[Arborviruses of the California encephalitis serogroup 1N Russia and their contribution to infectious pathology].

This review focuses on arborviral infections associated with California serocomplex (Bunyaviridae, Orthobunyavirus). Results of relevant eco-epidemiological and clinical studies in Russia are presented suggesting the ubiquitious nature of diseases caused by viruses of the California encephalitis serocomplex (Inko, Tahyna, Snowshoe Hare). The etiologic structure of these diseases in taiga and mixed woods of the European part and Western Siberia is dominated by the Inco virus and in southern regions by Tahina. The diseases have a well apparent seasonal pattern (July-August) in agreement with the peak summer activity of the pathogens. Two clinical forms of pathology are distinguished, influenza-like and generalized, the latter affecting lungs, kidneys, liver, and CNS. The Inco virus plays a key role in pathogenesis of the generalized form affecting CNS.

[Analysis of the genome of two Getah virus strains (LEIV 16275 Mar and LEIV 17741 MPR) isolated from mosquitoes in the North-Eastern Asia].

The complete nucleotide consequences of two Getah virus strains isolated in Russia (LEIV 16275 Mar) and Mongolia (LEIV 17741 MPR) were first determined and analyzed. The nucleotide sequences of the gene of surface glycoprotein E2 and complete genome were used to establish the phylogenetic relations of the strains with other representatives of the Semliki forest serocomplex. The study and reference strains of Getah virus were shown to form its own cluster that was far away from other representatives of the complex and the sequence of the E2 gene significantly reflected the identification of phylogenetical groups within the Sempliki forest serocomplex.

[Molecular genetic analysis of a diversity of Getah virus strains isolated from mosquitoes in the North-Eastern Asia].

A molecular genetic study was performed of the Getah virus strains isolated in Russia (Eastern Siberia and Far East) and Mongolia. A phylogenetic analysis was made, by examining the nucleotide sequences of genome fragments that had been obtained by RT-PCR and that included the portions of the E1 and E2 surface glycoprotein genes and the 6K gene. A genetic diversity of Getah virus strains in North-Eastern Asia is discussed.

[Phylogenetic analysis of the nucleotide sequences of Chatanga virus strains, the new representative of California encephalitis serocomplex, isolated in different regions of the Russian Federation].

The complete nucleotide sequences of the S segment and the fragments of M and L segments (on 900 and 410 nucleotides, respectively) were determined in 14 California encephalitis serocomplex (CES) strains isolated from different regions of the Russian Federation. Phylogenetic analysis by the sequences of genomic S, M, and L segments indicated that all Russian strains were an individual independent CES virus. The new virus is named Chatanga for the place of isolation of one of the strains. Two genetic groups of Chatanga virus have been identified. Snowshoe hare (Lepus americanus) virus and La Crosse virus are closest to Chatanga virus among CES viruses.

[Isolation of Getah virus (Togaviridae, Alfavirus) strains in North- Eastern Asia]. / Izoliatsiia shtammov virusa Geta (Togaviridae, Alfavirus) v Severo- Vostochno'i Azii.

Fifteen strains of Getah alfavirus were for the first time isolated from Aedes and Culex mosquitoes in Yakutia, Magadan region, Buryatia, and Khabarovsk region of the Russian Federation and in Mongolia. The area of this virus dissemination in the above regions was steppe, mixed forest, Northern taiga, and forest-tundra zones, reaching the tundra zone in the North. Getah virus is the only alfavirus occurring under such severe climatic conditions.

[Diseases associated with viruses of the California encephalitis serogroup, in Russia]. / Zabolevaniia v Rossii, assotsiirovannye s virusami serogruppy Kaliforniiskogo éntsefalita.

Studies of 1986-1995 revealed diseases etiologically connected with California serogroup viruses (Bunyaviridae, Bunyavirus) all over the country. Highly endemic zones are the tundra, taiga, and leafy forest. The disease occurs mainly in summer, the patients are mostly young: under 30 years of age. Analysis of 183 cases confirmed by laboratory findings enabled us to distinguish the following forms: influenza-like (70.9%) with the predominant involvement of the bronchopulmonary system (bronchitis and pneumonia) and neuroinfection (20.2%) (serous meningitis and meningoencephalitis).

