Ecological aspects of zoning the territory of the Saratov region by the risk level of formation of West Nile fever foci

The modern period is characterized by the expansion of the areas of a number of dangerous infectious diseases, previously endemic only for the countries with tropical climate. As a result of Palearctic climate warming and humidification and under the influence of anthropogenic factors, foci of a new transmissible arboviral zoonosis – West Nile fever (WNF) – have been formed in the Saratov region. On the territory of Russia, the circulation of the West Nile virus (WNV) has been recorded since 1963, and cases of human infection have been detected since 1967. In the studied region, the circulation of the virus has been known since the mid-90s of the last century, and epidemic complications – since 2012. 142 cases of the disease were reported in 2012–2020. The ecological prerequisites for a wide circulation of WNV are associated with the increase in the number of birds – carriers, and arthropods – blood-sucking vectors, the longer activity period of mosquitoes and ticks owing to the reduced frosty season of the year. As a result of landscape mapping with the use of modern methods for decoding images of satellite maps and remote sensing of the Earth (ERS), data have been obtained that served as the basis for epidemiological WNF zoning. There are three types of potential WNF foci on the territory of the region, namely: natural, natural-anthropourgic, and anthropourgic ones. The total area of biocenoses has been established, where natural, natural-anthropourgic and anthropourgic WNF foci could be formed: 6619.94 km2, 1484.62 km2, and 70.4 km2, respectively. Cluster analysis of the environmental conditions in 38 administrative districts of the region has distinguished four groups differing in the risk level of infection of the population with West Nile fever. The data obtained are used for planning, substantiating and conducting surveys and preventive measures, and form the basis for predicting the epidemiological situation in the region.