Named in honour of the German scientist Ostertag.
Genus of the nematode family Trichostrongylidae.
The adult worms (female about 10 mm long) live in the rennet-bag (4th stomach) of cattle. The larvae 1–3 develop within 3 weeks outside of the body. When larvae 3 are taken up with grass, they enter the glands of the rennet-bag and grow there via 2 molts until maturity. Males and females live free in the small intestine. The prepatent period takes 18–23 days in Ostertagia ostertagia and O.circumcincta.
Trichostrongylidae, Fig. 1.