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Leptospirosis is a zoonotic disease found virtually worldwide. Microscopic Agglutination Test with live leptospira (MAT) is the reference method for the serological diagnosis of leptospirosis. MAT is based on assessing serum potential to agglutinate live reference serovar Leptospira maintained at a reference laboratory. At some laboratories having own collections of isolated and reference Leptospira strains applicable for serological diagnosis, those microorganisms are maintained for many years by repeated subculturing, that increases markedly a chance of strain cross-contamination. The lack of adequate quality control for reference strains may affect data of epidemiological studies. Control of Leptospira spp. reference strains purity and stability of their antigenic composition is very important for diagnosis of leptospirosis. The study objective was to compare the 16S rRNA gene nucleotide sequences of some Leptospira strains from the collection of the St. Petersburg Pasteur Institute to with relevant sequences uploaded to GenBank. In this study, 38 Leptospira strains were investigated. Nucleotide sequences of 36 strains were deposited in the international GenBank database, inconsistencies were revealed in two strains. The study found that the control Leptospira strains from the collection of the St. Petersburg Pasteur Institute had minimal dissimilarities from international control strains. The analysis of the resultant 16S rRNA sequences has shown the presence of point mutations, transitions, deletions and insertions, regardless of the strain species. The open leptospira pan-genome demonstrates high genomic variability in species due to the capability of leptospira for lateral gene transfer in order to adapt to changing environmental conditions. The massive acquisition and loss of genes give rise to an increased species diversity. The 16S rRNA gene is suitable for screening diagnostics; however, high level of the fragment similarity and close phylogenetic relationship between different species put bounds to its use in genotyping. The presence of point nucleotide mutations is most likely associated with the evolutionary mechanisms of leptospira, their ability to horizontal gene transfer and crossing-over, including ribosomal genes, but this assumption necessitates additional research. For specimen genotyping it is necessary to select alternative genes with high specificity and sufficient level of nucleotide divergence. The study shows a need for genetic analysis of collection strains in order to control the purity of cultures.

The causative agent of Q fever, the intracellular pathogen Coxiella burnetii, is found almost worldwide; many types of blood-sucking ticks that are dangerous to animals and humans are involved in the circulation of the pathogen. Using molecular-genetic methods, closely related species of microorganisms of the genus Coxiella sp. have been discovered, some of which are endo-symbionts of ticks, and some can survive in the human body, causing an infectious process. The existence of species whose genes are similar in nucleotide sequence to those of C. burnetii makes it difficult to diagnose the pathogen in arthropod vectors. The aim of this work was to consider the use of PCR and sequencing of an extended 16S rRNA gene fragment for molecular diagnostics and differentiation of C. burnetii from Coxiella-like microorganisms. Materials and methods. Individual samples of blood-sucking ticks were examined to detect bacteria of the genus Coxiella sp. applying standard PCR. For positive samples, an extended fragment of the 16S rRNA gene was obtained and examined by sequencing and multiple alignment with homologous sequences. Results and discussion. Of the 96 examined ticks collected in the Ulyanovsk Region, one was positive for the presence of C. burnetii DNA and one – for the presence of Coxiella sp. The greatest similarity for the C. burnetii isolate was noted in comparison with Western European strains, for the Coxiella-like microorganism - with closely related bacteria from ticks of the same species. Unique polymorphisms for the detected microorganisms were identified. It has been established that genus-specific primers to the 16S rRNA gene fragment are able to amplify not only bacteria of the genus Coxiella sp., but also genetically distant species. Analysis of the sequence of the extended 16S rRNA gene fragment makes it possible to differentiate C. burnetii from Coxiella-like microorganisms; some gene polymorphisms appear to have arisen through microevolution in different geographic regions. In the European part of the Russian Federation, Coxiella-like bacteria have been uncovered for the first time.

