West Nile virus and other zoonotic viruses in Russia: examples of emerging-reemerging situations.

Studies of the interactions of vertebrates, viruses and arthropod vectors of these viruses were monitored in terms of different ecological groups of viruses transmitted by mosquitoes and ticks in Northern Eurasia in an area encompassing more than 15 million km2. About 90 viruses were isolated, including 24 new to science. Newly recognized infections of vertebrates, including humans, were described. Many unusual epidemic situations were analysed. Permanent efforts were established to prevent bioterrorist activities and their consequences. Extensive epidemic outbreaks of West Nile fever (WNF; i.e., fever caused by West Nile virus) and Crimean-Congo hemorrhagic fever (CCHF) with unusual high mortality appeared in the last four years in southern Russia. We determined infection rates in humans, domestic and wild animals, mosquitoes and ticks from natural and synanthropic biocenoses [Editorial note: "synanthropic" means, roughly, all species living with (c.f. lice, fleas) or near people, such as in houses (c.f. house mice), parks (c.f. Rattus spp.), and the like, rather like "peridomestic", but not strictly so; "biocenosis" is the biome, the "totality of living populations in a particular habitat, which itself is only a part of the ecosystem".]. CCHF virus strains were phylogenetically similar to strains isolated in this area 35 years ago but different from Central-South-Asian and African strains. Before the outset of the current emergence of epidemic WNF, three genetic variants of this virus had been isolated in USSR, two African and one Indian. Phylogenetic analysis of complete genome sequences of epidemic strains demonstrated considerable similarity to strains from USA and Israel and differences from strains isolated in the same USSR areas 20-30 years before. In addition to strains of genotype 1, we isolated strains of second and third lineages and a strain of a fourth genetic variant. Nucleotide differences of these strains from all three genotypes was about 30%. The emerging WNF situation in Russia for the last 4 years probably has been the result of not only natural and social factors, but also to introduction of more virulent strains or by evolution of the virus.

Isolation of two strains of West Nile virus during an outbreak in southern Russia, 1999.

From July to September 1999, a widespread outbreak of meningoencephalitis associated with West Nile virus (Flavivirus, Flaviviridae) occurred in southern Russia, with hundreds of cases and dozens of deaths. Two strains of West Nile virus isolated from patient serum and brain-tissue samples reacted in hemagglutination-inhibition and neutralization tests with patients' convalescent-phase sera and immune ascites fluid from other strains of West Nile virus.

Biological profile of a virus belonging to California encephalitis complex isolated in Karelian Autonomous Soviet Socialist Republic.

We investigated in white mice and in Syrian hamsters the pathogenesis of infection with a virus belonging to the California encephalitis complex isolated in the Karelian Autonomous Soviet Socialist Republic. The pathogenic properties of the virus were investigated also in green monkeys. The localization and character of lesions in the organs of given animals appeared to be similar. The virus appeared to possess neurotropic activity, it propagated in the animal body by haematogenous route. The virus was found to be heat-resistant and pH-sensitive.

Investigations on the structure and morphogenesis of some arboviruses isolated in the U.S.S.R.

The morphology and some stages of morphogenesis in suckling mouse brains of hitherto serologically unclassified viruses Kaspiy (LEIV-A-63), Zavashan (LEIV-Ap-6158), Artashat (LEIV-A-2366), and Paramushir (LEIV-C-2268), isolated in the U.S.S.R., of GM-710 virus isolated in Scotland, and of Sokuluk (LEIV-K-400) virus belonging to the genus Flavivirus (family Togaviridae) were studied. Virion sizes were determined and changes in infected cells described. Based on their structure and morphogenesis, the viruses Kaspiy, Artashat, Zavashan and Paramushir were referred to the family Bunyaviridae and GM-710 virus was referred to the genus Orbivirus (family Reoviridae).

Sikhote-Alin virus, a new member of the cardiovirus group (Picornaviridae) isolated from Ixodes persulcatus ticks in Primorie Region.

A virus, designated Sikhote-Alin, was isolated in 1970 from Ixodes persulcatus ticks collected from a wild boar in the Primorie region (U.S.S.R.) Sikhote-Alin virus showed no haemagglutinating activity and no antigenic relationships with arboviruses of 12 antigenic groups, 17 ungrouped tick-borne arboviruses, porcine enteroviruses and coxsackie A (types 1-18) viruses. An one-way antigenic relationship was demonstrated by complement fixation with cardioviruses (Mengo and Columbia-SK strains). The virus contains RNA, is resistant to lipid solvents, highly thermostable in the presence of 1 M MgCl2 and its size is over 20 nm but less than 25 nm. All these properties make it possible to consider it as a new member of the cardiovirus group (genus Enterovirus; Picornaviridae).

