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
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
Biology 103: Parasites & Pestilence Spring 2003
Scott Smith, MD