The Statens Serum Institut reports bird flu has been detected in a Danish harbor seal. The seal was found dead on a beach on Southwest Funen in September 2021 and examined at the Center for Diagnostics at Technical University of Denmark (DTU) as part of the disease monitoring of fallen game.
The seal was emaciated with pronounced skin changes on large parts of the body of uncertain significance and cause. Influenza virus was detected in the lung, but otherwise no other disease-causing organisms could be detected that could explain why the seal was dead.
The Center for Diagnostics at DTU has stated that they have examined 29 harbor seals and 15 gray seals in 2021, of which only this one was positive for influenza virus.
Upon further investigation at the Danish Veterinary Consortium, the virus turned out to be highly pathogenic avian influenza virus of the subtype H5N8.
The detected virus is closely related to the viruses that have been the cause of bird flu outbreaks in wild birds and domestic poultry since the autumn of 2020, both here and in the rest of Europe.
Seals are known to be susceptible to avian influenza virus.
In recent seasons with avian influenza in birds, the discovery of highly pathogenic avian influenza in wild mammals has been increasingly reported. Including seals and wild foxes in northern Europe. These findings have been primarily in animals with neurological symptoms, or who were found dead.
When mammals are infected with viruses from birds, there is a risk that the virus will mutate and adapt to its new host species and mammals in general. The Danish Veterinary Consortium has performed a detailed analysis of the virus genome from the wild seal and found some mutations in the virus that show signs of possible adaptation to mammals, although it was not possible to analyze the full genome due to the quality of the material.