The paper is devoted to the first experience of Russian-Malagasy cooperation in ensuring the sanitary-epidemiological well-being of the population on the island of Madagascar. It describes the results of the first expeditionary work on studying the activity of natural plague foci in the Amoron’i Mania region of the Republic of Madagascar.

The aim of the work was to summarize the experience gained during the joint expedition, as well as to develop recommendations for improving the system of epidemiological surveillance and prevention.

Materials and methods. During the expedition, methods of epidemiological analysis, epizootiological monitoring, and laboratory diagnostics (PCR, LAMP, ELISA, bacteriological method, and sequencing) were used.

Results and discussion. As part of the epizootiological monitoring, 22 communes of the Amoron’i Mania region were surveyed and 116 small mammals of 6 species were captured. 232 combined samples of small mammals’ organs (liver/spleen and kidneys/lungs), 82 samples of fleas, and 42 pools of ticks were tested for the presence of pathogens of various nature. The expedition has provided recommendations for improving plague monitoring in Madagascar. This work opens up opportunities for further collaboration between Russia and Madagascar in the field of plague surveillance, aimed at reducing the risks of infectious diseases and protecting the population from biological threats.

In 2025, high epizootic activity of highly pathogenic avian influenza virus (HPAIV) persisted globally, as evidenced by more than 7,000 outbreaks reported in poultry and wild birds across 75 countries, resulting in mortality or culling of birds exceeding 98 million specimens. The majority of outbreaks worldwide were associated with HPAIV A(H5N1) clade 2.3.4.4b, which has remained the predominant lineage in global circulation since 2021. In addition to the dominant A(H5N1) clade 2.3.4.4b subtype, circulation of other highly pathogenic subtypes was observed, including A(H5N5), A(H5N2), A(H5N8), and A(H5N9), as well as A(H7), indicating ongoing evolution of avian influenza viruses in natural and anthropogenic ecosystems. In the United States and several other countries, HPAIV A(H5N1) caused numerous infections in wild and domestic mammals as well as in humans. In 2025, the world’s first human case of A(H5N5) influenza was documented in the United States. A total of 74 zoonotic HPAIV human infections were reported globally in 2025, including 32 cases caused by A(H5) viruses of various clades (2.3.4.4b, 2.3.2.1e, 2.3.2.1a), reflecting a continuing increase in interspecies transmission that poses a potential public health threat. In the Russian Federation, high epizootic activity of HPAIV persisted throughout 2025, with outbreaks caused by A(H5N1) clade 2.3.4.4b viruses reported in both wild and domestic birds. Notably, in the Russian Far East, circulation of an A(H5N1) virus carrying mammalian-adaptive mutations associated with increased virulence in mammals was detected. Additionally, amino acid substitutions in antigenic sites were identified in several A(H5N1) isolates. Despite ongoing virus evolution, no substantial alterations in the antigenic properties of HPAIV A(H5N1) strains circulating in the Russian Federation have been observed to date.

Melioidosis is a particularly dangerous infectious disease that affects humans and animals primarily in Southeast Asia and northern Australia. The predicted spread of the natural range of the pathogen, Burkholderia pseudomallei, and the increase in melioidosis cases in the coming years threaten to become a serious public health issue. Since it takes up to seven days to isolate and identify a B. pseudomallei culture, a reliable test for its rapid direct detection in clinical samples is needed, which will allow for the initiation of treatment with appropriate antibiotics, preventing relapses and reducing mortality. The development of diagnostic approaches is complicated by the significant adaptive plasticity of the B. pseudomallei genome, which acquires new coding sequences as a result of horizontal gene transfer from microorganisms that share a common ecological niche with the causative agent of melioidosis. Most of the developed immunodiagnostic tests for the detection of B. pseudomallei were created without proper standardization and are not commercially available. These experimental tests have insufficient sensitivity and specificity and work best with an isolated bacterial culture, minimizing the advantages of rapid diagnostics. The selection of a diagnostic target remains the main challenge in developing a simple, cost-effective and valid rapid immunodiagnostic test for the detection of B. pseudomallei. This review presents an analysis of the literature data on existing and promising methodological approaches to the rapid detection of the causative agent of melioidosis using immunological methods and the search for new potential antigen targets.

