Phylogenetic analysis of variants of the Puumala virus (Hantaviridae: Orthohantavirus) circulating in the Saratov region.

The objective is to determine the complete nucleotide sequence and conduct a phylogenetic analysis of genome variants of the Puumala virus isolated in the Saratov region. MATERIALS AND METHODS: The samples for the study were field material collected in the Gagarinsky (formerly Saratovsky), Engelssky, Novoburassky and Khvalynsky districts of the Saratov region in the period from 2019 to 2022. To specifically enrich the Puumala virus genome in the samples, were used PCR and developed a specific primer panel. Next, the resulting PCR products were sequenced and the fragments were assembled into one sequence for each segment of the virus genome. To construct phylogenetic trees, the maximum parsimony algorithm was used. RESULTS: Genetic variants of the Puumala virus isolated in the Saratov region have a high degree of genome similarity to each other, which indicates their unity of origin. According to phylogenetic analysis, they all form a separate branch in the cluster formed by hantaviruses from other subjects of the Volga Federal District. The virus variants from the Republics of Udmurtia and Tatarstan, as well as from the Samara and Ulyanovsk regions, are closest to the samples from the Saratov region. CONCLUSION: The data obtained show the presence of a pronounced territorial confinement of strains to certain regions or areas that are the natural biotopes of their carriers. This makes it possible to fairly accurately determine the territory of possible infection of patients and/or the circulation of carriers of these virus variants based on the sequence of individual segments of their genome.

WEST NILE FEVER IN THE SARATOV REGION IN 2013-2015.

West Nile virus (WNV) circulation in the territory of Saratov region and its role in the infectious pathology were investigated. For this purpose, in studies conducted in 2013-2015, suspensions of bloodsucking arthropods, organs of birds and small mammals were analyzed for the presence of WNV markers (antigens and/or RNA). The seroprevalence level in live-stock animals and population of the region was evaluated; clinical samples from patients with symptoms compatible with West Nile fever (WNF) were analyzed. As a result of the investigations, WNV markers were detected in field samples gathered in natural biotopes and in the city of Saratov. Immunity to WNV was detected in horses. A stable domain of persons with immunity to this agent was revealed among regional population. Patients with WNF have been annually registered in the region since 2012. The obtained results confirm active circulation of WNF in the Saratov region, as well as formation of stable natural and anthropourgic foci.

[Formation of focus of West Nile fever on the territory of Saratov Region].

AIM: Detection of circulation of West Nile virus (WNV) on the territory of Saratov Region and prerequisites for formation of natural focus of West Nile fever (WNF), determination of the role of WNV in infectious pathology on the territory of the region. MATERIALS AND METHODS: of organs of small mammals, birds, blood-sucking arthropods for the presence of WNV markers (antigens and/or RNA) were studied. Clinical material from patients with symptoms not excluding WNF was studied. Donor blood sera samples were analyzed with the aim of detection of immune layer against WNV in population of Saratov Region. RESULTS: In 2010 WNV antigens were detected by EIA in 12 samples (7.1%) of mammal organ suspensions. In 2012 by using RT-PCR and EIA, markers of WNV were detected in 6 samples of bird brain suspensions (6.3%) and 1 sample of mammal organ suspension. Immune layer of population against WNV was 4% in 2011, 2.8% in 2012. In 2012 in 11 of 27 examined patients IgM against WNV in diagnostic titers and/or serconversion of IgG in paired sera were detected. In addition in 5 individuals virus RNA was detected in blood. Based on clinical, laboratory data and epidemiologic anamnesis 11 patients were diagnosed with WNF. CONCLUSION: The results obtained give evidence on the circulation of WNV on the territory of Saratov Region in 2010 - 2012. With the development of complications of WNF epidemiologic situation in 2012 an expansion of WNV areal onto the territory of the region took place and the process of formation of WNF natural foci is ongoing.

[Detection of arbovirus antigens in the mosquitoes and ticks inhabiting the Saratov Region].

The paper gives the results of a study dealing with the detection of the antigens of arboviruses of West Nile, Sindbis, Batai, Crimean-Congo hemorrhagic fever, a serocomplex of Californian encephalitis in the field material gathered in the Saratov Region in 2000-2006. The bloodsucking arthropods inhabiting the region were shown to be actively involved in the circulation of arboviruses in natural biotopes. The conclusion that it is expedient to organize an annual monitoring of arbovirus-induced infections in the areas where positive findings have been notified is justified.

[The ecology and prevalence of arboviruses on the territory of the Saratov Region].

The territorial spread of Tahyna, Batai, Sindbis, West Nile fever and Crimean-Congo hemorrhagic fever viruses throughout the Saratov region in 1998 - 2000 was analyzed. The characteristics of the epizootic activity of the natural foci of these arboviruses in different landscape zones (temperate forest-steppes, steppes and semi-deserts) were calculated. The species composition of small mammals, the natural reservoirs of the causative agents of arbovirus infections, was determined.

[The results of the measured oral infection of white mice with strains of the causative agent of plague differing in their plasmid profile]. / Rezul'taty dozirovannogo oral'nogo zarazheniia belykh myshei shtammami vozbuditelia chumy, otlichaiushchimisia po plazmidnomu profiliu.

The oral infection of mice with Y. pestis culture with different plasmid profiles by the method of feeding them with agar granules containing a definite number of these bacteria revealed that the virulence of subcultures which had lost Pst-plasmid and the capacity for fibrinolysin and plasma-coagulase production, encoded by this plasmid, decreased 10-1000 times, the loss of Fra-plasmid produced a less pronounced effect. In contrast to subcutaneous infection, in alimentary infection Y. pestis culture grown at 28 degrees C was more virulent than that grown at 37 degrees C. During the first hours after infection Y. pestis could be detected only in the lymph nodes along the gastrointestinal tract and in the intestine walls; later generalization of the infectious process or its latent course was observed. After oral infection specific antibodies were detected in surviving animals (up to 35%).