Features of the opisthorchid parasitic system existing in Novosibirsk region

Abstract

The results of studying the factors contributing to the spread of opisthorchiasis in Novosibirsk region (1990–2019) are presented. The analysis of the disease incidence among population was carried out on the basis of statistical material from the Federal Service for Surveillance on Consumer Rights Protection and Human Wellbeing. During the study period, the annual manifestation of opisthorchiasis was noted from 85.7 to 176.5 cases per 100 thousand of population, the average indicator being 125.6. The uneven distribution of morbidity in the administrative districts of the region was revealed. Studies of fish for infestation with opisthorchid metacercariae were carried out in the Novosibirsk reservoir and its tributaries, Berdsky Bay, the river Ob with tributaries. There were 2665 fish specimens of the family Cyprinidae examined. The highest degree of infestation was noted for ide (more than 40%). Metacercariae of opisthorchids of four species were found in the studied fish: Opisthorchis felineus, Metorchisbilis, M. xantosomus and M. spp . The epidemically significant ones are O. felineus and M. bilis . There were 280 specimens of bithyniidae mollusks examined for infestation by opisthorchid larvae in the river Tulka and 497 specimens in the Berdsky Bay (the extensiveness of the invasion was 0.4%). Bithyniidae of the species Bithynia troscheli and Bithynia tentaculata (0.01–3.5 pcs/m 2 ) were found. The limiting ecological factor of the presence of local foci of opisthorchiasis in the Novosibirsk reservoir is a strict hydrological regime. It allows bithyniidae mollusks to survive in winter only in certain places, which are bays of small rivers flowing into the reservoir, at the mouth of which there are sand bars that prevent water from leaving the riverbed during winter discharges of water.