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Over the last four decades, Barred Owls (Strix varia) have expanded their range to include much of western North America, including California. This expansion is suspected to have contributed to declining populations of a closely related species, the federally threatened Northern Spotted Owl (Strix occidentalis caurina). As a result, understanding potential health threats to Barred Owls has implications for Spotted Owl health and recovery. From 2016 to 2020, 69 Barred Owls were collected to determine the apparent prevalence of periorbital nematode infection, to identify the parasite species present, and to investigate the potential pathologic effects on their hosts. The nematodes were morphologically identified as Oxyspirura and Aprocta spp. On the basis of phylogenetic analyses, they were clearly divergent from published sequences of other species within these genera. Overall, 34 (49%) Barred Owls were infected with periorbital nematodes, with Oxyspirura sp. infections being much more common (94%) than Aprocta sp. (18%). Histopathology revealed varying severity of conjunctivitis in infected owls. Despite the frequency of infection and subsequent inflammation, parasite burden was not associated with reduced body weight in these owls. As a result, the potential health effect of these nematodes is unclear. Further taxonomic characterization is needed to determine potential novelty of these nematodes., (© Wildlife Disease Association 2023.)

A total of eight juvenile great horned owls (Bubo virginianus) were found lethargic and on the ground in spring 2015, 2016, and 2017, including one fledgling from Louisiana, USA and seven nestlings from California, USA. One bird survived to release after rehabilitation; seven birds died or were euthanized due to poor prognosis and were necropsied. Necropsy findings were similar and included general pallor of all tissues, particularly the subcutis and lungs, and enlarged liver and spleen. Histopathology revealed multi-organ necrosis, abundant meronts containing merozoites, and intracytoplasmic pigmented haemosporidian parasites in blood cells in one bird. Leucocytozoon lineages lSTOCC16 and BUVIR06 were identified by polymerase chain reaction and genetic sequencing. The systemic Leucocytozoon infections were likely associated with morbidity and mortality in these owls. A second parasite, Haemoproteus lineage hSTVAR01, was also identified in an owl from Louisiana. This is the first identification of Leucocytozoon lineages that have been associated with mortality in young great horned owls., (Copyright © 2018 Elsevier B.V. All rights reserved.)