The occurrence of Taenia arctos (Cestoda: Taeniidae) in brown bears (Ursus arctos) from Slovakia: genetic variation and notes on morphological identification

Taenia arctos is a cestode associated with ursids as definitive hosts. Although the species has been reported from brown bears ( Ursus arctos ) in several parts of the Northern Hemisphere, it has not previously been confirmed in Slovakia. The primary objective of this study was to determine whether this species occurs in brown bears in the country. The gastrointestinal tracts of 125 legally culled free-ranging brown bears collected across Slovakia between 2025 and 2026 were examined for helminths following conventional parasitological examination procedures. The morphology of all recovered cestodes was examined under a light microscope. Then, one cestode from each infected bear was selected, and a DNA fragment encompassing the complete mitochondrial cytochrome c oxidase subunit 1 ( cox1 ) gene was PCR-amplified, Sanger-sequenced, and compared with the reference cox1 sequence of T. arctos . Taenia arctos was detected in 14 of 125 examined bears, corresponding to a prevalence of 11.2% (95% CI 6.3–18.1%). A total of 52 cestode specimens were recovered. Intensity ranged from 1 to 16 worms per bear, with a median of 2. Molecular analysis of 14 specimens confirmed their identity as T. arctos and revealed two cox1 haplotypes among the Slovak isolates. The large hair-like structures in the copulatory part of the vagina were observed in all examined T. arctos specimens in which this feature could be evaluated, but were not observed in the available comparative material of Taenia krabbei , the most morphologically similar congener of T. arctos . The structures have not been reported in published descriptions of T. krabbei , supporting their potential diagnostic utility. This study confirms the occurrence of T. arctos in brown bears from Slovakia based on the morphological and molecular evidence. The consistently observed hair-like structures in the copulatory part of the vagina may represent a useful additional morphological character for distinguishing T. arctos from morphologically similar Taenia species.