In the XXI century, there has been a downward trend in the total number of cases of plague infection in Africa, North and South America, and Asia. The most unfavorable epidemiological situation was in the countries of the African region, where over 90 % of the global plague incidence was registered. The aim of this review is to analyze the spatial and temporal features of epidemic manifestations of plague on the African continent in the XX–XXI centuries. The literature data characterizing the outbreak and sporadic incidence of plague in African countries in the twentieth and twenty-first centuries are summarized. The information on the number of cases of plague infection in 1935–2024 is analyzed from a long-term perspective. A high annual incidence of plague (over 1000 cases) was recorded in the periods of 1935–1945 and 1986–2008. In 1946–1985 and 2009–2024, the total number of infections decreased significantly. It is also shown that in the first half of the past century (before 1950), cases of plague infection were registered in 25 countries located in the northern, western, eastern and southern regions of the African continent. In the second half of the last century, the number of African countries with cases of plague decreased to 20, and at the beginning of this century – to 9. It has been substantiated that in 1900–2024 the most persistent epidemic manifestations took place in the countries of East Africa and Madagascar. The noted stability of active epidemic manifestations in the natural and natural-anthropourgic plague foci is explained by a combination of ecological, epizootiological, and epidemiological factors that ensure the constant circulation of epidemiologically significant Yersinia pestis lineages (1.ANT, 1.ORI).

The aim of this study was to analyze the global plague epidemiological situation in 2025 and forecast the epizootic activity of natural foci of this particularly dangerous infection in the Russian Federation for 2026. Between 2016 and 2025, a continuing downward trend in the epidemic activity of natural plague foci was noted in many regions of the world. The total number of cases was 5,626, of which 516 were lethal (lethality rate – 9.2%). In 2025, cases of plague were registered in four countries: the Democratic Republic of the Congo (41 cases, 2 fatal), the Republic of Madagascar (18 cases, 7 fatal), the United States (5 cases, 1 fatal), and Mongolia (3 cases, 1 fatal). All in all, 67 cases of plague were reported, of which 11 (16.4%) were fatal. In the Russian Federation, despite the presence of epizootically active natural foci, epidemiological stability in terms of plague was ensured in 2017-2025. During the analyzed period, animals infected with plague were detected in three natural foci: the Central Caucasian high-mountain, Gorno-Altai high-mountain, and Tuva mountain ones. Over the past decade, a total of 337 strains of the plague pathogen have been isolated in the plagueendemic territory of the Russian Federation. The total area of identified plague epizootics was 14,570 km² (6.5% of the total foci area). In 2025, localized plague epizootics were registered in the Karachaevsky district of the Karachay-Cherkess Republic and the Elbrus district of the Kabardino-Balkarian Republic, the Kosh-Agach district of the Altai Republic, and the Mongun-Taiga Kozhuun of the Tuva Republic. Plague-infected animals were detected in three (the Central Caucasus Highland, Gorno-Altai Highland, and Tuva Mountain) of the 11 natural plague foci in the Russian Federation. The total epizootic area was 523,01 km². A total of 13 plague pathogen cultures were isolated in 2025, including 12 isolates of the 4.ANT phylogenetic branch of the ancient biovar and one isolate of the 2MED0 phylogenetic branch of the medieval biovar of the main subspecies – Yersinia pestis pestis. It is noted that from 2017 to 2025, annual preventive (anti-epidemic) measures in epizootically active natural plague foci had a consistent significant salutary effect in enzootic territories. In 2026, the low epizootic potential of lowland natural plague foci in the Caspian and Transbaikal regions will be retained. A forecast for the development of local plague epizootics in the Karachay-Cherkessia, Kabardino-Balkarian, Altai, and Tuva republics in 2026 has been developed.

An overview of the epidemiological situation on West Nile fever (WNF) in the world and the Russian Federation in 2025 is presented, a forecast for 2026 is provided. During the assessment of WNF epidemic process intensity in the Russian Federation in 2025, a three-fold decrease in the incidence (145 cases) compared to 2024 (440) and a 1,3-fold decrease compared to the long-term average values (183,2) was revealed. The incidence was registered in 22 constituent entities, including 4 previously unaffected: Republic of North Ossetia-Alania, Kirov and Kurgan Regions, Trans-Baikal Territory. Compared with long-term observation data, 2025 was characterized by a late onset of the epidemic season, a predominance of women among cases, and a significant increase in the proportion of West Nile virus infections by place of permanent residence in cities. The territorial distribution of cases, the age and social structure of the incidence and clinical manifestations of WNF were consistent with the long-term average data. In 2025, the trend of increasing volume and territorial coverage of monitoring studies continued: active detection of WNF cases was conducted in 68 constituent entities (in 2024 – 62, the long-term average – 44), epizootiological monitoring was carried out in 86 entities (81 and 68, respectively), and the immune cohort was studied in 78 (69 and 47, respectively). Enzootic circulation of West Nile virus was confirmed in 14 constituent entities, for the first time – in the Tambov Region. The proportion of positive findings in zoological and entomological material in 2025 was 0.12 % (in 2024 – 0.17 %, the long-term average – 0.18%), which may indicate a decrease in the intensity of the WNF epizootic process in Russia. In 2025, circulation of West Nile virus lineage 2 was detected in the European part of the country, with the ABB.1.1 genovariant predominating in its population structure. During the upcoming season, the Southern, Central, and Volga Federal Districts will be most actively involved in the epidemic process. With effective monitoring, incidence rates are expected to remain at the long-term average level in the medium term, in the long-run – the increase in incidence rate is predicted.

