Tick-borne encephalitis is a natural-focal infection damaging central nervous system, caused by the similarly-named virus transmitted by several species of ixodic ticks. Natural foci of tick-borne encephalitis (TBE) are widely spread in the forest and forest-steppe landscape zones of the temperate climate belt in the vast territory of Eurasia from the Atlantic to the Pacific Ocean. New TBE-endemic territories have been recently identified in Japan, the Netherlands, and in the UK – in 2019. The increasing risk of infection due to the development of tourism and visits to natural foci of TBE became a public health issue of international concern. The aim of the study is to identify modern features of TBE incidence dynamics in the Russian Federation, the state of laboratory diagnostics and prevention and to predict the incidence for 2021. The paper shows that there is a persistent downward trend in TBE-cases in Russia, which is observed through the past few years. The characteristic feature of the epidemic season-2020 was a significant reduction in the incidence of TBE: 989 cases were registered in 33 constituent entities of the Russian Federation (morbidity rate – 0.67 per 100 000 of the population). The sharp decrease of TBE cases in 2020 as compared to 2019 against the background of a decrease in vaccination can be explained, along with natural factors, by the introduction of restrictive measures during the COVID-19 epidemic. The paper also reflects the dynamics of morbidity, seeking the medical services because of tick bites, the infection rate of the carrier, the scope of vaccination, seroprophylaxis, acaricide treatments. The coverage of express-diagnostic tests of ticks for markers of associated pathogens and its availability for the population are presented. It is recognized that the epidemiological situation on TBE in the Russian Federation remains unfavorable. It demands constant attention on the part of healthcare organizations and Federal Service for Surveillance in the Sphere of Consumers Rights Protection and Human Welfare, as well as management decision making aimed at further decrement in TBE incidence through the improvement of prevention measures, specifically in the entities that are characterized by high TBE incidence. The situation requires monitoring of natural foci of infection, enhancement of prophylaxis and treatment of TBE. The paper provides the forecast of TBE incidence for 2021 and values of the 95 % confidence range of the indicator fluctuation, taking into account the presence or absence of trends in its changes in the territory of federal districts and constituent entities of the Russian Federation in 2011–2020.

The review presents an analysis of the epidemiological and epizootiological situation on Crimean hemorrhagic fever in the Russian Federation in 2020. During the stated period, 32 CHF cases were registered, which is the minimum indicator since the activation of the natural focus of CHF in 1999. The mortality rate was 3.1 %. The incidence was recorded in the Rostov, Astrakhan Regions, Stavropol Territory, the Republics of Dagestan and Kalmykia. A significant decrease in the incidence of CHF was noted in all entities of the Southern Federal District and the North-Caucasian Federal District. An imported from the Republic of Crimea case of CHF was detected in Moscow. The seasonality of morbidity, occupational, and age composition of CHF patients, modes of transmission, features of the clinical course of the disease in 2020 corresponded to the data of long-term observations. Epizootiological monitoring of the territory of the CHF natural focus showed that the abundance of Hyalomma marginatum adults and the percentage of Ixodidae tick pools positive for the presence of CCHF virus markers corresponded to the average long-term indicators at stationary observation points in 2020 , which indicates the persisting epizootiological disadvantage of the territory of the natural CHF focus in the Russian Federation. The persisting high numbers and infection rate of H. marginatum ticks can contribute to the development of an unfavorable epidemiological situation in the south of the country with a possible increase in the incidence of CHF in the Russian Federation in 2021. 

The purpose of this review is to characterize the current epidemiological and epizootiological situation in natural foci of hantavirus diseases in different regions of the world, and to analyze the literature data available. Currently, hantavirus diseases are a very urgent threat to the sanitary and epidemiological well-being of the population around the world, which can cause serious complications of the epidemiological situation. About 200 thousand cases of the disease are registered every year around the world, while the intensity and dynamics of the incidence varies significantly in different regions of the world. While in China – the country with the largest annual number of cases worldwide – the overall dynamics of the incidence has a downward trend, which is apparently due to the widespread use of specific disease prevention tools; the number of cases in European countries, on the contrary, shows a clear increase. In the Russian Federation, hemorrhagic fever with renal syndrome (HFRS) is currently the most common natural-focal disease of viral etiology. Data on the prevalence of hantavirus infection in the regions of South-East Asia and the African continent require further investigation, but it is quite obvious that hantavirus infection is a very underestimated public health issue in these regions, and its scale, due to the wide spread of carriers, may be much more considerable than is currently known.

