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All over the world, much attention is given to the comprehensive studies of parasites and their induced diseases in order to devise effective methods for the diagnosis, treatment, and prevention of parasitic diseases. This review summarizes the information available in the literature on the epidemiology of clonorchiasis caused by the Chinese liver fluke Clonorchis sinensis, including global and regional risk factors for the infection and its transmission. The existing knowledge of this important, but far from the most studied zoonosis, the cause of severe human hepatobiliary diseases, is required for the success of future investigations of parasitic infections.

The paper briefly reviews the current techniques for treatment for human clonorchiasis, which are both widely used in medical practice and developed at experimental research laboratories. It describes specific examples of chemotherapy, including combined therapy, clonorchiasis vaccines and drug resistance. Particular emphasis is placed on the prospects of use of minor interfering RNA as a source of new-generation diagnostic and remedial agents.

The mammalian liver parasite (Clonorchis sinensis flukes) has spread in the Primorye Territory. The areas of the first intermediate hosts for the parasite mollusks of the genus Parafossarulus have been found to recently become wider south-western predominantly due to lotus acclimatization, resulting in the expansion of a parasite habitation area. The intensity of newly formed foci of clonorchiasis is an order of magnitude greater than that of natural ones and they are a higher hazard since they have formed in the recreation areas used by the population for rest and fishing. The carp is the second intermediate host of trematodes. Patients' medical history data show that European and crucian carps (less frequently skygazer, rudd, gudgeon, minnow) have served as the main sources of human infection with trematodes.

The clinical manifestations of clonorchiasis were studied in 190 patients in the Amur River region. The severity of the disease correlated with the excretion rates of Clonorchis eggs. The peculiarity of the region is a rather low egg excretion; 66.8% of patients excreted as many as 100 eggs/g, 27.3%, up to 1000 eggs/g. Most examinees (94.3%) suffered from chronic gastroduodenitis and functional disorders of the biliary system.

Examinations of 1599 residents of a polyinvasion focus at a seaside province Ha Nam Nin, Vietnam, have revealed clonorchiasis in approximately 13.9% of the examinees; in subjects aged over 30 this value was 29.3%. Factors conducive to a lower incidence of clonorchiasis were detected, among them a moderate intensity of the invasion: the mean arithmetic was 1419 +/- 306 eggs/g, the mean geometric 673 egg/g, as shown by the Kato-Kats' technique. Analysis of five therapeutic schemes used in clonorchiasis, making use of chloxilin, medamin or praziquantel, has demonstrated a low efficacy of all of them. Praziquantel therapy in a daily dose of 25 mg/kg for 2 days was found the most effective (52%), being conducive to a reduction of the invasion intensity by at least 90%. Such therapy was associated with a high incidence of side effects (91.2%), this ruling out a higher dosage.

The authors described the clonorchiasis focus in the Vietnam province at the seaside delta of the Red River where the aforementioned invasion was accompanied with multiple invasions with intestinal nematodes. Clonorchiasis infestation rate was 28.4% ascaridiasis, 50.5%, trichocephaliasis, 21.3% ancylostomiasis, 7.0%. Clonorchiasis invasion was the result of consumed uncooked carp fish in the salad. It was revealed that the fish was reared in the ponds near the settlements and was fed untreated human and animal feces. The meal was more common among the male persons in the presence of the alcohol intake. Clinical symptoms of the mixed clonorchiasis and intestinal nematodiasis invasion was featured by pains, dyspepsia and the asthenoneurotic syndrome.