RESUMO
We studied two urban and two suburban biotypes of Tomsk City for tick-transmitted diseases prevalence in naturally collected ticks. Tick-borne encephalitis virus (TBEV) was found in 6.5% of tick samples, West Nile virus (WNV) in 2.2%, Borrelia spp. in 8%, Rickettsia spp. in 2.5%, and Ehrlichia spp. in 1.7% of samples. Genetic markers of Powassan virus, Bartonella spp., and Balbesia spp. were not found. Analysis of the genetic diversity of revealed pathogens resulted in the following conclusions: 1. TBEV strains belong to Siberian and Far-Eastern subtypes, and Far-Eastern subtype of TBEV is most frequent in urban biotypes (up to 43 % of urban strains of TBEV); 2. WNV strains belong to genotype la; 3. Borrelia spp. were classified as B. garinii; 4. Rickettsia spp. were classified as R. tarasevichiae and probably as a new Rickettsia raoultii subspecies; 5. Ehrlichia spp. were classified as E. muris. The coexistence of several pathogens was found in 5.7% of tick samples, and the most frequent combination was TBEV + Borrelia spp.
Assuntos
Borrelia/genética , Ehrlichia/genética , Vírus da Encefalite Transmitidos por Carrapatos/genética , Variação Genética , Ixodidae/microbiologia , Rickettsia/genética , Vírus do Nilo Ocidental/genética , Animais , Borrelia/classificação , DNA Bacteriano/genética , Ehrlichia/classificação , Vírus da Encefalite Transmitidos por Carrapatos/classificação , Genes Bacterianos/genética , Humanos , Filogenia , RNA Viral/genética , Rickettsia/classificação , Sibéria , Vírus do Nilo Ocidental/classificaçãoRESUMO
Four tick species, Ixodes persulcatus, I. pavlovskyi, I. trianguliceps, and Dermacentor reticulatus, were found in Tomsk and its suburbs in 2006. The species I. pavlovskyi was found to be dominant in the localities situated in Tomsk City, and I. persulcatus was dominant in its suburbs. Viral RNA and viral antigen of the West Nile virus (WNV) were detected in the ticks I. pavlovskyi and I. persulcatus collected in the city and its suburbs by the RT PCR method and enzyme immunoassay with monoclonal antibodies against protein E of the WNV. Average rate of the WNV infected ticks varied from 5.2 up to 11.7% in different localities. Identification of the nucleotide sequence of the protein E gene fragment allowed classifying the cDNA obtained as genotype Ia of the WNV. The sequences are proved similar to the strain LEIV-Vlg99-27889-human of the WNV isolated in Volgograd. The obtained data showed that natural foci of the WNV virus can appear in the city and its suburbs probably involving two dominant tick species. The WNV infected imagoes, larvae, and nymphs of I. persulcatus and I. pavlovskyi were collected from small mammals, lizards, and birds. Therefore we presume that these hosts can be involved in the circulation and distribution of WNV on the territory of Tomsk Region.
