The year 2023 saw a challenging epizootiological and epidemiological situation regarding highly pathogenic avian influenza. The virus affected 150 bird species and dozens of mammal species. More than 650 outbreaks were reported in poultry across 29 countries, resulting in the death or destruction of approximately 19 million specimens. There was a high incidence of the influenza among wild birds (approximately 3,000 outbreaks in 65 countries) and mammals (more than 16,000 cases). The majority of outbreaks in wild birds, poultry and mammals were caused by influenza A(H5N1) clade 2.3.4.4b viruses. Many countries in Europe, Asia, Africa, North and South America experienced the outbreaks throughout the year. For the first time, a polar bear death from A(H5N1) virus was documented. Moreover, molecular markers of virus adaptation to mammals were found in PB2 proteins of 50 % of influenza A(H5N1) viruses that caused the death of animals. During the year 2023, human infections with highly pathogenic avian influenza A(H5N1) viruses were reported in Cambodia, Chile, China, and the UK. In addition, human infections with A(H3N8), A(H5N6), A(H9N2) and A(H10N5) viruses were reported in China. In Russia in 2023, outbreaks among wild birds and poultry were registered in 25 regions, as well as an outbreak among fur seals in the Sakhalin Region. The stated outbreaks were caused by highly virulent influenza A(H5N1) clade 2.3.4.4b. Hemagglutinin sequences of all Russian viruses analyzed in this study in 2023 were genetically close to the WHO candidate vaccine strains A/Astrakhan/3212/2020 (H5N8), A/chicken/ Ghana/AVL-763_21VIR7050-39/2021 (H5N1) and A/American Wigeon/South Carolina/22-000345-001/2021 (H5N1). All studied A(H5N1) viruses were antigenically similar to the A/Astrakhan/3212/2020 vaccine strain.

Russian Research Anti-Plague Institute “Microbe” of the Rospotrebnadzor develops and implements methods for obtaining and purifying biologically active substances of the causative agents of plague, cholera, tularemia and anthrax, which are used in the design of preventive and diagnostic preparations.

The aim of the review is to summarize and systematize the accumulated data on the isolation, purification and assessment of antigens and toxins of plague, cholera, tularemia and anthrax pathogens. Attention is also paid to the application and prospects for using the obtained antigens for the design of medical immunobiological preparations (MIBPs). The Institute “Microbe” is a reference center for plague, hence modern immunodiagnostic drugs are necessary and in demand. Antigen-level preventive drugs against the infections listed above are also the subject of study by the institute’s staff. The main stages of isolation, purification and analysis of antigens include the selection or construction of a suitable strain; cultivation, extraction, concentration and purification of antigens and toxins using biotechnological techniques that allow for obtaining and preserving the biologically active substance of interest to the researcher. To study the antigenic activity of purified antigens, laboratory animals are involved, the immune response is recorded and analyzed, and antiserum is obtained. This is followed by the stage of investigating the physicochemical and immunobiological properties of the isolated antigen preparations and drawing up an antigen profile. The characterized antigens are used for the design of preventive and diagnostic drugs.

The aim of the review is to analyze the literature data on systems of resistance to lytic cholera phages in Vibrio cholerae strains. Cholera phages are both present in the water of open reservoirs and isolated together with the pathogen from cholera patients. The mechanisms of molecular protection of V. cholerae from phages are similar to these systems of other bacteria, act at all stages of phage infection and include the following stages: prevention of phage adsorption, degradation of phage nucleic acids and inhibition of the formation of phage particles. Blocking the interaction of a phage with a bacterial cell occurs as a result of modification of receptors and the production of extracellular polysaccharides that create a physical barrier between the phages and the cell surface. If the phage DNA does enter the cells, it is destroyed by restriction-modification enzymes, as well as by the adaptive immune system CRISPR-Cas. The most numerous are the mechanisms for blocking the formation of phage particles in cells. This process occurs with the participation of phage-inducible PLE islands, the BREX bacteriophage exclusion system and abortive Abi infection, including the cyclic oligonucleotide-based anti-phage signaling system (CBASS) and the toxin-antitoxin system. During Abi infection, cells infected with the phage self-destruct and die before mature phage particles are formed, which contributes to the preservation of the V. cholerae population. The molecular mechanisms of a number of anti-phage systems have not yet been fully elucidated, which indicates the need for further study of the phage-host relations.