The wide spread of hantavirus infection with a tendency to a constant increase in the number of cases is an urgent concern of practical healthcare worldwide. The aim of the work was to analyze the features of the epizootiological and epidemiological situation on hemorrhagic fever with renal syndrome in the Rostov Region. Materials and methods. Epizootiological monitoring in 2023–2024 was carried out in 23 administrative territories of the Rostov Region. 1202 specimens of 14 small mammal species were examined for the presence of orthohantavirus markers: in 2023 – 755, in 2024 – 447. The stratum of the local population that is immune to orthohantaviruses was identified using ELISA. Results and discussion. Throughout the study, hantavirus markers were detected in seven administrative territories of the region: Krasnosulinsky, Millerovsky, Kamensky, Bagaevsky, Azovsky, Orlovsky districts and the vicinity of Rostov-on-Don, in populations of six rodent species: house mouse, small white-toothed mouse, small forest mouse, field vole, social vole, gray rat. Screening study of blood sera from individuals who had not had HFRS before showed the presence of class G immunoglobulins in 2023 – 18.6 %, in 2024 – 3.3 %. Regular findings of orthohantavirus markers in populations of small mammals and the annual detection of seropositive samples among the conditionally healthy population confirm the existence of a polyhostal natural focus and indicate the population contacts with components of the parasitic system.

The aim of the work was to conduct a comparative study of the composition of preparations made of outer membrane vesicles (OMV) of toxigenic and atoxigenic strains of Vibrio cholerae O1 El Tor and O139 serogroups.

Materials and methods. The work used toxigenic and atoxigenic strains of V. cholerae O1 and O139 serogroups, from which OMV preparations were obtained. The structure of OMV preparations was investigated applying transmission electron microscopy. Genome-wide DNA sequencing was performed using the MiSeq and DNB-Seq-g50 platforms. The computer analysis of the obtained data was carried out using the SeqAnalayser 2.1 software. To conduct bioinformatic analysis, the following programs were used: Exonerate version 2.4.0 and SnapGene Viewer. Protein profiling was performed using MALDI-TOF mass spectrometry. The identification of antigenic determinants: cholera toxin and outer membrane proteins (OmpT, OmpU) was carried out by enzyme immunoassay (ELISA). Enzymatic activity was detected using appropriate media and substrates. Fatty acids were indicated through gas chromatography-mass spectrometry.

Results and discussion. A comparative analysis of the composition of OMV preparations obtained from toxigenic and atoxigenic V. cholerae O1 and O139 strains has been carried out. The difference/similarity in the composition of OMV preparations has been revealed. According to the data of genome-wide sequencing and bioinformatics analysis, fragments of chromosomes containing a different set of genes and mobile genetic elements were found in OMV preparations obtained from strains with different genotypes. V. cholerae O1 and O139 OMV are able to participate in sorting and docking of cell contents, in vesiculation, contributing to the evolutionary transformations of the genome. OMV may be an additional factor in the pathogenicity/adaptation/persistence/competitiveness of the cholera pathogen.

The aim of the work was to analyze the dynamics of the epidemic process and characterize the waves of the COVID-19 pandemic in 10 entities of the Siberian and Far Eastern Federal Districts. Materials and methods. A retrospective epidemiological analysis of weekly monitoring data of laboratory-confirmed COVID-19 cases, provided by the Rospotrebnadzor Administrations in ten regions of the Siberian and Far Eastern Federal Districts of the Russian Federation (Altai, Buryatia, Tuva and Khakassia Republics; Altai, Trans-Baikal and Krasnoyarsk Territories; Irkutsk, Kemerovo and Tomsk Regions), was conducted. Results and discussion. The import of new coronavirus infection from Western European countries to the territory of the Siberian and Far Eastern Federal Districts was registered in mid-March 2020. During the pandemic, 20,888,479 cases of COVID-19 were registered in 10 entities of 2 federal districts of the country. The COVID-19 incidence was characterized by a wave-like course of the epidemic process. The dynamics of the epidemic process and the features of seven pandemic waves of varying intensity and duration are described. People over 18 years of age were more likely to become ill, with mild and moderate forms predominating, and infection primarily occurring in households. The wave-like nature of the incidence was associated with the consistent variability and change of the dominant genovariant of SARS-CoV-2. The World Health Organization declared the lifting of the public health emergency of international concern when the seventh wave of the COVID-19 pandemic in 10 regions of the Siberian and Far Eastern Federal Districts was at its plateau.

