[Ecological bases of the combination of natural foci of Trematoda infections. 1. One- and two-host population-combined foci of Trematoda infections in the floodplain-river ecosystem of the Konda River].

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 brings to light the ecological bases of the combination of natural foci of metorchiases, bilharziasis, opisthorchiasis, and methorchiasis (M. xanthosomus). Two first foci are one-host population-combined and the latter focus is a two-host population-combined focus. While analyzing the combination of foci, it is expedient to consider in pairs since this provides a way of identifying the bases of the combination, which are unique to these foci, and determining the level, pattern, type, and degree of the combination of foci and, on their basis, the type of a combined focus. It is noted that in biohelminthiases, detection of even hemipopulations of parasites points to the presence of natural foci. The morphological structure of the floodplain-river landscape of the Konda River acts as the abiotic basis of the combination of foci. The parasitic systems of flukes, the parasitocenoses of co-acting hemipopulations of the pathogens and populations of hosts, the structure of foci, the species-specific composition of ecosystems, and the ecological relations of Trematoda hosts act as the biotic bases of the combination of foci of Trematoda infections. The host susceptibility to infection with Trematoda hemipopulations and the multihostality of B. polonica and M. xanthosomus act as the epizootic bases of the combination of foci. The abiotic, biotic, and epizootic bases of the combination are, in the aggregate, the ecological bases of the combination of natural foci of zoonoses.