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

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