[Lethal cases of lyssavirus encephalitis in humans after contact with bats in the Russian Far East in 2019-2021].

INTRODUCTION: On the territory of Russia four species of lyssaviruses (genus Lyssavirus) were identified, three of them caused human deaths. THE AIM OF WORK: to characterize fatal cases in humans after contacts with bats in the Far East in 20182021 and to perform typing of isolated pathogens. MATERIALS AND METHODS: Lyssavirus infection was confirmed in samples of sectional material from people who died in the Amur Region in 2019, in the Primorsky Krai in 2019 and 2021. Diagnostics was performed by fluorescent antibody test (FAT) and RT-PCR using diagnostic kits of domestic production. Viruses were isolated in a bioassay. The nucleoprotein sequences were analyzed after 1st passage. The analysis of phylogenetic relationships and the construction of a dendrogram were performed using the MEGA7 software. RESULTS: The viruses that caused the fatal cases in humans in the Amur Region and Primorsky Krai share more than 90% identity to Lyssavirus irkut detected in Russia and China. Together they form a separate monophyletic cluster with 100% bootstrap support. CONCLUSION: On the territory of Russia, monitoring of bat populations for infection with lyssaviruses is relevant. The material of people who died from encephalomyelitis of unknown etiology within 1015 days from the onset of the disease must be examined for lyssavirus infection. It is necessary to develop PCR assays that employ genus-specific primers. The use of molecular biological methods is promising for improving the diagnosis of rabies and epidemiological surveillance, as well as increasing the efficiency of the system of biological safety of the population of the Russian Federation.

Development and evaluation of a RT-qPCR assay for fast and sensitive rabies diagnosis.

Rabies virus is endemic to Russia, among other countries. It is therefore critical to develop a high-quality and high-precision diagnostic procedure for the control and prevention of infection. The main objective of the research presented here was to develop a reliable RT-qPCR assay for rabies diagnostics. For this purpose, a RABV strains from various biological and geographical origins were used. In addition, rabies-positive and rabies-negative samples, as well as nucleic acids from other viruses and DNA extracted from the brain tissues of mice, dogs, cats, bats and humans, were studied using the developed assay. The analytical sensitivity of the assay, as assessed using armored recombinant positive control dilutions, was 103 copies/ml, and the sensitivity measured using characterized strains was between 0.1 LD50/ml and 1.0 LD50/ml. A broad range of RNA from RABV strains circulating in different regions of Russia, as well as RNA from RABV-positive primary brain samples from 81 animals and two humans, was detected using the developed assay. No false-positive or false-negative results were obtained. Given that high analytical and diagnostic sensitivities and a high specificity were verified for this assay, it has high potential as a screening test that may be suitable for the epizootiological monitoring of animals and for the fast postmortem diagnosis of rabies.

[A summary of the data about antigenic and genetic diversity of rabies virus circulating in the terrestrial mammals in Russia].

The data about antigenic and molecular-genetic diversity of the rabies virus circulating in Russia are reviewed. Based on our studies and the literature data analysis circulation of two phylogenetic virus groups in Russia was revealed: Arctic and cosmopolitic. The Arctic group includes the subgroups of proper Arctic and Arctic-like viruses; the cosmopolitic--Central Russian, Northeastern European and steppe. It was found that the division into subgroups corresponded to the geographic distribution of rabies viruses.

Complete genome sequences of four virulent rabies virus strains isolated from rabid animals in Russia.

Rabies virus (RABV) strains Rus(Lipetsk)-8052f, Rus(Lipetsk)-8053c, Rus(Lipetsk)-8054f, and Rus(Lipetsk)-8057f were isolated from foxes (Vulpes vulpes) and a cat (Felis catus) in the Lipetsk region of Russia in 2011. Close relationships between these strains and the members of the "Cosmopolitan" group from Russia (98% homology) and from Europe (95% homology) were estimated.

[Epizootic situation and prospectives of rabies control among wild animals in the South of Western Siberia]. / Epizooticheskaia situatsiia i perspektivy bor'by s beshenstvom dikikh zhivotnykh na iuge Zapadnoi Sibiri.