[Regularities in the spread of hepatitis C virus and its genotypes in Russian and countries within the former USSR]. / Zakonomernosti rasprostraneniia virusa gepatita C i ego genotipov v Rossii i stranakh SNG.

The incidence of markers of hepatitis C virus (HCV in the blood of 4216 normal subjects living in the European Russia (Northern, North-Western, Central, Central Chernozem, Volga-Vyatka, Volga, and North Caucasian regions), in the Urals, in Siberia (Eastern Siberian region), in the Far East, and in Monogolia is assessed. The incidence of antibodies to HCV varied from 0.7% in the Central region to 3.8% in the Central Chernozem and 10.7% in Mongolia. HCV genotyping (identification of 1a, 1b, 2a, 2b, and 3a genotypes) was performed using 469 RNA of HCV-positive sera of donors and patients collected in Russia, Moldova, Turkmenistan, and Mongolia. The 1b genotype predominated everywhere (68.9%), its incidence being the highest in Moldova (96%). Unclassifiable variants of HCV were found in 28 (6%) of sera. The regularities of HCV genotypes circulation in the European Russia were the same as in other European countries, whereas their prevalence in Eastern Russia was rather like that in China or Japan. The prevalence of genotypes did not depend on the clinical manifestations of diseases caused by HCV.

[Further study of hantavirus circulation in the Russian Federation]. / Dal'neishee izuchenie tsirkuliatsii khantavirusov v Rossiiskoi Federatsii.

Lung specimens of 1514 small mammals of 35 species captured in 1991-1995 at 9 territories of Russia were tested in ELISA for virus antigens of hemorrhagic fever with the renal syndrome (HFRS). The antigens were detected in lung specimens of Clethrionomys glareolus, Microtus arvalis, Microtus gregalis, Microtus fortis, Arvicola terrestris, Apodemus agrarius, Micromys minutus, and Sorex sp., well known as Hantavirus reservoirs, captured in the Vologda, Yaroslavl, Saratov, Astrakhan, and Chita regions. Infection of Microtus maximoviczii revealed in the Chita region was first found in China. Previously there were no reports about the circulation of hantaviruses in this region. Our study added one more host to the list of HFRS virus hosts: Meliones tamariscinus.

[Distribution of viruses from the Californian encephalitis serogroup (Bunyaviridae, Bunyavirus) in the northern expanses of Russia]. / Rasprostranenie virusov serogruppy Kaliforniiskogo éntsefalita (Bunyaviridae, Bunyavirus) v severnykh shirotakh Rossii.

The study was carried out in 1983-1991 and covered a territory of about 10 x 10(6) km2 in various physico-geographic areas (East Fennoscandia, Northern Russian Plain, West Siberia, Central Siberia, North-Eastern Siberia, and Northern Pacific Region) in the Arctic, Subarctic, Northern-Central-Southern taiga, forest-steppe, and steppe in Northern Russia. A total of 251 strains were isolated from 1391,900 mosquitoes, identified as the California group snowshoe hare (83), Inkoo (44), and Tahyna (2) viruses; 122 strains were not completely identified. Some of the strains with uncommon antigenic composition can be natural reassortants. Fifty-two percent of strains were isolated from Aedes communis and the associate species of mosquitoes, other hosts were A. excrucians (8%), A. cantans (6.25%), A. flavescens (6.25%), A. ciprius (6.25%), A. punctor (4.5%), A. vexans (4.5%), A. cataphylla (3.6%), A. nigripes (3.6%), and A. hexodontus (2.6%). The infection rate of mosquitoes was 0.009% in the tundra, 0.012% in forest-tundra, 0.01% in Northern taiga, 0.02% in Central taiga, 0.017% in Southern taiga, 0.026% in forest-steppe, and 0.097% in steppe. The epidemic season is one month in the tundra (from the beginning of July till the beginning of August), two months in Northern taiga (July-August), and three months in Central taiga (from the second half of June till the beginning of September). The highest infection rate of mosquitoes was observed at the end of the epidemic season in all regions. SSH strains prevailed to the East from the Enisei river, whereas to the West and in the Subarctic regions INK virus predominated, SSH being rare; in the taiga the distribution was quite the opposite. TAH virus was virtually absent. Human morbidity was observed in all territories studied. The immune stratum of adult population is about 30% in the tundra and forest-tundra and about 50% in Northern and Central taiga.

