Tapeworm (Anoplocephala perfoliata)
The equine tapeworm is flat, triangular and relatively short compared to tapeworms found in dogs, cats and humans.
It has a small, round head which attaches to the lining of the gut by four suckers.
The equine tapeworm can grow to about 8 cm long by about 1.5 cm wide. It lives in the mid-part of the gut at a junction between the small and large intestine known as the ileo-caecal junction.
Infected horses pass eggs on to the pasture and these are eaten by tiny oribatid mites which are present in their thousands in every square metre of grass. Once inside the mite, the eggs hatch and develop into an intermediate infective stage. Grazing horses inadvertently eat mites with almost every mouthful. Very few of the mites will be infected but those that are will release the larvae, which continue to develop into adult tapeworm inside the horse. The adults attach in clusters to the lining of the gut at the ileo-caecal junction and release eggs, thereby completing their lifecycle.
At one time it was thought that the tapeworm was a relatively harmless inhabitant of the horses’ intestine. However, recent research has revealed that tapeworm are associated with certain types of colic in the horse.