Gross pathology associated with highly pathogenic avian influenza H5N8 and H5N1 in naturally infected birds in the UK (2020–2021)

Abstract

Background: Multiple outbreaks with highly pathogenic avian influenza virus (HPAIV) clade 2.3.4.4b viruses, including H5N8 and H5N1, have occurred in the United Kingdom, as well as in other European countries, since late 2020. Methods: This report describes the pathology among poultry species (chickens, turkeys, ducks, and pheasants) and captive birds (Black Swans, a whistling duck and peregrine falcons) naturally infected with HPAIV from 22 cases of HPAIV H5N8 and two cases of HPAIV H5N1 outbreaks investigated between October 2020 and April 2021. Results: On gross examination, pancreatic necrosis was easily identified and most commonly observed in galliformes infected with both subtypes of HPAIV but rarely in anseriformes. In addition, splenic necrosis was also frequently observed in chickens and turkeys infected with HPAIV H5N8. Other less common lesions included cardiac petechiae, serosal haemorrhages and ascites in a variety of species. Conclusion: Given the widespread dissemination of HPAIV infection in susceptible avian species during autumn/winter 2020-2021, these data, when evaluated along with clinical information, is a valuable first step for both veterinarians and field services to evaluate gross pathology at post-mortem to support the diagnosis of HPAIV infection.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Detection of Highly Pathogenic Avian Influenza Virus H5N1 Clade 2.3.4.4b in Great Skuas: A Species of Conservation Concern in Great Britain

“…Avian influenza virus (AIV) subtype H5Nx clade 2.3.4.4 has caused extensive outbreaks across the globe during the autumn/winter 2020/2021 period [1]. Whilst the factors Viruses 2022, 14, 212. https://doi.org/10.3390/v14020212 https://www.mdpi.com/journal/viruses associated with the outcome of infection with AIV in different avian species remain undefined, the impact on wild bird species has been significant [1][2][3]. During this period, H5Nx AIVs have been associated with (through nucleic acid detection) over 300 wild bird deaths in Great Britain (GB) alone, with a diverse range of viral genotypes being involved, including H5N8, H5N5, and H5N1 [4].…”

Transmission dynamics and pathogenesis differ between pheasants and partridges infected with clade 2.3.4.4b H5N8 and H5N1 high-pathogenicity avian influenza viruses

“…H5N8-2021 and H5N1-2021 pheasant infections caused severe neurological signs prior to death. Gross lesions included pancreatic necrosis, as observed during the pheasant outbreaks where both viruses originated, and also during earlier and subsequent UK H5Nx HPAIV pheasant cases [20,50,51]. Both H5N8-2021 and H5N1-2021 displayed similar systemic tropism, but stronger H5N1-2021 pheasant pathogenesis was evident in higher vRNA levels across most tissues compared to H5N8-2021, and was also reflected in pheasant MDT differences (Table 1).…”

Transmission dynamics and pathogenesis differ between pheasants and partridges infected with clade 2.3.4.4b H5N8 and H5N1 high-pathogenicity avian influenza viruses

“…H5N8-2021 and H5N1-2021 pheasant infections caused severe neurological signs prior to death. Lesions included pancreatic necrosis, as observed during the pheasant outbreaks where both viruses originated, and also during earlier and subsequent UK H5Nx HPAIV pheasant cases [20, 50, 51]. Both H5N8-2021 and H5N1-2021 displayed similar systemic tropism, but stronger H5N1-2021 pheasant pathogenesis was evident in higher vRNA levels across most tissues compared to H5N8-2021, although pheasant MDTs were similar for both viruses ().…”