The liver fluke Opisthorchis felineus is a member of the triad of epidemiologically important liver fluke species belonging to the family Opisthorchiidae and the major agent causing opisthorchiasis over a vast territory, covering Russia, Kazakhstan and several European countries. The similarity between the diseases caused by O. felineus and other liver flukes, O. viverrini and Clonorchis sinensis, in clinical manifestations and course suggests that the scenarios of their development and, possibly, complications have much in common. The International Agency for Research on Cancer classified O. viverrini and C. sinensis as group 1 agents and the major factors inducing cholangiocarcinoma in endemic regions. However, a carcinogenic potential of O. felineus is poorly studied. This review characterizes O. felineus, briefs the epidemiological situation in Western Siberia, the world's largest opisthorchiasis focus, and assesses the carcinogenic potential of this liver fluke. The review is based on a comprehensive analysis of the published medical data on opisthorchiasis and its complications in Western Siberia. Results of performed analysis reflect the actual epidemiological situation in opisthorchiasis focus and suggest an association of this disease with bile duct cancer.

The liver fluke Opisthorchis felineus is a member of the triad of epidemiologically relevant species of the trematode family Opisthorchiidae, and the causative agent of opisthorchiasis felinea over an extensive range that spans regions of Eurasia. The International Agency for Research on Cancer classifies the infection with the liver flukes Opisthorchis viverrini and Clonorchis sinensis as group 1 agents and a major risk factor for cholangiocarcinoma. However, the carcinogenic potential of the infection with O. felineus is less clear. Here, we present findings that support the inclusion of O. felineus in the Group 1 list of biological carcinogens. Two discrete lines of evidence support the notion that infection with this liver fluke is carcinogenic. First, novel oxysterol-like metabolites detected by liquid chromatography-mass spectroscopy in the egg and adult developmental stages of O. felineus, and in bile, sera, and urine of liver fluke-infected hamsters exhibited marked similarity to oxysterol-like molecules known from O. viverrini. Numerous oxysterols and related DNA-adducts detected in the liver fluke eggs and in bile from infected hamsters suggested that infection-associated oxysterols induced chromosomal lesions in host cells. Second, histological analysis of liver sections from hamsters infected with O. felineus confirmed portal area enlargement, inflammation with severe periductal fibrosis and changes in the epithelium of the biliary tract characterized as biliary intraepithelial neoplasia, BilIN. The consonance of these biochemical and histopathological changes revealed that O. felineus infection in this rodent model induced precancerous lesions conducive to malignancy.

The three epidemiologically important Opisthorchiidae liver flukes Opisthorchis felineus, O. viverrini, and Clonorchis sinensis, are believed to harbour similar potencies to provoke hepatobiliary diseases in their definitive hosts, although their populations have substantially different ecogeographical aspects including habitat, preferred hosts, population structure. Lack of O. felineus genomic data is an obstacle to the development of comparative molecular biological approaches necessary to obtain new knowledge about the biology of Opisthorchiidae trematodes, to identify essential pathways linked to parasite-host interaction, to predict genes that contribute to liver fluke pathogenesis and for the effective prevention and control of the disease. Here we present the first draft genome assembly of O. felineus and its gene repertoire accompanied by a comparative analysis with that of O. viverrini and Clonorchis sinensis. We observed both noticeably high heterozygosity of the sequenced individual and substantial genetic diversity in a pooled sample. This indicates that potency of O. felineus population for rapid adaptive response to control and preventive measures of opisthorchiasis is higher than in O. viverrini and C. sinensis. We also have found that all three species are characterized by more intensive involvement of trans-splicing in RNA processing compared to other trematodes. All revealed peculiarities of structural organization of genomes are of extreme importance for a proper description of genes and their products in these parasitic species. This should be taken into account both in academic and applied research of epidemiologically important liver flukes. Further comparative genomics studies of liver flukes and non-carcinogenic flatworms allow for generation of well-grounded hypotheses on the mechanisms underlying development of cholangiocarcinoma associated with opisthorchiasis and clonorchiasis as well as species-specific mechanisms of these diseases.