Heligmosomoides polygyrus

Heligmosomoides polygyrus
Female H. polygyrus from the digestive tractus of a woodmouse
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Chromadorea
Order:	Rhabditida
Family:	Heligmosomidae
Genus:	Heligmosomoides
Species:	H. polygyrus
Binomial name
Heligmosomoides polygyrus

Heligmosomoides polygyrus (formerly known as Nematospiroides dubius) is a common nematode found in the duodenum and small intestine of woodmice and other rodents.

They are 5–20mm in length and bright red due to the pigmentation of their tissues. They are usually heavily coiled, with the female having 12–15 coils and the male 8–12. The male can be distinguished from the female by a prominent copulatory bursa and two long, thin spicules at the posterior end.

They have a direct life cycle. The eggs pass out with the faeces of the host into the environment. After 2 days they hatch as larvae which are about 300μm in length. The larvae moult 3 days later but retain the shed cuticle for protection. It is at this point they become infective. The larvae shed the outer protective sheath after they are eaten by a suitable host. The larvae then penetrate the submucosa of the duodenum where they undergo 2 further molts. About 7 days later the male and female adult worms emerge into the lumen of the duodenum. They attach to the epithelial layer of the duodenum where they feed off the contents of the gut. The adult worms mate and eggs are shed in the feces. The complete life cycle from egg to egg takes a minimum of 15 days, and the female worms will live inside their host for 8 months.

These worms often form cysts in the wall of the intestine. These cysts often become infected with bacteria, but it is not yet known if these are harmful to the host.

This organism is often used to model human helminth infection in laboratory mice.