Prevalence of Tick-Borne Pathogens in Hard Ticks That Attacked Human Hosts in Eastern Siberia

The aim of this study was to evaluate the risk of tick-borne infections in humans. The prevalence of 4 tick-borne pathogens was studied in the population of Ixodid ticks attacking human hosts in Irkutsk city and neighbouring territories from 2007 to 2017. Methods and Results: In total, 46,357 tick specimens detached from bitten people were analyzed. The antigen of tick-borne encephalitis virus (TBEV) was detected in each tick individually by ELISA assay using a commercial kit for the envelope protein E of TBEV. Total RNA and DNA were extracted from ticks using a RiboPrep kit. Reverse transcription was performed using a Reverta-L kit and RNA\DNA of TBEV; B. burgdorferi sensu lato, A. phagocytophylum and Ehrlichia muris\E. chaffeensis were detected using a real-time multiplex PCR kit. In total, during 8 years of observations, I. persulcatus caused approximately 86% of bites, Dermacentor sp. 13.95 %, and H. concinna 0.05 %. The most prevalent tick-borne pathogen in I. persulcatus ticks was Lyme disease agent B. burgdorferi sensu lato, which was detected in 12 +/- 6.5% of specimens annually. A. phagocytophilum and Ehrlichia sp. were detected in 7.8 +/- 2.7% and 4.6 +/- 1.5% of specimens, respectively. TBEV was present in 1 +/- 0.7% of I. persulcatus. Conclusion: I. persulcatus remains the most important vector of tick-borne diseases to humans in Eastern Siberia. D. nuttalli and D. silvarum are much less aggressive to humans and are less infected with major tick-borne pathogens. H. concinna does not play any significant role as a disease vector. However, a rigorous analysis of TBEV spread in the Dermacentor sp. population is necessary.