High pathogenicity avian influenza (H5N1) in Northern Gannets (Morus bassanus): Global spread, clinical signs and demographic consequences

Abstract

During 2021 and 2022 High Pathogenicity Avian Influenza (HPAI) killed thousands of wild birds across Europe and North America, suggesting a change in infection dynamics and a shift to new hosts, including seabirds. Northern Gannets (Morus bassanus) appeared especially severely impacted, but a detailed account of the data available is required to help understand how the virus spread across the metapopulation, and the ensuing demographic consequences. Accordingly, we analyse information on confirmed and suspected HPAIV outbreaks across most North Atlantic Gannet colonies and for the largest colony (Bass Rock, UK), provide impacts on population size, breeding success, and preliminary results on apparent adult survival and serology. Unusually high numbers of dead Gannets were first noted at colonies in Iceland during April 2022. Outbreaks in May occurred in many Scottish colonies, followed by colonies in Canada, Germany and Norway. By the end of June, outbreaks had occurred in colonies in Canada and the English Channel. Outbreaks in 12 UK and Ireland colonies appeared to follow a clockwise pattern with the last infected colonies recorded in late August/September. Unusually high mortality was recorded at 40 colonies (75% of global total colonies). Dead birds testing positive for HPAIV H5N1 were associated with 58% of these colonies. At Bass Rock, the number of occupied nest sites decreased by at least 71%, breeding success declined by ~66% compared to the long‐term UK mean and the resighting of marked individuals suggested that apparent adult survival between 2021 and 2022 could have been substantially lower than the preceding 10‐year average. Serological investigation detected antibodies specific to H5 in apparently healthy birds indicating that some Gannets recover from HPAIV infection. Further, most of these recovered birds had black irises, suggestive of a phenotypic indicator of previous infection. Untangling the impacts of HPAIV infection from other challenges faced by seabirds is key to establishing effective conservation strategies for threatened seabird populations as the likelihood of further epizootics increases, due to increasing habitat loss and the industrialization of poultry production.

Avian influenza viruses in wild birds in Canada following incursions of highly pathogenic H5N1 virus from Eurasia in 2021/2022

“…Beyond gulls and Common Murre, certain seabird species, such as the Northern Gannet, exhibited remarkable susceptibility to HPAIV. Large-scale mortality was observed in a number of colonial nesting seabird species during the breeding season in Atlantic Canada and across the North Atlantic (53). Colonial nesting behaviour, characterized by dense populations, a high degree of social interaction, and shared foraging areas, can facilitate extensive transmission among conspecifics, leading to focal and large-scale die-offs following introduction of highly transmissible pathogens like HPAIV (54).…”

“…Colonial nesting behaviour, characterized by dense populations, a high degree of social interaction, and shared foraging areas, can facilitate extensive transmission among conspecifics, leading to focal and large-scale die-offs following introduction of highly transmissible pathogens like HPAIV (54). However, there is evidence of exposure and survival in some of these highly susceptible colonial nesting species (53). While an in-depth analysis of the impacts to seabirds in Atlantic Canada is the focus of Avery-Gomm et al, in prep and falls outside the scope of this manuscript, we wish to emphasize the importance of continued targeted AIV surveillance in these populations in order to understand the interacting mechanisms driving species- and colony-level differences in virus dynamics, transmission, and susceptibility.…”

Connectivity of marine predators over the Patagonian Shelf during the highly pathogenic avian influenza (HPAI) outbreak

“…During these periods, BBA and SAFS individuals conducted relatively short and frequent foraging trips to southern Argentina, regularly returning to colonies to incubate eggs or provision offspring. The incursion of HPAI or other zoonotic diseases to BBA or SAFS at the Falkland Islands during these critical life history stages, when there are large aggregations of conspecifics at colonies, may increase the likelihood of transmission (Duriez et al 2023, Lane et al 2023). As two species occurring in globally significant populations at the Falkland Islands, mass adult mortalities during the breeding period may have unprecedented conservation implications.…”

“…Since 2021, a highly pathogenic avian influenza (HPAI) panzootic has had dramatic impacts on wild populations around the world, causing mass mortalities in numerous seabird and marine mammal populations (Falchieri et al 2022, Klaassen & Wille 2023, Leguia et al 2023, Lane et al 2023). Driven by connectivity over vast spatial scales, HPAI is spreading at unprecedented rates (Boulinier 2023, Jeglinski et al 2023, Klaassen & Wille 2023) and is predicted to impact geographically remote, high-latitude marine predator communities in the southern hemisphere, which have traditionally been insulated from periodic HPAI outbreaks affecting wild populations in Eurasia, Africa and North America (Dewar et al 2022).…”

Highly pathogenic avian influenza causes mass mortality in Sandwich TernThalasseus sandvicensisbreeding colonies across north-western Europe

“…Between March and September 2022, the virus was detected in 80 wild avian species (EFSA et al 2022b(EFSA et al , 2022d, with some colonially nesting seabirds being affected the most. Great Skuas, Northern Gannets Morus bassanus, Great Cormorants, Common Terns Sterna hirundo, and Sandwich Terns Thalasseus sandvicensis all experienced major die-offs (Camphuysen and Gear 2022;EFSA et al 2022d;Rijks et al 2022;Pohlmann et al 2023;Lane et al 2023).…”