 The purpose of the review is to assess the trends in the development of epizootic activity in various territories of the Russian Federation in order to identify the regions of increased risk of infection of the population with tularemia pathogen in 2021 and to plan and carry out high-priority measures in these regions, such as vaccination, investments in water, sanitation and hygiene infrastructure, epizootiological monitoring of natural foci and other measures aimed at suppressing the activity of natural foci and the development of herd immunity to this infection. In 2020, 41 cases of human infection with tularemia pathogen were registered on the territory of the Russian Federation, 60 % of which occurred in the Northwestern Federal District. Epizootic manifestations of the infection of varying intensity were detected in 55 constituent entities of Russia. Against this background, sporadic cases of tularemia in humans were registered in 14 regions of the country. The most pronounced epidemic complications continue in the territory of Karelia – 23 patients. 12 cultures of Francisella tularensis subsp. holarctica from the ambient environment were isolated in the Vologda (3), Rostov Regions (6), in the Khanty-Mansi Autonomous District (2), and in St. Petersburg (1). Based on the analysis of the data presented, in 2021, epidemic complications in the form of sporadic cases of the disease among the unvaccinated population in the following territories are most likely to occur: Central Federal District – in the Oryol, Ryazan and Yaroslavl Regions, as well as in Moscow; Northwestern Federal District – in the Arkhangelsk and Leningrad Regions, the Republic of Karelia and in St. Petersburg; Volga Federal District – in Tatarstan, Mordovia, Chuvash Republic, Kirov and Orenburg Regions; Ural Federal District – in the Khanty-Mansiysk, Yamalo-Nenets Autonomous Districts and the Tyumen Region; Siberian Federal District – in the Novosibirsk, Kemerovo, Tomsk and Omsk Regions, as well as in the Altai Territory; Far Eastern Federal District – in some regions of Kamchatka and Khabarovsk Territories.

Aim of the work – to assess the epidemiological situation on cholera in 2020 and to make a forecast for 2021 based on the monitoring data and analysis of morbidity around the world for the period of 2011–2020. During the period between 2011 and 2020, 4 413 988 cases of cholera were recorded in 97 countries of the world with a general trend towards a decrease in the incidence (coefficient of accuracy of approximation R²  – 0.5705). However, due to the continuing epidemic manifestations of cholera in the endemic countries of Asia, Africa and America, the epidemiological situation on cholera on these continents was characterized as unfavorable in 2020. The emergence of a new “post-Haitian” lineage was observed among epidemically hazardous strains of Vibrio cholerae O1. In 2020, no epidemically dangerous strains of V. cholerae O1, O139 were isolated from humans on the territory of the Russian Federation. 25 non-toxigenic V. cholerae O1 El Tor strains were isolated from environmental objects, eight out of which (ctxA-, tcpA+), according to PCR-INDEL typing and SNP analysis of sequences, belonged to the clonal complex. The results of the analysis of biological properties and phylogenetic relations between the isolated non-toxigenic strains provided the basis for considering the epidemiological situation on cholera in Russia in 2020 as a stable one and a similar forecast of its development in 2021. At the same time, the possibility of importation of this infection from endemic countries cannot be ruled out, as well as the need to carry out a complex of differentiated anti-epidemic (preventive) measures within the framework of the state sanitary-epidemiological surveillance in order to localize and eliminate the imported focus and avoid the spread of the infection.

