Norway: Detection of H5N1 antibodies in sheep
A sheep that grazed in an area with dead and sick pheasants during the large-scale avian influenza outbreak in Finnmark, Norway, in 2023 has been found to possess antibodies against the H5N1 virus. This finding suggests that sheep may become infected when exposed to high levels of environmental contamination with the virus.
The detection was made as part of an ongoing research project at the Norwegian Veterinary Institute, which identified antibodies against avian influenza in the aforementioned sheep. This animal was one of several that had grazed in the affected area during the summer 2023 outbreak of highly pathogenic avian influenza (HPAI) in Finnmark. It is highly likely that the infection occurred during the avian influenza outbreak among guinea fowl in the summer of 2023.
In June 2024, the Veterinary Institute initiated a pilot study, collecting blood samples from 220 adult sheep in the municipality of Vadsø. The aim was to assess whether sheep may have been exposed to the virus during the 2023 outbreak. Several of the sampled animals had been in direct contact with dead or moribund wild birds during grazing, although no clinical illness was observed in the sheep.
The study results now indicate that infection with an avian influenza virus of the H5 subtype likely occurred in at least one sheep during the 2023 outbreak. Notably, in March 2025, the H5N1 virus was confirmed for the first time in a sheep in England—marking the first documented case of HPAI H5N1 infection in a ruminant species in Europe.
