Opisthorchiasis

Opisthorchiasis is a parasitic disease caused by species in the genus Opisthorchis (specifically, Opisthorchis viverrini and Opisthorchis felineus). Chronic infection may lead to cholangiocarcinoma, a malignant cancer of the bile ducts. Opisthorchiasis is a parasitic disease caused by species in the genus Opisthorchis (specifically, Opisthorchis viverrini and Opisthorchis felineus). Chronic infection may lead to cholangiocarcinoma, a malignant cancer of the bile ducts. Medical care and loss of wages caused by Opisthorchis viverrini in Laos and in Thailand costs about $120 million annually. Infection by Opisthorchis viverrini and other liver flukes in Asia affect the poor and poorest people. Opisthorchiasis is one of foodborne trematode infections (with clonorchiasis, fascioliasis and paragonimiasis) in the World Health Organization's list of neglected tropical diseases. Symptoms of opisthorchiasis (caused by Opisthorchis spp.) are indistinguishable from clonorchiasis (caused by Clonorchis sinensis). About 80% of infected people have no symptoms, though they can have eosinophilia. Asymptomatic infection can occur when there are less than 1000 eggs in one gram in feces. Infection is considered heavy when there are 10,000-30,000 eggs in one gram of feces. Symptoms of heavier infections with Opisthorchis viverrini may include: diarrhoea, epigastric and upper right quadrant pain, 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 that may lead to accumulation of fluid in the 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. 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. 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 silico analyses using techniques of genomics and bioinformatics is unraveling information on molecular mechanisms that may be relevant to the development of cholangiocarcinoma. 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. A few cases have appeared in later life among veterans of the Vietnam war in the United States, who consumed poorly cooked fish from streams in endemic areas near the border of Laos and Vietnam. The medical diagnosis is established by finding eggs of Opisthorchis viverrini in feces using the Kato technique. An antigen 89 kDa of Opisthorchis viverrini can be detected by ELISA test.