[Mosquito-borne arboviruses in the Baikal region]. / Peredavaemye komarami arbovirusy v pribaikal'e i zabaikal'e.

A total of 20 virus strains were isolated from arthropods and rodents in the Baikal region in 1992. Thirteen of these were California serogroup viruses, 4 Batai virus strains (Bunyaviridae, Bunyavirus), and 3 Gheta virus strains (Togaviridae, Alphavirus, Semliki complex). The rates of mosquito infection with California, Batai, and Gheta viruses were 1:6500, 1:24000, and 1:24000, respectively. The results of the neutralization test indicate the similarity of the isolated California complex strains to the mountain hare virus, the most pathogenic virus in this group.

[The characteristics of the pathogenic properties of new strains of viruses of the California encephalitis antigenic complex isolated in Arkhangelsk Province]. / Kharakteristika patogennykh svoistv novykh shtammov virusov antigennogo kompleksa kaliforniiskogo éntsefalita, izolirovannykh v Arkhangel'skoi oblasti.

Neurotropic properties of Leiv 12724 Ax and Leiv 13004 Ax strains were demonstrated by inoculation of green monkeys, Syrian hamsters and white mice using different routes. The strain Leiv 13004 Ax showed more marked pathogenicity for monkeys and rodents producing lesions in all parts of the brain: temporal, frontal, occipital, cerebellar, medulla oblongata and spinal cord where productive vasculitis, perivascular infiltrations, hemorrhages, and dystrophy of nerve cells were observed. In hamsters, the strains Leiv 13004 Ax and Leiv 12724 Ax inoculated subcutaneously produced latent infection with long-term virus carrier state.

[A comparative experimental study of pathogenic properties of new strains of California encephalitis virus serogroups]. / Sravnitel'noe izuchenie patogennykh svoistv novykh shtammov virusa serogruppy Kaliforniiskogo éntsefalita véksperimente.

Experiments in noninbred mice, Syrian hamsters and grey monkeys were made to characterize the pathogenic properties of new strain of the California encephalitis serogroup isolated for the first time on the island of Taimir, in the Murmansk, Leningrad, Tver regions and in Karelia. All the strains displayed marked tropism for the CNS. The strains isolated in the northern regions of this country turned out more pathogenic for the animals. The strain Leiv-12812 Kl (isolated in the Tver region) differed from the remaining ones in more pronounced pathogenicity for the monkeys, as well as in the site and intensity of brain lesions. The persistence of the virus in hamsters organs may play a role of a reservoir of infection in nature.

[The circulation of viruses of the California encephalitis and Bunyamwera groups (Bunyaviridae, Bunyavirus) on the northeastern Russian plain]. / Tsirkuliatsiia virusov kompleksov Kaliforniiskogo éntsefalita i Bun'iamvera (Bunyaviridae, Bunyavirus) na severo-vostoke Russkoi ravniny.

