Bat-associated soft tick Carios vespertilionis in Belarus.

The soft tick Carios vespertilionis is a nidicolous ectoparasite of bats with a wide Old World distribution, yet its occurrence in Belarus remains poorly documented. This study provides the first detailed account of C. vespertilionis in Belarus based on field surveys conducted between 2020 and 2023, supplemented by two additional records from a private collection. In total, 1113 bats representing 16 species were considered, including 1111 field-sampled individuals of 15 species. Carios vespertilionis was recorded at 23 localities in 16 districts of five regions of Belarus. Across all records, 297 larval specimens were collected from 68 bats belonging to seven host species. The largest numbers of infested bats and collected larvae were recorded on Pipistrellus pygmaeus and P. nathusii; additional records were obtained from Eptesicus serotinus, Nyctalus noctula, Vespertilio murinus, Plecotus auritus and Pipistrellus pipistrellus. The highest infestation loads were recorded on Pipistrellus nathusii and P. pygmaeus, with up to 12 larvae on a single host. Overall prevalence in the field sample was 5.9%, and mean intensity was 4.4 larvae per infested host. The species is currently documented in Brest, Gomel, Grodno, Minsk, and Mogilev regions; no records were obtained from the surveyed localities in Vitebsk Region. These findings substantially expand the known distribution of C. vespertilionis in Belarus and provide new data on its host associations and infestation parameters.