Clonorchis sinensis
Parasitology 101 is an educational blog that that can be used as a study guide for microbiology, infectious disease and medical technology students. The “bullet-point” format keeps the information concise and to the point.
General Information
Clonorchis sinensis is a trematode or fluke also known as the “Chinese liver fluke” or “Oriental liver fluke”
Clonorchiasis is a trematode disease of the bile ducts
Adult flukes produce an estimated 4,000 eggs per day per worm
Geography
Asia only
Mainland China, highly endemic in southeastern China
Taiwan, Korea, Vietnam
Reports outside of Asia are important (imported cases)
Morphology (adults)
Slender, pointed anterior, rounded posterior
1-2 cm long and 3-5 mm wide
Characteristic branching testes posterior
Morphology (eggs)
Small, 26-30 x 15-17 um
Ovoid, yellowish color
Operculated at one end, small knob at opposite end
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Life Cycle
Adults in biliary ducts, embryonated eggs pass to intestine and out with the feces
Eggs reach water, ingested by suitable snail (P. manchouricus)
In the snail (first intermediate host, eggs release miracidium and goes through several stages in host (sporocyst>rediae>cercariae)
Cercariae released from snail, free-swimming in water, penetrates under scales of an appropriate freshwater fish (second intermediate host)
Metacercariae encyst in the fish muscle
Humans infected by eating raw, partially cooked, smoked or pickled fish
Metacercariae excysts in the duodenum
Ascends up through intestine to bile ducts
Matures to adult in 30 days
Worms may live 30-40 years in final host
Carnivorous animals can serve as reservoir hosts
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Pathology
Most infections are asymptomatic
More progressive infections may see anorexia, jaundice, diarrhea, epigastric pain, fever
Some infections associated with severe complications: pancreatitis, cholangitis and cholangiocarcinoma (bile duct cancer)
Diagnosis
Finding the characteristic eggs in feces or duodenal aspirate
Treatment
Praziquantel or albendazole are the drugs of choice
Epidemiology
Clonorchiasis is endemic where there is poor sanitation, and
The right snail host, and
The right fish (cyprinoid fish) as the second intermediate host, and
A population who eats raw, poorly pickled, smoked, dried or salted freshwater fish
Prevention
Thoroughly cook all freshwater fish, irradiate or freeze at -10C for at least 5 days
Educate the public in endemic areas about the dangers of eating raw or improperly cooked fish
Proper disposal of feces