Spectrum of Ixodidae Ticks Attacking Humans in Russian Siberia and Their Association with Tick-Borne Bacterial Agents

Spectrum of ixodid ticks that bite people in Western Siberia significantly changed over the past two decades. In this study, we determined tick species attacking people in surroundings of Novosibirsk and the range of bacterial agents they infected with. This study included 301 ticks taken from people and 46% were Ixodes pavlovsky, followed by Ixodes persulcatus (19.6%), I. persulcatus / I. pavlovskyi interspecies hybrids (19.6%), and Dermacentor reticulatus (12.8%). Human DNA was determined in ticks, first demonstrating that all these tick species, including hybrids, were able effectively feed on humans. DNA of Borrelia spp., Rickettsia spp. and Anaplasmatacreae bacteria was detected in different tick species. Borrelia garinii prevailed in Ixodes species, being found in 8.8% ticks, whereas B. afzelii and B. bavariensis were found in single ticks. Borrelia miyamotoi was revealed in 3.7% ticks. Among Rickettsia spp., “Candidatus Rickettsia tarasevichiae” and R. raoultii were identified mainly in I. persulcatus and D reticulatus (44.8% and 26.3%, respectively), whereas Rickettsia helvetica was found only in 2.2% I. pavlovsky. The prevalence of Anaplasma phagocytophilum, Ehrlichia muris and Neoehrlichia mikurensis did not exceed 2%. The obtained results indicate a high risk for humans to be infected with agents of Lyme borreliosis, primarily B. garinii.