Detection and genetic characterization of a putative novel Borrelia genospecies in Ixodes apronophorus / Ixodes persulcatus / Ixodes trianguliceps sympatric areas in Western Siberia.

Four genospecies from the Borrelia burgdorferi sensu lato complex were detected in Ixodes persulcatus and Ixodes pavlovskyi ticks from Siberia and genetically characterized. The presence of Borrelia spp. in Ixodes apronophorus and Ixodes trianguliceps ticks found in Asia has never been studied. In this study, genetic diversity of B. burgdorferi s.l. was investigated in three I. persulcatus / I. trianguliceps / I. apronophorus sympatric habitats in Western Siberia. Three groups of samples were examined: (i) ticks that were taken from rodents and molted in a laboratory; (ii) non-molted ticks collected from rodents; (iii) specimens from small mammals. Expectedly, Borrelia afzelii and Borrelia bavariensis were detected in I. persulcatus and in small mammals from the studied locations. Borrelia bavariensis was first found in molted I. apronophorus and I. trianguliceps. Identical genovariants of B. bavariensis were found in I. apronophorus, I. trianguliceps, and I. persulcatus. In addition, a new Borrelia genovariant was discovered in non-molted and molted I. apronophorus and non-molted I. persulcatus and I. trianguliceps, as well as in small mammals. This new genovariant was genetically characterized using MLST and single locus sequence analysis, which indicated that the new Borrelia genovariant significantly differs from all known Borrelia species. We propose the name "Candidatus Borrelia sibirica" for this putative new species.

Ixodes persulcatus/pavlovskyi natural hybrids in Siberia: Occurrence in sympatric areas and infection by a wide range of tick-transmitted agents.

Ixodes persulcatus and Ixodes pavlovskyi ticks, two closely related species of the I. ricinus - I. persulcatus group, are widely distributed in the southern part of Western Siberia. Recently, the existence of natural hybrids of I. persulcatus and I. pavlovskyi ticks has been demonstrated. The aim of this study was to evaluate the abundance of I. persulcatus/pavlovskyi hybrids in several locations with different ratios of parental tick species and to investigate the prevalence and genetic variability of a wide range of infectious agents in these hybrids compared to the parental tick species. Natural hybrids of I. persulcatus and I. pavlovskyi ticks were identified in all examined locations in Altai and Novosibirsk, Western Siberia, Russia. The abundance of hybrids varied from 7% to 40% in different locations and was maximal in a location with similar proportions of I. persulcatus and I. pavlovskyi ticks. For the first time, it was shown that hybrids can be infected with the same agents as their parental tick species: tick-borne encephalitis and Kemerovo viruses, Borrelia afzelii, Borrelia bavariensis, Borrelia garinii, Borrelia miyamotoi, Rickettsia helvetica, Rickettsia raoultii, Rickettsia sibirica, "Candidatus Rickettsia tarasevichiae", Anaplasma phagocytophilum, Ehrlichia muris, "Candidatus Neoehrlichia mikurensis", and Babesia microti. The prevalence of most bacterial agents in hybrids was intermediate compared to their parental tick species. Most genetic variants of the identified agents have been previously found in the parental tick species. Wide distribution of I. persulcatus/pavlovskyi natural hybrids implies that I. persulcatus, I. pavlovskyi and their hybrids coexist in all I. persulcatus - I. pavlovskyi sympatric areas.

Multilocus sequence analysis of Borrelia burgdorferi sensu lato isolates from Western Siberia, Russia and Northern Mongolia.