The aim of the work was to substantiate the forecast of the epidemiological and epizootiological situation in natural foci of plague in the Russian Federation, countries of the near and far abroad for the year of 2021. Characteristics of the distribution of Yersinia pestis strains of the main subspecies (subspecies pestis) of medieval and antique biovars, Caucasian (ssp. caucasica) and central Asian (ssp. central asiatica) subspecies by 45 natural foci of the CIS countries are presented in the paper. The persistence of a multidirectional trend in the dynamics of epizootic activity of natural foci of the CIS countries with the circulation of Y. pestis pestis strains of the medieval biovar of the 2.MED1 phylogenetic branch and the antique biovar of the 0.ANT5, 4.ANT phylogenetic branches in the current decade has been outlined. For the Russian Federation, the development of epizootics is predicted in the Gorno-Altai highland and Tuva mountain natural foci caused by the circulation of Y. pestis pestis strains of the antique biovar 4.ANT and Y. pestis of the Altai biovar of the Central Asian subspecies 0.PE4a in 2021. For the Republic of Kazakhstan, there is a high probability of preserving epizootic activity in the North Aral, Aral-Karakum, Balkhash, Mojynkum, Taukum desert and Ili intermountain natural foci with the circulation of Y. pestis pestis strains of the medieval biovar of the phylogenetic branch 2.MED1. For the Kyrgyz Republic, the forecast for the development of plague epizootics caused by Y. pestis pestis strains of the antique biovar 0.ANT5 phylogenetic branch in the Sarydzhaz and Upper Naryn high-mountain natural foci has been substantiated. A high epidemic risk of epizootic manifestations caused by highly virulent strains of Y. pestis pestis of antique biovars 0.ANT5, 4.ANT and medieval biovar 2.MED1 for the entire territory of the CIS countries is noted. The relevance of implementing forecasts of the epidemiological situation into practice, taking into account the molecular-genetic and epidemiological characteristics of Y. pestis strains circulating in areas of expected epizootic manifestations of plague, is highlighted.

The paper presents an analysis of West Nile Fever incidence in the Russian Federation in 2020, summarizes the results and identifies problematic issues of the pathogen monitoring. Manifestations of West Nile Fever in 2020 were characterized by a low incidence rate (10 times lower than the average long-term value) with sporadic cases registration in the endemic areas of the Southern (9 cases) and Central (1 case) Federal Districts. A discrepancy between the morbidity structure (distribution by age, sex, social status) and the trends that have developed in Russia in recent years is shown. The analysis of officially recorded cases doesn’t characterize the epidemic process of West Nile fever in Russia during 2020-season as a whole. The generalized results of monitoring of the West Nile virus circulation in environmental objects in 2020 indicate a decrease in the effectiveness of its implementation and a low detectability of pathogen markers. A decrease in the volume of diagnostic studies for the active detection of patients with West Nile fever in the epidemic season (5.7 times lower compared to 2019), as well as serological screening of healthy population samples (1.6 times) has been established. The results of a molecular-genetic study of the pathogen showed that lineage 2 of the pathogen was circulating in the European part of Russia. The circulation of the lineage 4 of the virus in the enzootic cycle in the Republic of Kalmykia was found out. The genome sequences of 11 West Nile virus isolates allocated in 2019 and 2020 were obtained. Phylogenetic analysis revealed that all isolates allocated in the Volgograd Region and isolates from the Rostov and Astrakhan regions belong to the Volgograd clade of the lineage 2 of the West Nile virus. Based on the assessment of abiotic and biotic factors, possible local increases in the incidence of West Nile fever in 2021 in the regions of the Southern and North Caucasian Federal Districts and in the south of Western Siberia have been substantiated.

Objective is to analyze the incidence of Siberian tick typhus (STT) in the Russian Federation over the period of 2010–2020, Astrakhan spotted fever (ASF) and Mediterranean fever (MF) since the official registration, and to forecast the development of the epidemic process for endemic rickettsioses for 2021. The analysis of the incidence of STT, ASF and MF in Russia for the period of 2010–2020, 2013–2020 and 2014–2020, respectively, has been carried out. The forecast of endemic rickettsioses morbidity in the European and Asian parts of Russia for 2021 has been made. The average long-term incidence of STT for 2010–2020 in the Russian Federation as a whole was 1.04 (CI₉₅ 1.02÷1.05) ⁰/₀₀₀₀, with no tendency to change. The maximum relative incidence of STT is typical for the Siberian Federal District (SFD), where the average long-term incidence rate for 2010–2020 was 6.20 (CI₉₅ 6.08÷6.31) per 100 thousand of the population. The Far Eastern Federal District (FEFD) – 4.70 (CI₉₅ 4.53÷4.87) ⁰/₀₀₀₀ came in second place, the third place was taken by the Ural Federal District (UFD) – 0.08 (CI₉₅ 0.07÷0.10) ⁰/₀₀₀₀. When assessing the 11-year dynamics of the relative incidence of STT by the Federal Districts, we have detected a tendency to its stabilization in the SFD and the FEFD. In the UFD, a significant downward trend was revealed. The upward trend in the incidence of STT remained in the Altai Republic. Major decline in STT incidence was observed in the Kurgan Region, Trans-Baikal Territory, Krasnoyarsk Territory, and the Republic of Khakassia. There was a declining trend in the incidence of Astrakhan spotted fever in the Astrakhan Region and the Republic of Kalmykia. In the Republic of Crimea and the city of Sevastopol there is no trend to increase the incidence of Mediterranean fever.

