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The aim of the work was to study the genetic diversity and spatial-temporal genotype structure of Yersinia pestis subspecies central asiatica biovar altaica in the Gorno-Altai natural plague focus, using MLVA25-typing.Materials and methods. MLVA25-typing of 330 strains of Y. pestis ssp. central asiatica bv. altaica, isolated in the Gorno-Altai mountain natural plague focus during 1961–2015 was carried out. The phylogenetic tree was constructed with the help of UPGMA and MST algorithms.Results and discussion. The analyzed strains have been differentiated into 34 MLVA types based on cluster analysis. The formed major groups of strains show pronounced spatial confinedness. Three chorological groupings of the plague agent with peculiar genotype characteristics have been identified. Each of the groupings is circulating among the main carrier (Ochotona pallasi) population and within the limits of the similarly-named mesofocus, respectively (Ulandryksky, Tarkhatynsky and Kuraisky). MLVA25 structure of Y. pestis in Ulandryksky and Kuraisky mezofoci show stability over time; there are no significant changes from the time of their first detection in 1961 and 1999, respectively. The dramatic changes in MLVA25 structure are observed in Tarkhatynsky mesofocus, which is known from 1972. Mass expanding of the MLVA25 types which were very rare before took place there from the beginning of 1990-s, along with elimination of the types absolutely dominant up to 1980s. Most likely the changing of dominating genotypes is attributable to the bottleneck effect, arising from the sharp decline of the focal epizootic activity in the mid 1980s.

The aim of the work – analysis of peculiarities of the plague epizooty found in the southern steppe part of the Ukok Plateau in 2020.Materials and methods. Epizootiological survey was conducted over the area of 1573 km2 in July and August, 2020. 141 mammals, 157 ectoparasites (including 152 fleas), 17 bone remains samples, and 50 regurgitates of predatory birds have been tested for plague.Results and discussion. The background species of mammals – natural hosts of Yersinia pestis in the southern steppe part of the Ukok plateau are gray marmot, long-tailed souslik, and Daurian pika. Abundance of the gray marmot was high and amounted to 1.7±0.18 inhabited burrows per 1 ha (n=30) with 90 % occupancy. Three strains of Yersinia pestis ssp. pestis have been isolated: from Oropsylla alaskensis fleas collected from long-tailed souslik, gray marmot carcass, and regurgitates of predatory birds. Yersinia pestis DNA have been detected in 14 objects. Eight positive results of serological tests have been obtained. The epizooty area that was confirmed by Yersinia pestis isolation totaled 252 km2 . As a result of the survey the circulation of Yersinia pestis ssp. pestis have been for the first time established on the Ukok Plateau. The target species – the gray marmot, as well as the long-tailed souslik, are actively involved into the epizooty.

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.

The review presents the materials on the use of mobile laboratories, developed in the Russian Federation, in the framework of four main areas: monitoring of territories to identify the circulation of pathogens of natural-focal infectious diseases; monitoring of territories during the exacerbation of the epizootic situation; participation in the elimination of outbreaks of infectious diseases; monitoring of territories to control and predict the epidemiological and epizootiologic situation in preparation for mass events. The tactical and technical characteristics and the procedure for organizing the operation of the mobile laboratory for monitoring and diagnostics mounted on the platform of the KamAZ chassis are considered. A distinctive feature of the laboratory from the existing Russian and foreign counterparts is the availability of the necessary conditions for conducting research using bacteriological analysis, rapid and accelerated diagnostic methods, and performing a full cycle of works – from the preparatory stage to the destruction of infected material. Hightech equipment allows the realization of two research schemes: the first – bacteriological analysis alongside the PCR, which ensures high reliability of the results; the second – conducting the PCR at the first stage, and when identifying genetic markers of the pathogen – performing bacteriological analysis of positive samples in order to isolate the culture of the pathogen and identify it subsequently. The second scheme will reduce the volume of bacteriological studies; make changes in the tactics of epizootiological survey. Tests of the mobile laboratory have demonstrated the effectiveness of its use in the epizootiological examination of natural plague foci, including cross-border ones. Owing to the use of a mobile laboratory in the Gorno-Altaisk high-mountain natural focus of plague, a new epizootic site was identified, located in a remote area, used by the population as a summer pasture for grazing domestic animals. The use of mobile laboratories will strengthen the laboratory base of institutions that monitor particularly dangerous, natural-focal and other dangerous infectious diseases; will help to bring the advanced diagnostic technologies directly to the natural focus, reduce the risk of epidemic complications due to plague and other particularly dangerous infections in cross-border natural foci.