The analysis of the epizootic situation in rabies in the south of Western Siberia during the period of 1990-1999 was carried out on the basis of the analysis of statistical data, field observations and virological investigations. Foxes were found to be the principle virus host and in the steppe areas they probably shared this role with corsac foxes. No data on other orders of mammals taking part in the virus circulation were obtained. The foxes population structure of the territory of the above-mentioned region were studied. The epizootic process was shown to have a cyclic character which corresponds to the models, proposed by foreign researchers for Western Europe. The effectiveness of different methods used for the control of rabies among wild animals was considered. As shown by this study, due to the population ecology of foxes and corsac foxes on the above-mentioned territory the best effect should be expected from measures aimed at frequency limitation of these animals, and not from vaccinal prophylaxis. As an alternative, the possibility of non-interference in the circulation of the virus within the limits of the natural focus in combination with timely measures for the protection of domestic and agricultural animals, as well as humans, from infection was considered.

[Rabies prognosis in western Siberia and the regulatory factors of the epizootic process]. / Prognozirovanie beshenstva v Zapadnoi Sibiri i reguliatornye faktory épizooticheskogo protsessa.

In this article the regulatory factors of the epizootic process are considered and the spatial-temporal prognostication of rabies infection in the region is proposed on the basis of data on rabies morbidity among animals, the purchase of skins of carnivorous animals for 20-25 years, virological experiments on wild animals, calculation of the number of carnivores and small mammals, as meteorological observations. The study has shown that a variety of animal species serving as hosts for the virus and its population differences contribute to the stable existence of the infection. Rabies morbidity has been found to be positively linked with its preceding level, the number of wild animals, the height and hardness of the snow cover and negatively with the number of small mammals.

Experimental rabies in hibernator rodents.

Experiments carried out in different seasons with different strains of rabies virus have shown that hibernation prolonged the incubation period in sousliks (Citellus major Pall.). Mean survival of the animals infected during the active period was 32 days, while during hibernation it was 147.3 days (P less than 0.05), in some cases up to 251 days. The virus was isolated from and/or detected by fluorescent antibody test in 50% of cases in the brown fat and in some cases in the salivary glands and visceral organs. The brown fat biopsy allowed to detect the virus not earlier than 6 days before death. We propose to use heterothermal rodents for the study of mechanism of rabies virus persistence and suggest that these animals might represent a natural reservoir for rabies.

[Importance of the racoon dog in the epidemiology and epizootiology of rabies in the Far East]. / Znachenie enotovidnoi sobaki v épidemiologii i épizootologii beshenstva na Dal'nem Vostoke.

Raccoon dogs (Nyctereutes procyonoides Gray) have been shown to take part in the circulation of rabies virus within their natural area in the Far East and thus to be dangerous as a source of infection for humans and domestic animals. The disease has been registered in the areas with high population density of this species, the spread of infection reaching 13 +/- 4.6% in the years of survey. The results of the preliminary determination of the sensitivity of raccoon dogs and the schematic map showing the spread of rabies among the animals of this species are presented.

[Results of a study of natural foci of rabies and evaluation of the risk of hydrophobia in new construction areas of Eastern Siberia and the Far East]. / Rezul'taty kompleksnogo izucheniia prirodnykh ochagov beshenstva i otsenka riska zabolevaniia gidrofobiei v raionakh novostroek Vostochnoi Sibiri i Dal'nego Vostoka.

The tension of the rabies epidemiological situation in the regions of new constructions in Siberia and the Far East was the result of a wide spread of the infection foci and a great number of domestic animals affected by the disease. All over the territory the main-source of the infective agent for humans are dogs, and only in a few cases wild animals. In the mountainous and steppe regions of the south-eastern part of the Transbaikal territory a natural focus of rabies has been revealed. A scheme for dividing the territory into rabies epidemiological regions has been developed on the basis of studying the factors contributing to the dynamics of the epidemic and epizootic processes, as well as the epizootic situation (in the Chita and Amur regions used as an example).