In Russia, the epidemic situation on anthrax remains unstable despite achieved progress in its prevention and treatment. Regardless of the nature of the outbreak, epidemiological investigation requires establishing the probable origin and genetic relatedness of the strain responsible, which is attained through molecular typing. Bacillus anthracis is characterized by high genetic monomorphism, complicating molecular typing. The MLST variant, a multilocus sequence typing method for virulence genes (MVLST), allows for effective differentiation of pathogen strains. The aim of this study was to select the optimal MVLST scheme for the genetic typing of B. anthracis. Materials and methods. The study used complete genomes of 49 B. anthracis strains. Phylogenetic trees were constructed using UPGMA algorithm through identifying SNPs with PhyloViz software. Protein virulence assessment and gene selection were performed using the online resource “VirulentPred Prediction of Prokaryotic Virulent Proteins”. The Hunter-Gaston discriminatory index (D) was calculated online using the Discriminatory Power Calculator program. Results and discussion. The MVLST-pXO1 scheme included 5 genes: lef, cya, pagA, atxA, gerXC, located on the pXO1 toxin plasmid. Typing with the MVLST-pXO1 scheme divided 49 strains into 21 genotypes (D=0.9209). The MVLST-pXO2 scheme covered 6 genes: 4 structural genes of capsule polypeptide (capA, capB, capC, capD), and 2 regulatory genes (acpA, acpB) on the pXO2 capsule plasmid. Typing with this scheme distinguished 14 genotypes (D=0.6675) among 49 strains. The derived MVLST-15 scheme provided higher discriminatory power compared to MVLST-19, dividing 49 B. anthracis strains into 40 genotypes (D=0.9864), whereas MVLST-19 identified 33 genotypes (D=0.9633). These results demonstrate that the MVLST-15 scheme is optimal, as it provides better discrimination of B. anthracis strains using a smaller set of loci while maintaining the classical phylogenetic structure of the anthrax pathogen.

Krasnodar Territory is a territory that combines a variety of landscape and geographical conditions and a comfortable climate, contributing to the formation of natural foci of infectious diseases there. High population density, availability of recreational areas, and developed agriculture determine a high risk of close human contact with vectors and reservoirs of natural-focal infections, which requires constant monitoring of the epizootic and epidemiological situation to prevent the mass morbidity of these infections and outlines the relevance of research in this area. The aim of the work was to assess the epizootic and epidemiological situation on natural-focal infections in the Krasnodar Territory. Materials and methods. The study used the reports from annual epizootiological monitoring provided by the Rospotrebnadzor Administration in the Krasnodar Territory, Center of Hygiene and Epidemiology in the Krasnodar Territory, the Black Sea Plague Control Station of the Rospotrebnadzor, and the Stavropol Anti-Plague Institute of the Rospotrebnadzor. The vector maps were constructed using the ArcGIS 10 software. Results and discussion. According to the results of monitoring over the past 5 years, the epizootic and epidemiological situation on natural-focal diseases in the Krasnodar Territory was characterized as unstable. During the study period, 39 to 318 cases of natural-focal infections were recorded annually. The group of the most relevant ones included Ixodidae tick-borne borreliosis, West Nile fever, leptospirosis, hemorrhagic fever with renal syndrome, tularemia. The presence of combined foci of infectious diseases has been noted, which is a factor that can negatively affect the development of the epidemiological situation in the territories of their existence. Among the primary tasks of epidemiological surveillance of natural-focal infections in the region are: epizootiological monitoring, the introduction of advanced methods of epidemiological analysis (GIS, multidimensional monitoring, genomic profiling of the studied area).

The aim of the work was to conduct phylogeographic and evolutionary analysis of Brucella melitensis strains of genetic lineage II, isolated in the territory of the Russian Federation in the context of studying the global population of the species.

