Hemorrhagic fever with renal syndrome (HFRS) is classifed as a most widely spread natural-focal zoonotic infection in the forest and forest-steppe regions of Russia, taking a leading position by the incidence rate among the population. The Saratov region is enzootic as regards to HFRS, but it is not included in the list of constituent entities characterized by sustainably high morbidity rates. In some years, given favorable ecological conditions, explosive growth in the numbers of the red vole (the main carrier of Hantavirus) is registered, which leads to epidemic complications. In the winter 2018– 2019season, an intensive subniveal breeding of the red vole occurred, which led to an increase in the numbers of the species in the spring. The density of such animals increased, they began to spread widely across the territory. Intensive and extensive epizooties in rodent settlements developed in the natural foci of HFRS. This was especially evident in the territory of the forest park zone “Kumysnaya Polyana”, located in the vicinity of the regional center. The numbers of rodents in ravine and floodplain deciduous forests increased everywhere and amounted to 37.6% in spring and 53.7% in autumn per 100 capture gears, which was 1.6–2 times higher than the average long-term level. The index of dominance of the red vole has also doubled and amounted to 69.5%. In general, the infection rate of rodents increased by 2-3 times in the region. This indicator in the territory of the Saratov forest park was 20.6% in spring and 35.3% in autumn. Against this background, a record outbreak of HFRS was registered in 2019, namely, 109.7 cases per 100 thousand of the population, which was ten times higher than the long-term indicator (7.2). The results of this research should be taken into account when organizing and conducting epizootiological monitoring and preventive measures in the natural foci of HFRS and other zoonotic infections.
The aim of the research was to assess epizootic activity of natural plague foci in the Russian Federation in 2021 and provide a prognosis for 2022. Activation of epizootic process has been detected in Central-Caucasian high-mountain natural plague focus after a recess since 2007. Local epizootics persist to develop in Tuva Mountain and Gorno-Altai highmountain plague foci. Total area of epizooties in Russia in 2021 amounted to 1649.5 km2. 28 plague microbe strains were isolated. Animals infected with plague were not found in Tersko-Sunzhensky low-mountain, Dagestan plain-piedmont, Precaspian north-western steppe, Volga-Ural steppe, Trans-Baikal steppe, Volga-Ural sandy, Caspian sandy and EastCaucasian high-mountain natural plague foci. It is demonstrated that epidemiological welfare as regards plague in Russia in 2017–2021 was achieved through annual epizootic monitoring of plague-enzootic territories, timely epizooty detection and preventive activities aimed at reducing the risk of infection. Substantiated has been the forecast for tense epidemiological situation on the territory of Karachay-Cherkessia, Kabardino-Balkaria, Altai Republic and Tuva Republic in 2022. A new Epitracker application has been proven to be prospective for rapid assessment of actual epidemiological situation in natural plague foci.
The aim of the study was molecular-genetic identification and analysis of the phylogenetic relationship of Yersinia pestis strains isolated on the Ukok Plateau in 2020, in order to establish the current boundaries of the natural mega focus of plague in the Altai Mountains in Russia and Mongolia.Materials and methods. 37 strains of Y. pestis of the main subspecies isolated in the Tuva mountain and Gorno-Altai high-mountain plague foci and adjacent territories of Mongolia in 1971–2020 were studied. The whole genome sequencing of the strains was performed using the Ion S5 XL System (Thermo Fischer Scientific). Ion Torrent Suite software package 5.12 and Newbler gsAssembler 2.6 were used to process the data and assemble de novo the sequences of raw reads. The average size of the collected genome was 4.55 million base pairs. Core SNPs were detected by aligning the contigs of Y. pestis strains on the CO92 genome using the Snippy 4.6 program, then 28 SNP homoplasies were removed. The resulting set of SNPs contained only the core region of the genome (955 SNPs). The dendrogram was constructed using the Maximum Likelihood method applying the PhyML 3.1 program.Results and discussion. The current population structure of Y. pestis of the main subspecies, antique biovar, phylogenetic line 4.ANT, endemic to the foci of the Altai Mountains in Russia and Mongolia has been determined. The presence of 4.ANT-21 clone, which became widespread in the territory of these natural foci of plague at the begining of the XXI century, was revealed. It is shown that three strains isolated on the Ukok Plateau in 2020 belong to clone 4.ANT-21. According to phylogenetic analysis, evidence of 4.ANT circulation on the Ukok Plateau before 2018 was obtained. The lesson that has been learned is that it is necessary to study the territories of Mongolia, Kazakhstan and China bordering the Ukok Plateau in order to establish the current boundaries of the 4.ANT mega focus.
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