Symptoms
Symptoms of opisthorchiasis (caused by Opisthorchis spp.) are indistinguishable from clonorchiasis (caused by Clonorchis sinensis), so the disease should be referred as clonorchiasis.
About 80% of infected people have no symptoms, though they can have eosinophilia. This is when the infection is weak and there are less than 1000 eggs in one gram in feces.
When there are 10.000-30.000 eggs in one gram of feces, then the infection is heavy. Symptoms of heavier infections with Opisthorchis viverrini may include: diarrhoea, pain in epigastric and pain in the upper right quadrant, lack of appetite (anorexia), fatigue, yellowing of the eyes and skin (jaundice) and mild fever.
These parasites are long-lived and cause heavy chronic infections may led to accumulation of fluid in legs (edema) and in the peritoneal cavity (ascites), enlarged non-functional gall-bladder and also cholangitis, which can lead to periductal fibrosis, cholecystitis and cholelithiasis, obstructive jaundice, hepatomegaly and/or fibrosis of the periportal system.
Importantly, both experimental and epidemiological evidence strongly implicates Opisthorchis viverrini infections in the etiology of a malignant cancer of the bile ducts (cholangiocarcinoma) in humans which has a very poor prognosis. Indeed, Clonorchis sinensis and Opisthorchis viverrini are both categorized by the International Agency for Research on Cancer (IARC) as Group 1 carcinogens.
In humans, the onset of cholangiocarcinoma occurs with chronic opisthorchiasis, associated with hepatobiliary damage, inflammation, periductal fibrosis and/or cellular responses to antigens from the infecting fluke. These conditions predispose to cholangiocarcinoma, possibly through an enhanced susceptibility of DNA to damage by carcinogens. Chronic hepatobiliary damage is reported to be multi-factorial and considered to arise from a continued mechanical irritation of the epithelium by the flukes present, particularly via their suckers, metabolites and excreted/secreted antigens as well as immunopathological processes. In regions where Opisthorchis viverrini is highly endemic, the incidence of cholangiocarcinoma is unprecedented. For instance, cholangiocarcinomas represent 15% of primary liver cancer worldwide, but in Thailand's Khon Kaen region, this figure escalates to 90%, the highest recorded incidence of this cancer in the world. Of all cancers worldwide from 2002, 0.02% were cholangiocarcinoma caused by Opisthorchis viverrini.
The cancer of the bile ducts caused by opisthorchiasis occur in the ages 25–44 years in Thailand.
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