The Plague Epizootic in the Bityug-Tyube tract of the Central Caucasian High-Mountain Natural Focus in 2025: Main Characteristics and Simulation Results

Results of monitoring and analysis of the epizootic situation in the Central Caucasus high-mountain natural plague focus in 2025 are presented. The aim of the study was to characterize the case of Yersinia pestis strain isolation in the Bityug-Tyube tract and assess the features of the epizootic process. The epizootic is characterized as a single sporadic case, along with the identification of the plague pathogen strain as belonging to the main subspecies, biovar medievalis, genetic lineage 2.MED0, isolated from the carcass of a mountain ground squirrel (Spermophilus musicus). Material and methods. Laboratory testing of field material for the presence of the plague pathogen was carried out in accordance with MU 3.1/4.2.4065-24 “Epidemiological surveillance in natural plague foci in the territory of the Russian Federation: monitoring, diagnosis, and prevention”. To estimate the possible number of infected animals, a probabilistic calculation using the sequential sampling without replacement method (employing an algorithm verified with Python code) was applied, as well as computer simulation modeling of the epizootic process. The use of artificial intelligence systems, with mandatory verification of results by specialists, allows for the rapid execution of complex, reproducible calculations based on empirical data for an in-depth understanding of epizootic processes. Results and discussion. The studies showed that the epizootic manifestation in 2025 was a sporadic one and of low-intensity, likely due to two factors: a relatively low abundance of flea vectors and high resistance of local mountain ground squirrel populations to plague. Using mathematical modeling, it was established that the maximum number of infected ground squirrels in the focus during the observation period did not exceed six specimens (0.1–0.2 % of the population). The hypothesis of a latent epizootic process in the highlands, with rare manifestations in the form of animal deaths due to the high resistance of local mountain ground squirrel populations to plague, is discussed. The conclusion is made about the necessity of assessing the epidemic hazard of such sporadic cases. As a preventive measure, annual preliminary disinsection in areas of mass stay of people is recommended.

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