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

Monitoring the occurrence of <i>Borreliaceae</i> 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 <i>Borreliaceae</i> spirochetes and species identification were performed by nested PCR based on the <i>flaB</i> gene fragment and the region between the <i>mag</i> and <i>trnI</i> genes. Two species of ticks were identified: <i>Ixodes ricinus</i> (96.9%) and <i>Dermacentor reticulatus</i> (3.1%). The infection of <i>I. ricinus</i> ticks with <i>Borreliaceae</i> spirochetes was found to reach 18.3%, including <i>B. miyamotoi</i> (2.5%). Among <i>Borreliella</i> species, <i>Bl. afzelii</i> was the most frequent, followed by <i>Bl. burgdorferi</i>, <i>Bl. spielmanii</i>, <i>Bl. valaisiana</i>, <i>Bl. garinii</i>, <i>Bl. bissettiae</i>, <i>Bl. californiensis</i> and <i>Bl. carolinensis</i>. <i>Borreliaceae</i> spirochetes were also found in <i>D. reticulatus</i> ticks, of which <i>Bl. afzelii</i> and <i>B. miyamotoi</i> were the most common. In conclusion, ticks affecting humans in Poland represent a real risk of infection with <i>Borreliaceae</i> spirochetes, and knowledge of the prevalence and distribution of these bacteria is an important tool in assessing the risks of LB and BMD.