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Clonorchiasis and opisthorchiasis are clinically indistinguishable
Parasite eggs are shed into water in human or animal feces, where they infect snails, which release cercariae, which infect fish
Human infection follows ingestion of raw, undercooked, or pickled freshwater fish containing metacercariae
These parasites excyst in the duodenum and ascend into the biliary tract, where they mature and remain for many years, shedding eggs in the bile
Clonorchiasis
Infection by Clonorchis sinensis, the Chinese liver fluke, is endemic in areas of
An estimated 15 million people are infected (13 million in China)
In some communities, prevalence can reach 80%
Opisthorchiasis caused by
Opisthorchis felineus (regions of the former Soviet Union)
Opisthorchis viverrini (Thailand, Laos, Vietnam)
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Most patients harbor few parasites and are asymptomatic
Acute illness
In chronic heavy infections, findings include
Abdominal pain
Anorexia
Weight loss
Tender hepatomegaly
More serious findings can include
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Early diagnosis is presumptive, based on clinical findings and epidemiology
Subsequent diagnosis is made by finding characteristic eggs in stool or duodenal or biliary contents
The acute syndrome is difficult to diagnose, since ova may not appear in the feces until 3–4 weeks after onset of symptoms
The stool Kato-Katz test is widely used; performing repeated tests improves sensitivity
Imaging studies show characteristic biliary tract dilatations with filling defects due to flukes
Serologic assays for clonorchiasis with excellent sensitivity are available but cannot distinguish between past and current infection
Molecular tests have been developed but are not widely used
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Praziquantel
Drug of choice
Dosage: 25 mg/kg orally three times daily for 2 days
One day of treatment may be sufficient
Re-treatment may be required, especially in some areas with known decreased praziquantel efficacy
Albendazole
Tribendimidine