Prevalence of Borreliaceae Spirochetes in Ticks Removed from Humans in Poland During 2018-2022.

Monitoring the occurrence of Borreliaceae spirochetes in ticks may provide an indication of the risks of acquiring Lyme borreliosis (LB) and Borrelia miyamotoi disease (BMD). All ticks obtained in our study from humans in the years 2018-2022 (n = 1232) were identified morphologically for species, sex and developmental stage. The detection of Borreliaceae spirochetes and species identification were performed by nested PCR based on the flaB gene fragment and the region between the mag and trnI genes. Two species of ticks were identified: Ixodes ricinus (96.9%) and Dermacentor reticulatus (3.1%). The infection of I. ricinus ticks with Borreliaceae spirochetes was found to reach 18.3%, including B. miyamotoi (2.5%). Among Borreliella species, Bl. afzelii was the most frequent, followed by Bl. burgdorferi, Bl. spielmanii, Bl. valaisiana, Bl. garinii, Bl. bissettiae, Bl. californiensis and Bl. carolinensis. Borreliaceae spirochetes were also found in D. reticulatus ticks, of which Bl. afzelii and B. miyamotoi were the most common. In conclusion, ticks affecting humans in Poland represent a real risk of infection with Borreliaceae spirochetes, and knowledge of the prevalence and distribution of these bacteria is an important tool in assessing the risks of LB and BMD.