This is a parasitic worm that occurs throughout Asia and Europe. The worm has a complicated life cycle, which results in human infection. Snails ingest eggs from water contaminated by human or animal feces. The eggs turn into larvae that leave the snails, and then infect fish. The infected fish are then eaten by humans, and cause infection. The infection in humans spreads to the bile ducts (in the liver) and the gallbladder.