Materials and methods. The study used 282 strains of B. melitensis from the collection of pathogenic microorganisms at the Stavropol Anti-Plague Institute of the Rospotrebnadzor. Whole-genome sequencing was performed using the DNBSEQ G50RS sequencer (MGI, China) and the MGIEasy FAST FS DNA Library Prep Set V2.1 kit (MGI, China) according to the standard protocol. Evolutionary and phylogeographic analysis was carried out applying the BEAST v2.7.5 software package.

Results and discussion. It has been established that the B. melitensis strains in the Russian Federation belong to four sub-genotypes of the genetic line II, which presumably diverged in the 16th century: IIb, IIg, IIh, and IIi. The singular cases of sub-genotypes IIb and IIg detection in Russia indicate the importation of infection from the Middle East. Sub-genotype IIh is prevalent in Siberia, Mongolia, China, and Kazakhstan. Variants of the most representative and genetically heterogeneous sub-genotype IIi circulate in a vast area from the North Caucasus to Northern China and are usually identified during epidemiological investigations of brucellosis outbreaks in the European part of the country. The results indicate the prospect of using genome-wide SNP analysis as an effective tool for timely detection of non-endemic or atypical variants of the causative agent of brucellosis during genomic profiling of individual regions.

The aim of the study was the genotyping of Francisella tularensis subsp. mediasiatica strains using marker SNPs based on whole genome sequencing data. Materials and methods. The work used 50 complete genomes (WGS) of F. tularensis subsp. mediasiatica strains from the NCBI database and 25 genomes, which were sequenced directly by specialists from the Rostov-on-Don Anti-Plague Institute of the Rospotrebnadzor. The allocation of individual clusters on the dendrogram was carried out with a bootstrap support value of at least >90 % (when using 1000 replications). Results and discussion. A total of 5,251 SNPs identified in a representative sample of 75 F. tularensis subsp. mediasiatica genomes were selected, with each SNP detected in at least two strains. During the bioinformatics analysis, genomes with more than 500 SNPs in regions not covered by whole-genome sequencing (WGS) were excluded. Phylogenetic analysis resulted in a dendrogram that identified 11 major clusters named after the geographic locations of early or dominant strains. These clusters were supported by bootstrap values >90 % (1,000 replicates). For strain typing within the clusters, “marker” SNPs specific to each cluster and its subgroups – but absent in others – were identified. A software tool, “SNP Genotyper”, was developed to automate genotype determination based on those marker SNPs. Genetic variability of F. tularensis subsp. mediasiatica isolates of diverse origins was studied using whole-genome SNP (wgSNP) analysis. Genetic diversity was observed among subsp. mediasiatica strains isolated in Altai Territory (Russian Federation) and the Republic of Kazakhstan. Based on marker SNPs, an algorithm has been developed for the operational analysis of WGS data from F. tularensis subsp. mediasiatica genomes. The developed method for determining genetic lineages can be a useful tool both for operational analysis when isolating fresh strains, determining the phylogenetic relationships of strains, studying the genetic diversity of a population, and conducting retrospective studies.

Currently, much attention is paid to the study of mechanisms of pathogen adhesion to human cells and tissues. Along with standard microbiological techniques, advanced biophysical methods are widely used for this purpose, among which a special place is occupied by optical trapping, which allows catching and moving individual bacterial cells with measurement of the interaction force between them and target molecules. The aim of this work was to evaluate the significance of collagen and fibronectin in adhesion of Yersinia pseudotuberculosis O1b and the vaccine strain Yersinia pestis EV NIIEG, cultivated at different temperatures, applying optical trap. Materials and methods. Bacteria grown at two temperatures (+10 and +37 °C for Y. pseudotuberculosis or +27 and +37 °C for Y. pestis) were caught by a laser beam and stepwise brought to the protein-coated glass. One second after the contact, the cell was retracted in semi-automatic mode at a constant speed until a spike was observed on the signal chronogram, and its voltage then was converted into force units. Differences between data sets were determined by the mean and median forces, as well as by the results of constructing histograms of the distribution of interaction forces. Results and discussion. The significance of collagen in the adhesion of Y. pseudotuberculosis grown at +37 °C but not at +10 °C was shown. Fibronectin demonstrated no pronounced differences between the bacteria of the two Yersinia species at all the cultivation temperature modes. In all cases, affinity of Yersinia cells with collagen and fibronectin was higher compared to the control, bovine serum albumin: 7.2, 8.1, and 2.0 pN for 1b-10 cells; 12.4, 7.6, and 4.7 pN for 1b-37 cells; 6.1, 6.6, and 4.4 pN for EV-27 cells; 7.4, 7.3, and 4.3 pN for EV-37 cells, respectively. The binding of Yersinia to collagen and fibronectin is probably due to the physicochemical properties of the bacterial surface structures and components of connective tissue, as well as experimental conditions. Revealing the mechanisms of such interactions requires additional investigations of individual Yersinia antigens applied onto polystyrene beads. The method may be introduced when working with other pathogens too.