In the Komi ASSR, 102.2 thousand mosquitoes, 207 small mammals, 1487 blood serum specimens from people, 793 cow blood sera, 140 blood serum specimens from reindeer were collected in June-August, 1988. Twenty seven virus strains isolated from mosquitoes were classified into Bunyaviridae family according to the data of electron microscopic studies. Identification of the isolates by CFT and IFA showed 18 of the strains to belong to California encephalitis complex and 9 to Bunyamwera complex. Serological studies by neutralization test demonstrates a high frequency of contact of the human population and domestic animals with viruses of the California complex practically in the entire study area: an average of 45% among human subjects, 48% among cattle and 33% among reindeer. Such high values of the immune portions indicate the activity of the discovered natural foci of this complex. The results for Batai virus from the Bunyamwera complex do not indicate its high activity: approximately 2% of positive findings in human subjects and about 4% in the cattle. The results permit a prognosis of California encephalitis and Bunyamwera complex viruses spread in the northern part of Western Siberia.

[The isolation of tick-borne encephalitis virus strains and the determination of the scope of immune stratification among the population and the domestic animals on the northern Russian plain]. / Izoliatsiia shtammov virusa kleshchevogo éntsefalita i opredelenie velichiny immunnoi prosloiki sredi naseleniia i domashnykh zhivotnykh na severe Russkoi ravniny.

Between 1986 and 1987 the authors conducted virological survey of 689 Ixodes persulcatus and 420 mouse-like and insectivorous rodents at the territory of Arkhangelsk Province and the Republic of Komi. A total of 8 strains of tick-borne encephalitis virus were isolated. Out of them 3 strains were isolated from small mammalians (2 from Clethrionomys glareolus, 1 from Microtus oeconomus) at the southeastern areas of Arkhangelsk Province within the middle taiga subarea, 5 strains were isolated from I. persulcatus (the rate of infection was 1.25 per cent) gathered in the southeastern Komi within the southern margins of the middle taiga subarea. PHAT investigation of the sera (2064 human, 656 cow and 171 dear specimens) evidenced almost the absence of immunity among the studied populations of the tundra and forest tundra zones. Certain positive samples observed in the northern taiga region could be explained by the infection gained in areas situated more to the south. Among the middle taiga human populations the immunity reached 4.9 per cent.

[Isolation of viruses of antigenic complexes of California encephalitis and Bunyamwera (Bunyaviridae, Bunuavirus) from mosquitoes in northeast Asia]. / Izoliatsiia virusov antigennykh kompleksov Kaliforniiskogo éntsefalita i bun'iamvera (Bunyaviridae, Bunuavirus) iz komarov na severo-vostoke aziatskogo kontinenta.

Studies in suckling mice and by direct solid-phase enzyme immunoassay were carried out with 111,1 thousand Aedes mosquitoes collected in July, 1986, in tundra, forest-tundra, and northern taiga of Kamchatka region and Chukotka autonomous district of Magadan region (North-Pacific natural area within 69 degrees-53 degrees North and 156 degrees-177 degrees East). Eleven strains were isolated of which 7 were classified as members of the California encephalitis complex (Tahyna-like strains) and 4 as members of the Bunyamwera complex (Batai-like strains). According to electron-microscopic studies of 2 strains (one from each antigenic complex), both were classified as belonging to the family of Bunyaviridae. Strains of both complexes were isolated in all landscape zones examined--tundra, forest-tundra, northern taiga. Virus-neutralizing antibodies to them were found in human and reindeer sera also in all the landscape zones, to Tahyna virus in 11%-61%, to Batain virus in 2%-6% blood specimens. No antibody to Uukuniemi virus was found.

[Biological properties of the Tahyna virus isolated in the Arctic]. / Nekotorye biologicheskie svoistva virusa Tiaginia, vydelennogo v Zapoliar'e.

The results are presented of comparative studies over the course of experimental Tahyna infection of viremia in the blood and organs, localization and patterns of lesions in the same organs after different routes of inoculation of white mice and hamsters with a new strain LEIV 9843 Mur of Tahyna virus. The results of these experiments are compared with similar studies in monkeys with asymptomatic infection, including humoral antibody detection. The pattern of lesions in the organs of animals infected with Tahyna virus (LEIV 9843 Mur strain), the mode of virus spread, tissue tropism of the virus were established. The virus thermostability and sensitivity to different pH values of the medium were determined.