc.M414137200|url=http://www.jbc.org/content/280/13/13137.full|accessdate=6 November 2013}}</ref>|| 45,830 || 11 |
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|- |
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| Indian cobra (''N. naja'') || 0.80 mg/kg<ref name="Bro73" />|| 610 mg<ref name="M&M"/>|| 33,689 || 10 |
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|- |
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| Cape cobra (''N. nivea'') || 0.4 mg/kg<ref name="ErZug" />|| 250 mg<ref name="BB98">{{cite book|last=Branch|first=Bill|title=Field Guide Snakes and Other Reptiles of Southern Africa|year=1998|publisher=Struik Publishers|isbn=1868720403|page=108}}</ref>|| 31,250 || 9 |
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|- |
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| Terciopelo (''B. asper'') || 3.1 mg/kg<ref name="ErZug" />|| 1530 mg<ref name="War-C&L04" />|| 24,380 || 6 |
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| Gaboon viper (''B. gabonica'') || 5 mg/kg<ref name="ErZug" />|| 2400 mg<ref name="Mal03" />|| 24,000 || 6 |
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| Saw-scaled viper (''E. carinatus'') || 0.151 mg/kg<ref name="ErZug" /> || 72 mg<ref name="Daniels">Daniels,J. C. (2002) The Book of Indian Reptiles and Amphibians, BNHS & Oxford University Press, Mumbai, pp 151-153. ISBN 0-19-566099-4</ref>|| 23,841 || 6 |
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|} |
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=== Venom Spitting === |
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The African [[Black mamba]] (''Dendroaspis polylepis'') is a large and highly venomous snake species native to much of [[Sub-Saharan Africa]]. It is the second longest venomous snake species in the world and is the fastest moving land snake, capable of moving at 4.32 to 5.4 metres per second (16–20 km/h, 10–12 mph).<ref name="NG" /><ref name="record">{{cite book|last=Glenday|first=Craig|title=Guinness World Records 2009|year=2009|publisher=Bantam|isbn=0553592564|page=57}}</ref> It is by far the most feared snake species in Africa and it has a legendary reputation as a very fierce and territorial snake. Black mambas are well known to have an irascible temperament - they tend to be high-strung, nervous, agile, extremely quick, are highly aggressive and will attack with no provocation.<ref name="NG">{{cite web|title=Black Mamba|url=http://animals.nationalgeographic.com/animals/reptiles/black-mamba/|work=National Geographic|publisher=National Geographic|accessdate=20 October 2013}}</ref><ref name="NW">{{cite book|last=White|first=Nancy|title=Black Mambas: Susen Death!|year=2009|publisher=Bearport Publishing|isbn=1-59716-766-5}}{{page needed|date=October 2013}}</ref> They are among the world's most venomous snake species.<ref name="ErZug" /> When cornered or threatened, the black mamba can put up a fearsome display of defense and aggression. A black mamba will often mimic a cobra by spreading a neck-flap; exposing its black mouth, raising its body off the ground, and hissing. It can rear up around one-third of its body from the ground, which can put it at about four feet high. When warding off a threat, the black mamba delivers multiple strikes, injecting large amounts of virulently toxic venom with each strike, often landing bites on the body or head, unlike other snakes. Their strikes are very quick and extremely accurate and effective.<ref name="Chippaux" /> If the attempt to scare away the threat fails, it will strike repeatedly.<ref name="NG" /> This species of snake often shows an incredible amount of tenacity, fearlessness, and aggression when cornered or threatened, during breeding season, or when defending its territory.<ref name="ErZug" /> They are also known to have a 100% rate of envenomation. The probability of dry bites (no venom injected) in black mamba strikes is almost non-existent.<ref name="Davidson" /><ref name="Crisp">{{cite journal |pmid=4035489 |year=1985 |last1=Crisp |first1=NG |title=Black mamba envenomation |volume=68 |issue=5 |pages=293–4 |journal=South African Medical Journal}}</ref> The venom of the black mamba is a protein of low molecular weight and as a result is able to spread extraordinarily rapidly within the bitten tissue. The venom of this species is the most rapid-acting venom of any snake species<ref name="Chippaux">{{cite book|last=Chippaux|first=Jean-phillipe|title=Snake Venoms and Envenomations|year=2006|publisher=Krieger Publishing Company|location=United States|isbn=1-57524-272-9|page=300}}</ref><ref>{{cite web|title=Sii Polyvalent Anti-Snake Venom Serum (central Africa)|url=http://www.seruminstitute.com/content/products/product_antisera2.htm|work=Serum Institute of India|publisher=Serum Institute}}</ref><ref name="SD">{{cite journal|last=Strydom|first=Daniel J.|title=Purification and Properties of Low-Molecular-Weight Polypeptides of Dendroaspis polylepis polylepis (Black Mamba) Venom|journal=European Journal of Biochemistry|date=1 October 1976|volume=69|issue=1|pages=169–176|pmid=991854|url=http://onlinelibrary.wiley.com/doi/10.1111/j.1432-1033.1976.tb10870.x/pdf|accessdate=4 November 2013|doi=10.1111/j.1432-1033.1976.tb10870.x}}</ref> and consists mainly of highly potent [[neurotoxin]]s;<ref name="WCH">{{cite web|title=Dendroaspis polylepis – General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid, Antivenoms|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0170|work=WCH Clinical Toxinology Resource|publisher=University of Adelaide}}{{dead link|date=October 2013}}</ref><ref>Reed, Tim; Eaton, Katie; Peng, Cathy and Doern, BettyLou. [http://cogs.csustan.edu/~tom/bioinfo/groupwork/cobra/cobra-venom.ppt Neurotoxins in Snake Venom]. California State University Stanislaus. csustan.edu.</ref> it also contains [[cardiotoxin]]s,<ref name="Territory">{{cite book|last=Mitchell|first=Deborah|title=The Encyclopedia of Poisons and Antidotes|publisher=Facts on File, Inc.|date=September 2009|location=New York, USA|page=324|isbn=0-8160-6401-6}}</ref><ref name="MambaCDTX">{{cite journal |doi=10.1580/1080-6032(1996)007[0115:PCOTVO]2.3.CO;2 |title=Putative cardiotoxicity of the venoms of three mamba species |year=1996 |last1=Van Aswegen |first1=G. |last2=Van Rooyen |first2=J.M. |last3=Fourie |first3=C. |last4=Oberholzer |first4=G. |journal=Wilderness & Environmental Medicine |volume=7 |issue=2 |pages=115–21 |pmid=11990104}}</ref> fasciculins,<ref name="WCH" /> and [[calciseptine]].<ref name="Calciseptine">{{cite journal |doi=10.1073/pnas.88.6.2437 |title=Calciseptine, a peptide isolated from black mamba venom, is a specific blocker of the L-type calcium channel |year=1991 |last1=De Weille |first1=J. R. |last2=Schweitz |first2=H. |last3=Maes |first3=P. |last4=Tartar |first4=A. |last5=Lazdunski |first5=M. |journal=Proceedings of the National Academy of Sciences |volume=88 |issue=6 |pages=2437–40 |jstor=2356398 |bibcode=1991PNAS...88.2437D |pmid=1848702 |pmc=51247}}</ref> The [[median lethal dose]] (LD<sub>50</sub>) values for this species' venom varies greatly from one toxicological study to the next. Ernst and Zug ''et al.'' 1996 listed a value of 0.05 mg/kg for [[subcutaneous injection]] (SC).<ref name="ErZug" /> The Australian venom and toxin database provides values of 0.32 mg/kg [[subcutaneous injection|SC]] and 0.25 mg/kg for [[intravenous injection|IV]].<ref name="LD50" /> Spawls & Branch and Minton & Minton both listed a value of 0.28 mg/kg [[subcutaneous injection|SC]]<ref name="M&M">{{cite book|last=Minton, Minton|first=SA, MR|title=Venomous Reptiles|year=1969|publisher=New York Charles Scribner's Sons|location=USA}}{{page needed|date=October 2013}}</ref><ref name="SB95" /> and Brown lists a [[Subcutis|SC]] value of 0.12 mg/kg.<ref name="Bro73" /> It is estimated that only 10 to 15 mg will kill a human adult, and its bites delivers about 120 mg of venom on average. Although they may deliver up to 400 mg of venom in a single bite.<ref name="Chippaux" /><ref name="Bro73" /> To demonstrate just how deadly this species is, an estimate was made on the number of mice and adult human fatalities it is capable of causing in a single bite that yields the maximum dose of 400 mg. Based on the study by Ernst and Zug ''et al.'' 1996, which listed the {{LD50}} of the black mamba at 0.05 mg [[Subcutis|SC]], a bite yield of 400 mg, and the estimated lethal adult human dose of 10 mg, this would be sufficient enough to kill 400,000 mice and 107 adult humans in a single bite that delivers 400 mg of venom. |
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Venom spitting is another venom delivery method that is unique to some Asiatic and African [[cobra]]s. In venom spitting, a stream of venom is propelled at very high pressures outwards up to 3 meters (300 centimeters). The venom stream is usually aimed at the eyes and face of the target as a deterrent for predators. There are non-spitting cobras that provide useful information on the unique mechanics behind venom spitting. Unlike the elongated oval shaped exit orifices of non-spitting cobras, spitting cobras have circular exit orifice at their fang tips.<ref>{{cite journal | vauthors = Bar-On B | title = On the form and bio-mechanics of venom-injection elements | journal = Acta Biomaterialia | volume = 85 | pages = 263–271 | date = February 2019 | pmid = 30583109 | doi = 10.1016/j.actbio.2018.12.030 | s2cid = 58587928}}</ref> This combined with the ability to partially retract their fang sheath by displacing the palato-maxillary arch and contracting the adductor mandibulae, allows the spitting cobras to create large pressures within the venom delivery system.<ref>{{cite journal | vauthors = Young BA, Dunlap K, Koenig K, Singer M | title = The buccal buckle: the functional morphology of venom spitting in cobras | journal = The Journal of Experimental Biology | volume = 207 | issue = Pt 20 | pages = 3483–3494 | date = September 2004 | pmid = 15339944 | doi = 10.1242/jeb.01170 | doi-access = free}}</ref> While venom spitting is a less common venom delivery system, the venom can still cause the effects if ingested.{{citation needed|date=May 2021}} |
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== Society and culture == |
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If bitten, severe neurotoxicity often ensues. [[Neurology|Neurological]], [[Respiratory system|respiratory]], and [[cardiovascular]] symptoms rapidly begin to manifest, usually within less than ten minutes. Common symptoms are rapid onset of dizziness, drowsiness, headache, coughing or difficulty breathing, convulsions, and an erratic heartbeat. Other common symptoms which come on rapidly include neuromuscular symptoms, shock, loss of consciousness, [[hypotension]], [[pallor]], [[ataxia]], excessive salivation (oral secretions may become profuse and thick), limb paralysis, nausea and vomiting, [[Ptosis (eyelid)|ptosis]], fever, and very severe abdominal pain. Local tissue damage appears to be relatively infrequent and of minor severity in most cases of black mamba envenomation. [[Edema]] is typically minimal. Acute [[renal failure]] has been reported in a few cases of black mamba bites in humans as well as in animal models.<ref name="Davidson" /> The venom of this species has been known to cause permanent [[paralysis]] in some cases. Death is due to suffocation resulting from paralysis of the respiratory muscles.<ref name="Davidson">{{cite web|title=IMMEDIATE FIRST AID for bites by Black Mamba (Dendroaspis polylepis polylepis)|url=http://toxicology.ucsd.edu/Snakebite%20Protocols/Dendroa3.htm|publisher=University of California at San Diego}}</ref><ref name="Hilligan">{{cite journal |pmid=3603321 |year=1987 |last1=Hilligan |first1=R |title=Black mamba bites. A report of 2 cases |volume=72 |issue=3 |pages=220–1 |journal=South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde}}</ref> Untreated black mamba bites have a mortality rate of 100%.<ref name="Davidson" /><ref name=Z11>{{cite journal|last=Závada|first=J.|coauthors=Valenta J., Kopecký O., Stach Z., Leden P|title=Black Mamba Dendroaspis Polylepis Bite: A Case Report|journal=Prague Medical Journal|year=2011|volume=112|issue=4|pages=298–304|pmid=22142525|url=http://www.ncbi.nlm.nih.gov/pubmed/22142525|accessdate=3 December 2013}}</ref> [[Antivenom]] therapy is the mainstay of treatment for black mamba envenomation. A polyvalent antivenom produced by the South African Institute for Medical Research (SAIMR) is used to treat all black mamba bites from different localities.<ref name="Davidson" /><ref name="SB95" /> Due to antivenom, a bite from a black mamba is no longer a certain death sentence. But in order for the antivenom therapy to be successful, vigorous treatment and large doses of antivenom must be administered very rapidly post-envenomation. In case studies of black mamba envenomation, respiratory paralysis has occurred in less than 15 minutes. In a case of 10 envenomations in [[South Africa]] all ten received medical treatment but only five lived. One developed [[respiratory paralysis]] in ten minutes,<ref name=V&C78/> and all other patients were showing signs of neurotoxicity upon arrival at the hospital.<ref name=V&C78/> Symptoms initially included mild swelling at bite site, confusion, excessive sweating, [[urinary incontinence]], [[fecal incontinence]], loss of coordination, ptosis, erratic heartbeat, drowsiness, and breathing difficulties. Out of the 10 patients, five were fatal despite prompt hospitalization and induction of medical treatment. One patient died in just under 30 minutes. The four other patients all died within 3–8 hours post-envenomation. The other five patients survived but all of them required massive amounts of antivenom and assisted mechanical ventilation for a prolonged period. Three of the patients were on mechanical ventilation for 10 days, while the other two required assisted mechanical ventilation for 16 days. Cases of this nature are not at all uncommon among cases of envenomation by the black mamba.<ref name="V&C78">{{cite book|last=Visser, Chapman|first=John, David S|title=Snakes and Snakebite: Venomous snakes and management of snake bite in Southern Africa|year=1978|publisher=Purnell|isbn=0-86843-011-0}}</ref><ref name=VG>{{cite web|title=Venomous and Poisonous Animals Biology & Clinical Management (Dendroaspis sp)|url=http://www.vapaguide.info/catalogue/TER-ELA-27-37|work=VAPAGuide|accessdate=3 December 2013}}</ref> Envenomation by this species invariably causes very severe neurotoxicity due to the fact that black mambas often strike repeatedly in a single lunge, biting the victim up to 12 times in extremely rapid succession.<ref>{{cite web|title=Black Mamba (Dendroaspis polylepis)|url=http://www.thewildlifemuseum.org/exhibits/Africa-Deadly/doc/Black%20Mamba.pdf|publisher=The Wildlife Museum}}</ref> Such an attack is very fast, lasting less than one second and so it appears to be a single strike and single bite. With each bite the snake delivers anywhere from 100 to 400 mg of a rapid-acting and virulently toxic venom. As a result, the doses of antivenom required are often massive (10–30+ vials) for bites from this species. Although antivenom saves many lives, mortality due to black mamba envenomation is still at 14%, even with antivenom therapy.<ref name=Christensen>{{cite journal|last=Christensen|first=PA|title=Snakebite and the use of antivenom in southern Africa|journal=South Africn Medical Journal|date=20 June 1981|volume=59|issue=26|pages=934–938|pmid=7244896}}</ref> In addition to antivenom therapy, [[Tracheal intubation|endotracheal intubation]] and [[mechanical ventilation]] are required for supportive therapy.<ref name="Davidson" /><ref name="V&C78" /> |
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{{See also|Serpent (symbolism)}} |
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[[File:Benczur-kleopatra.jpg|thumb|right|According to tradition, [[Cleopatra|Cleopatra VII]] famously committed suicide by snakebite to her left breast, as depicted in this 1911 painting by Hungarian artist [[Gyula Benczúr]].]] |
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Snakes were both [[Snake worship|revered and worshipped]] and [[Ophidiophobia|feared]] by early civilizations. The [[ancient Egyptians]] recorded prescribed treatments for snakebites as early as the [[Thirteenth dynasty of Egypt|Thirteenth Dynasty]] in the [[Brooklyn Papyrus]], which includes at least seven venomous species common to the region today, such as the [[Cerastes (genus)|horned vipers]].<ref name="Schneemann2004">{{cite journal | vauthors = Schneemann M, Cathomas R, Laidlaw ST, El Nahas AM, Theakston RD, Warrell DA | title = Life-threatening envenoming by the Saharan horned viper (Cerastes cerastes) causing micro-angiopathic haemolysis, coagulopathy and acute renal failure: clinical cases and review | journal = QJM | volume = 97 | issue = 11 | pages = 717–727 | date = November 2004 | pmid = 15496528 | doi = 10.1093/qjmed/hch118 | quote = This echoed the opinion of the Egyptian physicians who wrote the earliest known account of the treatment of snake bite, the Brooklyn Museum Papyri, dating perhaps from 2200 BC. They regarded bites by horned vipers 'fy' as non-lethal, as the victims could be saved. | doi-access = free}}</ref> In [[Judaism]], the [[Nehushtan]] was a pole with a snake made of copper fixed upon it. The object was regarded as a divinely empowered instrument of God that could bring healing to Jews bitten by venomous snakes while they were wandering in the desert after their [[exodus from Egypt]]. Healing was said to occur by merely looking at the object as it was held up by [[Moses]].{{citation needed|date=March 2023}} |
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Historically, snakebites were seen as a means of execution in some cultures.<ref>{{cite book |last=Wilcox |first=Christie |url=https://books.google.com/books?id=tUsBCwAAQBAJ&pg=PA32 |title=Venomous: How Earth's Deadliest Creatures Mastered Biochemistry |date=2016-08-09 |publisher=Farrar, Straus and Giroux |isbn=978-0-374-71221-1 |language=en}}</ref> Reportedly, in [[Southern Han]] during [[China]]'s [[Five Dynasties and Ten Kingdoms period]] and in [[India]] a form of capital punishment was to throw people into [[snake pit]]s, leaving people to die from multiple venomous bites.<ref name="Anil2004" /> According to popular belief, the Egyptian queen [[Cleopatra|Cleopatra VII]] committed suicide by letting herself be bitten by an [[Asp (reptile)|asp]]—likely an [[Egyptian cobra]]<ref name="Schneemann2004" /><ref name="Smithsonian">{{cite web | vauthors = Crawford A |title=Who Was Cleopatra? Mythology, propaganda, Liz Taylor and the real Queen of the Nile |url=http://www.smithsonianmag.com/history-archaeology/biography/cleopatra.html |date=1 April 2007 |website=[[Smithsonian (magazine)|Smithsonian]] |access-date=4 September 2009}}</ref>—after hearing of [[Mark Antony]]'s death, while some contemporary ancient authors rather assumed a direct application of poison.<ref>{{cite book |last=Grant |first=Michael |url=https://books.google.com/books?id=7nk5AgAAQBAJ&pg=PP179 |title=Cleopatra: Cleopatra |date=2011-07-14 |publisher=Orion |isbn=978-1-78022-114-4 |language=en}}</ref> |
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====Coastal taipan==== |
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The [[Coastal taipan]] (''Oxyuranus scutellatus scutellatus'') is a large, highly venomous Australian elapid that ranges in an arc along the east coast of Australia from northeastern [[New South Wales]] through [[Queensland]] and across the northern parts of the [[Northern Territory]] to northern [[Western Australia]]. It has one subspecies the Papuan taipan (''Oxyuranus scutellatus canni''). The Papuan taipan is found throughout the southern parts of the island of [[New Guinea]]. This snake can be highly aggressive when cornered and will actively defend themselves.<ref name="DD" /> They are extremely nervous and alert snakes, and any movement near them is likely to trigger an attack. When threatened, this species adopts a loose striking stance with its head and forebody raised. It inflates and compresses its body laterally (not dorso-ventrally like many other species) and may also spread the back of its jaws to give the head a broader, lance-shaped appearance. In this position the snake will strike without much provocation, inflicting multiple bites with extreme accuracy and efficiency. The muscular lightweight body of the Taipan allows it to hurl itself forwards or sideways and reach high off the ground, and such is the speed of the attack that a person may be bitten several times before realizing the snake is there.<ref>{{cite web|title=Coastal Taipan|url=http://australianmuseum.net.au/Coastal-Taipan|publisher=Australian Museum|accessdate=5 November 2013}}</ref> This snake is considered to be one of the most venomous in the world. Ernst and Zug ''et al.'' 1996 and the Australian venom and toxin databse both list a {{LD50}} value of 0.106 mg/kg for subcutaneous injection.<ref name="ErZug" /><ref name="AVRU">{{cite web|title=Australian Venom Research Unit|url=http://www.avru.org/index.html|publisher=University of Melbourne}}</ref> Engelmann and Obst (1981) list a value of 0.12 mg/kg [[Subcutis|SC]], with an average venom yield of 120 mg per bite and a maximum record of 400 mg.<ref name="Engelmann" /> To demonstrate just how deadly this species is, an estimate was made on the number of mice and adult human fatalities it is capable of causing in a single bite that yields the maximum dose of 400 mg. Based on the study by Ernst and Zug ''et al.'' 1996, which listed the {{LD50}} of the coastal taipan at 0.106 mg [[Subcutis|SC]] and a venom yield of 400 mg, this would be sufficient enough to kill 208,019 mice and 56 adult humans in a single bite that delivers 400 mg of venom. The venom apparatus of this species is well developed. The fangs are the longest of any Australian elapid snake, being up to {{convert|12|mm|cm in}} long, and are able to be brought forward slightly when a strike is contemplated. Coastal taipans can inject large amounts of highly toxic venom deep into tissue. Its venom contains primarily [[taicatoxin]], a highly potent [[neurotoxin]] known to cause [[hemolytic]] and coagulopathic reactions.<ref name="DD" /> The venom affects the nervous system and the blood’s ability to clot, and bite victims may experience headache, nausea and vomiting, collapse, convulsions (especially in children), paralysis, internal bleeding, myolysis (destruction of muscle tissue) and kidney damage. In a single study done in [[Papua New Guinea]], 166 patients with enzyme immunoassay-proven bites by Papuan taipans (''Oxyuranus scutellatus canni'') were studied in Port Moresby, Papua New Guinea. Of the 166 bite victims, 139 (84%) showed clinical evidence of envenoming: local signs were trivial, but the majority developed hemostatic disorders and neurotoxicity. The blood of 77% of the patients was incoagulable and 35% bled spontaneously, usually from the gums. [[Microhematuria]] was observed in 51% of the patients. Neurotoxic symptoms (ptosis, ophthalmoplegia, bulbar paralysis, and peripheral muscular weakness) developed in 85%. Endotracheal intubation was required in 42% and mechanical ventilation in 37%. [[Electrocardiography|Electrocardiographic]] (ECG or EKG) abnormalities were found in 52% of a group of 69 unselected patients. Specific antivenom raised against Australian taipan venom was effective in stopping spontaneous systemic bleeding and restoring blood coagulability but, in most cases, it neither reversed nor prevented the evolution of paralysis even when given within a few hours of the bite. However, early antivenom treatment was associated statistically with decreased incidence and severity of neurotoxic signs. The low case fatality rate of 4.3% is attributable mainly to the use of mechanical ventilation, a technique rarely available in Papua New Guinea. Earlier use of increased doses of antivenoms of improved specificity might prove more effective.<ref name="Lalloo">{{cite journal|last=Lalloo|first=DG|coauthors=Trevett AJ, Korinhona A, Nwokolo N, Laurenson IF, Paul M, Black J, Naraqi S, Mavo B, Saweri A, et al.|title=nake bites by the Papuan taipan (Oxyuranus scutellatus canni): paralysis, hemostatic and electrocardiographic abnormalities, and effects of antivenom|journal=American Journal of Tropical Medicine and Hygiene|date=June 1995|volume=52|issue=6|pages=525–531|pmid=7611559|url=http://www.ncbi.nlm.nih.gov/pubmed/7611559|accessdate=5 November 2013}}</ref> The onset of symptoms is often rapid, and a bite from this species is a life threatening medical emergency. Prior to the introduction of specific antivenom by the Commonwealth Serum Laboratories in 1956, a coastal taipan bite was nearly always fatal. In case of severe envenomation, death can occur as early as 30 minutes after being bitten, but average death time after a bite is around 3–6 hours and it is variable, depending on various factors such as the nature of the bite and the health state of the victim.<ref name="DD" /> Envenomation rate is very high, over 80% of bites inject venom. The mortality rate among untreated bite victims is nearly 100%.<ref name="DD">{{cite web|title=IMMEDIATE FIRST AID for bites by Australian Taipan or Common Taipan (Oxyuranus scutellatus scutellatus)|url=http://toxicology.ucsd.edu/Snakebite%20Protocols/Oxyura~2.htm|publisher=University of California at San Diego|accessdate=4 November 2013}}</ref><ref name="OS">{{cite web|title=Oxyuranus scutellatus|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0518|work=Clinical Toxinology Resource|publisher=University of Adelaide|accessdate=4 November 2013}}</ref> |
