Tapeworms (Anoplocephala perfoliata) are a type of internal parasite that invade the gastrointestinal tract of horses. Tapeworms are widespread throughout North America, using oribatid mites as their intermediate host which are found often in moist areas of horse pastures. Regions with dry arid climate have lower tapeworm populations. Tapeworms cause damage to the horse's intestinal lining when they produce small mucosal erosions at the site where they attach themselves in the horse's GI system. High levels of tapeworms have been found to cause impactions and spasmodic colic. Lesions associated with tapeworm attachment may also alter the pattern of intestinal motility, thus being a potential cause of intussusception.