This parasite is rarely a problem.

Strongyloides papillosus ('threadworm') infects the small intestine of sheep, especially lambs, cattle and goats. Its life cycle is complex. It may be direct or, under moist conditions, a separate cycle may take place in the soil where multiplication can also occur.

They occur in moist conditions and are associated with high stocking rates. Larvae develop in the soil and infect sheep by skin penetration through the foot or orally through milk during suckling.

The adults are thin thread-like worms (two to three millimetres long). Although infection is common, disease, typified by weight-loss, diarrhoea and inflammation between the toes, is rare. Infected sheep pass small (50 x 25 microns) eggs containing larvae.