Leptospirosis poses a serious public health problem in many countries because about 1 million people suffer annually from this severe, often fatal, infection. At present, its importance has been increasing due to development of integration processes, globalization and intensification of economic activities, inevitable anthropogenic transformation of landscapes as well as rise in number of people with occupational risk of pathogen exposure. The burden of human leptospirosis is expected to rise with demographic shifts and climate change that result in heavy rainfall and flooding. Regarding leptospirosis, Southeast Asia, including Vietnam, is among the most vulnerable global regions. The objective of the review was to analyze available published data on the spread of leptospirosis in Vietnam. More than 100 research articles were analyzed allowing to state that in Vietnam synanthropic rodents (rats), agricultural (buffaloes, cattle, pigs) and domestic animals (cats, dogs) are the main sources of leptospirosis infection in humans. It is essential that rats (cats and dogs also) in Vietnam are used for food. Among all farm animals, pigs are of maximal importance as a source of infection in humans. In Vietnam, Leptospira prevalence in pigs varies widely, up to 73%. It depends significantly on the location, farm size, age and gender of animals, etc. A large variety of Leptospira serovars have been identified in pigs in Vietnam: Tarassovi, Bratislava, Australis, Javanica, Autumnalis, Grippotyphosa, and some others. Official Vietnam reporting of leptospirosis cases based on clinical data does not reflect the real-life incidence rate in humans. However, the available seroprevalence studies reveal that, on average, about 10% of the Vietnamese population are infected with Leptospira. Work in agriculture is the dominant risk factor for acquiring this infection. The highest Leptospira seroprevalence rates were detected in farmers, 63.2%. Serovar diversity is typical for pathogenic Leptospira circulating in Vietnam. In humans, the most frequent are antibodies to Hebdomadis, Wolffi and Icterohaemorrhagiae, but the frequency varied markedly across the country depending on the site, possibly with relation to the environment, as well as with economic activity of the local population. In Vietnam, geographic, climatic and social differences between northern, central and southern regions contribute to the specificity of local leptospirosis epidemiology. This emphasizes the advisability of developing special measures for leptospirosis prevention taking into account regional peculiarities.

Introduction. Knowledge about tick-borne disease (TBD) distribution is necessary to improve prevention, whereas detection of human serum IgG antibodies against relevant pathogens is a method for monitoring TBD prevalence in local population. The study objective was to estimate seroprevalence of IgG antibodies against tick-borne encephalitis virus (TBEV), Borrelia burgdorferi sensu lato, Coxiella burnetii, Anaplasma phagocytophilum, and Ehrlichia chaffeensis/E. muris in healthy residents from the five territories of the Northwestern Federal District of the Russian Federation (Arkhangelsk Oblast, Leningrad Oblast, Pskov Oblast, the Republic of Komi and the Republic of Karelia). Materials and methods. In 20172019, a total of 1244 serum samples from healthy residents, not vaccinated against TBDs or other flavivirus-caused infections was studied by ELISA. Results. 21.7% of the sera samples contained IgG antibodies against a single TBD pathogen, whereas 2.1% showed signs of coinfection with two or more pathogens. The most common were IgG antibodies against TBEV (5 territories, 12.2%), followed by Borrelia burgdorferi sensu lato (5 territories, 3.5%), C. burnetii (4 territories, 2.9%), Anaplasma phagoсytophilum (3 territories, 1.6%), E. chaffeensis/E. muris (5 territories, 1.5%). The IgG antibodies were more common in men (55.2%) than in women (44.8%), being found virtually evenly in age-independent manner (from juniors under 18 to seniors over 60). Conclusion. The results of this first comprehensive serosurveillance study in the Northwestern Federal District of the Russian Federation assessing serum IgG antibodies against tick-borne diseases indicate a wide distribution of such pathogens. Moreover, infections caused by C. burnetii, Anaplasma phagocytophilum, and Ehrlichia chaffeensis/E. muris might be highly underdiagnosed.