Mainly found in foals and young horses, as horses develop natural immunity to this parasite by about 18 months of age.

Size/Appearance: The large roundworm can be up to 40cm in length and is white in colour.

Location in Horse: The larvae migrate through the bloodstream to the liver and the lungs. These get coughed up and swallowed and return to the small intestine to develop into adults.

Symptoms: Symptoms include coughing, poor growth rate and a dull coat. Because of the worms size, they can cause a fatal blockage or rupture of the gut.