The aim of the work was to perform a brief overview of the data on the development, the main tasks of the Federal State Institution of Health “Rostov-on-Don Research Anti-Plague Institute of the Federal Service for Surveillance on Consumers’ Rights Protection and Human Wellbeing (Rospotrebnadzor) and its contribution to ensuring the sanitary and epidemiological welfare of the population of the Russian Federation. The review is based on the analysis of the reports on research work, archive materials and literature sources. Currently, priority and promising areas of research at the Institute are: epidemiological monitoring of cholera pathogens and natural-focal infections with an assessment of epidemiological risks and threats based on advanced methods of detection and identification of agents; development of measures aimed at preventing the spread of infections; epizootiological survey of natural foci of particularly dangerous infections; development of predictive modeling risk assessment systems, new techniques and approaches to improve laboratory diagnostics and epidemiological surveillance; development of sequencing; modernization of monitoring, including using molecular biological methods, and control of infectious diseases using geo-information technologies; transition to genomic epidemiological surveillance; improvement of unified online databases, creation of technologically independent, unified software platforms for bioinformatic analysis of the results of genome-wide sequencing; research of genetic markers of antibiotic resistance, as well as immunopathogenetic aspects of the course of particularly dangerous and other infections; ensuring interaction with all interested services and agencies in organizing and conducting events within the framework of sanitary protection of the territory. Relying on the vast experience of predecessors and stateof-the-art knowledge, the Rostov-on-Don Research Anti-Plague Institute of the Rospotrebnadzor actively takes part in solving topical issues to scientifically and practically support the provision of sanitary-epidemiological well-being and biological safety of the population of the Russian Federation.

Data on the incidence of brucellosis and main trends in the development of situation on this infection in countries around the world under current conditions are provided in the review. A detailed analysis of epizootiological and epidemiological situation regarding brucellosis in the Russian Federation over the last decade and a forecast for human brucellosis incidence for 2024 are given. It is established that global situation on brucellosis in different regions of the world has undergone changes over the past 15–20 years. One can observe an almost twofold increase in the number of countries affected by brucellosis in the world. A relatively high brucellosis morbidity rates were recorded in some countries in Africa, Central Asia, South and South-East Asia, Central and South America. In countries of the European Union, there is a trend towards an increase in the number of human brucellosis cases associated with travel to enzootic countries. In the Russian Federation, an unstable epidemiological situation has been observed over the past 10 years. 3537 cases were identified. In 2022–2023, an emerging trend towards an increase in incidence of brucellosis among population by 30–50 % as compared to long-term average values was recorded, linked to occurrence of cattle epizooties, including at large livestock enterprises; formation of group epidemic foci in previously relatively brucellosis-free territories of the Central, Volga and Southern Federal Districts; and the deterioration of epizootic situation on brucellosis in the Republic of Dagestan and a number of constituent entities of Siberian Federal District. Situation on brucellosis in the Smolensk and Bryansk Regions requires closer attention. There are signs of rooting (enzooty) and further spread of brucellosis among cattle there in 2023. In 2024, incidence rate can be predicted to be 35–40 % higher than the long-term average values. The number of human brucellosis cases may be approximately 480–530 (0.32–0.36 per 100 000 population).

Oral vaccines are drawing more attention due to their ease of administration, lesser invasiveness, and greater safety in general. The review discusses the benefits of oral vaccination in stimulating humoral and cellular immune responses at the systemic and mucosal level to provide expanded and longer-lasting protection. Aspects related to the structure of the intestine and immunological recognition of the antigen during the transformation process after penetration into the intestine are analyzed. Approaches used to improve the effectiveness of oral vaccines are considered. Problems such as instability and lack of effectiveness of oral vaccines are discussed, as well as recent developments of adjuvants and delivery systems based on mineral salts, substances of microbial origin, saponins, polymers, micro- and nanoparticles, liposomes, which have the potential to increase the effectiveness of oral vaccines. A brief analysis of licensed oral vaccines is given and the data on the development of prototype vaccine preparations using modern methods of genetics, molecular biology and immunology, as well as the mechanisms of inducing an immune response are summarized.

