FIRST REPORT OF CLINOSTOMUM SPP. IN THREE SPECIES OF STRIGIFORMES (MEGASCOPS ASIO, STRIX VARIA, BUBO VIRGINIANUS)

Clinostomum spp. are digenetic trematodes commonly found in piscivorous birds. At the Janet L. Swanson Wildlife Hospital in Ithaca, NY, trematode (also known as fluke) infections were identified in six owls admitted to the hospital from 2020 to 2023 representing three species: an Eastern screech owl (Megascops asio) (n = 1), barred owls (Strix varia) (n = 3), and great horned owls (Bubo virginianus) (n = 2). All individuals were presented to the wildlife hospital following vehicular trauma except for the two great horned owls. Trematodes observed in the oral cavities of these birds during initial physical examinations were presumptively identified as Clinostomum sp. based on their appearance and location. Molecular characterization based on cytochrome c oxidase subunit I (COX1) marker that was performed on specimens removed from the screech owl (Case 1) and a barred owl (Case 3) identified these trematodes as Clinostomum dolichorchum. The specimen from another barred owl (Case 2) did not have a strong match with any reported COX1 sequence and could only be identified to the genus level as Clinostomum sp. There are limited reports of Clinostomum spp. in raptors, and this is the first known documentation of infection in these three owl species. Though these parasites are often considered nonpathogenic, heavy parasitic loads can cause clinical disease and may have contributed to the clinical condition of two of these owls. Further study is needed to understand the effects of Clinostomum spp. in atypical hosts such as owls (Strigiformes).