Highly pathogenic avian influenza causes mass mortality in Sandwich tern (Thalasseus sandvicensis) breeding colonies across northwestern Europe

Abstract

In 2022, highly pathogenic avian influenza (HPAI) A(H5N1) virus clade 2.3.4.4b became enzootic and caused mass mortality in Sandwich terns and other seabird species across northwestern Europe. We present data on characteristics of the spread of the virus between breeding colonies and the number of dead adult Sandwich terns recorded at breeding sites throughout northwestern Europe. Within two months after the first mortalities were reported, in total 20,531 adult Sandwich terns were found dead, which is >17% of the total northwestern European breeding population. Losses are likely higher, as we expect that many victims were not found (mortality rate might be up to 74% of the breeding population). Inside the colonies almost all chicks died. After the peak of the outbreak, in a colony established by late breeders, 25.7% of adults showed immunity against HPAI subtype H5. Removal of carcasses helped in reducing the spread of the disease and consequently total mortality. More research on the sources and modes of transmission, incubation times, effective containment and immunity is urgently needed to combat this major threat for colonial seabirds.

Pathogen-prey-predator relations of avian raptors during epizootics of highly pathogenic avian influenza virus HPAIV H5N1 (clade 2.3.4.4b) in Germany

“…The latter have been hit severely by HPAIV H5, culminating even in mass mortalities (Anne Pohlmann et al, 2023). Removal of possibly HPAIV-infected carcasses by human activities has been shown to have positive effects on such colonies (Knief et al, 2023). Yet, this kind of carcass removal can never be as efficacious (and timely) as the scanning activities of birds of prey.…”

Fulmar Litter Monitoring in the UK : Update 2022

“…The relative low number of fulmars collected in year 2022 is mainly a consequence of the major outbreak of highly pathogenic avian influenza (HPAI) in seabirds. Considerable mortality was observed among great skuas (Stercorarius skua), Sandwich terns (Thalasseus sandvicensis) and northern gannets (Morus bassanus) in the UK (Camphuysen et al 2022;Lane et al 2023;Knief et al 2023).…”

Weathering the Storm of High Pathogenicity Avian Influenza in Waterbirds

“…During the 2022 breeding season, > 20,000 Sandwich Terns ( Thalasseus sandvicensis ) were found dead across Europe, comprising > 17% of the total northwestern European breeding population. In addition to the adult birds, within colonies, almost all chicks died (Knief et al 2023). Northern Gannets ( Morus bassanus ) were similarly heavily affected in the Atlantic, with unusually high mortality at colonies, including at Bass Rock in Scotland where the number of occupied nests decreased by 71% (Lane et al 2023).…”

“…A key feature of all HPAI outbreaks to date is the prioritization of response towards poultry, such that there is almost no, or limited information pertaining to waterbird outbreaks. For example, of the ∼20,000 Sandwich Terns reported in (Knief , et al 2023), only 68 were reported to the World Organisation for Animal Health (Klaassen and Wille 2023). Mortality data from wild bird outbreaks are critical for population assessments, conservation plans, International Union for Conservation of Nature (IUCN) status etc, so this mismatch between reports from the ground and notifications to the most comprehensive database is highly concerning.…”