Encephalitis and Death in Wild Mammals at a Rehabilitation Center after Infection with Highly Pathogenic Avian Influenza A(H5N8) Virus, United Kingdom.

Tobias Floyd,Alejandro Núñez,Nicola S Lewis,Edward Fullick,Ashley C Banyard,Fabian Z.X Lean,Benjamin C Mollett,Alexander M.P Byrne,Vanessa Swinson,Rowena Hansen,Steve Bexton,Elliot Whittard,Scott M Reid,Ian H Brown,Michele Macrelli,J Paul Duff

doi:10.3201/eid2711.211225

Abstract

We report a disease and mortality event involving swans, seals, and a fox at a wildlife rehabilitation center in the United Kingdom during late 2020. Five swans had onset of highly pathogenic avian influenza virus infection while in captivity. Subsequently, 5 seals and a fox died (or were euthanized) after onset of clinical disease. Avian-origin influenza A virus subtype H5N8 was retrospectively determined as the cause of disease. Infection in the seals manifested as seizures, and immunohistochemical and molecular testing on postmortem samples detected a neurologic distribution of viral products. The fox died overnight after sudden onset of inappetence, and postmortem tissues revealed neurologic and respiratory distribution of viral products. Live virus was isolated from the swans, seals, and the fox, and a single genetic change was detected as a potential adaptive mutation in the mammalian-derived viral sequences. No human influenza-like illness was reported in the weeks after the event.

Highlights

We report a disease and mortality event involving swans, seals, and a fox at a wildlife rehabilitation center in the United Kingdom during late 2020
Clinical Setting The swans, gray seal, and fox were housed within the quarantine unit of the center, a suite of 17 individual cubicles accessed by a central corridor (Appendix Figure 1, https://wwwnc.cdc.gov/EID/ article/27/11/21-1225-App1.pdf)
We determined that avian-origin influenza A(H5N8) virus was the cause of death in a red fox and the cause of seizures in a gray seal and several common seals housed at a wildlife rehabilitation center

Summary

Introduction

We report a disease and mortality event involving swans, seals, and a fox at a wildlife rehabilitation center in the United Kingdom during late 2020. The fox died overnight after sudden onset of inappetence, and postmortem tissues revealed neurologic and respiratory distribution of viral products. An episode of unusual disease resulting in deaths in different species at a wildlife rehabilitation center in the United Kingdom during late 2020 led to the retrospective detection of influenza A virus subtype H5N8 of avian origin in 5 mute swans, a fox, and 3 seals. The seals exhibited sudden-onset neurologic signs, including seizures before death or euthanasia (Figure 1) This mortality event occurred ≈1 week after the deaths or euthanasia of 5 mute swans (Cygnus olor) held in isolation at the center because of acute-onset malaise and terminal seizures. Avian Influenza A(H5N8) Virus, UK made until many weeks after the event, when the fox and seal tissues were assessed to attempt to define an etiologic diagnosis

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Conclusion