Phylum Flatworms

Flukes and tapeworms are adapted to parasitism: the body has a thick cuticle, and the tapeworm has no digestive organs. The liver fluke lives in the bile ducts of the liver of cattle, sheep and other mammals, clinging with oral and ventral suckers and sucking bile and blood. Its egg becomes a ciliated larva in water that enters a freshwater snail; then a tailed larva leaves into the water, attaches to a plant and forms a cyst; an animal that eats it ends up again with flukes in the liver. The definitive host is a mammal, the intermediate host a freshwater snail. The beef tapeworm lives in the human small intestine, is 8–10 m long, has four suckers on its head and a body of nearly a thousand segments. Egg-filled segments leave with faeces, cattle swallow eggs with fodder, and a bladder-like larva (finna) forms in their muscles. People are infected by undercooked meat with finna: the human is the definitive and cattle the intermediate host. To prevent infection cook meat well, wash greens and vegetables, keep hands clean, and see a doctor if infection is suspected.