The aim of the work was to use climate forecasts, including those from the Intergovernmental Panel on Climate Change (IPCC), in relation to Armenia to assess how climate changes could affect the habitat and populations of main reservoirs of plague and tularemia, as well as the epizootic potential of the territories; to develop ecological niche model of a natural-focal infectious disease by the example of tularemia focus in the southeastern region of Armenia under modern conditions and a forecast of the situation for 2040–2050.

Materials and methods. The work used forecast scenarios of changes in average annual temperatures and precipitation, literature data on the impact of climate change on the foci of particularly dangerous infections, and data from epizootiological survey. The model of the ecological niche of the tularemia focus in the southeastern region of Armenia was developed applying artificial intelligence.

Results and discussion. The currently registered and projected climate changes in Armenia, characterized by an increase in average annual temperatures and a decrease in average annual precipitation, will lead to an enlargement of arid areas in the republic. In this regard, the observed expansion of the little gerbil range to the north suggests the risks of epizootic manifestations of plague caused by the circulation of strains belonging to the main subspecies of Yersinia pestis ssp. pestis, in the border areas of the Transcaucasian high-mountain and the Pre-Araks low-mountain natural plague foci. Changing conditions affect the dynamics of the range of the common vole, contributing to the movement of its populations to optimal habitats located at altitudes higher than 2000 m above sea level, within which epizootic and epidemic risks for plague and tularemia are likely to increase. The predictive model of the ecological niche of the tularemia focus, developed for the southeastern region of Armenia, showed a reduction in the number of abiotic factors suitable for the circulation of the tularemia pathogen, which will lead to a 3–4-fold decrease in the intensity of epizootic manifestations of tularemia by 2040–2050.

This study was conducted in order to identify genetic markers of pathogens (RNA, 16S rRNA or DNA) of natural-focal infectious diseases of bacterial, viral and rickettsial origin in suspensions of Ixodidae ticks collected in certain regions of the Republic of the Congo. Materials and methods. The presence of markers of Q fever, rickettsiosis, anaplasmosis, ehrlichiosis, tularemia, Crimean hemorrhagic fever, tick-borne encephalitis agents was determined applying polymerase chain reaction using Russian-made diagnostic drugs. A total of 509 combined samples of ectoparasites of 5 species collected in the prefectures of Pool, Cuvette and the vicinity of Brazzaville in 2025 were studied. Results and discussion. As a result of the work, RNA of Crimean-Congo hemorrhagic fever virus (0.9 % of all samples studied), cDNA of Borrelia burgdorferi s.l. (3.9 %), DNA of Coxiella burnetii (1.8 %) and rickettsia of the tick-borne spotted fever group (45.2 %) were detected in the material from ticks. Positive results were recorded in 264 out of 509 samples (51.9 %). No genetic markers of tick-borne encephalitis, ehrlichiosis, anaplasmosis and tularemia agents were found. Some samples in which markers of the Crimean-Congo hemorrhagic fever virus, Rickettsia spp., and Coxiella burnetii in high concentrations had been identified were subjected to genetic analysis using high-throughput sequencing via nanopores on the MinIon platform (Oxford Nanopore Technologies, Great Britain); their taxonomic appurtenance to the stated systematic groups was confirmed. Based on the genetic analysis of the S segment sequences of Crimean-Congo hemorrhagic fever virus isolates, their belonging to the Africa-1 genotype with a degree of homology ranging from 98.8 % to 100 % was demonstrated. The data obtained evidences the need to continue studying the prevalence of naturalfocal infectious diseases transmitted by ticks in the Republic of the Congo and implement systematic epizootiological monitoring.

This paper presents the results of a three round seroepidemiological study of the population for SARS-CoV-2 virus antibodies presence.

The aim of the study was to assess herd immunity in the population of the Kyrgyz Republic stratified by age, gender and region.

Materials and methods. The material for the study was blood samples and personal data (questionnaire) of individuals, who agreed to participate in the study.

