Clonorchis sinensis

Clonorchis sinensis

Description, Causes and Risk Factors:

The Asiatic liver fluke, a species of trematodes (family Opisthorchiidae) that in the Far East infects the bile passages of humans and other fish-eating animals; cyprinoid fish serve as chief second intermediate hosts, and various operculate snails serve as the first intermediate hosts.

Clonorchis sinensis is a common parasite of man, of which geographical distribution is largely confined to Eastern Asia including `Japan, China, Taiwan, northern Vietnam and southern Korea.' In Korea, it has been well-known that the human infection of C. sinensis is widely spread along the great rivers and streams.

The disease is a kind of chronic parasitosis caused by clonorchis sinensis, which inhabit human intrahepatic ducts.

Clonorchis sinensis

The eggs of Clonorchis sinensis are ingested by a snails in fresh water. After the eggs hatch, infected snails will release microscopic larvae that will enter freshwater fish. People become infected when eating the parasite containing cysts within infected raw or undercooked fish. Once ingested, cysts travel to the small intestine and liver where they feed upon the bile created by the liver and mature. The life cycle takes 3 months to complete in humans. Infected people will then pass eggs in their feces or may cough them up.

Dwelling in the bile ducts, Clonorchis sinensis induces an inflammatory reaction, epithelial hyperplasia and sometimes even cholangiocarcinoma, the incidence of which is raised in fluke-infested areas.

One adverse effect of Clonorchis sinensis is the possibility for the adult metacercaria to consume all bile created in the liver, which would inhibit the host human from digesting, especially fats. Another possibility is obstruction of the bile duct by the parasite or its eggs, leading to biliary obstruction and cholangitis (specifically oriental cholangitis).


While normally asymptomatic most pathological manifestations result from inflammation and intermittent obstruction of the biliary ducts. The acute phase consists of abdominal pain with associated nausea and diarrhea. Long standing infections consist of fatigue, abdominal discomfort, anorexia, weight loss, diarrhea, and jaundice. The pathology of long standing infections consists of bile stasis, obstruction, bacterial infections, inflammation, periductal fibrosis, and hyperplasia. Development of cholangiocarcinoma is progressive.


Diagnosis of human Clonorchis sinensis is primarily made by detection of the eggs on fecal examination.The eggs are oval in shape, likened to sesame seeds by their slender opercular end and blunt abopercular end with a terminal knob. The operculum is well demarcated by the surroundingshoulder. The outer surface of the eggshell is wrinkled, which differentiates it from heterophyideggs, but it is hard to differentiate its eggs from those of Opisthorchis spp., which alsohave a wrinkled surface.

In addition to the qualitative fecal examination, quantitative fecal examination is necessary.For the quantitative examination, Stoll's egg counting technique and the Kato-Katz method arewidely used by counting the EPG (eggs per gram).

Many serodiagnostic techniques have been developed, but the ELISA is the most common. Recently multiantigen screening has been commonly applied for serodiagnosis of parasiticdiseases, including Clonorchis sinensis. Crude extract of the adult Clonorchis worms is usually used forthe serodiagnostic antigen. Polyacrylamide gel electrophoresis (PAGE) and immunoblotting techniques have been used to analyze the antigen. Several researches are investigating the useof other antigens to improve the sensitivity and speci?city of serodiagnosis, which has become ahot topic of present research on Clonorchis sinensis.

Additionally, ultrasound, CT, and MRI scanning may be used to discover parasite-containing cysts that contribute to a diagnosis.


Treatment: Praziquantel or albendazole are the drugs of choice.

Preventive Measures:

    Thoroughly cook all freshwater fish, irradiate or freeze at -10 °C 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.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.


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