Borrelia and Other Zoonotic Pathogens in Ixodes ricinus and Dermacentor reticulatus Ticks Collected from the Chernobyl Exclusion Zone on the 30th Anniversary of the Nuclear Disaster

Background: The 26th of April 2016 marked 30 years since the Chernobyl accident has occurred in Ukraine. As a result, the uninhabited Chernobyl region has been directly exposed to ionizing radiation for >30 years. Most work has focused on identifying associations between levels of radiation and the abundance, distribution, and mutation rates of plants and animals. Much less, however, is known about microbial communities in this affected region. To date, there are no reports on the prevalence of any tick-borne pathogens in Ixodes ricinus ticks from the Chernobyl exclusion zone (CEZ). The objective of our study was to examine the abundance of I. ricinus and Dermacentor reticulatus ticks in the CEZ and to investigate the prevalence of Borrelia burgdorferi sensu lato (s.l.) and other zoonotic agents in these ixodid ticks. Methods: A total of 260 questing I. ricinus and 100 D. reticulatus adult ticks were individually polymerase chain reaction analyzed for the presence of Anaplasma phagocytophilum, Babesia spp., Bartonella spp., Borrelia burgdorferi s.l., Francisella tularensis, and/or Rickettsia spp. Results: The respective infections rates were identified and compared with those of ixodid ticks that were concurrently collected from Kyiv. The significant differences between the infection rates of the CEZ and Kyiv ticks were observed for Rickettsia raoultii in D. reticulatus ticks (53.0% vs. 35.7%, respectively; p < 0.05) and Bartonella spp. (8.1% vs. 2.7%; P < 0.05) in I. ricinus ticks. Conclusions: Although the current data clearly demonstrated that the prevalence of some zoonotic pathogens were significantly higher in the ixodid ticks from the CEZ, a more comprehensive systematic approach is required to examine the causal effect of long-term ionizing radiation on adaptive changes of tick-borne pathogens.