Fluke

Fluke, name for various parasitic flatworms, some of which are important disease carriers. The sheep liver fluke lives in the bile duct of mammals. Its eggs pass out of the intestine into water, where the larvae infect water snails, then wait on vegetation to be eaten by mammals. The blood fluke (bilharzia) is responsible for the disease schistosomiasis, which is thought to affect 250 million people throughout the world.