A review of the epizootiological and epidemiological situation on anthrax in the world in 2020 was carried out. In the Russian Federation, five cases of human infection with cutaneous anthrax were registered in the entity of the North Caucasian Federal District – the Republic of Dagestan. A challenging situation was noted in the territory of border states – Azerbaijan, Georgia, Kazakhstan, Kyrgyzstan and Ukraine. Epizootics of anthrax among livestock and wild animals were identified mainly in African countries. At the same time, the largest number of confirmed human cases was detected in Africa (Zimbabwe, Kenya) and Asia (Indonesia). The infection of individuals with the causative agent of anthrax was primarily associated with the ingestion of meat from sick and dead anthrax animals, contact with animals during forced slaughter, skinning and processing of contaminated meat. The incidence of anthrax in the Russian Federation in 2021 will be determined by the realization of the planned volumes of preventive measures and, provided they are properly implemented, will be limited to identifying sporadic cases of infection that are potentially possible within the limits of certain regions of Russia.

The aim of our work was to compare the HBV, HCV and HIV vertical transmission risk in the Republic of Guinea.

Materials and methods. The material for the study was 305 blood plasma samples from pregnant women living in Conakry, Republic of Guinea. The samples were examined for the presence of serological (HBsAg, antibodies antiHBs IgG, anti-HBcore IgG, anti-HCV IgG, Ag/Ab-HIV) and molecular (HBV DNA, HCV RNA, HIV RNA) markers.

Results and discussion. When assessing the overall prevalence of serological markers among patients, the incidence of HBV markers was 76.06 %. Antibodies to HCV were detected only in 1 case, which amounted to 0.32 %. HIV markers were detected in 3 cases, which amounted to 0.98 %. The prevalence of HBsAg in the group under examination significantly differed between the groups of pregnant women aged 13–19 years (17.33 %) and 20–24 years (12.12 %), p<0.0001, RR=5.107 with 95 % CI: 2.458–10.612. When assessing the overall prevalence of molecular-biological markers among patients, we did not detect HIV RNA, in one patient, HCV RNA was determined, which was 0.32 %, while the incidence of HBV DNA was 20 %. Among HBsAg-positive individuals, HBV DNA was detected in 86.11 %, which was 10.16 % of the total group. Among the HBsAg-negative individuals, HBV DNA was detected in 11.15 % (9.84 % of the total group). It should be noted that in nine cases, HBV DNA was detected without any serological markers, which amounted to 14.75 % (2.95 % of the total group). Assessment of the blood-borne infections prevalence in pregnant women is significant for the subsequent identification of pathogen transmission routes in order to control and/or prevent the spread of infection.

Objective – genotyping by multilocus sequence-typing (MLST) and phylogenetic analysis of 40 Bacillus anthracis strains isolated in Russia and neighboring countries.

Materials and methods. In this study, the sequences of seven housekeeping genes of B. anthracis strains were assembled based on the data of a whole genome new generation sequencing, after which the identified mutations and their coordinates were described. The obtained sequences were used for genotyping of the investigated sample using the MLST method. The results are compared with the data presented in PubMLST database. A phylogenetic analysis was performed for the in silico fused sequences of the seven loci of the identified sequence types. The MEGA 7.0 software package was used to build the dendrograms.

Results and discussion. Two sequence types (ST) have been found in the examined sample: 35 strains belong to ST-1, and five strains that differed by one common mutation at the glpF locus – to ST-3 (according to PubMLST coding), which emphasizes the genetic separation of this group of strains. One strain has a unique mutation in the gmk gene located outside the region used for MLST. 