Objective: investigation of phylogenetic origin and affinity of Yersinia pestis strains isolated from field material collected during the epizootiologic survey of the Mongolian part of trans-boundary Sailyugem natural plague focus. Materials and methods: MLVA25-typing of 81 Y. pestis strains, including 55 isolates from the Mongolian part of transboundary Sailyugem natural plague focus, collected in 2017-2018 was carried out. The plague agent strains isolated in different years in the natural foci of Northwest Mongolia and Southern Siberia were used as comparison group. Whole genome sequencing was performed for 21 Y. pestis strains subspecies pestis isolated in Mongolia in 2018 and 1988-1990 and in Gorny Altai of the Russian Federation in 2012-2016. SNP-typing was conducted on the basis of whole genomes of Y. pestis strains identified in the current research and also genomes from GenBank international database. Search of single nucleotide polymorphisms in Y. pestis genomes was carried out in two ways: by means of snippy v. 4.3.5 software and using mummer v. 3.1 package and a set of the author’s scripts. Phylogenetic reconstruction was conducted with the help of RAxML method. Results and discussion: Results of MLVA25 typing of Y. pestis subsp. pestis demonstrated that the strains isolated in Mongolian and Russian parts of the Sailyugem and Khuukh-Serkh-Munkh-Khairkhan natural foci belong to one common cluster. SNP-typing placed the studied isolates from the Mongolian and Russian territories into 4. ANT phylogenetic line with high level of reliability which testifies to the genetic similarity of the specified pathogen groups. The data of MLVA- and SNP-typing showed insignificant variability of the plague agent in the territory of the Mongolian part of trans-boundary Sailyugem natural plague focus. On the basis of the conducted research and results of epizootiological monitoring of Russia and Mongolia border territories it is possible to draw a conclusion on gradual wide penetration of Y. pestis subsp. pestis mainly into grey marmot settlements in Southeast Altai from Northwest Mongolia.

Objective of the study was monitoring of epizootic situation in the Mongolian part of the trans-boundary Sailugem natural plague focus through 2018 for optimization of preventive and anti-epidemic activities to decrease the level of risk of human plague cases among the population in the border areas of Mongolia and Russia.Materials and methods. Epizootic survey was conducted across the area of 2668 km2 ; 282 mammals, 261 ectoparasites, including 257 fleas, were tested for plague. All laboratory investigations of the field material were carried out in the mobile laboratory for monitoring and diagnostics, mounted on the platform of KAMAZ. Field samples were subjected to molecular-genetic (PCR) and serological tests. Fresh and mummified pickings of birds of prey, corpses, caught rodents and lagomorphs, fleas collected from corpses, were tested using immune-chromatographic method (ICM) to detect capsular antigen (F1) of plague microbe. PCR and ICM positive samples were investigated applying bacteriological method. In the course of epizootiological survey, GIS-tools were employed. All the results obtained were plotted on electronic maps using QGIS 2.12.3 software package.Results and discussion. The total of 47 Yersinia pestis ssp. pestis strains were isolated from grey marmots and their fleas. Y. pestis DNA was detected in 60 objects. Serological testing showed 60 positive results. Contamination of the caught souslik with plague agent reached 4.5 % (n=22), fresh corpses and picking of predatory birds – 63.4 % (n=41), mummified corpses and leftovers, skeletal remains – 10.0 % (n=140). It was established that in the border territory, adjacent to Russia, an intensive diffused plague epizooty, caused by the agent of the main subspecies, takes place. All epizootic manifestations were revealed at the altitudes of 2400–2800 m above sea level, in densely populated grey marmot settlements. The epizooty was registered in most of the southern macro-slope of Sailugem ridge, throughout 100 km and along the whole Karalakhtu ridge – throughout 30 km. The epizooty area, confirmed by plague agent isolation, amounted to 1207 km2 (45.2 % of the examined territory).