The aim was to assess the level of toxin production in Vibrio cholerae El Tor genovariants and to determine the localization of cholera toxin in vesicles.

Materials and methods. The work is performed on typical strains and genovariants of V. cholerae El Tor, which were grown in AKI liquid nutrient medium and the one prepared according to J. Hyan recipe, providing for high toxin production under aeration conditions. The decontaminated supernatants of the studied strains served as a source for extraction of toxin preparations and membrane vesicles. The localization of cholera toxin inside or on the outer surface of vesicles was determined through polyacrylamide gel electrophoresis (PAGE), immunoblotting, GM1-ELISA, indirect uncompetitive ELISA, cell culture models CHO-K1, HuTu 80.

Results and discussion. Vesicle preparations containing cholera toxin have been isolated from the supernatants of genovariants and typical V. cholerae El Tor with a high level of toxin production. After separation of the vesicles using PAGE, followed by immunoblot with a specific antitoxic serum, it has been found that cholera toxin retains the complete structure, including both subunits. Unlike CT secreted into the culture medium, vesicle-associated one does not bind to both the GM1 receptor of gangliosides sensitized on plates and on the surface of cell cultures, which indicates its absence on the outer surface of vesicles. The location of CT in the cavity of vesicles is also evidenced by their positive reaction with specific antitoxic antibodies after degradation of EDTA. The absence of the toxin on the outer surface of vesicles in typical strains and strains of V. cholerae El Tor genovariants excludes its binding with the GM1 receptor and suggests the possibility of their penetration into target cells via GM-independent pathways. The choice of the pathways by which the vesicle-associated toxin is transferred to host cells is probably determined by the location of the toxin, i.e. it is associated with the internal structures of vesicles or placement on their surface.

The aim of the work was to determine the species diversity of the causative agents of Ixodidae tick-borne borrelioses in Ixodes persulcatus ticks in the Khabarovsk Territory.

Materials and methods. During the epidemic season (April–October) 2017–2023, 4751 specimens of I. persulcatus Schulze, 1930, removed after attachment to humans and 418 ones collected from vegetation in the Khabarovsk Region, were studied. Ixodidae ticks were collected in the green areas of Khabarovsk city during the snowless season of 2021–2023, as well as in the territory of the Khabarovsk Region on the flag. DNA of the borrelia complex Borrelia burgdorferi sensu lato (s.l.) and B. miyamotoi was detected in ticks using real-time polymerase chain reaction (PCR). Differentiation of borrelia species in samples containing genetic material of B. burgdorferi s.l. was carried out in two stages. At the first stage, the presence of DNA from borrelia of the B. garinii s.l. group (B. garinii + B. bavariensis) and B. afzelii DNA was determined in the sample. At the second stage, positive samples of B. garinii s.l. were differentiated into B. garinii sensu stricto (s.s.) and B. bavariensis.

Results and discussion. In engorged ticks, genetic material of B. burgdorferi s.l. was detected in 45.7 % of the cases, DNA of B. miyamotoi was identified in 7.2 % of samples. In ticks collected from vegetation, the DNA of B. burgdorferi s.l. was detected in 38.0 % of cases. Upon further study, the genetic material of B. afzelii and borrelia of the B. garinii s.l. group was identified in 47.2 % of cases for both pathogens. Within the group B. garinii s.l., DNA of B. bavariensis was detected in 18.6 %, B. garinii s.s. – in 8 % of samples, at the same time, mixed infection was noted in 53.3 % of cases. The infection rate with B. afzelii in I. persulcatus ticks turned out to be statistically significantly higher than that for B. garinii s.s. and B. bavariensis, thereat statistically significant differences in tick infection rates with B. garinii s.s. and B. bavariensis was not detected.

The aim of the work was to characterize sporulation genes and proteins in Bacillus anthracis strains of major genetic lineages.

