Animation of a tapeworm in the intestine. Tapeworms (Taenia sp.) are parasites that inhabit the human gut. They anchor themselves to the inside of the intestine and absorb nutrients through their body wall. They shed eggs into the gut, which are passed in faeces. The eggs are eaten by domesticated animals (cattle or pigs), and the embryo moves from the animal's gut to its muscle. When this muscle is eaten when not cooked properly, the tapeworm is ingested and becomes active in the human digestive tract. Tapeworms may grow to several metres in length, but infestation does not necessarily cause symptoms. In severe cases, loss of appetite and wasting may occur, and it may also spread to other tissues, and may be fatal if it spreads to the brain.