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Snakebite as a surreptitious form of murder has been featured in stories such as Sir [[Arthur Conan Doyle]]'s ''[[The Adventure of the Speckled Band]]'', but actual occurrences are virtually unheard of, with only a few documented cases.<ref name="Anil2004">{{cite journal| vauthors = Anil A |year=2004 |title=Homicide with snakes: A distinct possibility and its medicolegal ramifications |journal=Anil Aggrawal's Internet Journal of Forensic Medicine and Toxicology |volume=4 |issue=2 |url=http://www.geradts.com/anil/ij/vol_004_no_002/others/pg001.html |archive-url=https://web.archive.org/web/20070718031431/http://www.geradts.com/anil/ij/vol_004_no_002/others/pg001.html |archive-date=18 July 2007}}</ref><ref name="Warrell2009">{{cite journal | vauthors = Warrell DA | title = Commissioned article: management of exotic snakebites | journal = QJM | volume = 102 | issue = 9 | pages = 593–601 | date = September 2009 | pmid = 19535618 | doi = 10.1093/qjmed/hcp075 | doi-access = free}}</ref><ref name="Straight1994">{{cite journal | vauthors = Straight RC, Glenn JL |year=1994 |title=Human fatalities caused by venomous animals in Utah, 1900–90 |journal=[[Great Basin Naturalist]] |volume=53 |issue=4 |pages=390–4 |url=https://ojs.lib.byu.edu/ojs/index.php/wnan/article/viewFile/545/1430 |access-date=4 September 2009 |quote=A third unusual death was a tragic fatality (1987), recorded as a homicide, which resulted when a large rattlesnake (''G. v. lutosus'') bit a 22-month-old girl after the snake had been placed around her neck (Washington County). The child died in approximately 5 h. |url-status=live |archive-url=https://web.archive.org/web/20111008073525/https://ojs.lib.byu.edu/ojs/index.php/wnan/article/viewFile/545/1430 |archive-date=8 October 2011 |doi=10.5962/bhl.part.16607 |doi-access=free}}</ref> It has been suggested that [[Boris III of Bulgaria]], who was allied to [[Nazi Germany]] during [[World War II]], may have been killed with snake venom,<ref name="Anil2004" /> although there is no definitive evidence. At least one attempted suicide by snakebite has been documented in medical literature involving a [[Bitis arietans|puff adder]] bite to the hand.<ref name="Strubel2008">{{cite journal | vauthors = Strubel T, Birkhofer A, Eyer F, Werber KD, Förstl H | title = [Attempted suicide by snake bite. Case report and literature survey] | language = de | journal = Der Nervenarzt | volume = 79 | issue = 5 | pages = 604–606 | date = May 2008 | pmid = 18365165 | doi = 10.1007/s00115-008-2431-4 | trans-title = Attempted suicide by snake bite: Case report and literature survey | quote = Ein etwa 20-jähriger Arbeiter wurde nach dem Biss seiner Puffotter (''Bitis arietans'') in die Hand auf die toxikologische Intensivstation aufgenommen. Zunächst berichtet der Patient, dass es beim "Melken" der Giftschlange zu dem Biss gekommen sei, erst im weiteren Verlauf räumt er einen Suizidversuch ein. Als Gründe werden Einsamkeit angeführt sowie unerträgliche Schmerzen im Penis. | s2cid = 21805895}}</ref> |
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===Highly dangerous=== |
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In [[Jainism]], the goddess [[Padmavati (Jainism)|Padmāvatī]] has been associated with curing snakebites.<ref>Slouber, Michael. 2017. [https://www.google.com/books/edition/Early_Tantric_Medicine/tGl4DQAAQBAJ?hl=en&gbpv=1&dq=Tvarit%C4%81&pg=PA99&printsec=frontcover Early Tantric Medicine: Snakebite, Mantras, and Healing in the Garuda Tantras]. Page 99. [[Oxford University Press]].</ref> |
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====The Big Four==== |
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The [[Big Four (Indian snakes)|Big Four]] are the four venomous snake species responsible for causing the most snake bite cases in South Asia (mostly in India). The Big Four snakes cause far more snakebites because they are much more abundant in highly populated areas. They are the [[Indian cobra]] (''Naja naja''), [[common krait]] (''Bungarus caeruleus''), [[Russell's viper]] (''Daboia russelii'') and the [[Echis carinatus|Saw-scaled viper]] (''Echis carinatus'').<ref name="Whi90">Whitaker Z. 1990. Snakeman. Penguin Books Ltd. 192 pp. ISBN 0-14-014308-4.</ref> |
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==Research== |
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=====Indian cobra===== |
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In 2018, the [[World Health Organization]] listed snakebite envenoming as a neglected tropical disease.<ref>{{cite journal | vauthors = Minghui R, Malecela MN, Cooke E, Abela-Ridder B | title = WHO's Snakebite Envenoming Strategy for prevention and control | journal = The Lancet. Global Health | volume = 7 | issue = 7 | pages = e837–e838 | date = July 2019 | pmid = 31129124 | doi = 10.1016/S2214-109X(19)30225-6 | doi-access = free}}</ref><ref>{{cite journal | vauthors = Schiermeier Q | title = Snakebite crisis gets US$100-million boost for better antivenoms | language = EN | journal = Nature | date = May 2019 | pmid = 32409762 | doi = 10.1038/d41586-019-01557-0 | s2cid = 189458866}}</ref> In 2019, they launched a strategy to prevent and control snakebite envenoming, which involved a program targeting affected communities and their health systems.<ref>{{cite web |title=Snakebite: WHO targets 50% reduction in deaths and disabilities |url=https://www.who.int/news-room/detail/06-05-2019-snakebite-who-targets-50-reduction-in-deaths-and-disabilities |website=[[World Health Organization]] |access-date=30 May 2019 |language=en}}</ref><ref>{{cite journal | vauthors = Williams DJ, Faiz MA, Abela-Ridder B, Ainsworth S, Bulfone TC, Nickerson AD, Habib AG, Junghanss T, Fan HW, Turner M, Harrison RA, Warrell DA | display-authors = 6 | title = Strategy for a globally coordinated response to a priority neglected tropical disease: Snakebite envenoming | journal = PLOS Neglected Tropical Diseases | volume = 13 | issue = 2 | pages = e0007059 | date = February 2019 | pmid = 30789906 | pmc = 6383867 | doi = 10.1371/journal.pntd.0007059 | doi-access = free}}</ref> A policy analysis however found that the placement of snakebite in the global health agenda of WHO is fragile due to reluctance to accept the disease in the neglected tropical disease community and the perceived colonial nature of the network driving the agenda.<ref>{{cite journal |last1=Bhaumik |first1=Soumyadeep |last2=Zwi |first2=Anthony B. |last3=Norton |first3=Robyn |last4=Jagnoor |first4=Jagnoor |date=2023-08-01 |title=How and why snakebite became a global health priority: a policy analysis |url=https://gh.bmj.com/content/8/8/e011923 |journal=BMJ Global Health |language=en |volume=8 |issue=8 |pages=e011923 |doi=10.1136/bmjgh-2023-011923 |issn=2059-7908 |pmid=37604596 |pmc=10445399}}</ref> |
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The [[Indian cobra]] is a moderately venomous species, but has a rapid-acting venom. In [[mice]], the [[Subcutis|SC]] {{LD50}} for this species is 0.80 mg/kg and the average venom yield per bite is between 169 and 250 mg.<ref name="Bro73" /><ref name="ct">{{cite web|title= ''Naja naja''|work=University of Adelaide|url=http://toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0041}}</ref> Though it is responsible for many bites, only a small percentage are fatal if proper medical treatment and antivenom are given.<ref name="W&C04">{{cite book|last=Whitaker, Captain|first=Romulus, Ashok|title=Snakes of India, The Field Guide|year=2004|publisher=Draco Books|location=India|isbn=81-901873-0-9|page=372}}</ref> Mortality rate for untreated bite victims can vary from case to case, depending upon the quantity of venom delivered by the individual involved. According to one study, it is approximately 15–20%.<ref name="WHO">{{cite journal|author=World Health Organization|title=Zoonotic disease control: baseline epidemiological study on snake-bite treatment and management|journal=Weekly Epidemiological Record (WER)|issn=0049-8114|volume=62|issue=42|pages=319–320}}</ref> but in another study, with 1,224 bite cases, the mortality rate was only 6.5%.<ref name="Bro73" /> Estimated fatalities as a result of this species is approximately 15,000 per year, but they are responsible for an estimated 100,000-150,000 non-fatal bites per year.<ref name="RW">{{cite web|last=Whitaker|first=Romulus|title=Publicity Notes One Million Snake Bite|url=http://www.iconfilms.co.uk/assets/files/Publicity%20Notes/Publicity%20Notes%20Snake%20Bite.pdf|publisher=IconFilms|accessdate=21 October 2013}}</ref> |
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Key institutions conducting snakebite research on snakebite are the George Institute for Global Health, the Liverpool School of Tropical Medicine, and the Indian Institute of Science. |
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=====Common krait===== |
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The [[common krait]] (''Bungarus caeruleus'') is often considered to be the most dangerous Asian snake species. Its venom consists mostly of powerful [[neurotoxin]]s which induce muscle paralysis. Clinically, its venom contains pre[[Synapse|synaptic]] and postsynaptic neurotoxins,<ref name="ct2" /> which generally affect the nerve endings near the [[synaptic cleft]] of the [[brain]]. Due to the fact that krait venom contains many presynaptic neurotoxins, patients bitten will often not respond to antivenom because once paralysis has developed it is not reversible.<ref name="EMJ" /> This species causes an estimated 10,000 fatalities per year in [[India]] alone.<ref name="RW" /> There is a 70-80% mortality rate in cases where there is no treatment or poor and ineffective treatment (e.g., no use of [[mechanical ventilation]], low quantities of antivenom, poor management of possible infection). Average venom yield per bite is 10 mg (Brown, 1973), 8 to 20 mg (dry weight) (U.S. Dept. Navy, 1968), and 8 to 12 mg (dry weight) (Minton, 1974).<ref name="ct2">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0015|quote=Mortality rate:70-80%}}</ref> The lethal adult human dose is 60 mg.<ref name="EMJ">{{cite journal|last=Isbister|first=G K|title=Snake antivenom research: the importance of case definition|journal=Emergency Medical Journal|year=2005|volume=22|page=397|doi=10.1136/emj.2004.022251|url=http://emj.bmj.com/content/22/6/399.full.pdf|accessdate=26 October 2013|issue=6}}</ref> In [[mice]], the {{LD50}} values of its venom are 0.365 mg/kg [[Subcutis|SC]], 0.169 mg/kg [[Intravenous therapy|IV]] and 0.089 mg/kg [[Peritoneum#Layers|IP]].<ref name="Bro73" /> Another extremely venomous and dangerous krait species is the [[Malayan krait]] (''Bungarus candidus''). In [[mice]], the [[Intravenous injection|IV]] {{LD50}} for this species is 0.1 mg/kg.<ref name="Tan">{{cite web|last=Tan|first=Nget Hong|title=Toxins from Venoms of Poisonous Snake Indigenous to Malaysia: A Review|url=http://www.tanngethong.com/toxins_from_venoms_of_poisonous_.htm|work=Department of Molecular Medicine, Faculty of Medicine|publisher=University of Malaya|accessdate=21 October 2013}}</ref> Envenomation rate among this species is very high and the untreated mortality is 70%, although even with antivenom and mechanical ventilation the mortality rate is at 50%.<ref name="BCd">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0016|quote=Mortality rate:70%}}</ref> |
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==Other animals== |
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=====Russell's viper===== |
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Several animals acquired immunity against the venom of snakes that occur in the same habitat.<ref>{{cite web| vauthors = Bittel J |title=The Animals That Venom Can't Touch|url=https://www.smithsonianmag.com/science-nature/animals-venom-cant-touch-180960658/|website=[[Smithsonian (magazine)|Smithsonian]] |access-date=29 May 2018|language=en}}</ref> This has been documented in some humans as well.<ref>{{cite news| vauthors = Collins B |title=Poison pass: the man who became immune to snake venom|url=https://www.theguardian.com/environment/2018/feb/11/poison-pass-the-man-who-became-immune-to-snake-venom-steve-ludwin|access-date=29 May 2018|work=the Guardian|date=11 February 2018|language=en}}</ref> |
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[[Russell's viper]] (''Daboia russelii'') produces one of the most excruciatingly painful bites of all venomous snakes. Internal bleeding is common. Bruising, blistering and necrosis may appear relatively quickly as well.<ref name="Warrell">{{cite web|last=Warrell|first=David A.|title=Clinical Features of Snakebite|url=http://www.ilo.org/oshenc/part-vi/biological-hazards/item/255-clinical-features-of-snakebite|work=Encyclopedia of Occupational Health and Safety|publisher=Encyclopedia of Occupational Health and Safety|accessdate=21 October 2013}}</ref> The Russell's viper is irritable, short-tempered and a very aggressive snake by nature and when it gets irritated it coils tightly, hisses, and strikes with a lightning speed. This species is responsible for more human fatalities in India than any other snakes species, causing an estimated 25,000 fatalities annually.<ref name="RW" /> The {{LD50}} in mice, which is used as a possible indicator of snake venom toxicity, is as follows: 0.133 mg/kg intravenous, 0.40 mg/kg intraperitoneal, and about 0.75 mg/kg subcutaneous.<ref name="aa" /> For most humans, a lethal dose is approximately 40–70 mg. However, the quantity of venom produced by individual specimens is considerable. Reported venom yields for adult specimens range from 130–250 mg to 150–250 mg to 21–268 mg. For 13 juveniles with an average length of 79 cm, the average venom yield was 8–79 mg (mean 45 mg).<ref name="Mal03" /> |
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{{Clear}} |
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=====Saw-scaled viper===== |
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The [[Saw-scaled viper]] (''Echis carinatus'') is small, but it's ill-temper, irritability, highly aggressive nature, loud hissing, and lethal venom potency make it very dangerous. This species is one of the fastest striking snakes in the world, and mortality rates for those bitten are very high. In [[India]] alone, the saw-scaled viper is responsible for an estimated 5,000 human fatalities annually.<ref name="RW" /> However, because it ranges from [[Pakistan]], India (in rocky regions of Maharastra, Rajasthan, Uttar Pradesh and Punjab), [[Sri Lanka]], parts of the [[Middle East]] and [[Africa]] north of the equator,<ref name="McD99">McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).</ref> is believed to cause more human fatalities every year than any other snake species.<ref name="EB">{{cite web|title=Saw-scaled viper|url=http://www.britannica.com/EBchecked/topic/525886/saw-scaled-viper|work=Encyclopedia Britannica|publisher=Encyclopedia Britannica|accessdate=20 October 2013}}</ref> In drier regions of the [[Africa]]n continent, such as [[sahel]]s and savannas, the [[Echis carinatus|saw-scaled vipers]] inflict up to 90% of all bites.<ref name="Mackessy2010,p.456">{{harvnb|Mackessy|2010|p=456}}</ref> The rate of envenomation is over 80%.<ref name="Echis">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0057}}</ref> The saw-scaled viper also produces a particularly painful bite. This species produces on the average of about 18 mg of dry venom by weight, with a recorded maximum of 72 mg. It may inject as much as 12 mg, whereas the lethal dose for an adult human is estimated to be only 5 mg.<ref name="Daniels" /> Envenomation results in local symptoms as well as severe systemic symptoms that may prove fatal. Local symptoms include swelling and intense pain, which appear within minutes of a bite. In very bad cases the swelling may extend up the entire affected limb within 12–24 hours and blisters form on the skin.<ref name="Ali04">Ali G, Kak M, Kumar M, Bali SK, Tak SI, Hassan G, Wadhwa MB. 2004. Acute renal failure following echis carinatus (saw–scaled viper) envenomation. Indian Journal of Nephrology 14:177-181. [http://medind.nic.in/iav/t04/i4/iavt04i4p177.pdf#search=%22%22echis%20carinatus%22%20%2B%20envenomation%22 PDF] at [http://medind.nic.in/ Indian Medlars Centre]. Accessed 27 October 2013.</ref> Of the more dangerous systemic symptoms, [[Bleeding|hemorrhage]] and coagulation defects are the most striking. [[Hematemesis]], [[melena]], [[hemoptysis]], [[hematuria]] and [[epistaxis]] also occur and may lead to [[Hypovolemia|hypovolemic shock]]. Almost all patients develop [[oliguria]] or [[Oliguria|anuria]] within a few hours to as late as 6 days post bite. In some cases, [[Dialysis|kidney dialysis]] is necessary due to [[acute renal failure]] (ARF), but this is not often caused by [[hypotension]]. It is more often the result of intravascular [[hemolysis]], which occurs in about half of all cases. In other cases, ARF is often caused by [[disseminated intravascular coagulation]].<ref name="Ali04" /> |
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====Many-banded krait==== |
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The [[Many-banded krait]] (''Bungarus multicinctus'') is the most venomous krait species known based on toxinological studies conducted on mice. The venom of the many-banded krait consists of both pre- and postsynaptic [[neurotoxin]]s (known as [[α-bungarotoxin]]s and [[beta-Bungarotoxin|β-bungarotoxin]]s, among others). Due to poor response to antivenom therapy, mortality rates are very high in cases of envenomation - up to 50% of cases that receive antivenom are fatal. Case fatality rates of the many-banded krait envenoming reach up to 77%–100% without treatment.<ref name=W95>{{cite book|last=White; Meier|first=Julian; Jurg|title=Handbook of clinical toxicology of animal venoms and poisons|year=1995|publisher=CRC Press|isbn=978-0-84-934489-3|pages=493–588|accessdate=7 December 2013}}</ref> The average venom yield from specimens kept on snake farms was between 4.6—18.4 mg per bite.<ref name="aa">{{cite book |title= Snake of medical importance|publisher= Venom and toxins research group| location = Singapore|isbn=9971-62-217-3}}</ref> In another study, the average venom yield was 11 mg (Sawai, 1976).<ref name="BMc">{{cite web|url=http://toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0023|title=Clinical Toxinology-''Bungarus multicinctus''}}</ref> The venom is the most toxic of any ''Bungarus'' (krait) species and the most toxic of any snake species in Asia, with {{LD50}} values of 0.09 mg/kg<ref name="aa" />—0.108 mg/kg [[Subcutis|SC]],<ref name="Bro73" /><ref name="LD50">{{cite web|url=http://www.kingsnake.com/toxinology/LD50/LD50men.html|title=LD50 menu}}</ref> 0.113 mg/kg [[Intravenous therapy|IV]] and 0.08 mg/kg [[Peritoneum#Layers|IP]] on [[mice]].<ref name="LD50" /> The lethal dose for an 80 kg adult human is approximately 10–15 mg. Based on several {{LD50}} studies, the many-banded krait is among the [[venomous snake|most venomous land snake]] in the world.<ref name="ErZug" /> The Taiwan National Poison Control Center reports that the chief cause of deaths from snakebites during the decade (2002-2012) was respiratory failure, 80% of which was caused by bites from the many-banded krait.<ref name="Chi">{{cite journal|last=Chi|first=Wen Juan|title=Venomous Snake Bites in Taiwan|journal=Journal of Critical Care and Emergency Medicine|date=29 September 2012|volume=23|issue=4|page=98|url=http://www.seccm.org.tw/magazine/pdf/201223_0301.pdf|accessdate=22 October 2013}}</ref> |
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====Inland taipan==== |
