Clonorchiasis

clonorchiasis, chronic infection caused by the Chinese liver fluke (Clonorchis sinensis), a parasitic worm some 10 to 25 mm (0.4 to 1 inch) long that lives in the bile ducts of the liver in humans and other mammals. Clonorchiasis is a common disease in certain parts of Asia, including China, Vietnam, Korea, and Japan. It is acquired by eating freshwater fish that are infected with the fluke larvae. The fish become infected by swallowing the larvae, which have earlier undergone a stage of their development in the liver glands of freshwater snails.

Raw as well as smoked, salted, or dried fish may constitute a source of human infestation. Early in the infection, there may be signs of indigestion, followed later by enlargement and tenderness of the liver and a light jaundice. Frequently there are no symptoms. Heavy infestations (as many as 21,000 worms) may involve the pancreas and gallbladder and may be associated with fluid accumulation in the abdomen and signs of general body toxicity. Such infestations may be detected incidentally upon ultrasound or other imaging of the abdomen. Infestation may also be diagnosed by microscopic examination of the feces for eggs, which first appear in the stool about three or four weeks following initial infection. Similarities between C. sinensis eggs and the eggs of Opisthorchis, another type of liver fluke common in Asia, can complicate diagnosis.

Treatment for clonorchiasis typically is with either praziquantel or albendazole, which are anthelmintic agents that are toxic to the fluke. Infection can be prevented by thoroughly cooking all freshwater fish.