Aim - аnalysis and evaluation of efficiency of anti-epidemic, preventive actions for decrease of plague infection risk for the population and prevention of this illness export outside the Republic Altai limits. Analysis was performed by the data of practical and research Establishments of Rospotrebnadzor. Due to occurrence of three epidemic plague foci in local population in Gorno-Altai natural focus where the infection source was an Altai marmot, the complex of organizational, anti-epidemic, preventive actions was performed for its localization and liquidation and also minimization of risk of anthropogenous plague distribution in Republic Altai and its exportation from the endemic region. Interaction of the Services and Departments in realization of organizational, anti-epidemic, preventive actions in Kosh-Agach district created the necessary conditions for localization, liquidation of the epidemic plague foci in the shortest terms, prevented the illness distribution by the anthropogenous way and its exportation outside the limits of the enzootic territory.

Objective – to study the current epidemiological risks at plague enzootic frontier territory of the Bayan-Ulgy aimag of Mongolia. Materials and methods. Epidemiological analysis was performed according to the reporting documentation of the National Centre of Zoonotic Infections in Mongolia, results of anonymous questioning of 179 residents of the Bayan-Ulgy aimag of Mongolia, materials of the Department of Health of the Bayan-Ulgy aimag, the Aimag Centre of Zoonotic Infections and the Administration of the Aimag Governor. Results and discussion. Plague was first registered in the Bayan-Ulgy aimag in 1989. The total of 9 patients with plague and 4 lethal outcomes were revealed. In all cases marmots were an infection source, the infection occurred in the process of cutting the carcasses. The majority of the plague patients had bubonic form of plague. All patients were men aged 13 to 34 years. Public inquiry showed that 21,8 % of population considered meat of marmots as a delicacy, 54 % – hunted for the animals, 25,7 % – consumed uncooked organs of marmots as a folk remedy, 19,5 % – participated in cutting of marmot carcasses. Results of the inquiry indicated that a marmot was an object of active hunting for local population. Analysis of epizootic activity of the transboundary Sailugem natural plague focus, modern social and economic conditions in the Bayan-Ulgy aimag has showed that in this territory epidemic risks have shaped and act at present. They can be divided into two groups: epidemic risks capable to cause human sporadic plague cases and epidemic risks leading to anthropozoonotic plague dissemination among the population and exportation of Yersinia pestis beyond the limits of enzootic territories. Effective interaction of anti-epidemic Institutions of Mongolia and Russia and also the Agencies and Institutions of the executive power of all levels permits to counteract these risks.

Objective – estimation of current epizootic condition of Mongolian part of transboundary Sailugem natural plague focus. Materials and methods. Epizootiological survey was performed for the area of 2335 km2, 277 mammals and 516 ectoparasites were investigated for plague. Results and conclusions. Eight Yersinia pestis subsp. pestis strains were isolated, including 7 strains – from grey marmots (6 – from the remains of meals of predatory birds, 1 from a corpse) and 1 – from long-tailed souslik (corpse). Y. pestis DNA was detected in 52 objects. Serological samples showed 40 positive results. Epizootic manifestations, confirmed by isolation of Y. pestis cultures, detection of plague microbe DNA, and positive serological results, were observed across the area of 1611 km2 covering 69 % of the inspected territory. Epizootic results indicated high infection rate of mass mammal species and first of all grey marmots. The data demonstrated that the extended plague epizooty caused by Y. pestis of the main subspecies occurred in the inspected territory in the carrier settlements. For the first time the circulation of Y. pestis subsp. pestis was registered in the Mongolian part of the transboundary Sailugem focus.

Objective of the study is to analyze the appurtenance, numbers, and dynamics of interaction of acanthamoeba from soils of GornoAltai plague focus with Yersinia pestis 367 strain, isolated in 2016 in enzootic territory of this focus. Materials and methods. Utilized were soil amoeba from Gorno-Altai high-mountain focus and the strain Y. pestis 367 of the main subspecies of antique biovar, isolated there in 2016. Determination of systematic relation of the isolated amoeba was carried out using PCR with genus specific primers and sequencing of the obtained PCR fragments followed by identification of nucleotide sequences against GenBank database. Localization of Y. pestis cells in acanthamoeba was performed using fluorescent antibody technique by means of Axio Imager Z2 (Carl Zeiss, Germany). Results and conclusions. For the first time ever established has been the presence of Acanthamoeba castellanii in soils of burrows of Marmota altaica in the numbers of up to 300000 cells/gr in Gorno-Altai high-mountain focus. Investigated has been the dynamics of interaction of these microorganisms. Preservation of the agent in vacuoles of endoplasmatic reticulum within 14 days has been revealed. It is an indicative of the possibility of Y. pestis persistence in amoeba of Acanthamoeba subspecies in soil biocoenosis of Gorno-Altai high-mountain plague focus.

