Epidemiological Insights into Endoparasites of Brown Bears (Ursus arctos) in Greece

Brown bear populations in Greece face multiple threats, and parasitic infections may pose an additional risk to these vulnerable animals. This study represents the first comprehensive assessment of endoparasite occurrence, prevalence, and seasonality in brown bears in Greece, in relation to geographical location and the animal's different physiological phases. A total of 918 faecal samples were collected over a three-year period from regions with brown bear presence in Greece. For each sample, the date of collection and the coordinates of the site were recorded. Samples were examined using sedimentation, flotation, and McMaster techniques, while the Baermann method was additionally applied to a subset of 195 samples. Spatial and temporal patterns in parasite occurrence and diversity were analysed using generalised additive models (GAMs). Ten parasitic taxa were identified, with Baylisascaris transfuga being the most prevalent (39.8%), followed by Crenosoma spp. (26%), Uncinaria spp. (18.09%), and Dicrocoelium dendriticum (14.38%). Less prevalent taxa included Eucoleus aerophilus, Sarcocystis spp., Toxascaris leonina, Eimeria spp., Linguatula serrata, and Taeniidae. Μixed infections, involving two or more parasites, were detected in 22% of the samples. The prevalence of B. transfuga was higher in late autumn, with high-risk infection areas identified in both late summer and autumn. In contrast, Uncinaria spp. and D. dendriticum showed no seasonal variation, while D. dendriticum exhibited spatial clustering patterns similar to B. transfuga but without clear seasonal trends. These findings highlight the widespread occurrence and complexity of parasitic infections in Greek brown bears. Continued long-term monitoring is essential to improve understanding of transmission dynamics and the ecological processes shaping parasite distribution in this animal species.