The risk of exposure to rickettsial infections and human granulocytic anaplasmosis associated with Ixodes ricinus tick bites in humans in Romania: A multiannual study.

Anaplasma phagocytophilum and spotted fever group Rickettsia are obligate intracellular Gram-negative tick-borne bacteria, among which several may cause clinical infections in humans. Several Rickettsia spp. and A. phagocytophilum are transmitted in Europe by Ixodes ricinus, the most common tick species feeding on humans in this area. The aim of this study was to evaluate the annual prevalence of Rickettsia spp. and A. phagocytophilum in I. ricinus collected from humans during three consecutive years. The mean prevalences of the infection with the investigated pathogens in I. ricinus ticks collected from human patients were as follows: A. phagocytophilum (5.56%), R. helvetica (4.79%) and R. monacensis (1.53%). In the present study, no significant differences of pathogens prevalence between the three years study period were observed, except the prevalence of R. helvetica, which had a significant increase in 2015, suggesting an increasing risk for humans to be exposed to this zoonotic pathogen.