Horse intestine with multiple attached parasitic worms

The mucosal lining of the large intestine with multiple attached nematodes (worms) of the species Strongylus edentatus. They are also known as 'red worms' or 'blood worms'. The worms are transmitted through feces, and so horses grazing in herds are more likely to become infected. The ingested larvae are enclosed in a cuticle, or sheath, which is protective but prevents from them from feeding. Once in the intestine, the worms lose this sheath and bore through the walls of the gut, entering the blood stream to reach the liver. Here they cause inflammation and hepatitis. This type of parasitism is rare in well-wormed horses.