Diversity of Rickettsiaceae and Anaplasmataceae bacteria within and between species in Ixodes ricinus ticks collected from humans in Poland.

Ixodes ricinus is the most common tick species in Europe, widely distributed in natural environments, rural habitats, and urban green spaces. As a vector of diverse tick-borne pathogens, I. ricinus represents a significant public health concern. The aim of this study was to identify pathogenic species and strains of Rickettsia, Anaplasma phagocytophilum, and Neoehrlichia mikurensis in I. ricinus ticks removed from human skin, and to compare the prevalence of pathogenic species between ticks collected in urban and rural/suburban areas. A total of 1992 I. ricinus ticks were analyzed for the presence of Rickettsia spp., A. phagocytophilum, and N. mikurensis DNA using the PCR method. Selected amplicons were sequenced using the Sanger method, and the resulting nucleotide sequences were subjected to phylogenetic analysis to identify species and genetic variants. Among the tested I. ricinus ticks, three SFG Rickettsia were identified, with Rickettsia helvetica predominating and Rickettsia raoultii unexpectedly detected in this tick species. Four 16S rRNA and three groESL gene variants of A. phagocytophilum were identified, and the presence of the European variant of N. mikurensis was confirmed. A significantly higher prevalence of A. phagocytophilum was observed in ticks collected from urban areas (3.2%) compared to rural/suburban habitats (1.2%). The results of this study provide evidence of human exposure to tick-borne pathogens and contribute to the understanding of the diversity of pathogenic species and strains in ticks from human-inhabited areas.