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The [[Inland taipan]] (''Oxyuranus microlepidotus'') is considered the most venomous snake in the world with a [[murine]] {{LD50}} value of 0.025 mg/kg [[Subcutis|SC]].<ref name="inchem1">{{cite web |last=White |first=Julian |title=''Oxyuranus microlepidotus'' |url=http://www.inchem.org/documents/pims/animal/taipan.htm |date=November 1991 |publisher=[[International Programme on Chemical Safety]] |accessdate=6 November 2013}}</ref><ref name="InlandT" /> Ernst and Zug et al. 1996 list a value of 0.01 mg/kg [[Subcutis|SC]], which makes it the most venomous snake in the world in their study too. They have an average venom yield of 44 mg.<ref name="InlandT" /> Bites from this species have a mortality rate of 80% if left untreated, although it is very rare for this species to bite. This species known to be a very shy, reclusive and a laid-back snake that will most always slither away from disturbance. It is not an aggressive species and rarely strikes.<ref name="InlandT">{{cite web|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0520|title= University of Adelaide Clinical Toxinology Resources|quote=Mortality rate:80%}}</ref> |
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====Eastern brown snake==== |
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The [[Eastern brown snake]] (''Pseudonaja textilis'') has a venom {{LD50}} value of 0.053 mg [[Subcutis|SC]] according to (Brown, 1973) and a value of 0.0365 mg [[Subcutis|SC]] according to (Ernst and Zug et al. 1996).<ref name="ErZug" /> According to both studies, it is the second most venomous snake in the world. Average venom yield is 2–6 mg according to (Meier and White, 1995). According to (Minton, 1974) average venom yield (dry weight) is between 5–10 mg.<ref name="EBS">{{cite web|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0533|title= University of Adelaide Clinical Toxinology Resources}}</ref> Maximum venom yield for this species is 155 mg.<ref name="Mir06" /> This species is legendary for its bad temper, aggression, and for its speed. This species is responsible for more deaths every year in Australia than any other group of snakes.<ref name="AG">{{cite web|title=Australia's 10 most dangerous snakes|url=http://www.australiangeographic.com.au/journal/view-image.htm?gid=11893|work=Australian Geographic|publisher=Australian Geographic|accessdate=20 October 2013}}</ref> |
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====Common death adder==== |
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The [[Common death adder]] (''Acanthophis antarcticus'') is a highly venomous snake species with a 50-60% untreated mortality rate.<ref>{{cite web|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0491|title= University of Adelaide Clinical Toxinology Resources|quote=Mortality rate:50-60%}}</ref> It is also the fastest striking venomous snake in the world.<ref name="Strike">[http://www.animaldanger.com/australia.php Fastest striking snake]</ref> It lashes out with the quickest strike of any snake in the world. A death adder can go from a strike position, to strike and envenoming their prey, and back to strike position again, in less than 0.15 seconds.<ref name="Strike" /> The [[Subcutis|SC]] {{LD50}} value is 0.4 mg/kg<ref name="Database">{{cite web|title=LD50 of venomous snakes - Ultimate species list|url=http://snakedatabase.org/pages/LD50.php|publisher=Snake Database|accessdate=21 October 2013}}</ref> and the venom yield per bite can range anywhere from 70–236 mg.<ref name="DAVY">{{cite web|title=Common death adder Venom Yield|url=http://snakedatabase.org/referencevenomamount/495|accessdate=21 October 2013}}</ref> Unlike other snakes that flee from approaching humans crashing through the undergrowth, common death adders are more likely to sit tight and risk being stepped on, making them more dangerous to the unwary bushwalker. They are said to be reluctant to bite unless actually touched.<ref name="DA">{{cite web|title=Australia's 10 most dangerous snakes|url=http://www.australiangeographic.com.au/journal/view-image.htm?index=8&gid=11893|work=Australian Geographic|publisher=Australian Geographic|accessdate=20 October 2013}}</ref> |
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====Tiger snake==== |
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[[Tiger snake]]s (''Notechis spp'') are highly venomous. Their venoms possess potent [[neurotoxin]]s, [[Coagulation|coagulant]]s, [[haemolysin]]s and [[myotoxin]]s and the venom is quick-acting with rapid onset of breathing difficulties and paralysis. The untreated mortality rate from tiger snake bites is reported to be between 40 and 60%.<ref>[http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0540 University of Adelaide Clinical Toxinology Resource]</ref> They are a major cause of snakebites and occasional snakebite deaths in Australia.<ref name="TSB">{{cite web|title=Australian Tiger Snakes|url=http://www.toxinology.com/about/tiger_snake_snakebite.html|work=Clinical Toxinology Resources|publisher=University of Adelaide|accessdate=22 October 2013}}</ref> |
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=====Caspian cobra===== |
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The most medically important species of snake in [[Central Asia]] is the [[Caspian cobra]] (''Naja oxiana''). It is the most venomous species of [[Naja|cobra]] in the world, slightly ahead of the Philippines cobra based on a toxinological study from 1992 found in the Indian Journal of Experimental Biology, in which this species produced the highest potency venom among cobras. The venom of this species has the most potent composition of toxins found among any [[Naja|cobra]] species known. It is made up of primarily highly potent [[neurotoxin]]s but it also has [[cytotoxin|cytotoxic]] activity (tissue-death, necrosis) and [[Cardiotoxicity|cardiotoxins]].<ref name="cytotoxins">{{cite journal |doi=10.1042/BJ20041892 |title=Cancer cell injury by cytotoxins from cobra venom is mediated through lysosomal damage |year=2005 |last1=Sharonov |first1=George V. |last2=Sharonov |first2=Alexei V. |last3=Astapova |first3=Maria V. |last4=Rodionov |first4=Dmitriy I. |last5=Utkin |first5=Yuriy N. |last6=Arseniev |first6=Alexander S. |journal=Biochemical Journal |volume=390 |pages=11–8 |pmid=15847607 |issue=Pt 1 |pmc=1184559}}</ref> Two forms of "cytotoxin II" ([[cardiotoxin]]) were found in the venom of this species.<ref name="CTII">{{cite journal |doi=10.1046/j.1432-1327.1999.00478.x |title=Two forms of cytotoxin II (cardiotoxin) from Naja naja oxiana in aqueous solution . Spatial structures with tightly bound water molecules |year=1999 |last1=Dementieva |first1=Daria V. |last2=Bocharov |first2=Eduard V. |last3=Arseniev |first3=Alexander. S. |journal=European Journal of Biochemistry |volume=263 |pages=152–62 |pmid=10429199 |issue=1}}</ref> The Caspian cobra is the most venomous species of cobra in the world. The crude venom of this species produced the lowest known lethal dose (LCLo) of 0.005 mg/kg, the lowest among all cobra species, derived from an individual case of poisoning by [[Ventricular system|intracerebroventricular]] injection.<ref name=L&R>{{cite journal|last=Lysz|first=Thomas W.|coauthors=Rosenberg, Philip|title=Convulsant activity of Naja naja oxiana venom and its phospholipase A component|journal=Toxicon|date=May 1974|volume=12|issue=3|pages=253–265|doi=10.1016/0041-0101(74)90067-1|accessdate=6 December 2013}}</ref> A 1992 extensive toxinology study gave a value of 0.18 mg/kg (range of 0.1 mg/kg - 0.26 mg/kg) by [[Subcutis|subcutaneous injection]].<ref name=IJEB>{{cite journal|last=Khare|first=AD|coauthors=Khole V, Gade PR|title=Toxicities, LD50 prediction and in vivo neutralisation of some elapid and viperid venoms|journal=Indian Journal of Experimental Biology|date=December 1992|volume=30|issue=12|pages=1158–62|pmid=1294479|url=http://www.ncbi.nlm.nih.gov/pubmed/1294479|accessdate=6 December 2013}}</ref> According to Brown (1973), the [[Subcutis|subcutaneous]] {{LD50}} value is 0.4 mg/kg,<ref name="Bro73" /> while Ernst and Zug ''et al.'' list a value of 0.21 mg/kg [[Subcutis|SC]] and 0.037 mg/kg [[Intravenous injection|IV]].<ref name="ErZug" /> Latifi (1984) listed a subcutaneous value of 0.2 mg/kg.<ref name="Latifi84"/> In another study, where venom was collected from a number of specimens in Iran, the [[intravenous injection|IV]] {{LD50}} in lab mice was 0.078 mg/kg.<ref name=Iran>{{cite journal|last=Akbari|first=A|coauthors=Rabiei , H., Hedayat, A., Mohammadpour, N., Zolfagharian, H., Teimorzadeh, Sh.|title=Production of effective antivenin to treat cobra snake (Naja naja oxiana) envenoming|journal=Archives of Razi Institute|date=June 2010|volume=65|issue=1|pages=33–37|url=http://rockyourpaper.org/article/production-of-effective-antivenin-to-treat-cobra-snake-naja-naja-oxiana-envenoming-887be8012ae6d7d5cbc366419e6afe8c|accessdate=7 December 2013}}</ref> Average venom yield per bite for this species is between 75 and 125 mg (dry weight),<ref name="no">{{cite web|title=Naja oxiana|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0042|work=Clinical Toxinology Resource|publisher=University of Adelaide}}</ref> but it may yield up to 590 mg (dry weight) in a single bite.<ref name="Latifi84">{{cite journal|last=Latifi|first=M|title=Variation in yield and lethality of venoms from Iranian snakes|journal=Toxicon|year=1984|volume=22|issue=3|pages=373–380|pmid=6474490|accessdate=6 November 2013}}</ref> The bite of this species may cause severe pain and swelling, along with severe neurotoxicity. Weakness, drowsiness, ataxia, hypotension, and paralysis of throat and limbs may appear in less than one hour after the bite. Without medical treatment, symptoms rapidly worsen and death can occur rapidly after a bite due to respiratory failure. An adult woman bitten by this species in northwestern Pakistan suffered severe neurotoxicity and died while en route to the closest hospital nearly 50 minutes after envenomation. Between 1979 and 1987, 136 confirmed bites were attributed to this species in the former [[Soviet Union]]. Of the 136, 121 received antivenom, and only four died. Of the 15 who did not receive antivenom, 11 died. This species is an abundant snake in northeastern Iran and is responsible for a very large number of snakebite mortality.<ref name=L84>{{cite book|last=Latifi|first=Mahmoud|title=Snakes of Iran|year=1984|publisher=Society for the Study of Amphibians & Reptiles|isbn=978-0-91-698422-9}}</ref> Antivenom is not as effective for envenomation by this species as it is for other Asiatic cobras within the same region, like the Indian cobra (''Naja naja'') and due to the dangerous toxicity of this species' venom, massive amounts of antivenom are often required for patients. As a result, a monovalent antivenom serum is being developed by the Razi Serum and Vaccine Research Institute in Iran.<ref name=Iran/> The untreated mortality rate for this species is 70-75%, which is the highest among all cobra species of the genus ''Naja''.<ref name="medsnakes">{{cite book|last=Gopalkrishnakone, Chou|first=P., LM|title=Snakes of Medical Importance (Asia-Pacific Region)|year=1990|publisher=National University of Singapore|location=Singapore|isbn=9971-62-217-3}}{{page needed|date=October 2013}}</ref> |
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=====Forest cobra===== |
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The [[Forest cobra]] (''Naja melanoleuca'') is the largest true cobra of the ''Naja'' species and is a very bad-tempered, aggressive, and irritable snake when cornered or molested. According to Brown (1973) this species has a [[murine]] [[intraperitoneal|IP]] {{LD50}} value of 0.324 mg/kg, while the [[intravenous injection|IV]] {{LD50}} value is 0.6 mg/kg.<ref name="Bro73" /> Ernst and Zug ''et al.'' 1996 list a value of 0.225 mg/kg [[Subcutis|SC]].<ref name="ErZug" /><ref name=M67>{{cite journal|last=Minton|first=SA|title=Paraspecific protection by elapid and sea snake antivenins|journal=Toxicon|year=1967|volume=5|issue=1|pages=47–55|doi=10.1016/0041-0101(67)90118-3|accessdate=6 December 2013}}</ref> The average venom yield per bite is 571 mg and the maximum venom yield is 1102 mg.<ref name="Mir06">{{cite journal|last=Mirtschin|first=Peter J.|coauthors=Nathan Dunstan, Ben Hough, Ewan Hamilton, Sharna Klein, Jonathan Lucas, David Millar, Frank Madaras, Timothy Nias|title=Venom yields from Australian and some other species of snakes|journal=Ecotoxicology|date=26 August 2006|volume=15|issue=6|pages=531–538|doi=10.1007/s10646-006-0089-x|url=http://www.venomsupplies.com/assets/published-paper.pdf|accessdate=6 November 2013}}</ref> The forest cobra is one of the least frequent causes of snake bite among the African cobras, this is largely due to its forest-dwelling habits. It is the largest of the ''Naja'' cobras and the venom is considered highly toxic. If the snake becomes cornered or is agitated, it can quickly attack the aggressor, and if a large amount of venom is injected, a rapidly fatal outcome is possible. Clinical experience with forest cobras has been very sparse, and few recorded bites have been documented. However, in 2008, around the area of [[Friguiagbé]] in [[Guinea]], there were 375 bites attributed to the forest cobra and of those 79 were fatal. Most of the fatal bites were patients who received no medical treatment.<ref name="WHOafrica">{{cite web|last=Warrell|first=David A.|title=Guidelines for the Prevention and Clinical Management of Snakebite in Africa|url=http://www.afro.who.int/en/clusters-a-programmes/hss/essential-medicines/highlights/2731-guidelines-for-the-prevention-and-clinical-management-of-snakebite-in-africa.html|publisher=World Health Organization|accessdate=23 October 2013}}</ref> Deaths from respiratory failure have been reported, but most victims will survive if prompt administration of antivenom is undertaken as soon as clinical signs of envenomation have been noted.<ref>{{cite web|title=IMMEDIATE FIRST AID for bites by Forest Cobra (Naja melanoleuca)|url=http://toxicology.ucsd.edu/Snakebite%20Protocols/Naja1.htm|accessdate=22 October 2013}}</ref> |
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=====Philippine cobra===== |
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The [[Philippine cobra]] (''Naja philippinensis'') is one of the most venomous cobra species in the world based on [[murine]] {{LD50}} studies. The average [[Subcutis|subcutaneous]] {{LD50}} for this species is 0.20 mg/kg.<ref name="Bro73"/> The lowest {{LD50}} reported value for this snake is 0.14 mg/kg [[Subcutis|SC]], while the highest is 0.48 mg/kg [[Subcutis|SC]].<ref name=NP>{{cite journal|last=Watt|first=G|coauthors=Theakston RD, Hayes CG, Yambao ML, Sangalang R, et al.|title=Positive response to edrophonium in patients with neurotoxic envenoming by cobras (Naja naja philippinensis). A placebo-controlled study|journal=New England Journal of Medicine|date=4 December 1986|volume=315|issue=23|pages=1444–8|pmid=3537783|url=http://www.ncbi.nlm.nih.gov/pubmed/3537783|accessdate=6 December 2013|doi=10.1056/NEJM198612043152303}}</ref> and the average venom yield per bite is 90–100 mg.<ref name="Bro73" /> The [[Venom (poison)|venom]] of the Philippine cobra is a potent postsynaptic [[neurotoxin]] which affects respiratory function and can cause [[neurotoxicity]] and respiratory paralysis, as the neurotoxins interrupt the transmission of nerve signals by binding to the neuromuscular junctions near the muscles. Research has shown its venom is purely a neurotoxin, with no apparent necrotizing components and no [[cardiotoxicity|cardiotoxins]]. These snakes are capable of accurately spitting their venom at a target up to 3 metres (9.8 ft) away. Bites from this species produce prominent neurotoxicity and are considered especially dangerous. A study of 39 patients envenomed by the Philippine cobra was conducted in 1988. Neurotoxicity occurred in 38 cases and was the predominant clinical feature. Complete Respiratory failure developed in 19 patients, and was often rapid in onset; in three cases, apnea occurred within just 30 minutes of the bite. There were two deaths, both in patients who were moribund upon arrival at the hospital. Three patients developed necrosis, and 14 individuals with systemic symptoms had no local swelling at all. Both cardiotoxicity and reliable nonspecific signs of envenoming were absent. Bites by the Philippine cobra produce a distinctive clinical picture characterized by severe neurotoxicity of rapid onset and minimal local tissue damage.<ref name="Toxicity">{{cite journal |pmid=3177741 |year=1988 |last1=Watt |first1=G |last2=Padre |first2=L |last3=Tuazon |first3=L |last4=Theakston |first4=RD |last5=Laughlin |first5=L |title=Bites by the Philippine cobra (Naja naja philippinensis): Prominent neurotoxicity with minimal local signs |volume=39 |issue=3 |pages=306–11 |journal=The American journal of tropical medicine and hygiene}}</ref> |
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====Gaboon viper==== |
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The [[Gaboon viper]] (''Bitis gabonica''), although generally docile and sluggish, have the longest fangs of any venomous snake and their venom glands are enormous and each bite produces the largest quantities of venom of any [[venomous snake]]. Yield is probably related to body weight, as opposed to milking interval.<ref name="Mal03">Mallow D, Ludwig D, Nilson G. 2003. ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. 359 pp. ISBN 0-89464-877-2.</ref> Brown (1973) gives a venom yield range of 200–1000 mg (of dried venom),<ref name="Bro73">Brown JH. 1973. ''Toxicology and Pharmacology of Venoms from Poisonous Snakes''. Springfield, Illinois: Charles C. Thomas. 184 pp. LCCCN 73-229. ISBN 0-398-02808-7.</ref> A range of 200–600 mg for specimens 125–155 cm in length has also been reported.<ref name="Mal03" /> Spawls and Branch (1995) state from 5 to 7 ml (450–600 mg) of venom may be injected in a single bite.<ref name="SB95">Spawls S, [[William Roy Branch|Branch B]]. 1995. ''The Dangerous Snakes of Africa''. Ralph Curtis Books. Dubai: Oriental Press. 192 pp. ISBN 0-88359-029-8.</ref> Based on how sensitive [[monkey]]s were to the venom, Whaler (1971) estimated 14 mg of venom would be enough to kill a human being: equivalent to 0.06 ml of venom, or 1/50 to 1/1000 of what can be obtained in a single milking. Marsh and Whaler (1984) wrote that 35 mg (1/30 of the average venom yield) would be enough to kill a man of {{convert|70|kg|lb}}.<ref name="Mal03" /> A study by Marsh and Whaler (1984) reported a maximum yield of 9.7 ml of wet venom, which translated to 2400 mg of dried venom. They attached [[Crocodile clip|"alligator" clip electrodes]] to the angle of the open jaw of [[Anesthesia|anesthetized]] specimens (length 133–136 cm, girth 23–25 cm, weight 1.3–3.4 kg), yielding 1.3–7.6 ml (mean 4.4 ml) of venom. Two to three electrical bursts within a space of five seconds apart were enough to empty the venom glands. The snakes used for the study were milked seven to 11 times over a 12-month period, during which they remained in good health and the potency of their venom remained the same.<ref name="Mal03" /> In addition, Gaboon vipers produce the most painful bite of any venomous snake in the world. A bite causes very rapid and conspicuous [[Swelling (medical)|swelling]], intense [[pain]], severe [[Shock (circulatory)|shock]] and local [[blister]]ing. Other symptoms may include uncoordinated movements, [[defecation]], [[urination]], swelling of the tongue and eyelids, [[Seizure|convulsions]] and [[unconsciousness]].<ref name="Mal03" /> Blistering, [[Bruise|bruising]] and [[necrosis]] is often very extensive. There may be sudden [[hypotension]], heart damage and [[Dyspnea|dyspnoea]].<ref name="Spa04" /> The blood may become incoagulable with internal bleeding that may lead to [[haematuria]] and [[haematemesis]].<ref name="SB95" /><ref name="Spa04">Spawls S, Howell K, Drewes R, Ashe J. 2004. ''A Field Guide To The Reptiles Of East Africa''. London: A & C Black Publishers Ltd. 543 pp. ISBN 0-7136-6817-2.</ref> Local tissue damage may require surgical [[Surgery|excision]] and possibly [[amputation]].<ref name="SB95" /> Healing may be slow and fatalities during the recovery period are not uncommon.<ref name="Spa04" /> |
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====Green mambas==== |
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Green mambas (Western, Eastern, and Jameson's) are all highly venomous snakes with bad tempers and a tendency to strike repeatedly with little provocation. |
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The [[Western green mamba]] (''Dendroaspis viridis'') is highly venomous and aggressive with a {{LD50}} of 0.7 mg/kg [[Subcutaneous injection|SC]] and the average venom yield per bite is approximately 100 mg. The mortality rate of untreated bites is unknown but is thought to be very high (>80%). |
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The [[Eastern green mamba]] (''Dendroaspis angusticeps'') has an average venom yield per bite of 80 mg according to Engelmann and Obst (1981).<ref name="Engelmann">{{cite book|last=Engelmann|first=Wolf-Eberhard|title=Snakes: Biology, Behavior, and Relationship to Man|year=1981|publisher=Leipzig Publishing; English version published by Exeter Books (1982)|location=Leipzig; English version NY, USA|isbn=0-89673-110-3|pages=51}}</ref> The [[subcutaneous injection|subcutaneous]] {{LD50}} for this species ranges from 0.40 mg/kg to 3.05 mg/kg depending on different toxicology studies, authority figures and estimates. The mortality rate of untreated bites is unknown but is thought to be very high (70-75%). |
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The [[Jameson's mamba]] (''Dendroaspis jamesoni'') is known to be quite aggressive and defensive. The average venom yield per bite for this species is 80 mg, but some specimens may yield as much as 120 mg in a single bite. The [[Subcutaneous injection|SC]] {{LD50}} for this species according to Brown (1973) is 1.0 mg/kg, while the [[Intravenous therapy|IV]] {{LD50}} is 0.8 mg/kg.<ref name="Brown73">{{cite book|last=Brown|first=John H.|title=Toxicology and Pharmacology of Venoms from Poisonous Snakes|year=1973|publisher=Charles C. Thomas|location=Springfield, IL USA|isbn=0-398-02808-7|pages=81}}</ref> Envenomation by a Jameson's mamba can be deadly in as little as 30 to 120 minutes after being bitten, if proper medical treatment is not attained.<ref name="Davidson">{{cite web|url=http://drdavidson.ucsd.edu/Portals/0/snake/Dendroa1.htm|title=IMMEDIATE FIRST AID|last=Davidson|first=Terence|publisher=University of California, San Diego}}</ref> The mortality rate of untreated bites is not exactly known, but it's said to be very high (>80%).<ref name="WCH">[http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0169 Clinical Toxinology Resource (''Dendroaspis jamesoni'')]</ref> |
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===Considerably dangerous=== |
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====Terciopelo==== |
