Detection of Avian Influenza Antibodies in Dutch Dairy Cattle

In December 2025, a highly pathogenic avian influenza (HPAI) H5N1 virus, specifically the clade 2.3.4.4b genotype DI.2.1, was identified in a cat residing on a dairy cattle farm in the Netherlands. Following this discovery, milk and serum samples from the dairy cattle were collected and analyzed for the presence of the avian influenza virus.

The analysis revealed no viral RNA in the samples. However, antibodies specific to the H5N1 strain were identified in the serum of a significant portion of the cattle population on the farm. Specifically, 34 out of 72 lactating dairy cows, which is 47.2%, and 24 out of 38 youngstock, totaling 63.2%, tested positive for these antibodies.

This detection of H5N1-specific antibodies suggests that the virus has expanded its host range to include mammals, such as cattle, a phenomenon observed in Europe. This finding is significant as it indicates a potential shift in the epidemiology of the virus, which traditionally affects birds.

The research was conducted by a team from Wageningen Bioveterinary Research in Lelystad, in collaboration with the Incident and Crisis Centre for Animal Diseases and Zoonoses of the Netherlands Food and Consumer Product Safety Authority in Utrecht, and the Directorate Animal Supply Chain and Animal Welfare of the Ministry of Agriculture, Fisheries, Food Security and Nature in The Hague.

The results of this study highlight the importance of ongoing surveillance and research to monitor and understand the implications of HPAI H5N1's presence in mammalian hosts. Such findings are crucial for developing strategies to manage and mitigate the impact of avian influenza across different species.