Imported cases of dengue fever in Russia during 2010-2013.

OBJECTIVE: To confirm dengue infection among Russian tourists returned from Southeast and Mexico in 2010-2013 with clinical signs of infection. METHODS: Blood and serum samples from patients were collected. NS1 antigen and human IgM/IgG antibodies to dengue virus were identified using commercial tests manufactured by "Standard Diagnostics, INC.", Korea. ELISA test was used for the quantitative analyses of human IgM/IgG antibodies to dengue virus ("Orgenics Ltd.", Israel). Viral RNA was detected using commercial real-time PCR tests manufactured by "Genome Diagnostics Pvt. Ltd.", India and "Vector", Russia. Genotypes of revealed dengue viruses were determined employing nucleotide sequencing and phylogenetic analysis of 5'-UTR of the viral genome. RESULTS: A total of 98 collected blood samples were analyzed. Fifty samples were positive for at least one of four markers of dengue infection. IgM to dengue virus were revealed in 38 samples, in 25 samples IgM were combined with IgG. NS1 antigen was detected in 43 samples. 22 serum samples were positive for dengue virus RNA. The majority of samples (12 patients) from tourists returned from Thailand were positive for genotype 1 of dengue virus, 2nd and 4th genotype were identified each in 1 patient. CONCLUSIONS: Due to laboratory confirmed cases of imported dengue fever in Russia, the differential diagnosis of dengue is strictly recommended for tourists returning from endemic areas.

[Genetic diversity of the tick-borne encephalitis virus in Ixodes persulcatus ticks in northeastern European Russia].

The genetic diversity of the tick-borne encephalitis virus (TBEV) in the PCR-positive Taiga ticks collected in the Republic of Komi in 2010 was evaluated. The analyses of nucleotide sequences of the 5'-NCR fragments of viral genome from ticks had shown that 13 isolates of TBEV from 16 sequencing variants were represented by the highly pathogenic Far Eastern genotype of the TBEV and only 3 isolates were identified as the Siberian genotype of TBEV. The nucleotide sequences of 5'-NCR of viral genome strongly varied variable in individual ticks. Variability for the A1 element has been observed in all the tested samples, and for elements C1, B2, CS B--in more than 50%. A2 element and ATG codon of the 5'-NCR remained completely conservative. Computer simulation of conformations of the 5'-NCR of TBEV genome demonstrated the possibility of significant changes of the spatial structure of the 5'-NCR of viral genome in individual taiga ticks. The obtained data confirm the hypothesis that the variability in the 5'-NCR of TBEV genome can be crucial for efficient replication of TBEV in different hosts.

[The role of birds in the maintenance of tick-borne infections in the Tomsk anthropurgic foci].

The role of birds in the focus of tick-borne infections was studied from 2006 to 2011. The frequency index of ticks carried by ground dwelling birds is about 49.7%. The index of their abundance is 3.8. The larvae of ticks have been found on birds in 43.8% of cases. Nymphs and adult ticks have been found in 39.9 and 16.3%, respectively. It was revealed that Ixodex pavlovskyi was transferred and dominated in the urban microfoci because of its ornithophily. The markers of infectious agents have been recorded in 42 of 60 bird species under study.

[Genetic variants of the Crimean-Congo hemorrhagic fever virus circulating in endemic areas of the southern Tajikistan in 2009].

506 Hyalomma anatolicum ticks were collected and assayed in two Crimean-Congo hemorrhagic fever (CCHF) endemic regions of Tajikistan. Antigen and RNA of CCHF virus were detected in 3.4% of tick pools from Rudaki district using ELISA and RT-PCR tests. As of Tursunzade district, viral antigen was identified in 9.0% of samples and viral RNA was identified in 8.1% of samples. The multiple alignment of the obtained nucleotide sequences of CCHF virus genome S-segment 287-nt region (996-1282) and multiple alignment of deduced amino acid sequences of the samples, carried out to compare with CCHF virus strains from the GenBank database, as well as phylogenetic analysis, enabled us to conclude that Asia 1 and Asia 2 genotypes of CCHF virus are circulating in Tajikistan. It is important to note that the genotype Asia 1 virus was detected for the first time in Tajikistan.

[Complete genomic sequence of rapidly replicating strain MB-7 of hepatitis a virus and its characterization in comparison with nucleotide sequences of other hepatitis A virus strains].

Complete nucleotide sequence of genomic RNA of hepatitis A virus (HAV) rapidly replicating strain MB-7 was determined. Comparison of nucleotide and deduced amino-acid sequences demonstrated the highest level of identity of MB-7 with strain HAS-15 (above 99%) and high homology with other HAV strains (HM 175/7, CR326, and GBM/HFS) used in production of anti-hepatitis A vaccines. MB-7 was classified as subgenotype IA. Phylogenetic analysis showed that MB-7 is most closely related to the strain HAS-15 and the HAV variants circulating in Russia. Comparative analysis of genomic differences between MB-7 and HAS-15 with other HAV strains revealed among changes characteristic of MB-7 those typical of the described earlier rapidly replicating HAV strains (nt. 149-162 in 5'-untranslated region and changes in the VP3 and 2C genes). These results suggest the functional importance of changes in above-mentioned regions of HAV genome for the increased replication level of MB-7 in vitro.

[Genetic diversity of ixodid tick-borne pathogens in Tomsk City and suburbs].

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.

[Detection of the West Nile Virus and its genetic typing in ixodid ticks (Parasitiformes: Ixodidae) in Tomsk City and its suburbs].

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.

[Detection of the virus of hepatitis E isolates and elucidation of the possibility of their replication in vitro].

Blood serum samples collected from patients with acute hepatitis symptoms admitted to Infectious Disease Hospitals of Novosibirsk, Barnaul, and Irkutsk were studied. The serum samples were tested for the IgM and IgG antibodies to HEV using ELISA. Seropositive samples were tested using RT-PCR for HEV RNA. Two HEV strains were isolated, and thus HEV infection was identified for West Siberia. One of this strains is classified as HEV genotype I; the other, as genotype III. Cell culturing of these strains in green monkey kidney (4647) cells showed an ability of HEV genotype I strain to cause persistent infection.

[Genetic diversity of hepatitis A virus in Siberia].

The nucleotide sequences of a region of VP1/2A genes of a large group of hepatitis A virus (HAV) isolates circulating in Siberia (the Altai Territory, the Irkutsk and Novosibirsk Regions) were determined. Comparison of these sequences with those of prototype HAV of genotypes IA, IB, and IIA revealed their high similarity to prototype genotype IA strains. The above domains were shown to contain the types of viruses, which were close to both the European subtypes of HAV genotypes IA (78.3%) and the Far Eastern subtypes of this genotype (21.7%). The similar comparison of the derived amino acid sequences suggests that VP1 and 2A contains the amino acid substitutions that are typical of this geographical region.

[Lissavirus in bats residing in the South of West Siberia].

We caught, 2002-2003 in caves of Novosibirsk Region and Altai Territory, 52 bats (Myotis daubentoni, Myotis brandtii, Murina leucogaster, Plecotus auritus). Examinations of the animals' brain samples by fluorescence antibody microscopy and RT-PCR revealed lyssaviruses, genotype 1, which were close to strains provoking rabies in the local animals. According to the results, bats can be involved in keeping alive the rabies foci in Western Siberia, which must be taken into account in antiepizootic measures.