liver fluke

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several parasitic trematode worms that infest the liver of humans and other mammals, especially Clonorchis sinensis and several species in the genus Opisthorchis, acquired from eating infected freshwater fish, and two species in the genus Fasciola, acquired from ingesting contaminated water or aquatic vegetation.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun flatworm parasitic in liver and bile ducts of domestic animals and humans