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 to develop and assess the efficacy of a method for Lujo virus RNA detection in clinical and biological samples using one-step real-time RT-PCR.

Materials and methods. In order to select the conservative regions of the genome, we utilized the available in GenBank database Lujo virus sequences (https://www.ncbi. nlm.nih.gov/genbank) aligned in BioEdit 7.2.5 software package ( (IbisBiosciences, USA). To conduct one-round RTPCR, reverse transcriptase and TaqF-polimerase were used. Recombinant Escherichia coli strain, XL1-Blue, containing pGEM-T plasmid with inserted synthetically-generated fragment of the virus genome, was produced to make positive control sample (PCS). Constructed recombinant plasmids were used for creating RNA-containing PCS with protective protein shell of MS2-phage. Determination of specificity of the developed method was performed with the help of control panel of RNA and DNA of 23 viral strains related to 10 families; the sensitivity – the panel of biological samples artificially contaminated with PCS. Further testing was carried out at the premises of laboratory of the Russian-Guinean Center for Epidemiology and Prevention of Infectious Diseases (Kindia, Republic of Guinea) on 265 blood sera from practically healthy persons, 110 blood sera of cattle, 83 suspensions of ticks, and 165 suspensions of organs of small mammals collected in the territory of Guinea.

Results and discussion. Two conservative polymerase gene fragments have been chosen as targets for Lujo virus RNA detection using RT-PCR. The combination of primers and probes has been experimentally selected, optimum composition of reaction mixture for PCR and mode of RT-PCR set-up established, as well as control samples C+, internal control, positive control sample developed. Sensitivity of the proposed method is 5·10³  GE /ml, specificity – 100 %. 

The incidence of Ixodes tick-borne borreliosis (ITBB) at the Island Russky (Primorsk Territory) is higher than at the mainland. There is a bidominant structure of the tick population with mass occurrence of Ixodes persulcatus and I. pavlovskyi at the island. Due to the higher infectivity and aggressiveness of I. persulcatus, it is suggested that it plays a key role in high activity of the ITBB focus at the island.

The aim of the study: to characterize the role of I. pavlovskyi in the borreliosis epizootic process based on the study of the structure of the borrelia genotype complex isolated from Ixodes ticks at the Island Russky.

Materials and methods. The ticks were collected from vegetation at three sites. Ixodide species were determined morphologically and using PCR for mitochondrial gene cox1 and nuclear multicopy locus ITS2. Infection of 233 ticks was analyzed with the species identification confirmed by all methods. Borrelia genospecies were determined by multiplex two-round PCR with the primers specific to the gene fragments 5S and 23S rRNA of Borrelia burgdorferi sensu lato complex.

Results and discussion. Coexistence of I. persulcatus and I. pavlovskyi at the island was confirmed, with different ratios in space and a gradual increase in the proportion of the latter species. The circulation of three etiological agents of ITBB: Borrelia garinii (predominantly in I. pavlovskyi), B. bavariensis and B. afzelii (in I. persulcatus) was identified. Thus, an active natural focus of ITBB has formed at the island, probably including two uninsulated chains of borrelia circulation. One chain combines I. persulcatus and small and large mammals as the tick feeders. The second – I. pavlovskyi that can feed on mammals and birds. Due to the spatial variability of the ixodide population structure at different sections of the island, the ratio of the circulating borrelia species can change, and this species becomes the main vector of the pathogenic agents in areas of I. pavlovskyi absolute dominance.

Emergence of various genovariants of the SARS-CoV-2 virus, which are characterized by a higher ability to spread and a more severe clinical manifestations compared to the initial variants, require molecular-genetic monitoring of strains circulating in the Russian Federation.

The aim of the work was to identify the VOC SARS-CoV-2 genovariants in the territory of the Republics of Bashkortostan, Tatarstan, Udmurtia, and Samara, Penza, Saratov, Ulyanovsk, and Orenburg Regions.

Materials and methods. The identification of genovariants and the determination of the type of mutations was carried out by the Sanger fragment sequencing method.