Lyme borreliosis (LB) is the most frequently recorded tick-transmitted disease in Eurasia. Tomsk Province, Western Siberia in Russia and Selenge Aimag in Northern Mongolia are leading regions in the LB incidence rate in these countries. Spirochaetes of the Borrelia burgdorferi sensu lato (s.l.) complex isolated from Ixodes ticks from Tomsk Province (n = 56) and Ixodes persulcatus ticks from Selenge Aimag (n = 5) were genetically characterized using Multi Locus Sequence Typing (MLST), analysis of the 5S23S rRNA intergenic spacer (IGS) amplicons, and p83/100 gene sequencing. According to MLST, B. afzelii (n = 26), B. bavariensis (n = 23), B. garinii (n = 11), and B. valaisiana (n = 1) isolates were detected in Tomsk Province, while B. afzelii and B. bavariensis isolates were identified in Selenge Aimag. Of the 32 revealed sequence types (ST), 21 STs were new and 14 of the new STs belonged to B. afzelii. Several STs of B. afzelii, B. garinii and B. valaisiana identified in this study clustered with European STs found in I. ricinus ticks. Analysis of the 5S23S IGS demonstrated that the studied Borrelia strains showed RFLP pattern characteristic for the following 5S23S IGS types: VS461 (B. afselii), NT29 (B. bavariensis), 20047 (B. bavariensis and B. garinii), VS116 (B. valaisiana), and three new groups (B. afzelii and B. bavariensis). Notably, this is the first report of Asian B. bavariensis possessing a 5S23S IGS RFLP pattern identical to 20047, and analysis of the 5S23S IGS did not provide correct determination of Borrelia species occurring in Asia. Genotyping of Borrelia strains using the clpA, pepX, and p83/100 genes demonstrated the same result as genotyping based on MLST; and further investigations are required to confirm that these three genetic loci could be used for determination of bacterial species from the B. burgdorferi s.l. complex because data based on single loci may be misleading.

Detection and genetic characterization of a wide range of infectious agents in Ixodes pavlovskyi ticks in Western Siberia, Russia.

BACKGROUND: The Ixodes pavlovskyi tick species, a member of the I. persulcatus/I. ricinus group, was discovered in the middle of the 20th century in the Russian Far East. Limited data have been reported on the detection of infectious agents in this tick species. The aim of this study was to investigate the prevalence and genetic variability of a wide range of infectious agents in I. pavlovskyi ticks collected in their traditional and recently invaded habitats, the Altai Mountains and Novosibirsk Province, respectively, which are both located within the Western Siberian part of the I. pavlovskyi distribution area. RESULTS: This study reports the novel discovery of Borrelia bavariensis, Rickettsia helvetica, R. heilongjiangensis, R. raoultii, "Candidatus Rickettsia tarasevichiae", Anaplasma phagocytophilum, Ehrlichia muris, "Candidatus Neoehrlichia mikurensis" and Babesia microti in I. pavlovskyi ticks. In addition, we confirmed the previous identification of B. afzelii, B. garinii and B. miyamotoi, as well as tick-borne encephalitis and Kemerovo viruses in this tick species. The prevalence and some genetic characteristics of all of the tested agents were compared with those found in I. persulcatus ticks that were collected at the same time in the same locations, where these tick species occur in sympatry. It was shown that the prevalence and genotypes of many of the identified pathogens did not significantly differ between I. pavlovskyi and I. persulcatus ticks. However, I. pavlovskyi ticks were significantly more often infected by B. garinii and less often by B. bavariensis, B. afzelii, "Ca. R. tarasevichiae", and E. muris than I. persulcatus ticks in both studied regions. Moreover, new genetic variants of B. burgdorferi (sensu lato) and Rickettsia spp. as well as tick-borne encephalitis and Kemerovo viruses were found in both I. pavlovskyi and I. persulcatus ticks. CONCLUSION: Almost all pathogens that were previously detected in I. persulcatus ticks were identified in I. pavlovskyi ticks; however, the distribution of species belonging to the B. burgdorferi (sensu lato) complex, the genus Rickettsia, and the family Anaplasmataceae was different between the two tick species. Several new genetic variants of viral and bacterial agents were identified in I. pavlovskyi and I. persulcatus ticks.