This parasite is rarely a problem, although it is often seen in sheep pastured in south western and tropical coastal Queensland.
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. Larvae develop in the soil and infect sheep, goats and cattle by skin penetration through the foot, or orally through milk during suckling.
Infection is associated with moist unhygienic conditions and high stocking rates.
The adults are thin thread-like worms (2–3 mm long).
Although infection is common, disease, typified by weight-loss, diarrhoea, and inflammation between the toes, is rare. Infected sheep and goats pass small (50 x 25 microns) eggs containing larvae.
Further ecological information on worms and their control: