Abstract Title
Mortality among wild mammals in Denmark were caused by mammalian-adapted clade 2.3.4.4b H5Nx high pathogenicity avian influenza viruses
Abstract
Since 2020, clade 2.3.4.4b high pathogenicity avian influenza viruses (HPAIVs) have led to massive die-offs among wild and domestic birds, and findings in mammals worldwide have raised concerns for the zoonotic potential of these viruses.
HPAIV-infected wild mammals have also been observed in Denmark, specifically red foxes (Vulpes vulpes) and harbor seals (Phoca vitulina). In 2022, clade 2.3.4.4b HPAIV H5N1 was detected in four red foxes. More recently, in April 2023 and January 2024, two additional foxes were found positive for HPAIV H5N1.
In 2021 and 2022, two harbor seals tested positive for clade 2.3.4.4b H5N8 and H5N1 HPAIV in Denmark, respectively. Moreover, an unusually high mortality was observed among Danish harbor seals in August and September 2023. HPAIV H5N1 was detected in the brain of 17 out of 20 found dead seals. The full extent of the mortality event is likely greater than reported, as the exact number of seals affected remains unknown. The viruses were genetically highly similar and also closely related to HPAIVs from multiple mute swans that were found dead in the same area.
The viruses detected in the mammalian cases were all closely related to contemporary HPAIVs circulating in wild birds in Europe. However, some carried amino acids polymorphisms related to mammalian adaptation. To strengthen our pandemic preparedness, it is essential to enhance the avian influenza virus surveillance in wild animal populations to closely observe possible mammal-to-mammal transmission and the emergence of zoonotic adaptations.
HPAIV-infected wild mammals have also been observed in Denmark, specifically red foxes (Vulpes vulpes) and harbor seals (Phoca vitulina). In 2022, clade 2.3.4.4b HPAIV H5N1 was detected in four red foxes. More recently, in April 2023 and January 2024, two additional foxes were found positive for HPAIV H5N1.
In 2021 and 2022, two harbor seals tested positive for clade 2.3.4.4b H5N8 and H5N1 HPAIV in Denmark, respectively. Moreover, an unusually high mortality was observed among Danish harbor seals in August and September 2023. HPAIV H5N1 was detected in the brain of 17 out of 20 found dead seals. The full extent of the mortality event is likely greater than reported, as the exact number of seals affected remains unknown. The viruses were genetically highly similar and also closely related to HPAIVs from multiple mute swans that were found dead in the same area.
The viruses detected in the mammalian cases were all closely related to contemporary HPAIVs circulating in wild birds in Europe. However, some carried amino acids polymorphisms related to mammalian adaptation. To strengthen our pandemic preparedness, it is essential to enhance the avian influenza virus surveillance in wild animal populations to closely observe possible mammal-to-mammal transmission and the emergence of zoonotic adaptations.
Co-Author(s)
Yuan Liang1,*, Lars E. Larsen1, Tim K. Jensen1, Mia M. Jensen1, Anne Sofie V. Hammer1, Maibritt T. Ovesen1, Solvej Ø. Breum2, Charlotte K. Hjulsager2
1 Department of Veterinary and Animal Sciences, University of Copenhagen, 1870 Frederiksberg C, Denmark
2 Department of Virus and Microbiological Special Diagnostics, Statens Serum Institut, 2300 Copenhagen S, Denmark
Abstract Category
Avian influenza in mammals, pandemic preparedness, and one health