Results and discussion. The results of the three rounds study indicated that the proportion of seroprevalent persons at the 1st round was 30.8% (95% CI 29.5-32.1), at the 2nd round 71.2% (95% CI 69.9-72.5), at the 3rd round 92.3% (95% CI 91.5-93.1). High herd immunity in the population was defined by short-term and low incidence in the fourth wave of the pandemic compared to the global indicators of the COVID-19 fourth wave. Uneven territorial distribution of seroprevalence was observed through all rounds of the study. All three rounds of the study were characterized by the lack of coronavirus infection symptoms in some of the seropositive individuals. Symptoms presence in seropositive individuals in the second and third rounds tended to decrease compared to the 1st round results in general. The percentage of SARS-CoV-2 virus seropositive individuals among children was lower versus the adult population. The share of seropositive samples was less for men compared to women. Paired sera examination, collected after 8-20 months, showed the decreased level of antibodies by 64.6% compared to those collected 1-2 months after the disease. At the same time, an increased level of antibodies was observed in 35.4% of individuals.

The aim of the study was to create and study the immunogenic properties of Francisella tularensis strain 15 NIIEG without the sodC gene encoding CuZn-dependent superoxide dismutase. Materials and methods. Deletion of the sodC gene from the chromosome of the tularemia microbe was performed applying the allelic exchange method using the suicide plasmid vector pGM5. The modified chromosome fragment without the structural part of the sodC gene was constructed by combining amplicons synthesized via PCR using two pairs of primers. Electroporation was used to transfer plasmids into Escherichia coli and F. tularensis bacteria. BALB/c mice were used for immunization and infection. To assess the reactogenicity of the strains for mice, the average weight of animals in groups was determined. Results and discussion. The allelic exchange method was used to create the F. tularensis 15ΔsodC strain, in the chromosome of which a 545 bp fragment with the structural part of the sodC gene was missing. This strain did not differ in virulence and reactogenicity from the original strain 15 NIIEG, but mice immunized with the deleted version of the vaccine strain more easily tolerated the experimental infection caused by the natural strain F. tularensis subsp. mediasiatica A-678. It has been suggested that deletion of the sodC gene may improve the immunogenic properties of the tularemia microbe strain in the targeted design of a promising candidate for the creation of a modern tularemia vaccine with reduced reactogenicity.

The aim of the work was to evaluate the results of external quality control of molecular-genetic and immunological testing for plague in anti-plague laboratories using encrypted control panels. Materials and methods. A total of 19 anti-plague institutions participated in the external quality control program. The quality of laboratory testing was assessed using polymerase chain reaction (PCR) and fluorescent antibody method (FAM) with encrypted panels, in which the composition of samples was unknown to the participating laboratories. The PCR panels contained dried DNA preparations of Yersinia pestis EV NIIEG strain as positive samples, as well as DNA of Yersinia pseudotuberculosis and Escherichia coli at concentrations of at least 1 ng and a 15 % sucrose solution as negative samples. For assessment of plague detection applying fluorescent antibody method, fixed smears of the same microorganisms (Y. pestis EV NIIEG, Y. pseudotuberculosis and E. coli) were used at concentrations of 1·10⁶ microbial cells per milliliter. Results and discussion. The analysis of external quality control results obtained from anti-plague laboratories was performed over the period of 2011–2025. The proportion of false-positive results obtained through FAM was 0.7 %, while false-negative results accounted for 0.47 %. In PCR-based detection, false-positive results accounted for 1.27 % and false-negative results for 0.36%. The analysis made it possible to identify potential sources of analytical errors in plague detection and to determine measures aimed at their elimination. To prevent erroneous results, it is necessary to implement internal quality control procedures, ensure timely procurement of diagnostic reagents, maintain proper condition of laboratory equipment, strictly follow manufacturers’ recommendations regarding the use of validated instruments, and regularly confirm personnel qualifications. External quality control of plague diagnostics in anti-plague institutions using encrypted panels containing Y. pestis samples that simulate real biological samples is an effective tool for monitoring laboratory performance, ensuring the quality of laboratory testing, and maintaining the reliability of diagnostic results.

