Novel Helminth Findings from the Western Barbastelle (Chiroptera: Vespertilionidae) in Belarus with the First Data on Its Intraspecific Variability

Bats represent a vulnerable group of mammals, and their removal from the wild is exceptionally rare. Consequently, helminthological studies of these animals remain scarce and limited. We examined Barbastella barbastellus specimens that had died of natural causes during hibernation in Belarus. Helminthological examination of the animals revealed two trematode species, i.e. Pycnoporus heteroporus and Plagiorchis koreanus. This is the first study to identify B. barbastellus as a definitive host of Pl. koreanus. Our findings contribute to the understanding of bat helminth fauna in the region and provide new insights into host-parasite relationships. Additionally, we represent the first assessment of intraspecific genetic variability in B. barbastellus in Belarus, clarifying its phylogenetic affinities. All studied specimens belonged to the ‘East-Central Europe’ genetic lineage. While some individuals were associated with the central haplotype or closely related variant, most formed an independent subgroup, suggesting long-term isolation of these populations. Molecular analysis of the detected parasites not only verified their taxonomic status but also revealed genetic divergence among specimens identified as Plagiorchis koreanus.