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The [[Terciopelo]] (''Bothrops asper'') has been described as excitable and unpredictable when disturbed. They can, and often will, move very quickly,<ref name="C&L04">{{cite book|last=Campbell; Lamar|first=Jonathan; William|title=The Venomous Reptiles of the Western Hemisphere|year=2004|publisher=Comstock Publishing Associates|location=Ithaca and London|isbn=0-8014-4141-2}}{{page needed|date=October 2013}}</ref> usually opting to flee from danger,<ref name="VRO">{{cite web|last=Sierra|title=Captive care of B.asper|url=http://www.venomousreptiles.org/articles/133|work=A collection of captive care notes|publisher=www.venomousreptiles.org|accessdate=6 November 2006}}</ref> but are capable of suddenly reversing direction to vigorously defend themselves.<ref name="VRO"/><ref name=Mark>{{cite book|last=O'Shea|first=Mark|title=VENOMOUS SNAKES OF THE WORLD|year=first published in 2005|publisher=Princeton University Press (Princeton and Oxford)|location=USA|isbn=978-0-691-15023-9}}</ref> Adult specimens, when cornered and fully alert, should be considered dangerous. In a review of bites from this species suffered by field biologists, Hardy (1994) referred to it as the "ultimate pit viper".<ref name="C&L04" /> Venom yield (dry weight) averages 458 mg, with a maximum of 1530 mg (Bolaños, 1984)<ref name="War-C&L04">Warrell DA. 2004. Snakebites in Central and South America: Epidemiology, Clinical Features, and Clinical Management. ''In'' Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.{{page needed|date=October 2013}}</ref> and an {{LD50}} in mice of 2.844 mg/kg [[Intraperitoneal|IP]].<ref name="VRO" /> This species is an important cause of snakebite within its range. It is considered the most dangerous snake in [[Costa Rica]], responsible for 46% of all bites and 30% of all hospitalized cases; before 1947, the fatality rate was 7%, but this has since declined to almost 0% (Bolaños, 1984), mostly due to the Clodomiro Picado Research Institute,<ref name="Clodomiro Picado Research Institute">{{cite web| title = Clodomiro Picado Research Institute|url = http://www.icp.ucr.ac.cr/}}</ref> responsible for the production of [[antivenom]]. In the [[Colombia]]n states of [[Antioquia Department|Antioquia]] and [[Chocó Department|Chocó]], it causes 50-70% of all snakebites, with a [[sequelae]] rate of 6% and a fatality rate of 5% (Otero et al., 1992). In the state of [[Lara (state)|Lara]], [[Venezuela]], it is responsible for 78% of all envenomations and all snakebite fatalities (Dao-L., 1971). One of the reasons so many people are bitten is because of its association with human habitation and many bites actually occur indoors (Sasa & Vázquez, 2003). |
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====Jararaca ==== |
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The [[Bothrops jararaca|Jararaca]] (''Bothrops jararaca'') is a species that is often abundant within its range, where it is an important cause of snakebite.<ref name="C&L04" /> It is the best-known venomous snake in the wealthy and heavily populated areas of southeastern [[Brazil]], where it was responsible for 52% (3,446 cases) of snakebites between 1902 and 1945, with a 0.7% mortality rate (25 deaths).<ref name="War-C&L04" /> The average venom yield is {{convert|25|-|26|mg}} with a maximum of {{convert|300| mg}} of dried venom. The venom is slightly more toxic than that of the terciopelo or fer-de-lance (''B. asper''). In mice, the median lethal dose ({{LD50}}) is 1.2-1.3 mg/kg [[Intravenous therapy|IV]], 1.4 mg/kg [[Peritoneum#Intraperitoneal|IP]] and 3.0 mg/kg [[Subcutis|SC]]. For humans, the LD<span style="font-size:100%;"><sub>50</sub></span> is estimated to be {{convert|210|mg}} subcutaneous.<ref name="Bro73">{{cite book | author = Brown JH | year = 1973 | title = Toxicology and Pharmacology of Venoms from Poisonous Snakes | location = Springfield, IL | publisher = Thomas | lccn = 73000229 | isbn = 0-398-02808-7 }}{{page needed|date=October 2013}}</ref> |
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====South American bushmaster or Atlantic bushmaster==== |
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The [[Lachesis muta|South American bushmaster or Atlantic bushmaster]] (''Lachesis muta'') is the longest species of venomous snake in the [[Western Hemisphere]] and the longest [[pit viper]] in the world. It is native to parts of [[South America]], especially the equatorial forests east of the [[Andes]]. They are active at dusk or after dark and so they are very secretive and elusive. This species is large, fast and has a reputation for being particularly aggressive when cornered.<ref name="F&C">{{cite book|last=Fowler, Cubas|first=ME, ZS|title=Biology, Medicine, and Surgery of South American Wild Animals|year=2001|publisher=Wiley-Blackwell |edition=1st |isbn=0813828465|page=42}}</ref><ref name="B&B">{{cite book|last=Bartlett, Bartlett|first=Richard, Patricia|title=Reptiles and Amphibians of the Amazon: An Ecotourist's Guide|year=2003|publisher=University Press of Florida|location=USA|isbn=0813026237}}</ref> Some reports suggest that this species produces a large amount of venom that is weak compared to some other vipers.<ref name="SAP">[http://www.southamericanpictures.com/features/feat18/lachesis.htm ''Lachesis muta'', The Silent Fate] at [http://www.southamericanpictures.com/ South American Pictures]. Accessed 26 October 2013.</ref> Others, however, suggest that such conclusions may not be accurate. These animals are badly affected by stress and rarely live long in captivity. This makes it difficult to obtain venom in useful quantities and good condition for study purposes. For example, Bolaños (1972) observed that venom yield from his specimens fell from 233 mg to 64 mg while they remained in his care. As the stress of being milked regularly has this effect on venom yield, it is reasoned that it may also affect venom toxicity. This may explain the disparity described by Hardy and Haad (1998) between the low laboratory toxicity of the venom and the high mortality rate of bite victims.<ref name="RIP">Ripa, D. 2001. [http://www.venomousreptiles.org/articles/61 Bushmasters and the Heat Strike] at [http://www.venomousreptiles.org/ VenomousReptiles.org]. Accessed 26 October 2013.</ref> However, wild specimens have an average venom yield per bite of 280–450 mg (dry weight) (U.S. Dept. Navy, 1968). According to (Sanchez et al., 1992), who used wild specimens from [[Pará|Pará, Brazil]], the average venom yield per bite was 324 mg, with a range of 168–552 mg (dry weight).<ref name="lmuta">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0356}}</ref> Brown (1973) gives the following {{LD50}} values for mice: 1.5 mg/kg [[Intravenous|IV]], 1.6–6.2 mg/kg [[Peritoneum|IP]], 6.0 mg/kg [[Subcutaneous|SC]]. He also notes a venom yield of 200–411 mg.<ref name="Bro73" /> Human envenoming by this species, although infrequent, can be rather severe due to the large volumes of venom injected. Envenomation is characterized by pronounced local tissue damage and systemic dysfunctions, including massive internal bleeding.<ref name="Tox">{{cite journal |doi=10.1016/j.toxicon.2006.11.014 |title=Cytotoxicity of Lachesis muta muta snake (bushmaster) venom and its purified basic phospholipase A2 (LmTX-I) in cultured cells |year=2007 |last1=Damico |first1=Daniela C.S. |last2=Nascimento |first2=Juliana Minardi |last3=Lomonte |first3=Bruno |last4=Ponce-Soto |first4=Luis A. |last5=Joazeiro |first5=Paulo P. |last6=Novello |first6=José Camillo |last7=Marangoni |first7=Sérgio |last8=Collares-Buzato |first8=Carla B. |journal=Toxicon |volume=49 |issue=5 |pages=678–92 |pmid=17208264}}</ref> |
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====King cobra==== |
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[[King cobra]]s (''Ophiophagus hannah'') are not particularly venomous nor are they aggressive or bad tempered. The venom {{LD50}} is 1.80 mg/kg [[Subcutaneous injection|SC]] according to Broad et al. (1979).<ref name="tox">[http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0048 University of Adelaide Clinical Toxinology Resource]</ref> The mean value of subcutaneous {{LD50}} of five wild-caught king cobras in [[Southeast Asia]] was determined as 1.93 mg/kg.<ref name="CRC Press">{{cite book |title=Handbook of clinical toxicology of animal venoms and poisons|publisher=CRC Press|volume=236|year=1995|location=USA|isbn=0-8493-4489-1}}</ref> However, because the king cobra is the longest venomous snake in the world, it can inject very high volumes of venom in a single bite. Between 350 to 500 mg (dry weight) of venom can be injected at once (Minton, 1974). In another study by (Broad et al., 1979), the average venom quantity was 421 mg (dry weight of milked venom).<ref name="tox" /> The maximum venom yield is approximately 1000 mg (dry weight).<ref name="OHVY" /> The king cobra has a fearsome reputation. When annoyed, it spreads a narrow hood and growls loudly, but scientists claim that their "legendary aggressiveness" is grossly exaggerated.<ref name="Greene">{{cite book|last=Greene|first=HW|title=Snakes: The Evolution of Mystery in Nature|year=1997|publisher=University of California Press|location=California, USA|isbn=0520224876}}{{page needed|date=October 2013}}</ref> In most of the local encounters with live, wild king cobras, the snakes appear to be of rather placid disposition, and they usually end up being killed or subdued with hardly any hysterics. These support the view that wild king cobras generally have a mild temperament, and despite their frequent occurrence in disturbed and built-up areas, are adept at avoiding humans. Naturalist Michael Wilmer Forbes Tweedie felt that "this notion is based on the general tendency to dramatise all attributes of snakes with little regard for the truth about them. A moment’s reflection shows that this must be so, for the species is not uncommon, even in populated areas, and consciously or unconsciously, people must encounter king cobras quite frequently. If the snake were really habitually aggressive records of its bite would be frequent; as it is they are extremely rare."<ref name="Tweedie">{{cite book|last=Tweedie|first=MWF|title=The Snakes of Malaya|year=1983|publisher=Singapore National Printers Ltd|location=Singapore|oclc=686366097}}{{page needed|date=October 2013}}</ref> Mortality rates vary sharply depending on many factors. Most bites involve non-fatal amounts.<ref name="MG">{{cite web|last=Mathew, Gera|first=JL, T|title=http://www.priory.com/mehasophitoxaemia.htm|url=http://www.priory.com/med/ophitoxaemia.htm|work=MEDICINE ON-LINE|accessdate=20 October 2013}}</ref> Still, despite its mild disposition and reluctance to bite, the king cobra is capable of severely envenoming an adult human. Massive amounts of venom can cause severe neurotoxicity. In cases where envenomation is severe, death can be rapid.<ref name="tox" /> |
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====True cobras==== |
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The [[Naja|cobras]] (''Naja spp'') are a medically important group of snakes due number of bites and fatalities they cause across to their geographical range. The genus ''Naja'' consists of 20 to 22 [[species]], but has undergone several [[Taxonomy (biology)|taxonomic]] revisions in recent years, so sources vary greatly.<ref name="ITIS">{{ITIS |id=700233 |taxon=''Naja'' |accessdate=13 April 2008}}</ref> They range throughout [[Africa]] (including some parts of the Sahara where ''Naja haje'' can be found), [[Southwest Asia]], [[Central Asia]], [[South Asia]], [[East Asia]], and [[Southeast Asia]]. The most recent revison,<ref name=wallach>{{cite journal|last=Wallach|first=Van|coauthors= Wüster, W; Broadley, Donald G.|title=In praise of subgenera: taxonomic status of cobras of the genus Naja Laurenti (Serpentes: Elapidae)|journal=Zootaxa|year=2009|volume=2236|issue=1|pages=26–36|url=http://www.mapress.com/zootaxa/2009/f/zt02236p036.pdf}}</ref> listed 28 species after the synonymisation of ''Boulengerina'' and ''Paranaja'' with ''Naja''. But unlike some other members of the [[Elapidae]] family (the species of the genus ''Bungarus'', genus ''Oxyuranus'', genus ''Pseudohaje'', and especially genus ''Dendroaspis''), half of the bites by many species of both African and Asian origin of the genus ''Naja'' are "[[dry bite]]s" (a dry bite is a bite by a venomous snake in which no venom is released). Roughly 45-50% of bites by most cobra species are dry bites and thus don't cause envenomation.<ref name=WHO-03>{{cite journal|last=Warrell|first=DA|coauthors=Theakston RD; Griffiths E|title=Report of a WHO workshop on the standardization and control of antivenoms|journal=Toxicon|date=April 2003|volume=41|issue=5|pages=541–57|pmid=12676433|url=http://www.ncbi.nlm.nih.gov/pubmed/12676433|accessdate=8 December 2013}}</ref> Some of the species which are known and documented to deliver dry bites in a majority of cases (50% +) include: ''Naja naja'', ''Naja kaouthia'', ''Naja sputatrix'', ''Naja siamensis'', ''Naja haje'', ''Naja annulifera'', ''Naja anchietae'' and ''Naja nigricollis''. Some species will inject venom in the majority of their bites, but still deliver high number of dry bites (40-45%) include: ''Naja sumatrana'', ''Naja melanoleuca'', ''Naja atra'', ''Naja mossambica'' and ''Naja katiensis''. Within this [[genus]], there are a few species in which dry bites are very rare. Envenoming occurs in at least 75-80% of bite cases involving these species. The species which typically cause envenomation in the majority of their bites include some of the more dangerous and venomous species of this genus: ''Naja oxiana'', ''Naja philippinensis'', ''Naja nivea'', and ''Naja samarensis''. There are many more species within the genus which have not yet been subject to much researched and studies, and as a result, very little is known about their behaviour, venom, diet, habitat and general temperaments. Some of these species include ''Naja sagittifera'', ''Naja annulata'', ''Naja christyi'' and many others. |
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=====Chinese cobra===== |
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The [[Chinese cobra]] (''Naja atra'') is a highly venomous member of the true cobras (genus ''Naja''). Its venom consists mainly of postsynaptic [[neurotoxin]]s and [[cardiotoxin]]s. Four cardiotoxin-analogues I, II, III, and IV, account for about 54% of the dry weight of the crude venom and have [[cytotoxin|cytotoxic]] properties.<ref name="JBC">{{cite journal |pmid=7263715 |url=http://www.jbc.org/cgi/pmidlookup?view=long&pmid=7263715 |title=Crystallographic studies of snake venom proteins from Taiwan cobra (Naja nana atra). Cardiotoxin-analogue III and phospholipase A2 |year=1981 |author1=A H Wang |journal=Journal of Biological Chemistry |volume=256 |issue=17 |pages=9279–82 |last2=Yang |first2=CC}}</ref> The {{LD50}} values of its venom in [[mice]] are 0.29 mg/kg [[Intravenous therapy|IV]],<ref name="Engelmann">{{cite book|last=Engelmann|first=Wolf-Eberhard|title=Snakes: Biology, Behavior, and Relationship to Man|year=1981|publisher=Leipzig Publishing; English version published by Exeter Books (1982)|location=Leipzig; English version NY, USA|isbn=0-89673-110-3|page=53}}</ref> and 0.29<ref name= "LD50"/>—0.53 mg/kg [[Subcutis|SC]].<ref name="si">{{cite book |title= Snake of medical importance|publisher= Venom and toxins research group| location = Singapore|isbn= 9971-62-217-3|url=http://i55.tinypic.com/21jvc7p.jpg}}</ref> The average venom yield from a snake of this species kept at a snake farm was about 250.8 mg (80 mg dry weight).<ref name="si" /> According to Minton (1974), this cobra has a venom yield range of 150 to 200 mg (dry weight).<ref>{{cite web|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0039|title= University of Adelaide Clinical Toxinology Resources}}</ref> Brown listed a venom yield of 184 mg (dry weight).<ref name="Bro73" /> It is one of the most prevalent [[venomous snakes]] in [[mainland China]] and [[Taiwan]], which has caused many snakebite incidents to humans. |
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=====Monocled cobra===== |
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The Asian [[Monocled cobra]] (''Naja kaouthia'') is a medically important species as it is responsible for a considerable amount of bites throughout its range. The major toxic components in the Monocled cobras [[venom]] are postsynaptic [[neurotoxin]]s, which block the nerve transmission by binding specifically to the [[nicotinic]] [[acetylcholine receptor]], leading to flaccid [[paralysis]] and even death by respiratory failure. The major α-neurotoxin in ''Naja kaouthia'' venom is a long neurotoxin, α-[[cobratoxin]]; the minor α-neurotoxin is different from cobrotoxin in one [[Residue (chemistry)|residue]].<ref>{{cite journal |pmid=12897961 |year=2003 |last1=Wei |first1=JF |last2=Lü |first2=QM |last3=Jin |first3=Y |last4=Li |first4=DS |last5=Xiong |first5=YL |last6=Wang |first6=WY |title=Alpha-neurotoxins of Naja atra and Naja kaouthia snakes in different regions |volume=35 |issue=8 |pages=683–8 |journal=Sheng wu hua xue yu sheng wu wu li xue bao Acta biochimica et biophysica Sinica}}</ref> The neurotoxins of this particular species are weak.<ref name="WeakToxin">{{cite journal |doi=10.1016/j.toxicon.2004.09.014 |title=Weak neurotoxin from Naja kaouthia cobra venom affects haemodynamic regulation by acting on acetylcholine receptors |year=2005 |last1=Ogay |first1=Alexey Ya. |last2=Rzhevsky |first2=Dmitry I. |last3=Murashev |first3=Arkady N. |last4=Tsetlin |first4=Victor I. |last5=Utkin |first5=Yuri N. |journal=Toxicon |volume=45 |pages=93–9 |pmid=15581687 |issue=1}}</ref> The venom of this species also contains [[myotoxin]]s and [[cardiotoxin]]s.<ref name="Mahanta">{{cite journal |doi=10.1016/S0378-8741(00)00373-1 |title=Neutralisation of lethality, myotoxicity and toxic enzymes of Naja kaouthia venom by Mimosa pudica root extracts |year=2001 |last1=Mahanta |first1=Monimala |last2=Mukherjee |first2=Ashis Kumar |journal=Journal of Ethnopharmacology |volume=75 |pages=55–60 |pmid=11282444 |issue=1}}</ref><ref>{{cite journal |doi=10.1016/0041-0101(91)90005-C |title=Effects of a cardiotoxin from Naja naja kaouthia venom on skeletal muscle: Involvement of calcium-induced calcium release, sodium ion currents and phospholipases A2 and C |year=1991 |last1=Fletcher |first1=Jeffrey E. |last2=Jiang |first2=Ming-Shi |last3=Gong |first3=Qi-Hua |last4=Yudkowsky |first4=Michelle L. |last5=Wieland |first5=Steven J. |journal=Toxicon |volume=29 |issue=12 |pages=1489–500 |pmid=1666202}}</ref> The median lethal dose ({{LD50}}) is 0.28-0.33 mg per gram of mouse body weight.<ref name="chanhome11">Chanhome, L., Cox, M. J., Vasaruchaponga, T., Chaiyabutra, N. Sitprija, V. (2011). [http://abm.digitaljournals.org/index.php/abm/article/view/658 ''Characterization of venomous snakes of Thailand'']. Asian Biomedicine 5 (3): 311–328.</ref> In case of [[Intravenous injection|IV]] the {{LD50}} is 0.373 mg/kg, and 0.225 mg/kg in case of [[intraperitoneal injection|IP]]. The average venom yield per bite is approximately 263 mg (dry weight).<ref name="Bro73" /> The monocled cobra causes the highest fatality due to snake venom poisoning in Thailand.<ref name="Thai">{{cite journal |doi=10.1016/S0264-410X(97)00098-4 |title=Production of highly potent horse antivenom against the Thai cobra (Naja kaouthia) |year=1997 |last1=Pratanaphon |first1=Ronachai |last2=Akesowan |first2=Surasak |last3=Khow |first3=Orawan |last4=Sriprapat |first4=Supod |last5=Ratanabanangkoon |first5=Kavi |journal=Vaccine |volume=15 |issue=14 |pages=1523–8 |pmid=9330463}}</ref> |
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[[Envenomation]] usually presents predominantly with extensive local [[necrosis]] and systemic manifestations to a lesser degree. Drowsiness, neurological and neuromuscular symptoms will usually manifest earliest; [[hypotension]], flushing of the face, warm skin, and pain around bite site typically manifest within one to four hours following the bite; [[paralysis]], ventilatory failure or death could ensue rapidly, possibly as early as 60 minutes in very severe cases of envenomation. However, the presence of fang marks does not always imply that envenomation actually occurred.<ref name="Davidson">{{cite web |author=Davidson, T. |url=http://drdavidson.ucsd.edu/Portals/0/snake/Naja.htm |title=Snakebite Protocols: Summary for Human Bite by Monocellate Cobra (''Naja naja kaouthia'')}}</ref> |
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=====Egyptian cobra===== |
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The [[Egyptian cobra]] (''Naja haje'') is another species of cobra which causes a significant amount of bites and human fatalities throughout its range. The venom of the Egyptian cobra consists mainly of [[neurotoxin]]s and [[cytotoxin]]s.<ref name="toxins">{{cite journal |doi=10.1111/j.1432-1033.1978.tb12612.x |title=Naja haje haje (Egyptian cobra) Venom. Some Properties and the Complete Primary Structure of Three Toxins (CM-2, CM-11 and CM-12) |year=1978 |last1=Joubert |first1=Francois J. |last2=Taljaard |first2=Nico |journal=European Journal of Biochemistry |volume=90 |issue=2 |pages=359–67 |pmid=710433}}</ref> The average venom yield is 175 to 300 mg in a single bite, and the [[Mouse|murine]] [[Subcutis|subcutaneous]] {{LD50}} value is 1.15 mg/kg. This species has large fangs and can produce large quantities of venom. Envenomation by this snake is a very serious medical emergency.<ref name="Bro73" /> |
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=====Water cobras===== |
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The water cobras found in central and western Africa are the most venomous cobra species (''Naja'') in the world. These species were formerly under the genus ''Boulengerina''. The [[Banded water cobra]] (''Naja annulata'') and the [[Congo water cobra]] (''Naja christyi'') are dangerously venomous. The banded water cobra has one subspecies which is known as Storms water cobra (''Naja annulata stormsi''). Their venoms are extremely potent neurotoxins. A toxicological study listed the intraperitoneal (IP) {{LD50}} of ''N. annulata'' at 0.143 mg/kg.<ref name="Toxicon">{{cite journal |doi=10.1016/0041-0101(91)90118-B |title=Lethal toxins and cross-neutralization of venoms from the African water cobras, Boulengerina annulata annulata and Boulengerina christyi |year=1991 |last1=Weinstein |first1=Scott A. |last2=Schmidt |first2=James J. |last3=Smith |first3=Leonard A. |journal=Toxicon |volume=29 |issue=11 |pages=1315–27 |pmid=1814007}}</ref> Brown (1973) listed the intravenous LD<sub>50</sub> for ''N. a. annulata'' at 0.2 mg/kg.<ref name="Bro73" /> The same study listed the intraperitoneal (IP) {{LD50}} of ''N. christyi'' at 0.12 mg/kg. The venoms of these little-known [[Elapidae|elapids]] have the lowest intraperitoneal LD<sub>50</sub> of any ''Naja'' species studied thus far and have high concentrations of potent postsynaptic [[neurotoxin]]s.<ref name="Toxicon" /> Serious and dangerous envenomation can result from a bite from either of these snakes. There is at least one case of human envenomation caused by the Congo water cobra (''N. christyi''). Symptoms of the envenomation were mild. There is no specific antivenom currently produced for either of these two species.<ref name="NaNc">{{cite web|title=Venomous Animals - Boulengerina annulata and Boulengerina christyi|url=http://www.afpmb.org/content/venomous-animals-b#Boulengerinaannulata|work=Armed Forces Pest Management Board|publisher=United States Army|accessdate=24 October 2013}}</ref> |
