Highly pathogenic avian influenza virus H5N1 infection in skua and gulls in the United Kingdom, 2022

Abstract

The reemergence of the highly pathogenic avian influenza virus (HPAIV) subtype H5N1 in the United Kingdom in 2021–2022 has caused unprecedented epizootic events in wild birds and poultry. During the summer of 2022, there was a shift in virus transmission dynamics resulting in increased HPAIV infection in seabirds, and consequently, a profound impact on seabird populations. To understand the pathological impact of HPAIV in seabirds, we evaluated the virus antigen distribution and associated pathological changes in the tissues of great skua ( Stercorarius skua, n = 8), long-tailed skua ( Stercorarius longicaudus, n = 1), European herring gull ( Larus argentatus, n = 5), and black-headed gull ( Chroicocephalus ridibundus, n = 4), which succumbed to natural infection of HPAIV during the summer of 2022. Cases were collected from Shetland, including Scatness (mainland), No Ness (mainland), Clumlie (mainland), Hermaness (island), Fair Isle (island), Noss (island), and the West Midlands, South East, and South West of England. Grossly, gizzard ulceration was observed in one great skua and pancreatic necrosis was observed in 4 herring gulls, with intralesional viral antigen detected subsequently. Microscopical analysis revealed neuro-, pneumo-, lymphoid-, and cardiomyotropism of HPAIV H5N1, with the most common virus-associated pathological changes being pancreatic and splenic necrosis. Examination of the reproductive tract of the great skua revealed HPAIV-associated oophoritis and salpingitis, and virus replication within the oviductal epithelium. The emergence of HPAIV in seabirds Stercorariidae and Laridae, particularly during summer 2022, has challenged the dogma of HPAIV dynamics, posing a significant threat to wild bird life with potential implications for the reproductive performance of seabirds of conservation importance.

Confirmation of Highly Pathogenic Avian Influenza (HPAI) H5N1 Associated with an Unexpected Mortality Event in South Polar Skuas (Stercorarius maccormicki) during 2023-2024 Surveillance Activities in Antarctica

“…The confirmation of HPAI H5N1 in skua species in the other locations, as well as its apparent smaller population observed at the season at Fildes Peninsula, could suggest this species could present higher susceptibility of HPAI H5N1 compared to other Antarctic species. Other skua species such as Great skua have been confirmed positive for HPAI H5N1, and even a massive mortality event has been documented at Foula Island, United Kingdom (Furness et al, 2023; Lean et al, 2023). On the other hand, as top predators, and scavengers devoid of natural enemies, and with widely spaced nests due to territorial behavior, Antarctic skuas likely present a reduced risk for rapid virus dissemination between them.…”

A systematic review of laboratory investigations into the pathogenesis of avian influenza viruses in wild avifauna of North America

“…Given the apparent susceptibility of these species in the current HPAI outbreak, their large geographic distribution and long-distance migrations, as well as frequent overlap with agriculture, Laridae seem to be prime candidates for continued pathobiology research [15]. For similar reasons, other sea birds, such as skuas [44], have been implicated as possible long-distance carriers of the virus, but a lack of available research limits our ability to infer potential dynamics.…”

A multi-species, multi-pathogen avian viral disease outbreak event: Investigating potential for virus transmission at the wild bird – poultry interface

“…A semi-quantitative scoring system ranging from 0 (absence of staining) through to 4 (abundant staining) was applied for IHC and similarly from 0 (absence of lesions) through to 4 (marked changes) for H&E staining. The details of the classification criteria are as described by Lean et al [ 17 ].…”