Examples of large-duct obstruction include gallstone disease, chronic biliary fluke infestation, and primary sclerosing cholangitis (PSC). The biliary flukes endemic in Asia, Opisthorchis and Clonorchis species, are acquired by eating raw fish that carry larval cyst forms.29 Fasciola hepatica is found in all sheep-producing and cattleproducing areas of the world and infects humans as accidental hosts; it is acquired by eating fecally contaminated watercress and other aquatic plants that harbor the immature cysts. Immigrants from infected areas may be at risk for these chronic infestations.