Tick-borne pathogens in Ixodes ricinus (Acari: Ixodidae) and Ixodes inopinatus × I. ricinus hybrids in Central Europe: no link to bird diversity or abundance.

While the presence of Ixodes inopinatus in Central Europe has not been conclusively demonstrated, recent studies have provided evidence of Ixodes ricinus with introgressed I. inopinatus TROSPA alleles in the Czech Republic. Migratory birds have been hypothesized to carry I. inopinatus from North Africa to more northern regions, potentially leading to hybridization with I. ricinus in Southern and possibly Central Europe. In this study, we screened 659 tick nymphs collected from six sites in the Czech Republic, which were selected based on the diversity and abundance of birds and classified as bird-poor and bird-rich habitats. We did not detect any I. inopinatus, but hybrid tick prevalence (individuals bearing different TROSPA alleles) ranged from 0.7% to 5.5% per site and was not associated with habitat type. We found a decline in the occurrence of hybrids along a south-to-north latitudinal gradient. Overall, 22.9% of ticks tested positive for at least one tick-borne pathogen, with a higher prevalence in I. inopinatus/ricinus hybrids (30%) than in I. ricinus (22.7%). Hybrid ticks harbored Borrelia burgdorferi s. l., B. miyamotoi, and Rickettsia helvetica. In I. ricinus, B. burgdorferi s. l. was the most prevalent pathogen (11.8%), and by genospecies dominated by B. afzelii, followed by Rickettsia spp. (5.6%), Anaplasma phagocytophilum (4.7%, mostly ecotype I), and B. miyamotoi (2.5%), with several co-infection patterns observed. One tick was positive for Neoehrlichia mikurensis. The prevalence of Anaplasma phagocytophilum, Borrelia miyamotoi, Borrelia burgdorferi s. l., and Rickettsia spp. substantially varied among sites and was independent of habitat type.