Objective of the study is to comprehensively evaluate and forecast the development of epidemic process in case of anthrax in Altai Territory. Materials and methods. The data on stationary hazardous as regards anthrax areas (SHA) were obtained while analyzing cadastres of SHA in Altai Territory, as well as the reference book “Cadastre of stationary hazardous as regards anthrax areas in the Russian Federation”. Statistical and report forms from the institutions of the Rospotrebnadzor and Federal Service for Veterinary and Phytosanitary Surveillance in Altai Territory, and from Altai Plague Control Station were used for retrospective analysis of anthrax morbidity rates in Altai Territory over the period of 1953–2015. Laboratory investigations of field and clinical samples were carried out in compliance with Methodological Regulations 4.2.2413-08. Results and conclusions. Anthrax remains topical issue for Altai Territory as there are 1262 stationary hazardous areas situated in here, as well as registered animal and human infections. The density of such areas in Altai Territory is 7.5 times higher than across Siberia. Factors for the SHA formation and their sustainability are soilclimatic aspects of the region. The majority of hazardous areas are found in steppe and forest-steppe zones, predominantly along the cattle-driving paths. In Altai Territory, between 1953 and 2015, out of 1262 registered areas, 314 ones manifested epidemiological activity, including 246 new ones. Human infections were reported in 36 districts (59.1 %), while in 21 (34.4 %) – morbidity rates exceeded the territorial average. Cumulative dynamics of anthrax morbidity as regards livestock in Altai Territory in 1953–2015 showed downward trends. Complex evaluation of the situation and forecast of epidemic process development, employing composite index – epizootiological index and zoning of the territory according to the risk of epidemic complications – allows for the improvement of managerial decisions with the view to adequate anti-epidemic measures.

Objective of the study was a complex pheno- and genotypic investigation of Yersinia pestis I-3595 and Y. pestis I-3596 strains, isolated from marmots that were the source of human infection in 2015. Materials and methods. A comprehensive microbiological, molecular-genetic and mass-spectrometric studying of Y. pestis ssp. pestis strains, isolated from two grey marmots that became a cause of the plague case in Gorno-Altai high-mountain focus in 2015, was performed using up-to-date methods. Results and conclusions. It was established that the studied Y. pestis strains belonged to the main subspecies. Results of plasmid screening, multilocus VNTR-and mass-spectrometric analyses showed that those strains were closely related to Y. pestis variant detected in the focus in 2012 and in 2014, and circulating in Northwest Mongolia and Tuva natural focus.

Objective of the study is to substantiate performance, assess the conditions, and analyze the results of activities on non-specific plague prophylaxis in the epizootic territory. Materials and methods. Utilized were archival data and operational reports of Altai Plague Control Station, Irkutsk RAPI, RusRAPI “Microbe”, Center of Hygiene and Epidemiology in the Republic of Altai, and Rospotrebnadzor Administration in the Republic of Altai, as well as literature sources. Spatial analysis was carried out using GIS-technologies. Results and conclusions. Concerted and coordinated activities of the Rospotrebnadzor institutions, medical and veterinary institutions, local executive authorities have allowed for complex prophylactic and anti-epidemic measures on prevention of plague dissemination and transmission in the territory of the Republic of Altai in 2016. Demonstrated has been the necessity to expand the scope and scale of operations and scientific research in the focus, deploying advanced toolkit of methods and means.

