Intestinal Threadworm

These are generally only a problem in foals as horses develop a natural immunity at around 6 months of age. Larvae are passed to the foal through the mare's milk, and minimizing infection can be achieved by treating the mare for this parasite, particularly before foaling. However, foals can also pick the larvae up from the pasture themselves. The life cycle is only a few weeks long meaning a heavy worm burden can be acquired very quickly.

Size/appearance

The intestinal threadworm is slender and hair-like and up to 1cm long.

Location in horse

The larvae migrate to the lungs, are swallowed and develop into adults in the small intestine.

Symptoms

Symptoms include diarrhoea, anorexia and dullness as well as a reduced growth rate and loss of weight, which in foals can result in potential complications in later life.