[Ecological bases of the combination of natural foci of Trematoda infections in the floodplain-river ecosystem of the Konda River. Communication 2. Host population-combined foci of Trematoda infections].

In the context of the present-day teaching of parasitocenoses and the proposition that the pathogen's population is the only compulsory and specific component of a natural focus, the author discloses the ecological bases of the combination of natural foci of opisthorchiasis and methorchiasis (M. bilis), methorchiasis (M. bilis) and methorchiasis (M. xanthosomus). These foci are host population-combined. While analyzing the combination of foci, it is expedient to consider them in pairs since this provides a way of identifying only the combination bases that are unique to these foci. The parasitic systems of flukes, the parasitocenoses of co-acting parasitic systems of "twin types", the structure of foci, the species-specific composition of ecosystems, and the ecological relations of the Opisthorchis fluke hosts act as the biotic bases of a combination of foci of Trematoda infections. By coinciding, the multihost hemipopulations of parasites and the susceptibility of host populations predetermine the combination of Opisthorchis fluke foci. The susceptibility of hosts, the multihost pattern of Opisthorchis flukes, the identity of parasitic systems, and the common mechanism of pathogen transmission act as the epizootic bases of a combination of invasion foci. The morphological structure and hydrological regime of a landscape act as the abiotic bases of a combination of foci. The hydrological regime is by its nature a universal mechanism of pathogen transmission. The foci of Opisthorchis flukes at the level of parasitocenosis of metacercarium populations and fish populations in the Konda River ecosystem are combined in the age groups of only carp (Cyprinidae) underyearlings and yearlings. The abiotic, biotic, and epizootic bases of a combination of natural foci of Opisthorchis flukes are, in the aggregate, the ecological bases of a combination of foci.