Materials and methods. Genome analysis was carried out in silico using the genome of the Ames Ancestor strain as a reference one, 47 B. anthracis strains from the GenBank NCBI database, belonging to the main lineages A, B, C, the genome of the CI strain Bacillus cereus biovar anthracis, 7 strains from the collection of Stavropol Research Anti-Plague Institute of the Rospotrebnadzor, as well as the NCBI Protein Database resource. Identification of polymorphisms was performed in BLASTn, BLASTp, MEGA X, MAUVE, and Tandem Repeat Finder software. Gene and protein sequences were aligned using MEGA X program.

Results and discussion. A comparison of polymorphisms in sporulation proteins and genes of three major genetic lineages has showed that the number of all forms in B. anthracis strains of B, C lineages and Bacillus cereus biovar anthracis exceeds those in strains of lineage A by 4,5–10, 6,8–92 and 160–2078 times, respectively. A larger number of non-synonymous SNPs in sporulation genes with changes in the amino acid composition and function of proteins in B. anthracis strains of the major genetic lines B, C and B. cereus biovar anthracis than in strains of lineage A suggests their limited adaptive capabilities and may be one of the explanations for their lower prevalence as compared to line A.

The current study summarizes and analyzes new challenges to the sanitary protection of the Russian Federation related to the dynamics of the epidemiological situation in the countries of the world and trends in the structure of international passenger traffic.

The aim is to improve approaches to reducing the risks of importation of dangerous infectious diseases based on development of additional criteria for dynamic assessment of epidemiological disadvantage in foreign countries and individualization of risk determination in relation to all in-coming flights.

Materials and methods. The present-day epidemiological situation was analyzed using data from reports and periodicals of WHO, Centers for Disease Control and Prevention, Ministries of Health of the countries and scientific publications. Information on the structure of passenger traffic is provided according to the portal of the Unified Interagency Information and Statistical System (pre-pandemic period – 2018, first half of the year 2023). Statistics on transport communication was obtained from the public reports of the Ministry of Transport of the Russian Federation and the Federal Air Transport Agency for 2022 and the first half of the year 2023. Information on the results of the sanitary-quarantine control (SQC) is presented according to the data logged in the automated information system “Perimeter”.

Results and discussion. Taking into account the analyzed data in regard to the new threats to the system of sanitary protection of the territory of the Russian Federation, infections in the list of infectious diseases, requiring sanitary protection measures, should be differentiated into two categories based on the criteria of significance for implementation of SQC. A set of criteria, including retrospective analysis of morbidity, the presence of persistent conditions of stable circulation of the pathogen and the possibility of transmission from person to person in case of introduction into the territory of the Russian Federation, has been put forward for the most relevant medium-term assessment of the risk of importation. In addition, the increasing threats and challenges to sanitary protection dictate the need to use advanced information technologies within the framework of sanitary-quarantine control.

Ensuring the sanitary and epidemiological well-being of the population is impossible without the development of international cooperation in the field of preventing and responding to biological emergency situations. To date, a unified system of monitoring and prompt response to emergencies in the field of public health of sanitary-epidemiological nature has almost been formed in the space of the Commonwealth of Independent States (CIS). To implement legitimate interaction between the Commonwealth countries, it is necessary to develop a regulatory and methodological framework. For this purpose, the Coordination Council on the issues of sanitary protection of the territories of the member states of the Commonwealth of Independent States from the importation and spread of particularly dangerous infectious diseases has drawn a number of interstate documents, which were subsequently put into effect in the CIS. The paper presents the activities of the Coordination Council aimed at establishing and maintaining the functioning of a unified system for monitoring and prompt response to emergency situations and developing a regulatory and methodological framework that allows legitimate interaction between the Commonwealth countries.

The aim of the study was to test the possibility of identifying isolates of pathogenic Borrelia burgdorferi sensu lato by the specificity of linked sequences of their recA and ospA gene loci, i.e. using the optimized multilocus sequence analysis (MLSA) method.

