Expanding wildlife serosurveillance: a study of influenza A virus exposure in Irish carnivores

Abstract Increasing reports of zoonotic avian influenza virus (AIV) spillovers to mammals signal critical shift in their ecology and raise substantial public health concerns. The highly pathogenic avian influenza H5N1 clade 2.3.4.4b has driven this expansion, with genetic adaptations enhancing replication in mammalian hosts. Adaptations have been identified in diverse carnivore species, including American mink ( Neogale vison ), red foxes ( Vulpes vulpes ), and otters ( Lutra lutra ). These carnivores often feed on, or share habitat with, wild birds, making them suitable species for monitoring AIV presence in mammals. Here we investigated exposure to influenza A viruses (IAVs), including H5 and H7 subtypes in three mesocarnivore species (red foxes, American mink, and European badgers) in Ireland. Using enzyme-linked immunosorbent assays, we detected a seroprevalence for IAVs of 24.6% (28/114) in foxes, 22.2% (2/9) in mink, and 1% (1/96) in badgers. Among red fox samples positive for antibodies against IAVs, 82.1% (23/28) were positive for antibodies against the H5 subtype. No antibodies against the H7 subtype were detected. We also examined the use of Nobuto filter paper as a reliable alternative to serum samples for IAVs antibody detection via ELISA and assessed the use of haemolysed serum samples. These findings, as well as those gathered from ongoing passive surveillance of wild birds, highlight that influenza A is circulating in wildlife in Ireland. If we are to better understand influenza A dynamics in Ireland, and globally, it is imperative that surveillance programmes are supported, and serosurveys provide one valuable tool for active surveillance.