Differentiation of the Southern Part of the Transboundary Volga-Ural Sandy Natural Plague Focus by the Frequency of Epizootic Manifestations Using Circular Extrapolation

The Volga-Ural sandy natural plague focus is a transboundary one. Its greater part (66,036 km 2 ) is located on the territory of two regions of the Republic of Kazakhstan, the smaller part (8,625 km 2 ) is on the territory of the Russian Federation. The aim of the work was to conduct epizootiological differentiation of the southern part of the Volga-Ural sandy plague focus. Materials and methods . Retrospective data from epizootiological survey of the focus conducted by the Astrakhan (Russian Federation) and Atyrau (Republic of Kazakhstan) Plague Control Stations were used. The coordinates (latitude and longitude) of 865 sites where the plague agent was detected over the period of 1936–2005 were determined. Using the method of circular extrapolation of each point with plague manifestations, annual maps of epizootic areas were drawn. By successive overlay of the created electronic maps, the dislocation of the activity cores of the natural focus and the zones of short-term registration of the epizootic process were revealed, and their quantitative characteristics were determined. Results and discussion . Identification of a detailed configuration of the most active zones of manifestation of the epizootic process has significant prognostic value in the search for plague-infected animals, especially during inter-epizootic periods. The cartographic model of differentiation of the focal territory by activity and duration of epizootics is intended for substantiated planning of epidemiological surveillance measures, prevention and further study of the issues of plague enzootics. The obtained data can be used for epidemiological zoning of the territory as regards plague.