Molecular evidence of haemosporidian infections in tawny owls (Strix aluco) from central Norway.

Haemosporidians, including Leucocytozoon spp., Plasmodium spp., and Haemoproteus spp., are vector-borne parasites that cause avian malaria and malaria-like diseases in birds. These infections can result in anaemia, reduced body condition, impaired reproductive success, and mortality, thereby acting as selective agents within host populations. Climate change is expected to influence dynamics of some haemosporidians, particularly in northern regions, by altering vector distributions and extending transmission seasons. In this study, tawny owls (Strix aluco; n = 27) from central Norway, were screened for Leucocytozoon spp., Haemoproteus spp.,and Plasmodium spp., using polymerase chain reaction (PCR). Samples were also screened for herpesvirus and Chlamydia spp., via PCR, to assess potential co-infections. Ten individuals (37%) tested positive for Leucocytozoon spp., with sequencing confirming the lineages STAL3 and STAL1, both previously detected in raptors. While seven individuals (26%) were positive in the Haemoproteus/Plasmodium PCR, sequencing was unsuccessful and infection could not be confirmed. Neither herpesvirus nor Chlamydia spp. were detected. This study provides the first molecular evidence of haemosporidian infections in raptors in Norway, underscoring the importance of continued surveillance of avian haemosporidians in resident northern species, to detect potential climate-driven changes in infection prevalence and associated health impacts.