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=====Black desert cobra===== |
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The [[Walterinnesia aegyptia|Black desert cobra]] (''Walterinnesia aegyptia'') is a highly venomous snake found in the [[Middle East]]. The subcutaneous {{LD50}} for the venom of this species is 0.4 mg/kg. For comparison, the [[Indian cobra]]'s (''naja naja'') subcutaneous {{LD50}} is 0.80 mg/kg, while the [[Cape cobra]]'s (''naja nivea'') subcutaneous {{LD50}} is 0.72 mg/kg. This makes the black desert cobra a more venomous species than both.<ref name="Bro73" /> The venom is strongly [[Neurotoxicity|neurotoxic]] and also has mild hemotoxic factors. Envenomation usually causes some combination of local pain, swelling, fever, general weakness, headache, & vomiting. This is not a typically aggressive snake, but it will strike and hiss loudly when provoked. It can strike at a distance of ⅔ of its body length. It does not usually spread a hood nor hold up its body up off the ground like [[Naja|true cobras]] do. Envenomation by this species should be considered a serious medical emergency. Reports of human fatalities due to envenomation by this species has been reported.<ref name="WE">{{cite web|title=Venomous Animals - Walterinnesia aegyptia|url=http://www.afpmb.org/content/venomous-animals-wxyz#Walterinnesiaaegyptia|work=Armed Forces Pest Management Board|publisher=United States Army|accessdate=24 October 2013}}</ref> |
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====Spitting cobras==== |
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[[Spitting cobra]]s are another group of cobras that belong the ''Naja'' genus. Spitting cobras can be found in both Africa and Asia. These cobras have the ability to eject venom from their fangs when defending themselves against predators. The sprayed venom is harmless to intact skin. However, it can cause permanent blindness if introduced to the eye and left untreated (causing chemosis and corneal swelling). The venom sprays out in distinctive geometric patterns, using muscular contractions upon the venom glands. These muscles squeeze the glands and force the venom out through forward-facing holes at the tips of the fangs.<ref>{{Cite journal |doi=10.1242/jeb.01170 |title=The buccal buckle: The functional morphology of venom spitting in cobras |year=2004 |last1=Young |first1=B. A. |journal=Journal of Experimental Biology |volume=207 |issue=20 |pages=3483}}</ref> The explanation that a large gust of air is expelled from the lung to propel the venom forward has been proven wrong.<ref>{{Cite journal |
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|doi=10.1111/j.1469-7998.1995.tb02743.x |
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|title=On the 'spitting' behaviour in cobras (Serpentes: Elapidae) |
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|year=1995 |
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|last1=Rasmussen |
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|first1=Sara |
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|last2=Young |
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|first2=B. |
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|last3=Krimm |
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|first3=Heather |
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|journal=Journal of Zoology |
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|volume=237 |
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|pages=27}}</ref> When cornered, some species can "spit" their venom a distance as great as {{convert|2|m|ft|abbr =on}}. While spitting is typically their primary form of defense, all spitting cobras are capable of delivering venom through a bite as well. Most species' venom exhibit significant [[hemotoxin|hemotoxic]] effects, along with more typical [[neurotoxin|neurotoxic]] effects of other cobra species. |
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=====Samar cobra===== |
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The [[Samar cobra]] (''Naja samarensis'') is a highly venomous species of spitting cobra that is found in the southern islands of the Philippines. Although it is a spitting cobra, this species only rarely spits its venom.<ref name="Nsamarensis" /> It is considered to be an extremely aggressive snake that strikes with little provocation. The venom of this species is not well studied, but is known to be an extremely potent postsynaptic neurotoxin that also contains cytotoxic agents.<ref name="MedTox">{{cite book|last=Dart|first=Richard C|title=Medical Toxicology|year=2003|publisher=Lippincott Williams & Wilkins; 3 edition|location=USA|isbn=0-7817-2845-2|pages=1569}}</ref> According to Ernst & Zug ''et al'' the murine [[Subcutis|SC]] {{LD50}} value is 0.23 mg/kg,<ref name=M67/> while Brown lists a {{LD50}} value of 0.36 mg/kg,<ref name="Bro73"/> making it one of the most venomous cobras in the world. Severe envenomation is likely in case of a bite and envenomation rate is high. The untreated mortality rate is not known, but is thought to be high (~60%). Envenomation results in marked local effects such as pain, severe swelling, bruising, blistering, and [[necrosis]]. Other effects include headache, nausea, vomiting, abdominal pain, [[diarrhea]], dizziness, collapse or [[convulsion]]s. There may also be moderate to severe [[flaccid paralysis]] and [[Renal failure|renal damage]]. [[Cardiotoxicity]] is possible, but rare.<ref name="Nsamarensis">{{cite web|title= ''Naja samarensis''|work=University of Adelaide|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0044}}</ref><ref name="W&T">{{cite journal |doi=10.1007/BF01945429 |title=Asiatic cobras: Systematics and snakebite |year=1991 |last1=Wüster |first1=W. |last2=Thorpe |first2=R. S. |journal=Experientia |volume=47 |issue=2 |pages=205–9 |pmid=2001726}}</ref> |
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=====Indochinese spitting cobra===== |
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The [[Indochinese spitting cobra]] (''Naja siamensis'') is a venomous spitting cobra whose venom consists of postsynaptic neurotoxins, metalloproteinases, powerful cardiotoxins, with cytolytic activity, and Phospholipase A<sub>2</sub> with a diversity of activities. The {{LD50}} of its venom is 1.07-1.42 mg/gram of [[mouse]] body weight.<ref name="chanhome11" /> Cranial palsy and respiratory depression are reported to be more common after bites by Naja siamensis than by Naja kaouthia. Indochinese sptting cobras will use their venom for self-defense with little provocation, and as the name implies, are capable of spitting venom when alarmed, often at the face and eyes of the animal or human threatening them. A case report in the literature describes pain and irritation of the eyes, bilateral redness, excessive tear production and whitish discharge, with superficial corneal opacity but normal acuity.<ref name="WJO">{{cite web|last=Williams, Jensen, O'Shea|first=David J., Simon D., Mark|title=Snake Management in Cambodia|url=http://garudam.info/files/WHO2009-Cambodia.pdf|accessdate=23 October 2013}}</ref> |
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=====Black-necked spitting cobra===== |
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The [[Black-necked spitting cobra]] (''Naja nigricollis'') is a species of spitting cobra found mostly in [[Sub-Saharan Africa]]. They possess medically significant [[venom]], although the mortality rate for untreated bites on humans is relatively low (~5-10%). Like other [[spitting cobras]], this species is known for its ability to project [[venom]] at a potential threat. The venom is an irritant to the skin and eyes. If it enters the eyes, symptoms include extreme burning pain, loss of coordination, partial loss of vision and permanent blindness. ''N. nigricollis'' is known for its tendency to liberally spit venom with only the slightest provocation. However, this aggressiveness is counterbalanced by it being less prone to bite than other related species.<ref name="WCH">{{cite web|title=Naja nigricollis - General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid, Antivenoms|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0185|work=WCH Clinical Toxinology Resource|publisher=University of Adelaide}}</ref><ref name="SB95" /> The venom of the black-necked spitting cobra is somewhat unique among elapids in that it consists primarily of [[cytotoxin]]s,<ref name="Marais">{{cite book|last=Marais|first=Johan|title=A Complete Guide to the Snakes of Southern Africa|year=2004|publisher=Struik Nature|location=Cape Town, South Africa|isbn=1-86872-932-X}}{{page needed|date=October 2013}}</ref> but with other components also. It retains the typical [[elapid]] [[neurotoxic]] properties while combining these with highly potent [[cytotoxins]] ([[Necrosis|necrotic agents]])<ref name="cytotoxins">{{cite journal |doi=10.1016/0024-3205(87)90126-3 |title=Cytotoxic activity of various snake venoms on melanoma, B16F10 and chondrosarcoma |year=1987 |last1=Chaim-Matyas |first1=Adina |last2=Ovadia |first2=Michael |journal=Life Sciences |volume=40 |issue=16 |pages=1601–7 |pmid=3561167}}</ref> and [[cardiotoxin]]s.<ref name="Cardiotoxins">{{cite journal |doi=10.1021/bi00684a012 |title=Complete covalent structure of a cardiotoxin from the venom of Naja nigricollis (African black-necked spitting cobra) |year=1975 |last1=Fryklund |first1=Linda |last2=Eaker |first2=David |journal=Biochemistry |volume=14 |issue=13 |pages=2865–71 |pmid=1148181}}</ref> Bite symptoms include severe external [[hemorrhaging]] and tissue [[necrosis]] around the bite area and difficulty breathing. Although mortality rate in untreated cases is low (~5-10%),<ref name="Snakebite">{{cite journal |doi=10.1016/S0140-6736(09)61754-2 |title=Snake bite |year=2010 |last1=Warrell |first1=David A |journal=The Lancet |volume=375 |issue=9708 |pages=77}}</ref> when death occurs it is usually due to asphyxiation by paralysis of the [[Thoracic diaphragm|diaphragm]]. The {{LD50}} of this species is 2 mg/kg [[Subcutaneous injection|SC]] and 1.15 mg/kg [[Intravenous therapy|IV]]. The average venom yield per bite of this species is 200 to 350 mg (dry weight) according to Minton (1974).<ref name="WCH" /> |
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=====Mozambique spitting cobra===== |
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Another medically important African spitting cobra is the [[Mozambique spitting cobra]] (''Naja mossambica''). This species is considered irritable and highly aggressive. The Mozambique spitting cobra is responsible for a significant amount of bites throughout its range, but most are not fatal. The venom is both neurotoxic and cytotoxic.<ref>{{cite web|last=Tilbury|first=CR|title=Observations on the bite of the Mozambique spitting cobra|url=http://archive.samj.org.za/1982%20VOL%20LXI%20Jan-Jun/Articles/02%20February/4.6%20OBSERVATIONS%20ON%20THE%20BITE%20I=OF%20THE%20MOZAMBIQUE%20SPITTING%20COBRA%20%28NAJA%20MOSSAMBICA%20MOSSAMBICA%29,%20C.R.pdf|accessdate=23 October 2013}}</ref> |
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=====West African spitting cobra===== |
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The [[West African spitting cobra]] (''Naja katiensis'') is a venomous species of spitting cobra native to western Africa. The venom of this species consists of postsynaptic [[neurotoxin]]s<ref name="najak">{{cite web|title=Naja katiensis|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0182|work=Clinical Toxinology Resource|publisher=University of Adelaide|accessdate=24 October 2013}}</ref> and [[cardiotoxin]]s with [[cytotoxin|cytotoxic]] (necrotizing) activity.<ref name="MedTox" /> An average wet venom yield of 100 mg has been reported for this species.<ref name="SB95" /> The average murine {{LD50}} value of this species is 1.15 mg/kg [[Intravenous therapy|IV]], but there is an [[Intravenous therapy|IV]] {{LD50}} range of 0.97 mg/kg-1.45 mg/kg.<ref name="Leong">{{cite journal |doi=10.1371/journal.pntd.0001672 |title=Cross Neutralization of Afro-Asian Cobra and Asian Krait Venoms by a Thai Polyvalent Snake Antivenom (Neuro Polyvalent Snake Antivenom) |year=2012 |editor1-last=De Silva |editor1-first=Janaka |last1=Leong |first1=Poh Kuan |last2=Sim |first2=Si Mui |last3=Fung |first3=Shin Yee |last4=Sumana |first4=Khomvilai |last5=Sitprija |first5=Visith |last6=Tan |first6=Nget Hong |journal=PLoS Neglected Tropical Diseases |volume=6 |issue=6 |pages=e1672 |pmid=22679522 |pmc=3367981}}</ref> The West African spitting cobra is one of the most common causes of snakebite in [[Senegal]]. Over 24 years, from 1976 to 1999, a prospective study was conducted of overall and cause-specific mortality among the population of 42 villages of southeastern Senegal. Of 4228 deaths registered during this period, 26 were caused by snakebite, four by invertebrate stings and eight by other wild or domestic animals. The average annual mortality rate from snakebite was 14 deaths per 100,000 population. Among persons aged one year or over, 0.9% (26/2880) of deaths were caused by snakebite and this cause represented 28% (26/94) of total deaths by accidents. Of 1280 snakes belonging to 34 species collected, one-third were dangerous, and the proportions of Viperidae, Elapidae and Atractaspidae were 23%, 11% and 0.6%, respectively. This species was third, responsible for 5.5% of the snakebites.<ref name="Trape">{{cite journal |doi=10.1016/S0035-9203(01)90202-0 |title=High mortality from snakebite in south-eastern Senegal |year=2001 |last1=Trape |first1=J.F. |last2=Pison |first2=G. |last3=Guyavarch |first3=E. |last4=Mane |first4=Y. |journal=Transactions of the Royal Society of Tropical Medicine and Hygiene |volume=95 |issue=4 |pages=420–3 |pmid=11579888}}</ref> |
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=====Rinkhals===== |
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The [[Rinkhals]] (''Hemachatus haemachatus'') is a not a true cobra in that it does not belong to the genus ''Naja''. However, it is closely related to the true [[cobra]]s and is considered to be one of the true [[spitting cobras]].<ref name="Hunter">{{cite web|url=http://www.venomousreptiles.org/articles/34|title=Venomous Reptiles|accessdate=|author=S. Hunter|authorlink= |coauthors= |year=2000 |format= |work= |publisher=|pages= |language= |archiveurl= |archivedate= |quote= }}</ref> The venom of this species is less viscous than that of other African elapids, naturally, as thinner fluid is naturally easier to spit. However, the venom of the rinkhals is produced in copious amounts. Average venom yield is 80–120 mg and the murine {{LD50}} is 1.1-1.6 mg/kg [[Subcutis|SC]] with an estimated lethal dose for humans of 50–60 mg. Actual bites from this species are fairly rare, and deaths in modern times are so far unheard of. Local symptoms of swelling and bruising is reported in about 25% of cases. General symptoms of drowsiness, nausea, vomiting, violent abdominal pain and vertigo often occur, as does a mild pyrexial reaction. Neurotoxic symptoms are however rare and have only included diplopia and dyspnoea. Ophthalmia has been reported, but has not caused as severe complications as in some of the spitters in the genus ''Naja'' (especially ''N. nigricollis'' and ''N. mossambica'').<ref name="rinkhals">{{cite web|title=The Natural History and Captive Care of the Rinkhals spitting cobra|url=http://www.venomousreptiles.org/articles/34|accessdate=23 October 2013}}</ref> |
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====African vipers==== |
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=====Puff adder===== |
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The [[Bitis arietans|Puff adder]] (''Bitis arietans'') is responsible for more fatalities than any other African snake. This is due to a combination of factors, including its wide distribution, common occurrence, large size, potent venom that is produced in large amounts, long fangs, their habit of basking by footpaths and sitting quietly when approached.<ref name="Mal03" /><ref name="SB95" /><ref name="Spa04" /> The venom has [[cytotoxic]] effects<ref name="Wid94">{{cite journal |doi=10.1007/BF00176504 |title=Load cycling closure of fasciotomies following puff adder bite |year=1994 |last1=Widgerow |first1=A.D. |last2=Ritz |first2=M. |last3=Song |first3=C. |journal=European Journal of Plastic Surgery |volume=17}}</ref> and is one of the most [[toxin|toxic]] of any vipers based on LD50 studies.<ref name="Mal03" /> The {{LD50}} values in mice vary: 0.4–2.0 mg/kg [[Intravenous|IV]], 0.9–3.7 mg/kg [[Peritoneum|IP]], 4.4–7.7 mg/kg [[Subcutaneous|SC]].<ref name="Bro73" /> Mallow et al. (2003) gives a LD<span style="font-size:100%;"><sub>50</sub></span> range of 1.0–7.75 mg/kg SC. Venom yield is typically between 100–350 mg, with a maximum of 750 mg.<ref name="Mal03" /> Brown (1973) mentions a venom yield of 180–750 mg.<ref name="Bro73" /> About 100 mg is thought to be enough to kill a healthy adult human male, with death occurring after 25 hours. In humans, bites from this species can produce severe local and systemic symptoms. Based on the degree and type of local effect, bites can be divided into two symptomatic categories: those with little or no surface [[extravasation]], and those with [[hemorrhage]]s evident as [[ecchymosis]], bleeding and swelling. In both cases there is severe pain and tenderness, but in the latter there is widespread superficial or deep [[necrosis]] and [[compartment syndrome]].<ref name="pmid21226389">{{cite journal |pmid=21226389 |url=http://archive.rubicon-foundation.org/9565 |title=Case report: Hyperbaric oxygen in the treatment of puff adder (Bitis arietans) bite |year=2010 |last1=Rainer |first1=PP |last2=Kaufmann |first2=P |last3=Smolle-Juettner |first3=FM |last4=Krejs |first4=GJ |volume=37 |issue=6 |pages=395–8 |journal=Undersea & hyperbaric medicine}}</ref> Serious bites cause limbs to become immovably flexed as a result of significant [[hemorrhage]] or [[coagulation]] in the affected muscles. Residual induration, however, is rare and usually these areas completely resolve.<ref name="Mal03" /> The fatality rate highly depends on the severity of the bites and some other factors. Deaths can be exceptionally rare and probably occur in less than 10% of all untreated cases (usually in 2–4 days from complications following blood volume deficit and a disseminated intravascular [[coagulopathy]]), although some reports show that very severe envenomations have a 52% mortality rate.<ref name="Davidson">{{cite web|url=http://drdavidson.ucsd.edu/Portals/0/snake/Arietans.htm|title=IMMEDIATE FIRST AID|accessdate=2011-09-14|last=Davidson|first=Terence|publisher=University of California, San Diego}}</ref><ref name="USN91">U.S. Navy. 1991. ''Venomous Snakes of the World''. US Govt. New York: Dover Publications Inc. 203 pp. ISBN 0-486-26629-X.{{page needed|date=October 2013}}</ref> Most fatalities are associated with bad clinical management and neglect.<ref name="SB95" /><ref name="Spa04" /> |
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=====Rhinoceros viper===== |
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The [[Rhinoceros viper]] (''Bitis nasicornis'') is a large species of viper that is similar to the [[Gaboon viper]], but not as venomous, smaller and with a less dangerous bite. They are slow moving, but like other ''Bitis'' species, they're capable of striking quickly, forwards or sideways, without coiling first or giving a warning. Holding them by the tail is not safe; as it is somewhat prehensile, they can use it to fling themselves upwards and strike.<ref name="Mal03" /> They have been described as generally placid creatures, not as bad-tempered as the [[Bitis arietans|Puff adder]]. When approached, they often reveal their presence by hissing,<ref name="Mal03" /> said to be the loudest hiss of any African snake—almost a shriek.<ref name="Spa04" /> Relatively little is known about the toxicity and composition of the venom, but it has very minor neurotoxic, as well as hemotoxic venom, as do most other venomous snakes. The hemotoxic venom in rhinoceros vipers is much more dominant. This venom attacks the [[circulatory system]] of the snake's victim, destroying [[Tissue (biology)|tissue]] and [[blood vessel]]s. Internal bleeding also occurs. In mice, the intravenous {{LD50}} is 1.1 mg/kg. The venom is supposedly slightly less toxic than those of the Puff adder and the Gaboon viper. The maximum wet venom yield is 200 mg.<ref name="SB95" /> In only a few detailed reports of human envenomation, massive swelling, which may lead to necrosis, had been described.<ref name="SB95" /> In 2003, a man in [[Dayton, Ohio]], who was keeping a specimen as a pet, was bitten and subsequently died.<ref name="CC03">[http://www.channelcincinnati.com/news/2380861/detail.html Firefighter Dies After Bite From Pet Snake] at [http://www.channelcincinnati.com/index.html channelcincinnati.com]. Accessed 24 October 2013.</ref> At least one antivenom protects specifically against bites from this species: India Antiserum Africa Polyvalent.<ref name="VR">[http://www.venomousreptiles.org/pages/antbnk Miami-Dade Fire Rescue Venom Response Unit] at [http://www.venomousreptiles.org/ VenomousReptiles.org]. Accessed 24 October 2013.</ref> |
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====Australian black snakes==== |
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=====King brown snake or Mulga snake===== |