Materials and methods. 25 Borrelia isolates from adult hungry Ixodes ricinus ticks collected in the forest-steppe part of the Voronezh Region were studied. Isolates were obtained through seeding the mid-gut of ticks on BSK medium. Their primary identification was performed by analyzing the linked sequences of the recA and ospA gene loci with a total length of 360 bp. Selective control of species affiliation of Borrelia isolates was carried out according to the protocol of full MLSA via assessment of the nucleotide sequences of 6 genes (recA, ospA, rrs, hbb, groEL, fla) and the intergenic spacer rrf-rrl (total length of all 7 loci being 1187 bp) using the BLAST platform, Sequence scanner 2 and MEGA11 programs.

Results and discussion. The heterogeneity of the nucleotide sequences of recA and ospA genes in 25 Borrelia isolates has been investigated. Construction of dendrograms has revealed at least 5 different sequence variants among the isolates. The similarity of isolates within each of these five groups, as well as their distinction from comparable linked sequences of other pathogenic species of the B. burgdorferi sensu lato complex is demonstrated. To confirm the results obtained, a set of isolates from each group was sampled using the full MLSA protocol. It has been established that five Borrelia species circulate in the studied ecosystems of the Voronezh Region: B. afzelii, B. garinii, B. bavariensis, B. burgdorferi sensu stricto, and B. valasiniana.

The paper considers the key areas of international activities of the Federal Service for Surveillance on Consumers’ Rights Protection and Human Well-being in strengthening cooperation with specialized agencies of foreign countries in the global provision of sanitary-epidemiological welfare of the population at the current stage. Consistent work to strengthen the international network to counter emergency situations of a sanitary and epidemiological nature through effective interaction in the field of rapid response with partner countries in the near and far abroad, including through the organization of joint scientific and practical centers for the study and prevention of infectious diseases is presented. It is shown that the programs being implemented are aimed at strengthening the national healthcare structures of partner countries to achieve independence in the implementation of monitoring and anti-epidemic measures and building a single epidemiological space, independent of the influence of global and regional geopolitical fluctuations. The relevance of increasing interstate cooperation in the field of analysis and control of biological threats, primarily infectious diseases with the potential for emergencies of a sanitary and epidemiological nature of international concern, in the South American region is considered. The currently expanding strategic biosecurity collaboration with the Bolivarian Republic of Venezuela through the establishment of the first joint research center in the South American region is described. The first results of the joint work of Russian and Venezuelan specialists are presented, confirming the successful integration of Russian experience in monitoring and preventing biological threats into the system of ensuring the sanitary and epidemiological well-being of the Venezuelan population. Promising areas for further joint research are discussed.

The aim was to determine the phylogenetic position and features of the genome organization of individual groups of Vibrio cholerae strains isolated in Siberia and the Far East under different epidemiological situations during the seventh cholera pandemic.

Materials and methods. We examined 275 V. cholerae strains, isolated during epidemic complications and during the cholera-free period in Siberia and the Far East, with different profiles of the main genomic loci of pathogenicity. The genomes of 969 V. cholerae strains from GenBank were used for phylogenetic analysis. The phylogeny reconstruction was carried out through calculating the distances between strains based on the occurrence of k-mers. The search, analysis and visualization of the loci structure in mobile genetic elements in V. cholerae genomes were performed using the blastn and Prokka programs and the author’s R and Python scripts.

Results and discussion. Strains of V. cholerae isolated in Siberia and the Far East have been included in three global phylogenetic lines – L2, L3, L4. The distribution of strains from Siberia and the Far East along phylogenetic lines corresponds to the epidemiological situation in which they were isolated. We have identified the differentiation of strains by groups consistent with the global waves of spread of the etiological agent of the seventh cholera pandemic. We also traced potential paths for the import of the cholera pathogen into the territory of the Russian Federation. It has been revealed that spontaneous mutants that lost cholera toxin genes during storage and cultivation on nutrient media belong to the L2 phylogenetic lineage as well as toxigenic El Tor vibrios. The structural analysis confirms the differences in their genome organization and strains that do not have a CTX prophage during primary PCR screening. We recommend a two-stage algorithm of phylogenetic analysis within the framework of genomic monitoring of cholera agent: the first stage is a simplified assessment based on the occurrence of k-mers for express epidemiological analysis; the second stage is an in-depth analysis of genomes using a complex of phylogenetic methods for the reconstruction of links in individual epidemic complications, to establish patterns of origin and time of divergence of the pathogen clones.

