Opisthorchis viverrini, adult worm
Image from Ash, 1997

Marquardt et al. (2000), Markell et al. (1999)

What is it?
Opisthorchiasis is a parasitic disease that can infect fish eating mammals, including humans. The trematode liver fluke worms, Opisthorchis viverrini and Opisthorchis felineus, cause opisthorchiasis by parasitizing the liver and biliary passages of their hosts.

Who gets it?
Human infection occurs through consumption of pickled, raw, or poorly cooked fish that contain the developing worms known as metacercariae. Infection most frequently occurs in Thailand, Laos, and southeast Asia as a result of the cultural preference for raw fish cuisine.

What happens if you get it?
Infected persons may present with mild symptoms of general malaise to abdominal distress, epigastric pain, and eventually cholangiocarcinoma (liver cancer), especially when the infection becomes heavy and long standing.

How is it treated?
Treatment with the drug Praziquantiel has been reported as extremely effective with a single dose. Disturbingly though, use of Praziquantiel has not been associated with a decrease in cholangiocarcinoma. This indicates that infection must be entirely avoided to prevent a future diagnosis of cancer.

Are there other names for this disease?
Opisthorchiasis may also be referred to as "Siberian liver fluke disease," and "cat liver fluke disease."

It is often associated with the parasitic disease Chlonorchiasis, which is also caused by a trematode liver fluke. Though the flukes that cause Clonorchiasis and Opisthorchiasis have similar life cycles, produce the same clinical symptoms in their hosts, and require similar treatment, they are differentiated by the shape of their testes, which are highly branched in Clonorchis and only lobed or slightly branched in Opisthorchis. The parasites also differ in their larval stage morphology, providing support for the retention of both Clonorchis and Opisthorchis genera.


Created by: Felicia Frizzell

Human Biology 103: Parasites & Pestilence Spring 2003

Instructor: D. Scott Smith, MD