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The Australian [[Pseudechis australis|King brown snake or Mulga snake]] is a the second longest species of venomous snake in Australia. The venom of this snake is relatively weak compared to many other Australian species. The [[Median lethal dose|LD<sub>50</sub>]] is 2.38 mg/kg [[subcutaneous]].<ref>The Australian venom research unit (August 25, 2007). [http://www.avru.org/compendium/biogs/A000084b.htm "Which snakes are the most venomous?"]. [[University of Melbourne]]. Retrieved October 24, 2013.</ref> However, these snakes can deliver large amounts of venom when they bite, compensating for the lower venom potency. Average venom yield is 180 mg and they have a maximum yield of 600 mg.<ref name="Shea">{{cite journal |doi=10.1111/j.1751-0813.1999.tb12947.x |title=The distribution and identification of dangerously venomous Australian terrestrial snakes |year=1999 |last1=Shea |first1=GM |journal=Australian Veterinary Journal |volume=77 |issue=12 |pages=791–8 |pmid=10685181}}</ref><ref name="Sutherland">{{cite book|last=Sutherland|first=SK|title=Australian Animal Toxins|year=1983|publisher=OUP Australia and New Zealand|isbn=019554367X}}</ref> The venom of this species contains potent [[myotoxin]]s and [[anticoagulant]]s, that can inhibit blood clotting. The neurotoxic components are weak. This snake can cause severe envenomation of humans. They are a moderately common cause of snakebites and uncommonly to rarely cause snakebite deaths in Australia at present. Envenomation can cause anticoagulation coagulopathy, renal damage or renal failure (kidney failure). They do not cause significant neurotoxic paralysis (muscle weakness, respiratory failure), though rarely they may cause ptosis (drooping of the upper eyelids). Bites can also cause myolysis (rhabdomyolysis, muscle damage) which can be very severe and is the major effect of bites.<ref name="mulga">{{cite web|title=Australian Mulga Snakes|url=http://toxinology.com/about/mulga_snake_snakebite.html|work=Clinical Toxinology Resource|publisher=University of Adelaide|accessdate=24 October 2013}}</ref> Rate of envenomation is 40-60%, while untreated mortality rate is 30-40%.<ref name="mulga2">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0521|quote=Mortality rate:30-40%}}</ref> |
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=====Red-bellied black snake===== |
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The [[Red-bellied black snake]] (''Pseudechis porphyriacus'') is a venomous species native to Australia. The venom of the red-bellied black snake consists of myotoxins, coagulants and also has haemolytic and cytotoxic properties. It also contains weak pre-synaptic neurotoxins. The murine {{LD50}} is 2.52 mg/kg [[Subcutis|SC]]. Average venom yield per bite is 37 mg and a maximum yield of 97 mg.<ref name="Shea" /> Bites from red-bellied black snake are rarely life-threatening due to the snake usually choosing to inject little venom toxin, but are still in need of immediate medical attention. Rate of envenomation is 40-60%, but the untreated mortality rate is less than 1%.<ref name="pp">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0525|quote=Mortality rate:<1%}}</ref> |
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====Australian brown snakes==== |
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=====Dugite===== |
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The [[Dugite]] (''Pseudonaja affinis'') is a highly venomous Australian brown snake species. The venom of this species contains highly potent presynaptic and postsynaptic neurotoxins and procoagulants. The murine {{LD50}} is 0.66 mg/kg [[Subcutis|SC]].<ref name="Cheng">{{cite web|last=Cheng|first=David|title=Brown Snake Envenomation|url=http://misc.medscape.com/pi/iphone/medscapeapp/html/A772066-business.html|accessdate=24 October 2013}}</ref> The average venom yield per bite is 18 mg (dry weight of milked venom) according to Meier and White (1995). Rate of envenomation is 20-40% and the untreated mortality rate is 10–20 %by cardiac arrest, renal failure, or cerebral hemorrhage. |
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=====Western Brown snake===== |
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The [[Western brown snake]] (''Pseudonaja nuchalis'') is a highly venomous species of brown snake common throughout northern Australia. Its venom contains powerful [[neurotoxin]]s, [[nephrotoxin]]s and a [[Prothrombin|procoagulant]], although humans are not usually affected by the neurotoxins.<ref name="vensup">{{cite web | author = Venom Supplies Pty Ltd | title = Brown Snakes | url = http://www.venomsupplies.com/brown-snakes/}}</ref> The bite is usually painless and difficult to see due to their small fangs. Human symptoms of a Western Brown snake bite are headache, nausea/vomiting, abdominal pain, severe coagulopathy and sometimes, kidney damage.<ref name="wbs">{{cite web | author = Toxinology Department, Women's & Children's Hospital, Adelaide, Australia | title = CSL Antivenom Handbook - Brown Snake Antivenom | url = http://www.toxinology.com/generic_static_files/cslavh_antivenom_brown.html}}</ref> The {{LD50}} in mice is 0.47 mg/kg and the average venom yield per bite is 18 mg (dry weight of milked venom) according to Meier and White (1995). The western brown snake can cause rapid death in humans by cardiac arrest, renal failure, or cerebral hemorrhage. The envenomation rate is 20-40% and the untreated mortality rate is 10-20%.<ref name="pn">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0532|quote=Mortality rate:10-20%}}</ref> |
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====Rattlesnakes==== |
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Some [[Crotalus|rattlesnake]] species can be quite dangerous to humans. |
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=====Tiger rattlesnake===== |
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The [[Crotalus tigris|Tiger rattlesnake]] (''Crotalus tigris''), although it has a comparatively low [[venom]] yield,<ref>Weinstein and Smith (1990)</ref> its venom toxicity is considered to be the highest of all rattlesnake venoms, and the highest of all snakes in the Western Hemisphere. Although they're reluctant to bite, tiger rattlensakes are known to be cantankerous and they are an aggressive species. This tendency to stand their ground and aggressively defend themselves along with their highly potent venom, they pose a serious threat to humans. It has a high [[neurotoxin|neurotoxic]] fraction that is [[antigen]]ically related to Mojave toxin (see ''[[Crotalus scutulatus]]'', venom A), and includes another component immunologically identical to crotamine, which is a [[myotoxin]] also found in tropical rattlesnakes (see ''[[Crotalus durissus#Venom|Crotalus durissus]]''). A low but significant [[protease]] activity is in the venom, although there does not seem to be any hemolytic activity.<ref name="Nor-C&L04">Norris R. 2004. Venom Poisoning in North American Reptiles. ''In'' Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.{{page needed|date=October 2013}}</ref> Brown (1973) lists an average venom yield of 11 mg (dried venom) and {{LD50|LD<sub>50</sub>}} values of 0.07 mg/kg [[Peritoneum#Intraperitoneal|IP]], 0.056 mg/kg [[intravenous injection|IV]], and 0.21 mg/kg [[subcutaneous|SC]].<ref name="Venom">{{cite journal |doi=10.1021/pr201021d |title=Snake Venomics of Crotalus tigris: The Minimalist Toxin Arsenal of the Deadliest Neartic Rattlesnake Venom. Evolutionary Clues for Generating a Pan-Specific Antivenom against Crotalid Type II Venoms |year=2012 |last1=Calvete |first1=Juan J. |last2=Pérez |first2=Alicia |last3=Lomonte |first3=Bruno |last4=Sánchez |first4=Elda E. |last5=Sanz |first5=Libia |journal=Journal of Proteome Research |volume=11 |issue=2 |pages=1382–90 |pmid=22181673 |pmc=3272105}}</ref> Minton and Weinstein (1984) list an average venom yield of 6.4 mg (based on two specimens). Weinstein and Smith (1990) list a venom yield of 10 mg.<ref name="ctigris">{{cite web|title= University of Adelaide Clinical Toxinology Resources|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0471}}</ref> There is very little information available for bite symptoms. Human bites by the tiger rattlesnake are infrequent, and literature available on bites by this snake is scarce. The several recorded human envenomations by tiger rattlesnakes produced little local pain, swelling, or other reaction following the bite, and despite the toxicity of its venom no significant systemic symptoms. The comparatively low venom yield (6.4–11 mg dried venom) and short {{convert|4.0|mm|cm|abbr=on}} to {{convert|4.6|mm|cm|abbr=on}} fangs of the tiger rattlesnake possibly prevent severe envenoming in adult humans. However, the clinical picture could be much more serious if the person bitten was a child or an individual with a slight build. The early therapeutic use of [[antivenom]] is important if significant envenomation is suspected. Despite the low venom yield, a bite by this rattlesnake should be considered a life-threatening medical emergency. Untreated mortality rate is unknown but this snake has a very high venom toxicity and its bites are capable of producing major envenomation.<ref name="Nor-C&L04" /><ref name="ctigris" /> |
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=====Cascabel===== |
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The [[Crotalus durissus|Neotropical rattlesnake or Cascabel]] (''Crotalus durissus'') is a medically important species due to its venom toxicity and the human fatalities it is responsible for. The [[Peritoneum#Intraperitoneal|IP]] {{LD50}} value is 0.17 mg/kg with an average venom yield between between 20–100 mg/kg per bite. Bite symptoms are very different from those of [[Nearctic]] species<ref name="Kla97">{{cite book| author = Laurence Monroe Klauber| title = Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind |edition=2nd | year = 1997| publisher = University of California Press| isbn = 978-0-520-21056-1 }}{{page needed|date=October 2013}}</ref> due to the presence of [[neurotoxin]]s (crotoxin and [[crotamine]]) that cause progressive paralysis.<ref name="War-C&L04" /> Bites from ''C. d. terrificus'' in particular can result in impaired vision or complete blindness, auditory disorders, [[Ptosis (eyelid)|ptosis]], paralysis of the peripheral muscles, especially of the neck, which becomes so limp as to appear broken, and eventually life-threatening respiratory paralysis. The ocular disturbances, which according to Alvaro (1939) occur in some 60% of ''C. d. terrificus'' cases, are sometimes followed by permanent blindness.<ref name="Kla97" /> Phospholipase A<span style="font-size:100%;"><sub>2</sub></span> neurotoxins also cause damage to skeletal muscles and possibly the heart, causing general aches, pain, and tenderness throughout the body. [[Myoglobin]] released into the blood results in dark urine. Other serious complications may result from systemic disorders (incoagulable blood and general spontaneous bleeding), hypotension, and shock.<ref name="War-C&L04" /> Hemorrhagins may be present in the venom, but any corresponding effects are completely overshadowed by the startling and serious neurotoxic symptoms.<ref name="Kla97" /> [[Subcutaneous]] venom {{LD50}} for this species is 0.193 mg/kg.<ref name="Lima">{{cite journal |doi=10.1016/0041-0101(91)90070-8 |title=Susceptibility of different strains of mice to South American rattlesnake (Crotalus durissus terrificus) venom: Correlation between lethal effect and creatine kinase release |year=1991 |last1=d'Império Lima |first1=Maria Regina |last2=Dos Santos |first2=Maria |last3=Tambourgi |first3=Denise Vilarinho |last4=Marques |first4=Thaís |last5=Da Silva |first5=Wilmar |last6=Kipnis |first6=Thereza |journal=Toxicon |volume=29 |issue=6 |pages=783–6 |pmid=1926179}}</ref> The neotropical rattlesnake in Brazil is of special importance because of the high incidence of envenoming and mortality rates. Clinically, venom of this snake does not usually cause local effects at the bite site and is usually painless. However, the etiology progresses to systemic neurotoxic and myalgic symptoms, with frequent renal failure accompanied by acute tubular necrosis.<ref name="furtado">{{cite journal |doi=10.1590/S1678-91992003000200005 |title=Age-related biological activity of South American rattlesnake (Crotalus durissus terrificus) venom |year=2003 |last1=Furtado |first1=M. F. D. |last2=Santos |first2=M. C. |last3=Kamiguti |first3=A. S. |journal=Journal of Venomous Animals and Toxins including Tropical Diseases |volume=9 |issue=2 |pages=186}}</ref> The huge area of distribution, potent venom in fairly large quantities and a definite willingness to defend themselves are important factors in their dangerousness. In Brazil and probably also in other countries in their area of distribution, this species is probably the most dangerous rattlesnake. After the fer-de-lance (''Bothrops asper''), it is the most common cause of snake envenoming. In the first half of the 20th century as well as in the 1950s and 1960s, 12% of treated cases ended fatally. Untreated cases apparently had a mortality rate of 72% in the same period, but this was due to the fact that there was no antivenom, poor medical care and neglect (Rosenfeld, 1971). In more recent times, an average of 20,000 snakebites are registered each year in Brazil, almost 10% of them caused by the neotropical rattlesnake. The mortality rate is estimated at 3.3% and is thus much lower than in the past (Ribeiro, 1990b). A study from southeastern Brazil documented only one fatality from 87 treated cases (Silveira and Nishioka, 1992).<ref name="C.durissus">{{cite web|title=Venomous and Poisonous Animals Biology & Clinical Management|url=https://www.vapaguide.info/catalogue/TER-PIT-61|work=VAPAGuide|publisher=Biomedical database|accessdate=25 October 2013}}</ref> |
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=====Mojave rattlesnake===== |
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The [[Mojave rattlesnake]] (''Crotalus scutulatus'') is another species which is considered to be dangerous. Although they have a reputation for being aggressive towards people, such behavior is not described in the scientific literature. Like other rattlesnakes, they will defend themselves vigorously when disturbed. The [[Peritoneum#Intraperitoneal|IP]] {{LD50}} value is 0.18 mg/kg with an average venom yield between between 50–150 mg/kg per bite. The most common subspecies of Mohave rattlesnake (type A) has venom that is considered to be one of the most debilitating and potentially deadly of all North American snakes, although chances for survival are very good if medical attention is sought as soon as possible after a bite.<ref name="cbsnews">"Mojave Green snake bites 6-year-old California boy, 42 vials of antivenom needed", Jaslow, Ryan, CBS News, 10 July 2012, http://www.cbsnews.com/8301-504763_162-57469802-10391704/mojave-green-snake-bites-6-year-old-california-boy-42-vials-of-antivenom-needed/</ref> Based on median LD<sub>50</sub> values in lab mice, venom A from subspecies A Mojave rattlesnakes is more than ten times as toxic as venom B, from type B Mohave green rattlesnakes which lacks Mojave toxin.<ref>Hendon, R.A., A.L. Bieber. 1982. Presynaptic toxins from rattlesnake venoms. In: Tu, A. (ed) ''Rattlesnake Venoms, Their Actions and Treatment''. New York: Marcel Dekker, Inc.{{page needed|date=October 2013}}</ref> Medical treatment as soon as possible after a bite is critical to a positive outcome, dramatically increasing chances for survival.<ref name="cbsnews" /> However, venom B causes pronounced [[Proteolysis|proteolytic]] and [[Bleeding|hemorrhagic]] effects, similar to the bites of other rattlesnake species; these effects are significantly reduced or absent from bites by venom A snakes.<ref name="Norris">Norris RA. 2004. Venom poisoning by North American reptiles. ''In'' Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.{{page needed|date=October 2013}}</ref> Risk to life and limb is still significant, as with all rattlesnakes, if not treated as soon as possible after a bite. All rattlesnake venoms are complex cocktails of enzymes and other proteins that vary greatly in composition and effects, not only between species, but also between geographic populations within the same species. The Mojave rattlesnake is widely regarded as producing one of the most toxic snake venoms in the New World, based on {{LD50}} studies in laboratory mice.<ref name="Glenn1">Glenn, J.L., R.C.Straight. 1982. The rattlesnakes and their venom yield and lethal toxicity. In: Tu, A. (ed) ''Rattlesnake Venoms, Their Actions and Treatment''. New York: Marcel Dekker, Inc.{{page needed|date=October 2013}}</ref> Their potent venom is the result of a [[Chemical synapse|presynaptic]] [[neurotoxin]] composed of two distinct [[peptide]] subunits.<ref name="Aird">{{cite journal |doi=10.1021/bi00346a005 |title=Rattlesnake presynaptic neurotoxins: Primary structure and evolutionary origin of the acidic subunit |year=1985 |last1=Aird |first1=Steven D. |last2=Kaiser |first2=Ivan I. |last3=Lewis |first3=Randolph V. |last4=Kruggel |first4=William G. |journal=Biochemistry |volume=24 |issue=25 |pages=7054–8 |pmid=4084559}}</ref> The basic subunit (a [[Phospholipase|phospholipase A<sub>2</sub>]]) is mildly toxic and apparently rather common in North American rattlesnake venoms.<ref name="Powell">Powell, R.L. 2003. ''Evolutionary Genetics of Mojave Toxin Among Selected Rattlesnake Species (Squamata: Crotalinae)''. Unpublished PhD dissertation. El Paso: University of Texas.{{page needed|date=October 2013}}</ref> The less common acidic subunit is not toxic by itself, but in combination with the basic subunit, produces the potent neurotoxin called "Mojave toxin". Nearly identical neurotoxins have been discovered in five North American rattlesnake species besides the Mojave rattlesnake.<ref name="Powell" /> However, not all populations express both subunits. The venom of many Mojave rattlesnakes from south-central Arizona lacks the acidic subunit and has been designated "venom B," while Mojave rattlesnakes tested from all other areas express both subunits and have been designated "venom A" populations.<ref name="Glenn2">{{cite journal |doi=10.1016/0041-0101(83)90055-7 |title=Geographical variation in Crotalus scutulatus scutulatus (Mojave rattlesnake) venom properties |year=1983 |last1=Glenn |first1=James L. |last2=Straight |first2=Richard C. |last3=Wolfe |first3=Martha C. |last4=Hardy |first4=David L. |journal=Toxicon |volume=21 |pages=119–30 |pmid=6342208 |issue=1}}</ref> |
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====Pit vipers==== |
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=====Malayan pit viper===== |
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The [[Malayan pit viper]] (''Calloselasma rhodostoma'') is an Asian species of pitviper that is reputed to be an ill-tempered snake that is quick to strike in defense. This species is one of the main causes of snakebite envenoming in Southeast Asia. However, mortality rate among untreated bite victims is very low (1-10%).<ref name="cr">{{cite web|title=Calloselasma rhodostoma|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&mode=PrintFriendly&id=SN0080|work=Clinical Toxinology Resource|publisher=University of Adelaide|accessdate=3 November 2013}}</ref> Although bites are common, death is very rare. When a victim dies of a bite it is chiefly caused by haemorrhages and secondary infections.<ref name="Warrell86" /> Before specific antivenom became available, the mortality rate in hospitalised patients was around 1% (Reid et al. 1963a). In the study of Reid et al. (1963a), of a total of 291 patients with verified ''C. rhodostoma'' bites, only 2 patients died, and their deaths could only be indirectly attributed to the snakebites. One patient died of [[tetanus]] and one from a combination of an anaphylactic reaction to the antivenom, an intracerebral haemorrhage and severe pre-existing anaemia. In 23 fatalities due to ''C. rhodostoma'' bites recorded in northern Malaysia between 1955 and 1960, the average time between the bite and death was 64.6 h (5–240 h), the median time 32 h (Reid et al. 1963a). According to a study of fatal snakebites in rural areas of Thailand, 13 out of 46 were caused by ''C. rhodostoma'' (Looareesuwan et al. 1988). The local necrotising effect of the venom is a common cause of morbidity. [[Gangrene]] can lead to the loss of toes, fingers or whole extremities; chronic infections ([[osteomyelitis]]) can also occur.<ref name="Warrell86">{{cite book|last=Warrell|first=DA|title=Natural toxins : animal, plant, and microbial|year=1986|publisher=Clarendon Press; Oxford University Press|isbn=0198541732|pages=25–45}}</ref> The intravenous {{LD50}} for Malayan pit viper venom is 6.1 mg/g mouse<ref name="Tan" /> and the average venom yield per bite is 40–60 mg (dry weight).<ref name="cr" /> |
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=====Sharp-nosed pit viper===== |
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The [[Deinagkistrodon acutus|Sharp-nosed pit viper or hundred pacer]] (''Deinagkistrodon acutus'') is another Asian species of pitviper that is medically important. This species is considered dangerous, and fatalities are not unusual. According to the U.S. Armed Forces Pest Management Board, the venom is a potent [[hemotoxin]] that is strongly hemorrhagic. Bite symptoms include severe local pain and bleeding that may begin almost immediately. This is followed by considerable swelling, blistering, necrosis, and ulceration.<ref name="afpmb">{{cite web|title=Deinagkistrodon acutus|url=http://www.afpmb.org/content/venomous-animals-d#Deinagkistrodonacutus|work=Armed Forces Pest Management Board|publisher=United States Army|accessdate=3 November 2013}}</ref> Brown (1973) mentions a venom yield of up to 214 mg (dried) and {{LD50}} values of 0.04 mg/kg [[Intravenous|IV]], 4.0 mg/kg [[Peritoneum|IP]] and 9.2-10.0 mg/kg [[Subcutaneous|SC]].<ref name="Bro73" /> The envenomation rate is up to 80% and the untreated mortality rate is very low (1-10%).<ref name="da">{{cite web|title=Deinagkistrodon acutus|url=http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0081|work=Clinical Toxinology Resource|publisher=University of Adelaide|accessdate=3 November 2013}}</ref> Antivenom is produced in China and Taiwan.<ref name="Meh87">Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. ISBN 0-8069-6460-X.</ref> |
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== Society and culture == |
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{{See also|Serpent (symbolism)}} |
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[[File:Benczur-kleopatra.jpg|thumb|right|According to tradition, [[Cleopatra VII]] famously committed suicide by snakebite to her left breast, as seen in this 1911 painting by Hungarian artist [[Gyula Benczúr]].]] |