The aim of the work was to determine the pheno- and genotypic features of the aquatic CTX⁺ strain of Vibrio cholerae isolated in 2023 and a comparative bioinformatic analysis of whole-genome sequencing data.

Materials and methods. Whole-genome sequencing was performed on MiSeq (Illumina) and MinIon Oxford Nanopore Technologies (ONT) platforms; hybrid assembly of the whole genome was carried out using the Trycycler algorithm; assembly errors were eliminated by means of the Medaka algorithm and the Pilon program. Dendrogram construction and bioinformatics analysis were carried out with the help of the scipy and Graphviz packages, BioEdit, BLASTN, BLASTP, CARD, ICE Genotyper, and Vector NTI programs. The ability to produce cholera toxin was tested using the GM1ELISA.

Results and discussion. The isolated strain was identified as V. cholerae O1 Ogawa, sensitive to most antibiotics. Based on the totality of genetic properties, it was classified as the first genovariant, distinct from the typical El Tor strains only by the presence of ctxB1 gene of classical type instead of ctxB3 of the El Tor type. It has been established that it contains a tandemly duplicated CTX prophage on the small chromosome and a tandem of two copies of RS1 prophage on the large chromosome. Thereat, the rstR gene of the CTX prophage belonged to the classical type, and the RS1 prophage – to the El Tor type. The remaining criteria of epidemic hazard – tcpA^elt, rtxA1 and intact VSP-II did not differ from the prototypes. The genome of the strain carries the ICE element VchBan11, which contains the trimethoprim resistance gene dfrA1, and phenotypically the strain is resistant to this antibiotic. Under in vitro conditions, the strain did not produce cholera toxin, as shown by ELISA results. This may be due to the presence of a deletion within the toxR regulatory gene. Strains similar to the 2023 isolate are mainly attributed to the second wave of the seventh pandemic. Currently, they are almost replaced by new genovariants, but occasionally can emerge and even cause diseases. Therefore, their importation into Russian territory potentially pose a threat to public health.

The aim of the work was to study the species diversity of pathogenic and non-pathogenic hantaviruses circulating in populations of small mammals in the Republic of Bashkortostan using molecular-genetic methods.

Materials and methods. Individual samples from small mammals were tested by the nested PCR using genus-specific primers that amplify the L segment of hantaviruses. The resulting PCR products were sequenced by the Sanger’s method from internal nested PCR primers. For samples containing Puumala virus, fragments of the S, M, and L segments of the viral genome were sequenced using Sanger’s method. The construction of phylogenetic trees was carried out using the MEGA X software.

Results and discussion. Out of 300 examined samples of small mammals collected on the territory of the Republic of Bashkortostan in 2023, 14 samples have been found positive for the presence of hantavirus RNA: Seewis (8), Tula (3), Puumala (3). The circulation of the non-pathogenic hantavirus Seewis and the opportunistic hantavirus Tula has been established for the first time in the Republic of Bashkortostan. The circulation of the Seewis hantavirus has been confirmed in populations of the common shrew (Sorex araneus) and the pygmy shrew (S. minutus); the Tula hantavirus – in populations of the common vole (Microtus arvalis). Results of phylogenetic analysis substantiate the reassortment origin of one of the genetic variants of the Puumala hantavirus on the territory of the Republic of Bashkortostan. The prerequisites for the formation of combined natural foci of hantaviruses Puumala, Seewis, and Tula on the territory of the Republic of Bashkortostan are discussed.

The aim of the study was to develop an algorithm for intraspecific differentiation of tularemia agent strains using a set of approaches based on amplification and sequencing technologies.

Materials and methods. 97 strains of Francisella tularensis of various subspecies, biovars and subpopulations from the State Collection of Pathogenic Bacteria of the Russian Research Anti-Plague Institute “Microbe” were used in the work. The intraspecific identification of tularemia agent strains was carried out using the “F. tularensis-4c” system; analysis of the variability of the RD1 differentiation region, the sdhA gene, by applying the disk diffusion method using disks with erythromycin. Fragment Sanger sequencing was performed on a 3500 XL genetic analyzer (Applied Biosystems, USA) taking into account the manufacturer’s recommendations. Sequence homology assessment was conducted using the BLAST algorithm, the GenBank NCBI database, MEGA11 v11.0.13 and Unipro UGENE v50.0 software.