Results and discussion. The study examined 298 samples of clinical material obtained from the Centers for Hygiene and Epidemiology in the Republics of Bashkortostan, Tatarstan, Udmurtia, Samara, Penza, Saratov, Ulyanovsk, and Orenburg Regions. In 17 % of cases, the variability of the SARS-CoV-2 virus was observed for one or more markers: in three samples, a new coronavirus of the B. 1.1.7 line (“British”) was detected; in a number of cases, only one mutation was detected in the virus found in samples – deletion Y144 or substitution D138Y, E484K, N501Y, and very rarely two mutations – deletion Y144 and substitution E484K. The presence of the L141-G142-V143 deletion localized in the recurrent deletion region RDR2 of the S-gene was shown in 10 % of the cases. The data obtained indicate the heterogeneity in macroorganism of the population of the new coronavirus with the deletion L141-G142-V143, which leads to a change in the antigenic structure of the virus, which probably allows the virus to evade the immune response.

The aim of this work was to study the composition and functions of intracellular and extracellular proteases of the production Vibrio cholerae strains 569B serovar Inaba and M41 serovar Ogawa using zymographic and proteomic analysis.

Materials and methods. Samples of intracellular proteases were obtained from cell lysates by ultrasonication of bacterial cells in a 9 M urea solution. The extracellular protease fraction was precipitated from the culture liquid by adding 50 % trichloroacetic acid to a final concentration of 10 % and incubating on ice. Lyophilized preparations of proteinase K and proteovibrin enzyme complex were used as a control of proteolytic activity. Proteases were detected by substrate gel electrophoresis in 12.5 % polyacrylamide gel impregnated with 0.1 % gelatin, followed by identification of the composition of protein fractions of lysates and exoproteins of both strains using molecular mass spectrometric scanning.

Results and discussion. A comparative study of the production strains of V. cholerae 569B serovar Inaba and M41 serovar Ogawa using zymographic and proteomic analysis showed that the greatest enzymatic activity was detected in the fraction of extracellular proteases sample of V. cholerae M41 strain, where five major and four minor zones of gelatin hydrolysis were identified, and high-intensity zones with MW 20–23 and 37–40 kDa were also found in the preparation of proteovibrin isolated from the culture fluid of that strain. As a result of proteomic analysis of the studied strains, 66 enzymes of V. cholerae with different functional activity were reliably identified, among which 15 enzymes had protease activity. The high information content of the complex of modern methods provided for the possibility of identifying qualitative and quantitative differences in the composition of intracellular and extracellular proteases in production strains of V. cholerae, which offers an effective means of screening inter-strain differences in the protease spectrum in production strains.

The study presents a characteristic of the current epidemiological situation on leptospirosis in the Republic of Tatarstan, investigation of the circulation of leptospirosis agents among the population of small mammals, and the species composition of Leptospira that caused diseases in humans.

Materials and methods. The paper contains the data on the incidence of leptospirosis among the population in the Russian Federation (RF) for the period between 2000 and 2018, in the Republic of Tatarstan – since 1998, submitted by the Rospotrebnadzor Administrations in the constituent entities of the Russian Federation, materials of the Center for Hygiene and Epidemiology in the Republic of Tatarstan and the Main Veterinary Administration of the Republic of Tatarstan.

Results and discussion. We have carried out the analysis of the epidemiological situation in the Republic of Tatarstan for the period of 1998–2018, by the administrative territories of the republic. The incidence of human leptospirosis caused by various leptospira serogroups has been assessed. In total, 112 people got infected with leptospirosis during the analyzed period. Also the data of epizootiological survey of small mammals inhabiting the natural foci of leptospirosis in the republic are presented. Laboratory tests of 1565 samples from mouse-like rodents for the presence of leptospirosis pathogens have been performed. 1.9 % of the tests gave a positive result. Dominant in the Republic of Tatarstan are the serogroups of Leptospira – Leptospira grippotyphosa and L. hebdomadis. The results of laboratory studies on the carriage of leptospira among small mammals and contamination of environmental objects indicate the circulation of pathogens of leptospirosis in the population of small mammals, habitant in forest shrub, near-water and meadow field stations of the republic. The red vole prevails in this community, the average index of its dominance is 66.7 %. Epizootiological monitoring point to a latent epizootic process in the community of mouse-like rodents.

Objective of the study was to assess the infection rate in the population of the main CCHF virus vector Hyalomma marginatum and its impact on the CHF incidence in the Stavropol Region.

