Tapeworms are an important and potentially very damaging parasite affecting the horse. They preferentially attach themselves to the junction of the small and large intestine the ileocaecal junction. Here, they can cause bowel irritation, intussusception (where one part of the intestine telescopes into another), rupture, or twisting of the intestine.
It is thought that tapeworm may be responsible for up to 20% of surgical colics. Tapeworms are present, to a greater or lesser extent, in the majority of horses.
Parts of the country with acidic soils (for example, heath land), which favour the survival of the intermediate host of the tapeworm (the forage or oribatid mite), tend to have the highest level of infection.
Tapeworms in horses are generally much shorter than dog or cat tapeworms, they are flat, triangular and relatively short being approximately 8 cm long by about 1.5 cm wide. Segments can detach it is it is these segments that may on rare occasion be spotted by horse owners. However the equine tapeworm grow up to 20cm long, white in colour. Rarer species can be up to 80cm long. They live in huge numbers attached to the gut wall at a natural narrowing of the gut (the ileocaecal junction).