Objective of the study is to sum-up the results of prophylactic (anti-epidemic) measures associated with elimination of epidemic focus in Kosh-Agach Region of the Republic of Altai in 2016. Materials and methods. Utilized were the data of reporting and source documentation from Altai Plague Control Station, Rospotrebnadzor Administration in the Republic of Altai, RusRAPI “Microbe”, and Irkutsk RAPI. Results and conclusions. It is pointed out that carried out in 2016 complex of organizational, anti-epidemic, and sanitary-prophylactic activities against plague is the importnant stage of rehabilitation of Gorno-Altai high-mountain natural plague focus, the final goal of which is maximally possible decrement of risks of primary human infection with plague, and in case of occurrence of such – performing of prompt response measures on localization and elimination of epidemic focus. It has been substantiated that for epidemic risk minimization in 2017 it is necessary to continue prophylactic vaccination, desinsection and deratization in the areas of predictive epizootic situation aggravation, which is contained in “Complex Action Plan of the Rospotrebnadzor Institutions for Sanitation and Rehabilitation of Gorno-Altai high-mountain natural plague focus in Kosh-Agach Region of the Altai Republic in 2017”. It is also necessary to provide for implementation of the Program on lowering risks of importation from cross-border Sailyugemsky natural focus and spread of plague in the territory of the Russian Federation, within the frames of RF Government Order No 1864-p, dated 05.09.2016.

Relevance. Despite significant advances in modern medicine in the treatment of infectious diseases, the plague has not lost its relevance and is one of the socially significant epidemic threats as a particularly dangerous infection. Every year, there are nearly 2.5 thousand cases of plague in the world, and the mortality rate 7 - 13%. Goal. Analysis of the current epizootic and epidemiological situation of the plague, and to determine the optimal set of preventive measures to ensure epidemiological welfare of population of the Republic of Altai on this particularly dangerous infectious disease. Materials and methods. Used the results of monitoring in 1961 - 2015 years of Gorno-Altai natural foci of plague. For more than 50 years bacteriologically were examined more than 290 thousand. small mammals, more than 1545 thousand fleas, isolated 2435 strains of the plague pathogen. Results. In recent years, the Gorno-Altai foci of plague most active of the 11 natural focis, located in Russia. On the Gorno-Altai territory in 2001 to 2014 isolated 801 strain of the pathogen, in 2015 - 23 strains, including 17 main subspecies. currently in the Gorno-Altai natural foci of plague there is a joint circulation of the two subspecies of the plague microbe: Y. pestis subsp. altaica and Y. pestis subsp. pestis. In September 2014 the first time since the detection foci of plague (1961) recorded the local human case of bubonic plague. in August 2015 identified a new case of the plague Conclusions. Introduction of the plague pathogen main subspecies into the ecosystem of the Gorno-Altaisk natural foci of plague greatly increases the possibility of dangerous epidemiological situation

Objective of the study is to characterize the case of human plague in the territory of Gorno-Altaisk high-mountain natural focus in 2015 and to analyze the initiated measures, associated with localization and elimination of epidemic focus. Materials and methods. Utilized are the data contained in reporting and source (primary) documentation of the FGHI “Altai Plague Control Station”, records of the Rospotrebnadzor Administration in the Republic of Altai, and information collected by the FGHI “Irkutsk Research Anti-Plague Institute”. Results and conclusions. Human infection occurred as a result of gray marmot dressing, which was caught in the Elangash River-Valley, against the background of unfavorable epizootic situation, caused by proliferation of the plague agent of main subspecie in the territory of the focus. Clinical material investigations, performed by means of bacteriological and molecular-genetic methods, showed negative findings. Applying serological method within the system of indirect hemagglutination test (IHAT)/antigen neutralization test (ANT), in blood sera, obtained at the time of hospitalization, low-titred specific antibodies to plague microbe (recognized as post-vaccinal ones) were detected. In blood serum sample, obtained 7 days later, identified were high-titer antibodies, which allowed for confirmation of clinical diagnosis - “bubonic plague”. Due to efficient cooperation between Rospotrebnadzor institutions and medical facilities, as well as municipal authorities it was possible to avoid further development of anthropogenic transmission of plague; to localize and eliminate epidemic outbreak of this dangerous infectious disease in Kosh-Agach Region of the Republic of Altai in the shortest possible time.

