Liver Flukes

Liver flukes are parasites that can infect humans and cause liver and bile duct disease. There are two families of liver flukes that cause disease in humans: Opisthorchiidae (which includes species of Clonorchis and Opisthorchis) and Fasciolidae (which includes species of Fasciola). These two families of liver flukes differ in their geographic distribution, life cycle, and long-term outcome after clinical infection.

 

Clonorchis is a liver fluke parasite that humans can get by eating raw or undercooked fish, crabs, or crayfish from areas where the parasite is found. Found across parts of Asia, Clonorchis is also known as the Chinese or oriental liver fluke. Liver flukes infect the liver, gallbladder, and bile duct in humans. While most infected persons do not show any symptoms, infections that last a long time can result in severe symptoms and serious illness. Untreated, infections may persist for up to 25–30 years, the lifespan of the parasite.

Opisthorchis species are liver fluke parasites that humans can get by eating raw or undercooked fish, crabs, or crayfish from areas in Asia and Europe where the parasite is found, including Thailand, Laos, Cambodia, Vietnam, Germany, Italy, Belarus, Russia, Kazakhstan, and Ukraine. Liver flukes infect the liver, gallbladder, and bile duct in humans. While most infected persons do not show any symptoms, infections that last a long time can result in severe symptoms and serious illness. Untreated, infections may persist for up to 25–30 years, the lifespan of the parasite. Typical symptoms include indigestion, abdominal pain, diarrhea, or constipation. In severe cases, abdominal pain, nausea, and diarrhea can occur.

Fascioliasis is a parasitic infection typically caused by Fasciola hepatica, which is also known as “the common liver fluke” or “the sheep liver fluke.” A related parasite, Fasciola gigantica, also can infect people. Fascioliasis is found in all continents except Antarctica, in over 70 countries,  especially where there are sheep or cattle. People usually become infected by eating raw watercress or other water plants contaminated with immature parasite larvae. The young worms move through the intestinal wall, the abdominal cavity, and the liver tissue, into the bile ducts, where they develop into mature adult flukes that produce eggs. The pathology typically is most pronounced in the bile ducts and liver. Fasciola infection is both treatable and preventable.

Page last reviewed: January 14, 2019