Opisthorchis FAQs

What is Opisthorchis?

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

What are the signs and symptoms of infection with Opisthorchis?

Most infected persons have no symptoms. In mild cases, symptoms may include indigestion, abdominal pain, diarrhea, or constipation. With infections of longer duration, an enlarged liver and malnutrition may occur. In rare cases, inflammation of the gall bladder and ducts, and cancer of these structures may develop. In addition, infections due to O. felineus can resemble acute schistosomiasis, with fever, facial edema, swollen lymph glands, sore joints, and rash. Chronic O. felineus infections present the same signs and symptoms as O. viverrini, but in addition can involve the pancreatic ducts.

What should I do if I think I might be infected?

See your health care provider.

How is infection with Opisthorchis diagnosed?

Diagnosis is based on identification of eggs in stool specimens with a microscope. More than one stool sample may be needed to identify the eggs. The eggs of Opisthorchis are very similar to those of Clonorchis, another liver fluke.

Is medication available to treat infection with Opisthorchis?

Yes, safe and effective medication is available to treat Opisthorchis infection (praziquantel).

How did I get infected with Opisthorchis?

Infection is caused by eating raw or undercooked freshwater fish containing the larvae. Lightly salted, smoked, or pickled fish may contain infectious organisms.

Who is at greatest risk of infection?

O. viverrini is found mainly in northeast Thailand, Laos, and Cambodia. O. felineus is found mainly in Europe and Asia, including the former Soviet Union.