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bioRxiv · 10.1101/2023.11.16.567398

Outbreak of Highly Pathogenic Avian Influenza Virus H5N1 in Seals in the St. Lawrence Estuary, Quebec, Canada

Lair, S.·Quesnel, L.·Berhane, Y.·Delnatte, P.·Embury-Hyatt, C.·Nadeau, M.-S.·Lung, O.·Ferrell, S.
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Abstract

We describe an unusual mortality event caused by a highly pathogenic avian influenza virus (HPAI) H5N1 clade 2.3.4.4b involving harbor (Phoca vitulina) and grey (Halichoerus grypus) seals in the St. Lawrence Estuary, Quebec, Canada. Fifteen (56%) of the seals submitted for necropsy were considered to be fatally infected by H5N1 containing fully Eurasian (EA) or Eurasian/North American genome constellation. Concurrently, presence of large numbers of bird carcasses infected with H5N1 at haul-out sites most likely contributed to the spill-over of infection to the seals. Histologic changes included meningoencephalitis (100%), fibrinosuppurative alveolitis, and multi-organ acute necrotizing inflammation. This is the first report of fatal H5N1 infection in pinnipeds in Canada, raising concerns about the expanding host of this virus, potential for establishment of a marine mammal reservoir, and the public health risks associated with spillover to mammals.

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Lair, S., Quesnel, L., Berhane, Y., Delnatte, P., Embury-Hyatt, C., Nadeau, M.-S., Lung, O., Ferrell, S.. 2023-11-17. Outbreak of Highly Pathogenic Avian Influenza Virus H5N1 in Seals in the St. Lawrence Estuary, Quebec, Canada. https://doi.org/10.1101/2023.11.16.567398

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