Tick-borne pathogens in Finnish wildlife: The role of non-native raccoon dog and European hare.

The role of different host species in the circulation dynamics of tick-borne pathogens (TBPs) in northern ecosystems remains insufficiently characterized, despite the widespread distribution of these pathogens in European wildlife. In particular, the contribution of medium-sized mammals, including non-native species, to TBP circulation is poorly understood. We screened 446 skin samples from nine wildlife species in Finland for multiple zoonotic TBPs to assess pathogen occurrence across host species with particular emphasis on the invasive raccoon dog (Nyctereutes procyonoides) and non-native European hare (Lepus europaeus). Borrelia burgdorferi s.l., Anaplasma phagocytophilum, and Rickettsia helvetica were the most frequently detected pathogens, with prevalence varying among host species. Babesia spp. was predominantly detected in ungulates, whereas Spiroplasma ixodetis and Borrelia miyamotoi were rare. Raccoon dogs and European hares showed generally low pathogen prevalence, while the highest TBP prevalences were observed in squirrels, hedgehogs, and ungulates. We also screened for two Ixodes-associated endosymbionts (Rickettsiella spp. and Midichloria mitochondrii) as potential indicators of tick exposure. Although Rickettsiella spp. was associated with TBP infections, the low prevalence of both endosymbionts suggests their limited utility as tick bite markers. These findings provide a cross-sectional overview of TBP occurrence in Finnish wildlife and demonstrate that host-pathogen associations vary among species. The relatively low pathogen prevalence observed in the raccoon dog and European hare suggests that these species are unlikely to play a major role in maintaining TBP transmission in northern ecosystems, although they may contribute to tick abundance and dispersal.