Results and discussion. Subspecies- and biovarspecific mutations have been detected in the 23S rRNA gene. Promising regions of this gene for further investigation have been identified using fragment sequencing. A comprehensive scheme for intraspecific differentiation of tularemia microbe strains has been put forward, where at the first stage the subspecies and biovar japonica are determined, and at the second stage, the results are verified based on the determination of mutations in the 23S rRNA gene. The effectiveness of the proposed integrated approach has been confirmed in a study of 97 collection strains of tularemia agent. The conducted research allows for rapid identification of tularemia agent strains of different subspecies and verification of their taxonomic appurtenance using molecular-genetic methods, expanding data on the circulation of various subspecies, biovars and subpopulations of the pathogen in Europe, Asia and other regions of the world.

The aim of the work was to study the epidemiological situation on West Nile fever (WNF) in the Republic of Tatarstan in 2023.

Materials and methods. An operational epidemiological analysis of WNF cases registered in the Republic of Tatarstan in 2023 was performed. In order to establish sources and risk factors for infection of the population, 987 samples of zoo-entomological material were examined for the presence of West Nile virus (WNV) markers. A set of laboratory diagnostic methods was used: ELISA, RT-PCR, sequencing.

Results and discussion. It has been established that all cases of WNF were registered in the region in the summer-autumn period of 2023, mainly in August, among residents of the city of Kazan who had not traveled outside the Russian Federation and the Republic of Tatarstan over the past six months. The incidence rate of WNF in the Republic of Tatarstan was 0.20 per 100 thousand population, the mortality rate reached 12.5 %. Signs of damage to the central nervous system were present in 6 out of 8 (75 %) patients. The majority of people with severe clinical symptoms belonged to older age groups and had concomitant diseases. Cases of the infection were reported in all age groups, with the exception of children and adolescents. The spatial characteristics of morbidity have been investigated, indicating the diffuse nature of the distribution of cases. The integrated use of methods, consisting in the concurrent use of polymerase chain reaction and enzyme-linked immunosorbent assay, made it possible to laboratory confirm cases of WNF in patients at different stages of the disease. The circulation of a subvariant of the WNV of the second genotype in the Republic of Tatarstan, currently dominant in the southern and central regions of Russia, has been established. A set of measures has been proposed to optimize epidemiological surveillance and control of WNF in the Republic of Tatarstan.

The study presents the data on organization of laboratory testing of clinical and environmental samples within the framework of establishing the etiology of the acute intestinal infections outbreak, performed by the specialists of the joint SAET of the Rospotrebnadzor in Dolisie (Republic of the Congo) in the period of 07–24 July, 2023.

Materials and methods. In order to identify the causative agents of cholera and other acute intestinal infections of bacterial and viral nature, 177 clinical and environmental samples were tested, as well as cultures on solid nutrient media and bacterial suspensions. A total of 1023 tests were carried out by polymerase chain reaction (PCR) and 305 – using bacteriological method.

Results and discussion. The causative agent of cholera has not been detected in any of the samples tested. Using the PCR method, markers of acute intestinal diseases agents (Salmonella spp., Shigella spp., Campylobacter spp., Rotavirus A) have been identified in 23 clinical samples and 1 sample of bacterial suspension. No DNA/RNA of pathogens has been detected in environmental samples. During culture studies, Salmonella enterica serovar Typhi have been isolated from 8 clinical samples, and their antibiotic sensitivity has been determined. Applying whole-genome nanopore sequencing, using the MinIon platform (Oxford Nanopore Technologies, UK), nucleotide sequences of 4 S. Typhi isolates have been investigated and deposited in the international database NCBI GenBank (No. CP141260, CP141193, CP141194, CP141195). Additionally, the analysis of initially sterile samples (blood, peritoneal fluid, intraoperational samples) from the patients of General and Reference hospitals of Dolisie has resulted in the identification of 5 cultures of non-fermenting bacteria, and their antibiotic sensitivity has been determined.