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Snakes were both [[Snake worship|revered and worshipped]] and [[Ophidiophobia|feared]] by early civilizations. The [[ancient Egyptians]] recorded prescribed treatments for snakebites as early as the [[Thirteenth dynasty of Egypt|Thirteenth dynasty]] in the [[Brooklyn Papyrus]], which includes at least seven venomous species common to the region today, such as the [[Cerastes (genus)|horned viper]]s.<ref name="Schneemann2004">{{Cite journal |last=Schneemann |first=M. |coauthors=R. Cathomas, S.T. Laidlaw, A.M. El Nahas, R.D.G. Theakston, and D.A. Warrell |year=2004 |title=Life-threatening envenoming by the Saharan horned viper (Cerastes cerastes) causing micro-angiopathic haemolysis, coagulopathy and acute renal failure: clinical cases and review |journal=QJM: an International Journal of Medicine |pmid=15496528 |volume=97 |issue=11 |pages=717–27 |doi=10.1093/qjmed/hch118 |url=http://qjmed.oxfordjournals.org/cgi/reprint/97/11/717.pdf |accessdate=2009-09-04 |quote=This echoed the opinion of the Egyptian physicians who wrote the earliest known account of the treatment of snake bite, the Brooklyn Museum Papyri, dating perhaps from 2200 BC. They regarded bites by horned vipers 'fy' as non-lethal, as the victims could be saved.}}</ref> In [[Judaism]], the [[Nehushtan]] was a pole with a snake made of copper wrapped around it, similar in appearance to the [[Rod of Asclepius]]. The object was considered sacred with the power to heal bites caused by the snakes which had infested the desert, with people merely having to touch it in order to save themselves from imminent death. |
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Historically, snakebites were seen as a means of execution in some cultures. In [[Middle Ages|medieval Europe]], a form of capital punishment was to throw people into [[snake pit]]s, leaving people to die from multiple venomous bites. A similar form of punishment was common in [[Southern Han]] during [[China]]'s [[Five Dynasties and Ten Kingdoms period]] and in [[India]].<ref name="Anil2004" /> Snakebites were also used as a form of suicide, most notably by Egyptian queen [[Cleopatra VII]], who reportedly died from the bite of an [[Asp (reptile)|asp]]—likely an [[Egyptian cobra]]<ref name="Schneemann2004" /><ref name="Smithsonian">{{cite web |last=Crawford |first=Amy |title=Who Was Cleopatra? Mythology, propaganda, Liz Taylor and the real Queen of the Nile |url=http://www.smithsonianmag.com/history-archaeology/biography/cleopatra.html |date=April 1, 2007 |publisher=Smithsonian.com |accessdate=4 September 2009}}</ref>—after hearing of [[Mark Antony]]'s death. |
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Snakebite as a surreptitious form of murder has been featured in stories such as Sir [[Arthur Conan Doyle]]'s ''[[The Adventure of the Speckled Band]]'', but actual occurrences are virtually unheard of, with only a few documented cases.<ref name="Anil2004">{{Cite journal |last=Anil |first=Aggrawal |year=2004 |title=Homicide with snakes: A distinct possibility and its medicolegal ramifications |journal=Anil Aggrawal's Internet Journal of Forensic Medicine and Toxicology |volume=4 |issue=2 |url=http://web.archive.org/web/20070718031431/http://www.geradts.com/anil/ij/vol_004_no_002/others/pg001.html}}</ref><ref name="Warrell2009">{{Cite journal |last=Warrell |first=D.A. |year=2009 |title=Commissioned article: management of exotic snakebites |journal=QJM: an International Journal of Medicine |volume=102 |issue=9 |pages=593–601|pmid=19535618 |doi=10.1093/qjmed/hcp075}}</ref><ref name="Straight1994">{{Cite journal |last=Straight |first=Richard C. |coauthors=James L. Glenn |year=1994 |title=Human fatalities caused by venomous animals in Utah, 1900–90 |journal=Great Basin Naturalist |volume=53 |issue=4 |pages=390–4 |url=https://ojs.lib.byu.edu/ojs/index.php/wnan/article/viewFile/545/1430 |accessdate=2009-09-04 |quote=A third unusual death was a tragic fatality (1987), recorded as a homicide, which resulted when a large rattlesnake (G. v. lutosus) bit a 22-month-old girl after the snake had been placed around her neck (Washington County). The child died in approximately 5 h.}}</ref> It has been suggested that [[Boris III of Bulgaria]], who was allied to [[Nazi Germany]] during [[World War II]], may have been killed with snake venom,<ref name="Anil2004" /> although there is no definitive evidence. At least one attempted suicide by snakebite has been documented in medical literature involving a [[Bitis arietans|puff adder]] bite to the hand.<ref name="Strubel2008">{{Cite journal |last=Strubel |first=T. |coauthors=A. Birkhofer, F. Eyer, K.D. Werber, H. Förstl |year=2008 |title=Suizidversuch durch Schlangenbiss: Kasuistik und Literaturübersicht |trans_title=Attempted suicide by snake bite: Case report and literature survey |journal=Der Nervenarzt |volume=79 |issue=5 |pages=604–6 |doi=10.1007/s00115-008-2431-4 |language=German |quote=Ein etwa 20-jähriger Arbeiter wurde nach dem Biss seiner Puffotter (Bitis arietans) in die Hand auf die toxikologische Intensivstation aufgenommen. Zunächst berichtet der Patient, dass es beim „Melken“ der Giftschlange zu dem Biss gekommen sei, erst im weiteren Verlauf räumt er einen Suizidversuch ein. Als Gründe werden Einsamkeit angeführt sowie unerträgliche Schmerzen im Penis. |pmid=18365165}}</ref> |
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{{-}} |
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== References == |
== References == |
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{{Reflist |
{{Reflist}} |
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;Bibliography |
;Bibliography |
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{{Refbegin}} |
{{Refbegin}} |
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* {{cite book |title=Snakes: The Evolution of Mystery in Nature | |
* {{cite book |title=Snakes: The Evolution of Mystery in Nature | vauthors = Greene HW |author-link=Harry W. Greene |year=1997 |publisher=University of California Press |location=Berkeley, CA |isbn=978-0-520-20014-2 |url=https://archive.org/details/snakesevolutiono00fogd}} |
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* {{cite book |title=Handbook of Venoms and Toxins of Reptiles | |
* {{cite book |title=Handbook of Venoms and Toxins of Reptiles | veditors = Mackessy SP |year=2010 |publisher=CRC Press |location=Boca Raton, FL |isbn=978-0-8493-9165-1 |edition=2nd}} |
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* {{cite book |title=Venomous Snakes: Envenoming, Therapy | |
* {{cite book |title=Venomous Snakes: Envenoming, Therapy | vauthors = Valenta J |year=2010 |publisher=Nova Science Publishers |location=Hauppauge, NY |isbn=978-1-60876-618-5 |edition=2nd}} |
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{{Refend}} |
{{Refend}} |
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== Further reading == |
== Further reading == |
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{{Library resources box|onlinebooks=yes}} |
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{{Refbegin|30em}} |
{{Refbegin|30em}} |
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* Campbell, Jonathan A. |
* {{cite book | vauthors = Campbell JA, Lamar WW | author-link1 = Jonathan A. Campbell | date = 2004 | title = The Venomous Reptiles of the Western Hemisphere | location = Ithaca, NY | publisher = Cornell University Press 978-0-8014-4141-7}} |
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* Spawls, |
* {{cite book | vauthors = Spawls S, Branch B | date = 1995 | title = The Dangerous Snakes of Africa: Natural History, Species Directory, Venoms and Snakebite | location = Sanibel Island, FL | publisher = Ralph Curtis Publishing | isbn = 978-0-88359-029-4}} |
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* Sullivan JB, Wingert WA, Norris Jr RL |
* {{cite journal | vauthors = Sullivan JB, Wingert WA, Norris Jr RL | date = 1995 | title = North American Venomous Reptile Bites. | journal = Wilderness Medicine: Management of Wilderness and Environmental Emergencies | volume = 3 | pages = 680–709}} |
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* Thorpe, |
* {{cite book | vauthors = Thorpe RS, Wüster W, Malhotra A | author-link2 = Wolfgang Wüster | title = Venomous Snakes: Ecology, Evolution, and Snakebite | date = 14 May 1997 | location = Oxford, England | publisher = [[Oxford University Press]] | isbn = 978-0-19-854986-4}} |
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{{Refend}} |
{{Refend}} |
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== External links == |
== External links == |
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* [http://apps.who.int/bloodproducts/snakeantivenoms/database/ WHO Snake Antivenoms Database] |
* [https://web.archive.org/web/20100506022208/http://apps.who.int/bloodproducts/snakeantivenoms/database/ WHO Snake Antivenoms Database] |
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* {{cite book |last1=Organization |title=Guidelines for the management of snakebites |date=2016 |publisher=Regional Office for South-East Asia, World Health Organization |isbn=978-92-9022-530-0 |language=en|hdl=10665/249547}} |
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{{Medical resources |
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| DiseasesDB = 29733 |
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| ICD10 = {{ICD10|T|63|0|t|51}}, T14.1, W59 (nonvenomous), X20 (venomous) |
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| ICD9 = {{ICD9|989.5}}, {{ICD9|E905.0}}, {{ICD9|E906.2}} |
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| ICDO = |
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| OMIM = |
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| MedlinePlus = 000031 |
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| eMedicineSubj = med |
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| eMedicineTopic = 2143 |
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| MeshID = D012909 |
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| Scholia = Q68854 |
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}} |
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{{General injuries}} |
{{General injuries}} |
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{{Poisoning and toxicity}} |
{{Poisoning and toxicity}} |
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{{Animal bites and stings}} |
{{Animal bites and stings}} |
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{{Reptiles in culture}} |
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{{Authority control}} |
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[[Category:Animal |
[[Category:Animal bites]] |
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[[Category:Snake attacks]] |
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[[Category:Medical emergencies]] |
[[Category:Medical emergencies]] |
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[[Category:Parasitic infestations, stings, and bites of the skin]] |
[[Category:Parasitic infestations, stings, and bites of the skin]] |
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[[Category:Venomous snakes]] |
[[Category:Venomous snakes]] |
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[[Category:Wilderness medical emergencies]] |
[[Category:Wilderness medical emergencies]] |
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[[Category:Tropical diseases]] |
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[[Category:Wikipedia medicine articles ready to translate]] |
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{{Link FA|as}} |
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[[Category:Wikipedia emergency medicine articles ready to translate]] |
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{{Link FA|sl}} |
Latest revision as of 06:15, 9 January 2025
Snakebite | |
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A cobra bite on the foot of a girl in Thailand | |
Specialty | Emergency medicine |
Symptoms | Two puncture wounds, redness, swelling, severe pain at the area[1][2] |
Complications | Bleeding, kidney failure, severe allergic reaction, tissue death around the bite, breathing problems, amputation, envenomation[1][3] |
Causes | Snakes[1] |
Risk factors | Working outside with one's hands (farming, forestry, construction);[1][3] harassment;[4][5] drunkenness[6] |
Prevention | Protective footwear, avoiding areas where snakes live, not handling snakes[1] |
Treatment | Washing the wound with soap and water, antivenom[1][7] |
Prognosis | Depends on type of snake[8] |
Frequency | Up to 5 million a year[3] |
Deaths | 94,000–125,000 per year[3] |
A snakebite is an injury caused by the bite of a snake, especially a venomous snake.[9] A common sign of a bite from a venomous snake is the presence of two puncture wounds from the animal's fangs.[1] Sometimes venom injection from the bite may occur.[3] This may result in redness, swelling, and severe pain at the area, which may take up to an hour to appear.[1][2] Vomiting, blurred vision, tingling of the limbs, and sweating may result.[1][2] Most bites are on the hands, arms, or legs.[2][10] Fear following a bite is common with symptoms of a racing heart and feeling faint.[2] The venom may cause bleeding, kidney failure, a severe allergic reaction, tissue death around the bite, or breathing problems.[1][3] Bites may result in the loss of a limb or other chronic problems or even death.[11][3]
The outcome depends on the type of snake, the area of the body bitten, the amount of snake venom injected, the general health of the person bitten, and whether or not anti-venom serum has been administered by a doctor in a timely manner.[11][8] Problems are often more severe in children than adults, due to their smaller size.[3][12][13] Allergic reactions to snake venom can further complicate outcomes and can include anaphylaxis, requiring additional treatment and in some cases resulting in death.[11]
Snakes bite both as a method of hunting and as a means of protection.[14] Risk factors for bites include working outside with one's hands such as in farming, forestry, and construction.[1][3] Snakes commonly involved in envenomations include elapids (such as kraits, cobras and mambas), vipers, and sea snakes.[7] The majority of snake species do not have venom and kill their prey by constriction (squeezing them).[2] Venomous snakes can be found on every continent except Antarctica.[14] Determining the type of snake that caused a bite is often not possible.[7] The World Health Organization says snakebites are a "neglected public health issue in many tropical and subtropical countries",[13] and in 2017, the WHO categorized snakebite envenomation as a Neglected Tropical Disease (Category A). The WHO also estimates that between 4.5 and 5.4 million people are bitten each year, and of those figures, 40–50% develop some kind of clinical illness as a result.[15] Furthermore, the death toll from such an injury could range between 80,000 and 130,000 people per year.[16][15] The purpose was to encourage research, expand the accessibility of antivenoms, and improve snakebite management in "developing countries".[17]
Prevention of snake bites can involve wearing protective footwear, avoiding areas where snakes live, and not handling snakes.[1] Treatment partly depends on the type of snake.[1] Washing the wound with soap and water and holding the limb still is recommended.[1][7] Trying to suck out the venom, cutting the wound with a knife, or using a tourniquet is not recommended.[1] Antivenom is effective at preventing death from bites; however, antivenoms frequently have side effects.[3][18] The type of antivenom needed depends on the type of snake involved.[7] When the type of snake is unknown, antivenom is often given based on the types known to be in the area.[7] In some areas of the world, getting the right type of antivenom is difficult and this partly contributes to why they sometimes do not work.[3] An additional issue is the cost of these medications.[3] Antivenom has little effect on the area around the bite itself.[7] Supporting the person's breathing is sometimes also required.[7]
The number of venomous snakebites that occur each year may be as high as five million.[3] They result in about 2.5 million envenomations and 20,000 to 125,000 deaths.[3][14] The frequency and severity of bites vary greatly among different parts of the world.[14] They occur most commonly in Africa, Asia, and Latin America,[3] with rural areas more greatly affected.[3][13] Deaths are relatively rare in Australia, Europe and North America.[14][18][19] For example, in the United States, about seven to eight thousand people per year are bitten by venomous snakes (about one in 40 thousand people) and about five people die (about one death per 65 million people).[1]
Signs and symptoms
[edit]The most common first symptom of all snakebites is an overwhelming fear, which may contribute to other symptoms, and may include nausea and vomiting, diarrhea, vertigo, fainting, tachycardia, and cold, clammy skin.[2][23] Snake bites can have a variety of different signs and symptoms depending on their species.[11]
Dry snakebites and those inflicted by a non-venomous species may still cause severe injury. The bite may become infected from the snake's saliva. The fangs sometimes harbor pathogenic microbial organisms, including Clostridium tetani, and may require an updated tetanus immunization.[24][15]
Most snakebites, from either a venomous or a non-venomous snake, will have some type of local effect.[25] Minor pain and redness occur in over 90 percent of cases, although this varies depending on the site.[2] Bites by vipers and some cobras may be extremely painful, with the local tissue sometimes becoming tender and severely swollen within five minutes.[18] This area may also bleed and blister and may lead to tissue necrosis. Other common initial symptoms of pit viper and viper bites include lethargy, bleeding, weakness, nausea, and vomiting.[2][18] Symptoms may become more life-threatening over time, developing into hypotension, tachypnea, severe tachycardia, severe internal bleeding, altered sensorium, kidney failure, and respiratory failure.[2][18]
Bites by some snakes, such as the kraits, coral snake, Mojave rattlesnake, and the speckled rattlesnake, may cause little or no pain, despite their serious and potentially life-threatening venom.[2] Some people report experiencing a "rubbery", "minty", or "metallic" taste after being bitten by certain species of rattlesnake.[2] Spitting cobras and rinkhalses can spit venom in a person's eyes. This results in immediate pain, ophthalmoparesis, and sometimes blindness.[26][27]
Some Australian elapids and most viper envenomations will cause coagulopathy, sometimes so severe that a person may bleed spontaneously from the mouth, nose, and even old, seemingly healed wounds.[18] Internal organs may bleed, including the brain and intestines,[29] and ecchymosis (bruising) of the skin is often seen.[30]
The venom of elapids, including sea snakes, kraits, cobras, king cobra, mambas, and many Australian species, contains toxins which attack the nervous system, causing neurotoxicity.[2][18][31] The person may present with strange disturbances to their vision, including blurriness. Paresthesia throughout the body, as well as difficulty in speaking and breathing, may be reported.[2] Nervous system problems will cause a huge array of symptoms, and those provided here are not exhaustive. If not treated immediately they may die from respiratory failure.[32]
Venom emitted from some types of cobras, almost all vipers, and some sea snakes cause necrosis of muscle tissue.[18] Muscle tissue will begin to die throughout the body, a condition known as rhabdomyolysis. Rhabdomyolysis can result in damage to the kidneys as a result of myoglobin accumulation in the renal tubules. This, coupled with hypotension, can lead to acute kidney injury, and, if left untreated, eventually death.[18]
Snakebite is also known to cause depression and post-traumatic stress disorder in a high proportion of people who survive.[33]
Cause
[edit]In the developing world most snakebites occur in those who work outside such as farmers, hunters, and fishermen. They often happen when a person steps on the snake or approaches it too closely. In the United States and Europe snakebites most commonly occur in those who keep them as pets.[34]
The type of snake that most often delivers serious bites depends on the region of the world. In Africa, it is mambas, Egyptian cobras, puff adders, and carpet vipers. In the Middle East, it is carpet vipers and elapids. In Latin America, it is snakes of the Bothrops and Crotalus types, the latter including rattlesnakes.[34] In North America, rattlesnakes are the primary concern, and up to 95% of all snakebite-related deaths in the United States are attributed to the western and eastern diamondback rattlesnakes.[2] The greatest number of bites are inflicted on the hands.[citation needed] People get bitten by handling snakes or in the outdoors by putting their hands on the wrong places. The next largest number of bites occur on the ankles, as snakes are often hidden or camouflaged extremely well to fend off predators. Most bite victims are bitten by surprise, and it is a comfortable fiction that rattlesnakes always forewarn their bite victims - often the bite is the first indication a snake is near. Since most venomous snakes move about during the dawn dusk or night, one may expect more encounters during the early morning or late afternoon, though many species such as the Western Diamondback may be encountered at any time of day and in fact most bites occur during the month of April when both snakes and humans are out and about and encounter one another hiking, in yards, or on pathways. Children playing within short distances of their homes crawl under porches, jump into bushes, pull boards of wood from a pile and are bitten. Most however occur when people handle rattlesnakes.[35] In South Asia, it was previously believed that Indian cobras, common kraits, Russell's viper, and carpet vipers were the most dangerous; other snakes, however, may also cause significant problems in this area of the world.[34]
Pathophysiology
[edit]Since envenomation is completely voluntary, all venomous snakes are capable of biting without injecting venom into a person. Snakes may deliver such a "dry bite" rather than waste their venom on a creature too large for them to eat, a behaviour called venom metering.[36] However, the percentage of dry bites varies among species: 80 percent of bites inflicted by sea snakes, which are normally timid, do not result in envenomation,[31] whereas for pit viper bites the number is closer to 25 percent.[2] Furthermore, some snake genera, such as rattlesnakes, can internally regulate the amount of venom they inject.[37] There is a wide variance in the composition of venoms from one species of venomous snake to another. Some venoms may have their greatest effect on a victim's respiration or circulatory system. Others may damage or destroy tissues. This variance has imparted to the venom of each species a distinct chemistry. Sometimes antivenins have to be developed for individual species. For this reason, standard therapeutic measures will not work in all cases.
