LONG-TERM TRENDS OF CHANGES IN INFESTATION RATE OF THE BAIKAL REGION POPULATION BY IXODIC TICKS

Ixodid ticks are the vectors of many pathogens including tick-borne encephalitis virus and the Lyme disease agent Borrelia burgdorferi sensu lato. In Pribaikalye, Ixodes persulcatus, Dermacentor nuttalli, D. silvarum and Haemaphysalis concinna are regarded as main vectors of the diseases. Recently, significant changes in world tick fauna have been reported and this affects the spread of tick-borne pathogens. We studied the current species diversity, population structure and the number of attacks of hard ticks (Acari:Ixodidae) on humans in Irkutsk region and nearby territories during the season 2015. Long-term trends of changes in attack rate were analyzed as well. In total, 4268 individual ticks were identified and analyzed during the season 2015. The majority (86 %) of victims was bitten by I. persulcatus; 13.55 % of attacks on humans were caused by D. nuttalli and D. silvarum; whereas H. concinna was documented only in 2 cases (~0.05 %). No non-endemic or invasive tick species were documented in 2015. The seasonal activity and the age/gender structure of tick population that bite human hosts were described as well. The comparison of the results of 2015 with previously reported datasets on tick bite ratesfrom 1992-2001 andfrom 2007-2014 indicates that, after the burst of tick bites in 1992-2001, there are no significant increase of attack rate since 2007. Possible implications to human health and epidemiology of tick-borne infections are discussed.