The aim of the work was to study the features of the infectious process in the lungs of animals used as models for assessing SARS-CoV-2 pathogenicity.

Materials and methods. The strain of SARS-CoV-2 alpha variant virus was used in the work. The experiments were carried out on linear and transgenic mice, Syrian hamsters, guinea pigs, ferrets and two types of primates: rhesus macaques and green monkey. The pathomorphological examination was performed by optical microscopy of histological lung preparations using a computerized microscope with digital microphotography.

Results and discussion. A comparative histological analysis of the lungs in six different types of laboratory animals was carried out when modeling a new coronavirus infection; similar morphometric signs of the severity of the disease caused by the SARS-CoV-2 virus in sensitive animals were determined, and a dose-dependent correlation of pathological changes in lung tissues with intranasal administration of various infectious doses was revealed. The features of pathomorphological changes in six different animal species in the simulation of a new coronavirus infection have been characterized, and their dose-dependent nature determined. The presented research results can be used to select a model animal for the purpose of in-depth study of the pathogenesis of COVID-19 caused by newly isolated coronavirus variants, the dynamics of immune reactions of the body during the development of the disease, as well as in vivo studies of the protective effect of promising therapeutic drugs and vaccines.

The aim of the study was to investigate asymptomatic malaria in health-conscious population across four selected districts. Malaria is a life-threatening disease caused by Plasmodium spp. transmitted through bites of infected female Anopheles mosquitoes. Asymptomatic malaria refers to the presence of malaria parasites in vivo without symptoms, which usually provides a reservoir for the disease transmission.

Materials and methods. Blood collected in EDTA underwent testing through RDT (SD Bioline one-step malaria antigen P.f. (HRP-II) rapid test kits), while thin and thick blood smears Giemsa stained were microscopically examined.

Results and discussion. Out of 385 individuals examined, 84 people (21.8 %) tested positive for malaria using RDT and 101/385 (26.2 %) – through microscopy. Microscopic examination further identified 27 individuals (7.0 %) with gametocytes and 74 (19.2 %) – with trophozoites. Intriguingly, 17 (4.4 %) samples showed negative results in RDT but exhibited trophozoites and gametocytes upon smear examination. District-wise analysis demonstrated the highest malaria positivity rate in Kanchibiya district, with 32 cases (8.3 %) detected by RDT and 35 (8.5 %) – through microscopy. Chitambo district followed closely: with RDT and microscopy values of 25 (6.5 %) and 33 (8.4 %), respectively; while Mpika and Serenje districts had 13 (3.4 %) and 14 (3.6 %) prevalence, respectively, with RDT and microscopy at 12 (3.1 %) in both districts [x² =16.3, p-value=0.0118]. The study also revealed that 365/385 (95 %) of the participants demonstrated knowledge and positive attitudes toward malaria. Our findings accentuate the presence of asymptomatic malaria, encompassing trophozoites and gametocytes, among seemingly healthy individuals which poses a health risk to the community. Therefore, it is imperative to implement preventive chemotherapy and strengthen vector control efforts against malaria in order to reduce the infection rate.

The possibility of cholera importation into our country and the increase in the number of Vibrio cholerae strains that are resistant to antibacterial agents necessitate the development of alternative therapeutic and prophylactic biological products based on bacteriophages.

The aim of the work was to study the effectiveness of application of cholera bacteriophages for the prevention of experimental cholera.

Materials and methods. The work involved cholera bacteriophages Rostov-M3, Rostov-13, active against cholera vibrios of the O1 serogroup; and FB1, which has lytic activity against the O139 serogroup. The effectiveness of cholera prevention was assessed using a model of an isolated loop of the small intestine in an adult rabbit.

Results and discussion. The use of Rostov-M3 and Rostov-13 for five and especially seven days before infection with virulent strains of V. cholerae O1 serogroup prevents the development of infection in the small intestine of experimental animals. Bacteriophage FB1 did not have that ability against V. cholerae O139. These studies indicate the effectiveness of using phages Rostov-M3 and Rostov-13 for the prevention of experimental cholera caused by V. cholerae O1 serogroup.