Liver Fluke

(Fasciola hepatica), a parasitic worm of the class Trematoda. The leaf-shaped body has a length of 2–5 cm. At the anterior end are the oral and ventral suckers. The liver fluke infests the liver, bile ducts, and gallbladder usually of herbivorous mammals, and more rarely of humans. The ova develop in water; the larvae that hatch from these ova and the partheno-genetic generations develop in an intermediate host, which is usually a mollusk, for example, the small freshwater snails of the family Lymnaeidae. The larva—a cercaria—emerges from the mollusk, swims, and settles on aquatic and coastal plants, becoming encysted as it converts to an adolescaria. The larvae that are swallowed by the definitive host penetrate the liver, where they grow and mature, eventually causing the disease fascioliasis.

Liver flukes are controlled by draining swamps, where lym-naeids hatch, by exterminating lymnaeids, by rotating pastures, and by treating cattle with anthelmintic drugs.