The purpose of our research was to study the formation, functioning and structure of the nosological profile of infectious and invasive pathology of animals (birds) under conditions of the NorthWestern Region of the Russian Federation, to identify the main nosological units that form the epizootic and epidemic risk in the region and based on this to justify and determine the priority of measures for optimisation the anti-epizootic support of poultry farming in the region. In modern veterinary and biological sciences, there had been formed a concept about systemic understanding of ecologization in epizootology and epidemiology. A holistic scientific concept about the infectious parasitic system and self-regulation of the epizootic process of infectious and invasive parasitic systems had been formed (V. D. Belyakov et al., 1987). The notions "infection" and "infectious disease" are full-fledged components of parasitism (I. A. Bakulov, 1997; V. V. Sochnev, 1997; V. P. Urban, 1997; V. V. Makarov, 2022). In global epizootology the global epizootological category had been formulated – epizootological parameters of animals population, including population health, population reproduction, its economic utility and epidemic danger (V. V. Makarov, V. V. Sochnev, O. V. Kozyrenko, 2022; V. V. Sochnev, Yu. V. Pashkina, 2019). Animals health level largely depends on comfortness of the environment for their organisms, on epizootic safety of the territories, on the sustainability of ecological niche of parasitic systems pathogens and their epizootological geography. In the paper the animals infectious pathology nosological profile is studied under conditions of the North-Western Region of the Russian Federation, under conditions of a metropolis and its suburbs. The ecological niche of disease pathogens, its dependence on density axis and on host populations diversity were measured in quantities. It was discovered that the territorial boundaries for epizootic manifestation of the animals (birds) infectious pathology nosological units in the region tend to be formed under multifactorial influence, one of the main factors being the formation of the ecological niche of pathogens. In the North-Western Region the animals (birds) infectious pathology was formed from bacterioses in 11.49 %, from virosis in 12.4 %, from mycoses in 2.46 % and from invasive units in 73.6 %. The parasitic diseases of the ecosystem and their monoand polyhost epizootic manifestation were studied; the involvement of productive and unproductive animals populations co-members in the parasitic systems functioning was analysed; animals (birds) infectious pathologies dominating in the region were identified and the visualization of dominance semiotics of the specific nosological units was achieved by constructing Pareto diagrams.

Introduction. Urbanisation of territories creates a critical risk related to contagious animal diseases. The agro-industrial complex (AIC) of the Northwestern region is an important component of the food security system of the Russian Federation. The research is aimed at studying and defining the degree of epizootic risk of contagious animal diseases in the region, determining the degree of epizootic threat thereof at the population and interpopulation levels.Materials and methods. For conducting the study the comprehensive epizootological approach (analysis) was used, along with the methods of evidence-based epizootology, epizootological diagnostics, methods of modern prognostics and statistical methods of quality control.Results. Functioning of infectious parasitic systems have been studied under specific conditions of place and time, using digitalisation achievements and statistical quality control. The epizootological categories have been proposed and applied for the three-dimensional measurement of the epizootic manifestation of contagious diseases using the corresponding units for their mathematical measurement (indicator of ill-being, epizootic index, incidence and prevalence, pathogenicity spectrum, frequency, recurrence, seasonal epizootic growth and year-round disease incidence). All the above allows carrying out the epizootic supervision over the formation and functioning of separate nosological units in animal populations under specific conditions of place and time. Using the comprehensive epizootological approach and the evidence-based epizootological methodology, the degree of epizootic risk of contagious animal (bird) diseases in the agro-industrial complex of the Northwestern region was studied in relation to the various economic and technological levels of animal husbandry and the degree of territory urbanisation.Discussion and conclusions. It has been found that in the agro-industrial complex of the metropolis suburban area of the Northwestern region, there have formed and periodically appear 45 animal diseases, predominantly of infectious etiology (62.2 %). The different degree of diseases epizootic risk was revealed: from its absence, in case of 4 nosological units, up to high and very high degree, in case of 15 nosological units (33.3 % of the total number). Therefore, the purpose of the present work was to study the degree of the risk of infectious diseases potential occurrence in populations of production animals in various areas of the Northwestern region and to identify the cause-andeffect indicators underlying the differences.