Prevalence, Genetic Diversity, and Pathogenicity of Avian Haemosporidian Parasite Co‐infection in Free‐Living Long‐Eared Owls ( <i>Asio otus</i> )

In wild birds, a frequent and significant aspect of co-evolution is simultaneous infections of a single avian host with multiple parasites from different haemosporidian genera, or from the same genus. To date, the majority of haemosporidian phylogenetic studies have been focused on Passerines. Other bird groups, such as nocturnal species, particularly owls, even though they play an important role in ecosystems, have been largely neglected. In our study, the use of a combination of different methodologies, including Illumina sequencing and a nested PCR protocol along with blood smear examination, provided valuable insights into detecting multiple infections. Out of 101 screened long-eared owl (Asio otus), screened in Vojvodina, Serbia, the overall prevalence was 69.3%, among which 26.73% individuals carried co-infections. With a prevalence of 41.58%, the most prevalent genus was Haemoproteus. However, no correlation was found between the presence of single or multiple infections and the body condition of long-eared owls, indicating that chronic haemosporidian infections may be harmless to the hosts during the non-breeding period. Furthermore, no significant differences in prevalence between adult and young birds were found. Additionally, long-eared owls represent a new host for 5 of 10 parasite lineages identified in this study, previously documented elsewhere. For this reason, continued research during the nesting period, when vectors are active, is crucial to better understand the full haemosporidian diversity in this top predator.