High prevalence and frequent co-infections of vector-borne pathogens in dead moose (Alces alces) calves in Norway

Understanding the role of vector-borne pathogens in ungulate health is essential for evaluating infection risks under changing environmental conditions. This study investigated the occurrence of vector-borne pathogens in 32 moose ( Alces alces ) calves found dead in Agder County, southern Norway, and considered their potential relevance to calf health and wildlife disease surveillance. The target pathogens were those previously reported in European cervids or their associated vectors, including Anaplasma phagocytophilum , Bartonella spp., Babesia spp., Borrelia spp., Rickettsia spp., Neoehrlichia mikurensis , and haemotropic Mycoplasma spp. We detected A. phagocytophilum in all animals (100%), while Bartonella spp. and Babesia cf. odocoilei were found in 81.3% and 28.1% samples, respectively. Co-infections involving two or more pathogens were frequent. In contrast, Borrelia spp., Rickettsia spp., N. mikurensis , and Mycoplasma spp. were not detected. Our findings provide novel data on the epidemiology of vector-borne pathogens in moose and complement existing knowledge of their distribution in northern Europe. The findings highlight the importance of continued surveillance of wildlife hosts to better understand pathogen ecology and potential impacts on animal health.