Some dry bites may also be the result of imprecise timing on the snake's part, as venom may be prematurely released before the fangs have penetrated the person.[36] Even without venom, some snakes, particularly large constrictors such as those belonging to the Boidae and Pythonidae families, can deliver damaging bites; large specimens often cause severe lacerations, or the snake itself pulls away, causing the flesh to be torn by the needle-sharp recurved teeth embedded in the person. While not as life-threatening as a bite from a venomous species, the bite can be at least temporarily debilitating and could lead to dangerous infections if improperly dealt with.[citation needed]
While most snakes must open their mouths before biting, African and Middle Eastern snakes belonging to the family Atractaspididae can fold their fangs to the side of their head without opening their mouth and jab a person.[38]
Snake venom
[edit]It has been suggested that snakes evolved the mechanisms necessary for venom formation and delivery sometime during the Miocene epoch.[39] During the mid-Tertiary, most snakes were large ambush predators belonging to the superfamily Henophidia, which use constriction to kill their prey. As open grasslands replaced forested areas in parts of the world, some snake families evolved to become smaller and thus more agile. However, subduing and killing prey became more difficult for the smaller snakes, leading to the evolution of snake venom. The most likely hypothesis holds that venom glands evolved from specialized salivary glands. The venom itself evolved through the process of natural selection; it retained and emphasized the qualities that made it useful in killing or subduing prey. Today we can find various snake species in stages of this hypothesized development. There are the highly efficient envenoming machines - like the rattlesnakes - with large capacity venom storage, hollow fangs that swing into position immediately before the snake bites, and spare fangs ready to replace those damaged or lost.[40][39] Other research on Toxicofera, a hypothetical clade thought to be ancestral to most living reptiles, suggests an earlier time frame for the evolution of snake venom, possibly to the order of tens of millions of years, during the Late Cretaceous.[41]
Snake venom is produced in modified parotid glands normally responsible for secreting saliva. It is stored in structures called alveoli behind the animal's eyes and ejected voluntarily through its hollow tubular fangs.[citation needed]
Venom in many snakes, such as pit vipers, affects virtually every organ system in the human body and can be a combination of many toxins, including cytotoxins, hemotoxins, neurotoxins, and myotoxins, allowing for an enormous variety of symptoms.[2][42] Snake venom may cause cytotoxicity as various enzymes including hyaluronidases, collagenases, proteinases and phospholipases lead to breakdown (dermonecrosis) and injury of local tissue and inflammation which leads to pain, edema and blister formation.[43] Metalloproteinases further lead to breakdown of the extracellular matrix (releasing inflammatory mediators) and cause microvascular damage, leading to hemorrhage, skeletal muscle damage (necrosis), blistering and further dermonecrosis.[43] The metalloproteinase release of the inflammatory mediators leads to pain, swelling, and white blood cell (leukocyte) infiltration. The lymphatic system may be damaged by the various enzymes contained in the venom leading to edema; or the lymphatic system may also allow the venom to be carried systemically.[43] Snake venom may cause muscle damage or myotoxicity via the enzyme phospholipase A2 which disrupts the plasma membrane of muscle cells. This damage to muscle cells may cause rhabdomyolysis, respiratory muscle compromise, or both.[43] Other enzymes such as bradykinin potentiating peptides, natriuretic peptides, vascular endothelial growth factors, proteases can also cause hypotension or low blood pressure.[43] Toxins in snake venom can also cause kidney damage (nephrotoxicity) via the same inflammatory cytokines. The toxins cause direct damage to the glomeruli in the kidneys as well as causing protein deposits in Bowman's capsule. Or the kidneys may be indirectly damaged by envenomation due to shock, clearance of toxic substances such as immune complexes, blood degradation products, or products of muscle breakdown (rhabdomyolysis).[43]
In venom-induced consumption coagulopathy, toxins in snake venom promote hemorrhage via activation, consumption, and subsequent depletion of clotting factors in the blood.[43] These clotting factors normally work as part of the coagulation cascade in the blood to form blood clots and prevent hemorrhage. Toxins in snake venom (especially the venom of New World pit vipers (the family crotalina)) may also cause low platelets (thrombocytopenia) or altered platelet function also leading to bleeding.[43]
Snake venom is known to cause neuromuscular paralysis, usually as a flaccid paralysis that is descending; starting at the facial muscles, causing ptosis or drooping eyelids and dysarthria or poor articulation of speech, and descending to the respiratory muscles causing respiratory compromise.[43] The neurotoxins can either bind to and block membrane receptors at the post-synaptic neurons or they can be taken up into the pre-synaptic neuron cells and impair neurotransmitter release.[43] Venom toxins that are taken up intra-cellularly, into the cells of the pre-synaptic neurons are much more difficult to reverse using anti-venom as they are inaccessible to the anti-venom when they are intracellular.[43]
The strength of venom differs markedly between species and even more so between families, as measured by median lethal dose (LD50) in mice. Subcutaneous LD50 varies by over 140-fold within elapids and by more than 100-fold in vipers. The amount of venom produced also differs among species, with the Gaboon viper able to potentially deliver from 450 to 600 milligrams of venom in a single bite, the most of any snake.[44] Opisthoglyphous colubrids have venom ranging from life-threatening (in the case of the boomslang) to barely noticeable (as in Tantilla).[citation needed]
Prevention
[edit]Snakes are most likely to bite when they feel threatened, are startled, are provoked, or when they have been cornered. Snakes are likely to approach residential areas when attracted by prey, such as rodents. Regular pest control can reduce the threat of snakes considerably. It is beneficial to know the species of snake that are common in local areas, or while travelling or hiking. Africa, Australia, the Neotropics, and South Asia in particular are populated by many dangerous species of snake. Being aware of—and ultimately avoiding—areas known to be heavily populated by dangerous snakes is strongly recommended.[citation needed]
When in the wilderness, treading heavily creates ground vibrations and noise, which will often cause snakes to flee from the area. However, this generally only applies to vipers, as some larger and more aggressive snakes in other parts of the world, such as mambas and cobras,[45] will respond more aggressively. If presented with a direct encounter, it is best to remain silent and motionless. If the snake has not yet fled, it is important to step away slowly and cautiously.[citation needed]
The use of a flashlight when engaged in camping activities, such as gathering firewood at night, can be helpful. Snakes may also be unusually active during especially warm nights when ambient temperatures exceed 21 °C (70 °F). It is advised not to reach blindly into hollow logs, flip over large rocks, and enter old cabins or other potential snake hiding places. When rock climbing, it is not safe to grab ledges or crevices without examining them first, as snakes are cold-blooded and often sunbathe atop rock ledges.[citation needed]
In the United States, more than 40 percent of people bitten by snakes intentionally put themselves in harm's way by attempting to capture wild snakes or by carelessly handling their dangerous pets—40 percent of that number had a blood alcohol level of 0.1 percent or more.[46]
It is also important to avoid snakes that appear to be dead, as some species will roll over on their backs and stick out their tongue to fool potential threats. A snake's detached head can immediately act by reflex and potentially bite. The induced bite can be just as severe as that of a live snake.[2][47] As a dead snake is incapable of regulating the venom injected, a bite from a dead snake can often contain large amounts of venom.[48]
Treatment
[edit]It may be difficult to determine if a bite by any species of snake is life-threatening. A bite by a North American copperhead on the ankle is usually a moderate injury to a healthy adult, but a bite to a child's abdomen or face by the same snake may be fatal. The outcome of all snakebites depends on a multitude of factors: the type of snake, the size, physical condition, and temperature of the snake, the age and physical condition of the person, the area and tissue bitten (e.g., foot, torso, vein or muscle), the amount of venom injected, the time it takes for the person to find treatment, and finally the quality of that treatment.[2][49] An overview of systematic reviews on different aspects of snakebite management found that the evidence base from majority of treatment modalities is low quality.[50] An analysis of World Health Organization guidelines found that they are of low quality, with inadequate stakeholder involvement and poor methodological rigour.[51] In addition, access to effective treatment modalities is a major challenge in some regions, particularly in most African countries.[52]
Snake identification
[edit]Identification of the snake is important in planning treatment in certain areas of the world but is not always possible. Ideally, the dead snake would be brought in with the person, but in areas where snake bite is more common, local knowledge may be sufficient to recognize the snake. However, in regions where polyvalent antivenoms are available, such as North America, identification of snakes is not a high-priority item. Attempting to catch or kill the offending snake also puts one at risk for re-envenomation or creating a second person bitten, and generally is not recommended.[53]
The three types of venomous snakes that cause the majority of major clinical problems are vipers, kraits, and cobras. Knowledge of what species are present locally can be crucial, as is knowledge of typical signs and symptoms of envenomation by each type of snake. A scoring system can be used to try to determine the biting snake based on clinical features,[54] but these scoring systems are extremely specific to particular geographical areas and might be compromised by the presence of escaped or released non-native species.[53]
First aid
[edit]Snakebite first aid recommendations vary, in part because different snakes have different types of venom. Some have little local effect, but life-threatening systemic effects, in which case containing the venom in the region of the bite by pressure immobilization is desirable. Other venoms instigate localized tissue damage around the bitten area, and immobilization may increase the severity of the damage in this area, but also reduce the total area affected; whether this trade-off is desirable remains a point of controversy. Because snakes vary from one country to another, first aid methods also vary.[citation needed]
Many organizations, including the American Medical Association and American Red Cross, recommend washing the bite with soap and water. Australian recommendations for snake bite treatment are against cleaning the wound. Traces of venom left on the skin/bandages from the strike can be used in combination with a snake bite identification kit to identify the species of snake. This speeds the determination of which antivenom to administer in the emergency room.[55]
Pressure immobilization
[edit]As of 2008, clinical evidence for pressure immobilization via the use of an elastic bandage is limited.[56] It is recommended for snakebites that have occurred in Australia (due to elapids which are neurotoxic).[57] It is not recommended for bites from non-neurotoxic snakes such as those found in North America and other regions of the world.[57][58] The British military recommends pressure immobilization in all cases where the type of snake is unknown.[59]
The object of pressure immobilization is to contain venom within a bitten limb and prevent it from moving through the lymphatic system to the vital organs. This therapy has two components: pressure to prevent lymphatic drainage, and immobilization of the bitten limb to prevent the pumping action of the skeletal muscles.[citation needed]
Antivenom
[edit]Until the advent of antivenom, bites from some species of snake were almost universally fatal.[60] Despite huge advances in emergency therapy, antivenom is often still the only effective treatment for envenomation. The first antivenom was developed in 1895 by French physician Albert Calmette for the treatment of Indian cobra bites. Antivenom is made by injecting a small amount of venom into an animal (usually a horse or sheep) to initiate an immune system response. The resulting antibodies are then harvested from the animal's blood.[citation needed]
Antivenom is injected into the person intravenously, and works by binding to and neutralizing venom enzymes. It cannot undo the damage already caused by venom, so antivenom treatment should be sought as soon as possible. Modern antivenoms are usually polyvalent, making them effective against the venom of numerous snake species. Pharmaceutical companies that produce antivenom target their products against the species native to a particular area. The availability of antivenom is a major concern in some areas, including most of Africa, due to economic reasons (antivenom crisis).[52] In Sub-Saharan Africa, the efficacy of antivenom is often poorly characterised and some of the few available products have even been found to lack effectiveness.[61]
Although some people may develop serious adverse reactions to antivenom, such as anaphylaxis, in emergency situations this is usually treatable in a hospital setting and hence the benefit outweighs the potential consequences of not using antivenom. Giving adrenaline (epinephrine) to prevent adverse reactions to antivenom before they occur might be reasonable in cases where they occur commonly.[62] Antihistamines do not appear to provide any benefit in preventing adverse reactions.[62]
Chronic Complications
[edit]Chronic health effects of snakebite include but are not limited to non-healing and chronic ulcers, musculoskeletal disorders, amputations, chronic kidney disease, and other neurological and endocrine complications.[63][64] The treatment of chronic complications of snakebite has not been well researched and there a systems approach consisting of a multi-component intervention.[65][50]
Outmoded
[edit]The following treatments, while once recommended, are considered of no use or harmful, including tourniquets, incisions, suction, application of cold, and application of electricity.[58] Cases in which these treatments appear to work may be the result of dry bites.
- Application of a tourniquet to the bitten limb is generally not recommended. There is no convincing evidence that it is an effective first-aid tool as ordinarily applied.[66] Tourniquets have been found to be completely ineffective in the treatment of Crotalus durissus bites,[67] but some positive results have been seen with properly applied tourniquets for cobra venom in the Philippines.[68] Uninformed tourniquet use is dangerous since reducing or cutting off circulation can lead to gangrene, which can be fatal.[66] The use of a compression bandage is generally as effective, and much safer.
- Cutting open the bitten area, an action often taken before suction, is not recommended since it causes further damage and increases the risk of infection; the subsequent cauterization of the area with fire or silver nitrate (also known as infernal stone) is also potentially threatening.[69]
- Sucking out venom, either by mouth or with a pump, does not work and may harm the affected area directly.[70] Suction started after three minutes removes a clinically insignificant quantity—less than one-thousandth of the venom injected—as shown in a human study.[71] In a study with pigs, suction not only caused no improvement but led to necrosis in the suctioned area.[72] Suctioning by mouth presents a risk of further poisoning through the mouth's mucous tissues.[73] The helper may also release bacteria into the person's wound, leading to infection.
- Immersion in warm water or sour milk, followed by the application of snake-stones (also known as la Pierre Noire), which are believed to draw off the poison in much the way a sponge soaks up water.
- Application of a one-percent solution of potassium permanganate or chromic acid to the cut, exposed area.[69] The latter substance is notably toxic and carcinogenic.
- Drinking abundant quantities of alcohol following the cauterization or disinfection of the wound area.[69]
- Use of electroshock therapy in animal tests has shown this treatment to be useless and potentially dangerous.[74][75][76][77]
In extreme cases, in remote areas, all of these misguided attempts at treatment have resulted in injuries far worse than an otherwise mild to moderate snakebite. In worst-case scenarios, thoroughly constricting tourniquets have been applied to bitten limbs, completely shutting off blood flow to the area. By the time the person finally reached appropriate medical facilities, their limbs had to be amputated.[citation needed]
In development
[edit]Several new drugs and treatments are under development for snakebite. For instance, the metal chelator dimercaprol has recently been shown to potently antagonize the activity of Zn2+-dependent snake venom metalloproteinases in vitro.[78] New monoclonal antibodies, polymer gels and a small molecule inhibitor called Varespladib are in development.[79] A core outcome set (minimal list of consensus outcomes that should be used in future intervention research) for snakebite in South Asia is being developed.[80]
Epidemiology
[edit]Earlier estimates for snakebite vary from 1.2 to 5.5 million, with 421,000 to 2.5 million being envenomings, and causing 20,000 to 125,000 deaths.[3][14] More recent modelling estimates that in 2019, about 63,400 people died globally from snakebite, with 51,100 of these deaths happening in India.[81] Since reporting is not mandatory in much of the world, the data on the frequency of snakebites is not precise.[14] Many people who survive bites have permanent tissue damage caused by venom, leading to disability.[18] Most snake envenomings and fatalities occur in South Asia, Southeast Asia, and sub-Saharan Africa, with India reporting the most snakebite deaths of any country.[14] Available evidence on the effect of climate change on the epidemiology of snakebite is limited but it is expected that there will be a geographic shift in the risk of snakebite: northwards in North America and southwards in South America and Mozambique, and increase in the incidence of bite in Sri Lanka.[82]
Most snakebites are caused by non-venomous snakes. Of the roughly 3,000 known species of snake found worldwide, only 15% are considered dangerous to humans.[2][14] Snakes are found on every continent except Antarctica.[14] The most diverse and widely distributed snake family, the colubrids, has approximately 700 venomous species,[83] but only five genera—boomslangs, twig snakes, keelback snakes, green snakes, and slender snakes—have caused human fatalities.[83]
Worldwide, snakebites occur most frequently in the summer season when snakes are active and humans are outdoors.[14][84] Agricultural and tropical regions report more snakebites than anywhere else.[14][28] In the United States, those bitten are typically male and between 17 and 27 years of age.[2][84][85] Children and the elderly are the most likely to die.[2][49]
Mechanics
[edit]When venomous snakes bite a target, they secrete venom through their venom delivery system. The venom delivery system generally consists of two venom glands, a compressor muscle, venom ducts, a fang sheath, and fangs. The primary and accessory venom glands store the venom quantities required during envenomation. The compressor muscle contracts during bites to increase the pressure throughout the venom delivery system. The pressurized venom travels through the primary venom duct to the secondary venom duct that leads down through the fang sheath and fang. The venom is then expelled through the exit orifice of the fang. The total volume and flow rate of venom administered into a target varies widely, sometimes as much as an order of magnitude. One of the largest factors is snake species and size, larger snakes have been shown to administer larger quantities of venom.[86]
Predatory vs. defensive bites
[edit]Snake bites are classified as either predatory or defensive. During defensive strikes, the rate of venom expulsion and total volume of venom expelled is much greater than during predatory strikes. Defensive strikes can have 10 times as much venom volume expelled at 8.5 times the flow rate.[87] This can be explained by the snake's need to quickly subdue a threat. While employing similar venom expulsion mechanics, predatory strikes are quite different from defensive strikes. Snakes usually release the prey shortly after the envenomation allowing the prey to run away and die. Releasing prey prevents retaliatory damage to the snake. The venom scent allows the snake to relocate the prey once it is deceased.[86] The amount of venom injected has been shown to increase with the mass of the prey animal.[88] Larger venom volumes allow snakes to effectively euthanize larger prey while remaining economical during strikes against smaller prey. This is an important skill as venom is a metabolically expensive resource.[citation needed]
Venom Metering
[edit]Venom metering is the ability of a snake to have neurological control over the amount of venom released into a target during a strike based on situational cues. This ability would prove useful as venom is a limited resource, larger animals are less susceptible to the effects of venom, and various situations require different levels of force. There is a lot of evidence to support the venom metering hypothesis. For example, snakes frequently use more venom during defensive strikes, administer more venom to larger prey, and are capable of dry biting. A dry bite is a bite from a venomous snake that results in very little or no venom expulsion, leaving the target asymptomatic.[89] However, there is debate among many academics about venom metering in snakes. The alternative to venom metering is the pressure balance hypothesis.[citation needed]
The pressure balance hypothesis cites the retraction of the fang sheath as the many mechanisms for producing outward venom flow from the venom delivery system. When isolated, fang sheath retraction has experimentally been shown to induce very high pressures in the venom delivery system.[90] A similar method was used to stimulate the compressor musculature, the main muscle responsible for the contraction and squeezing of the venom gland, and then measuring the induced pressures. It was determined that the pressure created from the fang sheath retraction was at times an order of magnitude greater than those created by the compressor musculature. Snakes do not have direct neurological control of the fang sheath, it can only be retracted as the fangs enter a target and the target's skin and body provide substantial resistance to retract the sheath. For these reasons, the pressure balance hypothesis concludes that external factors, mainly the bite and physical mechanics, are responsible for the quantity of venom expelled.[citation needed]
Venom Spitting
[edit]Venom spitting is another venom delivery method that is unique to some Asiatic and African cobras. In venom spitting, a stream of venom is propelled at very high pressures outwards up to 3 meters (300 centimeters). The venom stream is usually aimed at the eyes and face of the target as a deterrent for predators. There are non-spitting cobras that provide useful information on the unique mechanics behind venom spitting. Unlike the elongated oval shaped exit orifices of non-spitting cobras, spitting cobras have circular exit orifice at their fang tips.[91] This combined with the ability to partially retract their fang sheath by displacing the palato-maxillary arch and contracting the adductor mandibulae, allows the spitting cobras to create large pressures within the venom delivery system.[92] While venom spitting is a less common venom delivery system, the venom can still cause the effects if ingested.[citation needed]
Society and culture
[edit]Snakes were both revered and worshipped and feared by early civilizations. The ancient Egyptians recorded prescribed treatments for snakebites as early as the Thirteenth Dynasty in the Brooklyn Papyrus, which includes at least seven venomous species common to the region today, such as the horned vipers.[93] In Judaism, the Nehushtan was a pole with a snake made of copper fixed upon it. The object was regarded as a divinely empowered instrument of God that could bring healing to Jews bitten by venomous snakes while they were wandering in the desert after their exodus from Egypt. Healing was said to occur by merely looking at the object as it was held up by Moses.[citation needed]
Historically, snakebites were seen as a means of execution in some cultures.[94] Reportedly, in Southern Han during China's Five Dynasties and Ten Kingdoms period and in India a form of capital punishment was to throw people into snake pits, leaving people to die from multiple venomous bites.[95] According to popular belief, the Egyptian queen Cleopatra VII committed suicide by letting herself be bitten by an asp—likely an Egyptian cobra[93][96]—after hearing of Mark Antony's death, while some contemporary ancient authors rather assumed a direct application of poison.[97]
Snakebite as a surreptitious form of murder has been featured in stories such as Sir Arthur Conan Doyle's The Adventure of the Speckled Band, but actual occurrences are virtually unheard of, with only a few documented cases.[95][98][99] It has been suggested that Boris III of Bulgaria, who was allied to Nazi Germany during World War II, may have been killed with snake venom,[95] although there is no definitive evidence. At least one attempted suicide by snakebite has been documented in medical literature involving a puff adder bite to the hand.[100]
In Jainism, the goddess Padmāvatī has been associated with curing snakebites.[101]
Research
[edit]In 2018, the World Health Organization listed snakebite envenoming as a neglected tropical disease.[102][103] In 2019, they launched a strategy to prevent and control snakebite envenoming, which involved a program targeting affected communities and their health systems.[104][105] A policy analysis however found that the placement of snakebite in the global health agenda of WHO is fragile due to reluctance to accept the disease in the neglected tropical disease community and the perceived colonial nature of the network driving the agenda.[106]
Key institutions conducting snakebite research on snakebite are the George Institute for Global Health, the Liverpool School of Tropical Medicine, and the Indian Institute of Science.
Other animals
[edit]Several animals acquired immunity against the venom of snakes that occur in the same habitat.[107] This has been documented in some humans as well.[108]
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- Bibliography
- Greene HW (1997). Snakes: The Evolution of Mystery in Nature. Berkeley, CA: University of California Press. ISBN 978-0-520-20014-2.
- Mackessy SP, ed. (2010). Handbook of Venoms and Toxins of Reptiles (2nd ed.). Boca Raton, FL: CRC Press. ISBN 978-0-8493-9165-1.
- Valenta J (2010). Venomous Snakes: Envenoming, Therapy (2nd ed.). Hauppauge, NY: Nova Science Publishers. ISBN 978-1-60876-618-5.
Further reading
[edit]- Campbell JA, Lamar WW (2004). The Venomous Reptiles of the Western Hemisphere. Ithaca, NY: Cornell University Press 978-0-8014-4141-7.
- Spawls S, Branch B (1995). The Dangerous Snakes of Africa: Natural History, Species Directory, Venoms and Snakebite. Sanibel Island, FL: Ralph Curtis Publishing. ISBN 978-0-88359-029-4.
- Sullivan JB, Wingert WA, Norris Jr RL (1995). "North American Venomous Reptile Bites". Wilderness Medicine: Management of Wilderness and Environmental Emergencies. 3: 680–709.
- Thorpe RS, Wüster W, Malhotra A (14 May 1997). Venomous Snakes: Ecology, Evolution, and Snakebite. Oxford, England: Oxford University Press. ISBN 978-0-19-854986-4.
External links
[edit]- WHO Snake Antivenoms Database
- Organization (2016). Guidelines for the management of snakebites. Regional Office for South-East Asia, World Health Organization. hdl:10665/249547. ISBN 978-92-9022-530-0.