Molecular detection and phylogenetic characterization of Anaplasma phagocytophilum in brown bears (Ursus arctos) in Slovakia.

Wild animals play a crucial role in the maintenance of tick-borne pathogens, acting as reservoir and sentinel hosts within natural ecosystems. The ongoing expansion of tick populations across Europe has intensified the circulation of zoonotic tick-borne pathogens, including Anaplasma phagocytophilum. Although the epidemiology of this bacterium has been extensively investigated in domestic animals and small wild mammals, the contribution of large omnivores such as the brown bear (Ursus arctos) remains poorly understood, particularly with respect to their exposure to genetically distinct lineages with zoonotic potential, which requires further molecular characterization. This study aimed to determine the detection rate of Anaplasma spp. in free-ranging brown bears (n = 76) and to molecularly characterize detected A. phagocytophilum isolates regarding their potentially zoonotic lineages. Spleen and liver samples were screened for Anaplasma spp. by nested PCR targeting the 16S rRNA gene, with subsequent molecular characterization focused on groEL gene and ankA gene. In total, 8 out of 76 samples were positive for Anaplasma spp., corresponding to a PCR detection rate of 10.53% (95% CI: 4.7-19.7%), with subsequent sequence analysis confirming the presence of A. phagocytophilum. Phylogenetic reconstruction based on groEL and ankA gene fragments allowed classification of the isolates into known European genetic lineages. This research confirms A. phagocytophilum exposure within the Slovak brown bear populations, identifying genetic variants relevant to public and veterinary health. These results suggest that brown bears may be exposed to A. phagocytophilum and could potentially play a role in its enzootic cycle, though further studies are needed.