The aim of the work was to conduct a comparative analysis of the structure of genes encoding regulatory proteins in strains of Vibrio cholerae O1 biovar El Tor genovariants isolated in cholera endemic and non-endemic territories in different years of the seventh cholera pandemic, and their phylogenetic analysis. Materials and methods. Nucleotide sequences of complete genomes of 75 toxigenic genovariants of V. cholerae O1 El Tor with ctxB1 and ctxB7 alleles listed in NCBI GenBank, ENA, VGARus were used. Bioinformatics analysis was performed using the Blast algorithm (http://blast.ncbi), MEGA X. Phylogenetic analysis was carried out using the REALPHY server. Results and discussion. The structure of 13 loci (toxT, aphA, aphB, luxO, luxT, gntR, hapR, lysR_vc2383, lysR_vc1617, hns, vieA, carR, carS) was studied. Stable preservation of the aphB and carS genes in the genome of all strains has been established, and toxT, aphA, and luxT have been found in 99 % of them. All genovariants have an altered gntR gene (G565A) encoding a protein that represses gluconate fermentation. The majority of genovariants have an intact hapR gene, unlike the reference strain N16961, which has a thymine deletion at the position 219 in this gene. Some foreign strains include additional mutations in this gene. High variability of the luxO gene has been revealed. Mutations in other regulatory genes have been piling up gradually and stably persisted. During phylogenetic analysis, all the studied strains isolated in different endemic countries and imported to the Russian Federation and neighboring states fell under four clusters in accordance with the structure of regulatory genes. Thus, highly virulent genovariants currently isolated in the endemic territory and imported to the Russian Federation have the genotype hapR (insT219), lysR_vc2383 (C110T), hns (G319A), lysR_vc1617 (A650C), vieA (C235T), carR (G265A).

The Russian Research Anti-Plague Institute “Microbe” of the Rospotrebnadzor is the only manufacturer of medical products for phage diagnostics of plague and cholera registered in the Russian Federation. The main stage of diagnostic bacteriophage production is their accumulation in the producer strain culture, which involves the use of nutrient media (NM) with various protein bases. Researchers have noted an increasing number of cases of non-standardization of the latter, which often leads to deterioration in the qualitative and quantitative parameters of phage lysates. The aim of the work was to investigate the possibility of using fibrin peptone as an alternative basis for nutrient media at the stage of bacteriophage accumulation in the production of preparations for phage diagnostics of plague and cholera. Materials and methods. Yersinia pestis EV NIIEG was used as producer strain together with specific bacteriophages such as diagnostic Pokrovskaya and L-413C ones; Vibrio cholerae cholerae O1 145 and V. cholerae El Tor O1 75M and their specific bacteriophages – classical (C) and El Tor (XII and XV), were also used, respectively. The activity and specificity of plague bacteriophages accumulated on experimental nutrient media were tested using Y. pestis and Y. pseudotuberculosis strains, serotypes I–VI. The activity and specificity of cholera bacteriophages accumulated on experimental nutrient media were monitored using the corresponding strains of V. cholerae cholerae and V. cholerae El Tor O1. The composition of liquid nutrient media based on fibrin peptone varied depending on the needs of the cultured microorganisms in terms of the following parameters: amine nitrogen, inorganic and organic cofactor content, and hydrogen index. Results and discussion. The use of fibrin peptone as a nutrient medium base for the accumulation of plague (Pokrovskaya and L-413S) and cholera (C, XII, and XV) bacteriophages has demonstrated the results equal to or superior to those of control nutrient media specified by production regulations. Experimental bacteriophage series, compared with commercial preparations, showed compliance with regulatory requirements.

The aim of the study was to determine the prevalence of dirofilariasis agents in mosquitoes in urban areas of Belarus. Materials and methods. Female mosquitoes were collected in 3 regions of Belarus (Vitebsk, Mogilev, Gomel) from May to September 2021–2025. А total of 5039 mosquitoes were collected. Real-time PCR was conducted to detect the presence of Dirofilaria repens and D. immitis in mosquitoes. The rate of infection in mosquitoes was determined using the estimated infection rate. Results and discussion. In 2021–2025, our research revealed 23 mosquito species belonging to 5 genera (Aedes, Anopheles, Culex, Culiseta, Coquillettidia) in urban areas of Belarus. Aedes cantans was the most abundant species, accounting for 37.6 % of the mosquitoes captured, followed by A. sticticus at 36.5 %. Dirofilaria DNA was detected in 11 mosquito species (Aedes rossicus, A. cantans, A. cataphylla, A. excrucians, A. intrudens, A. riparius, A. sticticus, A. vexans, Anopheles claviger, A. maculipennis, Coquillettidia richiardii). The estimated infection rate of Anopheles, Aedes, Coquillettidia genera was 12.8 %, 1.0 %, and 0.6 %, respectively. The total infection rate was 1.4 %. The estimated infection rate of mosquitoes with D. repens was 1.3 %, while the rate for D. immitis was 0.1 %. The highest estimated infection rate was found in Anopheles maculipennis (16.7 %), and the lowest was in Aedes intrudens (0.3 %). Dirofilaria DNA was detected in mosquitoes from May to August. The highest mosquito infection rate was recorded in August.