Epidemiology & Risk Factors

Opisthorchis species are liver fluke parasites (trematodes or worms). Opisthorchis viverrini is known as the Southeast Asian liver fluke and O. felineus is known as the cat liver fluke.

Liver fluke infections occur mostly in people living in some areas where the parasites are found. O. viverrini is found mainly in northeast Thailand, Laos, Cambodia, and central and southern Vietnam. O. felineus is found mainly in Italy, Germany, Belarus, Russia, Kazakhstan, and Ukraine. Travelers to Asia or Europe who consume raw or undercooked fish are at risk for liver fluke infection.

People become infected by eating raw or undercooked freshwater fish containing the larvae. Lightly salted, smoked, or pickled fish may contain infectious parasites. Drinking river water or other nonpotable water will not lead to infection with Opisthorchis.

Page last reviewed: February 20, 2018