Clonorchis sinensis (Chinese or oriental liver fluke).
are discharged in the biliary ducts and in the stool
Eggs are ingested by a suitable snail intermediate host
there are more than 100 species of snails that can serve as intermediate
hosts. Each egg releases a miracidia
which go through several developmental stages (sporocysts
The cercariae are released from the snail and after a short period of
free-swimming time in water, they come in contact and penetrate the
flesh of freshwater fish, where they encyst as metacercariae
Infection of humans occurs by ingestion of undercooked, salted, pickled,
or smoked freshwater fish
After ingestion, the metacercariae excyst in the duodenum
ascend the biliary tract through the ampulla of Vater
Maturation takes approximately 1 month. The adult flukes (measuring 10
to 25 mm by 3 to 5 mm) reside in small and medium sized biliary ducts.
In addition to humans, carnivorous animals can serve as reservoir hosts.
Endemic areas are
in Asia including Korea, China, Taiwan, and Vietnam. Clonorchiasis has
been reported in non endemic areas (including the United States). In
such cases, the infection is found in Asian immigrants, or following
ingestion of imported, undercooked or pickled freshwater fish containing
manifestations result from inflammation and intermittent obstruction of
the biliary ducts. In the acute phase, abdominal pain, nausea,
diarrhea, and eosinophilia can occur. In long-standing infections,
cholangitis, cholelithiasis, pancreatitis, and cholangiocarcinoma can
develop, which may be fatal.
demonstration of eggs in the stool or in duodenal aspirate is the most
practical diagnostic method. The adult fluke can also be recovered at
comparison with other intestinal parasites.
albendazole* are the drugs of choice.
* This drug is
approved by the FDA, but considered investigational for this purpose.