Razdan virus, a new ungrouped bunyavirus isolated from Dermacentor marginatus ticks in Armenia.

A virus, designated Razdan, was isolated from Dermacentor marginatus ticks in the Armenian S.S.R. in 1973. The complement fixation tests revealed no antigenic relationships to 74 tick-borne arboviruses. The size of the virus is about 100 nm; it agglutinates goose erythrocytes at pH 5.5--7.0, is pathogenic for newborn, 14-day-old and adult white mice and multiplies in primary and continuous cell cultures. Morphological properties of the virus permit its classification as a member of the family Bunyaviridae.

Khasan virus, a new ungrouped bunyavirus isolated from Haemaphysalis longicornis ticks in the Primorie region.

Strain LEIV-776P, possessing no haemagglutinating activity was isolated in 1971 in the Primorie region (U.S.S.R.) from Haemaphysalis longicornis Neumann 1091 tick. Complement fixation (CF) tests revealed no antigenic relationship with 24 antigenic groups of arboviruses or 21 ungrouped viruses isolated from ticks. The virus isolate contains RNA and is relatively sensitive to ether and sodium deoxycholate; it is pathogenic for suckling mice and two-week-old white mice by the intracerebral route, and replicates in primary cultures of chick and duck fibroblasts and green monkey kidneys and in a continuous line of pig embryo kidney cells without any cytopathic effect. According to electron microscopy, its size is 90-110 nm. Its morphological properties permit to classify it as a member of the family Bunyaviridae.

"Karshi" virus, a new flavivirus (Togaviridae) isolated from Ornithodoros papillipes (Birula, 1895) ticks in Uzbek S.S.R.

Three identical strains of an arbovirus were isolated from 475 Ornithodoros papillipes ticks collected in June, 1972, in burrows of the great gerbil (Rhombomys opimus Licht., 1882) in the environs of Beshkent, Karshinsk steppe, Uzbek S.S.R. The isolate was found to range among flaviviruses. Complement-fixation, agar diffusion precipitation and neutralization tests is tissue culture and mice indicated a one-way antigenic relationship between the isolate and West Nile virus. However, the pattern of differences between them made it possible to consider the isolated agent as a new virus, "Karshi" virus. The results of electron microscopic studies of this virus are presented.

Virus "Tamdy"--a new arbovirus, isolated in the Uzbee S.S.R. and Turkmen S.S.R. from ticks Hyalomma asiaticum asiaticum Schulee et Schlottke, 1929, and Hyalomma plumbeum plumbeum Panzer, 1796.

Eleven virus strains were isolated from ticks Hyalomma asiaticum asiaticum Schulce et Schlottke, 1929, and Hyalomma plumbeum plumbeum Panzer, 1796,collected in 1971-1974 in desert regions of the Uzbee S.S.R. and the Turkmen S.S.R. According to CF test the strains were closely related to each other and not antigenically connected with viruses from antigenic groups A, B, California, CHF-Congo, Bakau, Bunyamwera, Gajam, Kaisodi, Qalyub, Kemerovo, Quaranfil, Simbu, Turlock, Hughes, Uukuniemi, Tete and 21 ungrouped viruses isolated from ticks. The virus was named "Tamdy" after the place of isolation of a prototype strain LEIV-1308 Uz. The virus does not agglutinate goose erythrocytes, it is pathogenic for suckling mice and 3 weeks old mice by intracerebral infection. Replication of a virus with CPE in cell cultures--L, Rh, A1--and without CPE--in pig embryo kidney cell cultures--was demonstrated. According to ultrafiltration and electron microscope data the size of the virus is about 90 nm. It is rather sensitive to lipid solvents and is an RNA-virus. Morphologically the virus resembles the Bunyaviridae.

Ecology of tick-borne viruses in colonies of birds in the USSR.

During 1969--1974, 66,000 argasid and ixodid ticks from bird colonies in different parts of the USSR were studied. 247 strains of 8 different viruses were isolated. West Nile, Baku and Caspiy viruses were found from argasid ticks in the Caucasus and Middle Asia whereas ixodid ticks from seabird colonies in the North of the Far East and in the European part of the country yielded Tyuleniy, Zaliv Terpenya, Okhotskiy, Sakhalin and Paramushir viruses. The implications of the findings in the ecology of arboviruses is discussed.