Materials and methods. The data on spontaneous infection of H. marginatum ticks in the territory of the CHF natural focus in the Stavropol Region for the period 2012–2018 are presented. In total, more than 22.000 H. marginatum specimens pooled in 1546 samples were tested. The indication of CCHF virus was performed by PCR method using the reagent set for detecting RNA of the CCHF virus “AmplySens® CCHFV-FL” (produced by Central Research Institute of Epidemiology, Russia). To determine the individual infection rate in pools Beklemishev`s method was used. The data on CCHF incidence and amount of tick-bitten persons are taken from official statistics and Annual Epidemiological Report on CHF Incidence provided by the Rospotrebnadzor Administration in the Stavropol Region for the period of 2012–2018.

Results and discussion. RNA of CCHF virus was detected in 161 (10.4 %) out of 1546 pooled ticks. The highest infection rate (20 %) was among nymphs. The infection rate for pooled males of H. marginatum was 11 % and for females – 8.5 %. Circulation of Crimean-Congo hemorrhagic fever virus is confirmed in major part of the Stavropol Region. The average infection rate among H. marginatum population was 1.54 % for the period of 2012–2018, ranging from 0.23 % in 2014 to 2.97 % in 2017. It is established that the level of infection rate among H. marginatum population does not affect the CHF incidence in the Stavropol Region. Probably it is not the number of infected ticks in the population that determines the CHF incidence rate but their abundance.

The goal is to study the features of the biological properties of Vibrio cholerae strains found in environmental objects (EO) on the territory of Rostov-on-Don from 1989 to 2018.

Materials and methods. Bacteriological, molecular biological and statistical methods were used to study 73 strains of cholera vibrios O1, O139 and 1702 strains of nonO1/nonO139 serogroups isolated over a 30-year period.

Results and discussion. It was found that in Rostovon-Don, 78.0 % of toxigenic strains were isolated from all isolated from environmental protection in Russia, among which 2 were genetically unchanged. The V. cholerae O1 classical strain and 72 V. cholerae El Tor strains were found, of which 70 % belonged to the Ogawa serovar, and 3 % of the nontoxigenic strains were susceptible to the classical phage. A “very weak direct relationship” was statistically revealed between the isolation of V. cholerae O1, O139 and V. cholerae nonO1/nonO139 strains, in which the dominant serogroups (O67, O76, O75, O53, O16) were identified, and 18 % of the strains showed atypical agglutinability. Revealing the biological characteristics of V. cholerae strains contributes to the optimization of monitoring studies.

Objective of the study was an assessment of the degree of contamination of cholera chemical vaccine at the stages of preparation and determination of the ways to reduce it.

Materials and methods. Liquid and lyophilized components of the cholera chemical vaccine used in the study: cholerogen-anatoxin and O-antigens of Vibrio cholerae 569B and V. cholerae M-41 strains, as well as auxiliary substances (sucrose, talc, calcium stearate, starch). Granulation was carried out in a device that works on a fluidized bed principle, GPCG 2 (GLATT, Germany). Subsequent tabletizing of the mixture was performed using MiniTabT compression machine (LUXNER, Germany). Studies were conducted on the evaluation of “microbiological purity” at the stages of manufacturing of the cholera chemical vaccine, tablets coated with an enteric coating. Positive or negative growth of microorganisms on Petri dishes with nutrient media was determined on visual inspection.

Results and conclusions. The dynamics of changes in microbial contamination at certain technological stages of vaccine production has been revealed. It is shown that the solutions of antigens in the process of separation are subject to microbial contamination which is associated with the use of ammonium sulfate during precipitation and non-sterile water at the stage of dialysis. Sterility of semi-finished products has been achieved through twophase filtration of choleragen-anatoxin and sterilization of O-antigens of V. cholerae 569B and V. cholerae M-41 strains with flowing steam at (100±1) °C for 30 minutes. In order to decrease microbial contamination at the stage of granulation additional fine filters were installed in the air-supply system. Further on comparative assessment of microbial purity of vaccine batches obtained using both, direct compression and preliminary granulation, was carried out. It has been experimentally demonstrated that granulation of the components of a tablet mixture of cholera vaccine leads to a decrease in the level of bacterial contamination and improves the microbiological purity of the finished dosage form.