The data, describing epizootical and epidemical activity of the Gorno-Altai natural plague focus in 2012 - 2016 are shown. The wide dissemination of the major Yersinia pestis subtype in Marmota baibacina’s settlements led to the focus epidemical potential growth and became the reason of epidemical complications in Kosh-Agatch district of the Republic of Altai in 2012 - 2016.

Laboratory diagnostics of plague was carried out in compliance with valid operational guidelines and regulations. But its peculiarity consisted in the performance of diagnostic investigations secondary to antimicrobial therapy with application of preparations characterized by the expressed activity towards gram-negative microorganisms, including the agent of plague (ceftriaxone, ciprolet, and amikacin). The studies revealed that under antibiotic treatment during the early phase of infection the most effective method for the laboratory plague diagnostics was PCR. Based on the results of the assay it was possible to establish not only provisional, but also the final diagnosis in a patient. Obtained was genetic characteristics of the strains isolated from the patient and the marmot, withdrawn at the patient’s place, using techniques of molecular-genetic analysis, in particular PCR, multilocus VNTR, and multilocus and genome-wide sequencing. Thereupon the strains were attributed to antique biovar of the main subspecies of plague agent. In addition, close relation to Y. pestis of the main subspecies isolated in the same focus in 2012 and to the strains from Mongolian Altai and Tuvinian mountain focus was determined based on phylogenetic analysis of the isolates.

For the first time ever since the discovery of the Gorno-Altaisk high-mountain natural focus in 1961, registered has been a case of human plague infection. It occurred in the consequence of the grey marmot cutting that was caught in the territory of one of the persistent epizootic regions of the natural plague focus. The outbreak was localized and eliminated following complex anti-epidemic measures, including medical treatment of the patient; identification, isolation and management of the contact persons, both to the patient and marmot; withdrawal and disposal of marmots’ carcasses, obtained during unauthorized commercial hunting; specific and non-specific prophylaxis of the disease. Also for the first time ever received have been the evidences of concurrent circulation of the strains, subspecies Y. pestis ssp pestis and Y. pestis ssp. altaica in the regions of cohabitation of Pallas’ pika (Ochotona pallasi), Siberian souslik (Citellus undulatus), and grey marmot. Specified is the necessity to reconsider the tactics of epizootiological plague monitoring in enzootic territories where circulation of various Y. pestis subspecies is registered.

Analysis of the epizootical situation in the North-West Mongolia and bordering regions of Russia has revealed the fact that plague agent of the main ssp., for the first time ever isolated in the Altai mountain natural plague focus in 2012, is imported from Serkh-Munkh-Khairkhan, which stands approximately 240 km away from it on the straight. It has been demonstrated that possibility of Yersinia pestis ssp. pestis transfer into the territory of Gorny Altai via slow natural migration of infected rodents, lagomorphs and their ectoparasites, as well as transmission by birds or terrestrial varmints in the mountainous environment over that large distance even within the period of several decades, is extremely negligible. The situation is conditioned by the presence of numerous physical-geographical barriers between the two regions involved and ecological peculiarities of the plague vectors and carriers. It is more likely that the agent of the main spp. has appeared in Gorny Altai due to the importation of infected fleas with isabelline wheatear ( Ocenanthe isabellina ) during a spring migration.

Performed is a complex microbiological, molecular-genetic and mass-spectrometric identification of Yersinia pestis main ssp. strain, which was isolated for the first time in the history of surveillance over the Altai mountain natural plague focus in June, 2012. Determined is its high universal virulence. Plasmid screening, multi-locus VNTR- and mass-spectrometric analyses have revealed the strain to be more closely related to the plague agent variant, circulating in the territory of the natural focus Khuukh-Serkh-Munkh-Khairkhan, Bayan-Ul’giisk aimak, Mongolia.

Carried out is the analysis of spatial location of tryptophan-dependent variants of plague microbe in the territory of Altai mountain plague natural focus. 1166 Y. pestis strains isolated in 1990–2010, were studied as regards nutrient requirements. 140 of them (12 %) were determined as tryptophan-dependent. The highest occurence of such strains was registered in Ulandryk focal region (21.6 % in average). Among strains isolated in Tarkhatin focal region only 2.3 % were tryptophan-dependent, and in Kuray region they were absent. Thus, the data obtained suggest that spatial heterogeneity of Y. pestis subsp. altaica in the focus takes place.