Genotyping of tick-borne pathogens and determination of human attacking tick species in Novosibirsk and its suburbs

Abstract

The south of Western Siberia traditionally belongs to the regions with unfavorable epidemiological situation for tick-transmitted infections. In Novosibirsk and its suburbs, approximately 20 thousand people annually seek for medical care after tick bites. The purpose of this work was to determine human-attacking tick species composition in the territory of Novosibirsk and its suburbs by identifying nucleotide sequence of tick mitochondrial gene cytochrome oxidase COI fragment during the 2018 spring-summer season, determination of infections of individual ticks with viral and bacterial tick-borne infections, followed by genotyping identified pathogens by PCR methods, by determining nucleotide sequences and phylogenetic analysis. It is established that ticks of five species attack the humans: Ixodes persulcatus, Ixodes pavlovskyi, Dermacentor reticulatus, Dermacentor marginatus, Dermacentor nuttali in the Novosibirsk metropolis. The majority of tick attacks on humans are associated with I. pavlovskyi (43.6%) and D. reticulatus (41.2%) ticks. The genetic material of the tick-borne encephalitis virus was detected in 3.6%, borrelia 13.8% and Rickettsia 23.1% individual ticks collected from humans. Genotyping of the tick-borne encephalitis virus (TBEV) in the collected ticks showed the presence of TBEV Siberian and Far Eastern genotype in 83% and 17% cases, respectively. The Kemerovo virus could not be detected. Genetic material from Borrelia spp. and Rickettsia spp. has been detected in all five tick species attacking the local human population. The bulk of the identified Borrelia spp. isolates were genotyped as Borrelia garinii (86%) and 13% of the isolates as Borrelia afzelii species. The genetic material of Borrelia miyamotoi was found in one individual tick. Ticks of the genus Dermacentor have been found to be infected by Rickettsia raoultii, and ticks of the genus Ixodes were largely infected with Rickettsia tarasevichiae, and I. persulcatus tick was infected by Rickettsia helvetica in a single case. Thus, the human population of Novosibirsk and its suburbs is attacked by five species of ixodid ticks dominated by I. pavlovskyi and D. reticulatus ticks. The genetic material of the following tick-borne pathogens was found: Siberian and Far Eastern TBEV genotype, B. garinii, B. afzelii, B. miyamotoi, R. raoulti, R. tarasevichiae and R. helvetica in the individual ticks collected from humans.