This week, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service reported the first confirmed case of highly pathogenic avian influenza in a dairy cattle herd in Wisconsin.
Detections of avian influenza in dairy cattle have been limited this year, in contrast to 2024, when an outbreak that began in March spread nationwide and led to infected herds being reported in 18 states.
“This detection does not pose a risk to consumer health or affect the safety of the commercial milk supply. The U.S. Food and Drug Administration is confident that pasteurization is effective at inactivating HPAI virus, and that the commercial, pasteurized milk supply is safe,” APHIS said in a news release.
Samples from the herd were tested initially by the Wisconsin Veterinary Diagnostic Laboratory and the positive findings confirmed by the National Veterinary Services Laboratories. DATCP said it is responding in coordination with the U.S. Department of Agriculture, Food and Drug Administration, Centers for Disease Control and Prevention, and other state and federal partners.
The affected farm has been placed under quarantine, and cattle exhibiting any signs of illness are being segregated for observation and treatment. USDA officials reminded that pasteurization indeed neutralizes the HPAI virus, and only milk from healthy animals is allowed into the commercial food supply. Milk from affected animals is diverted or destroyed to assure that it does not reach consumers. Meanwhile, the CDC maintains that the risk to human health from this virus remains low.
The detection was made through routine surveillance under a national milk testing program. According to USDA’s Animal and Plant Health Inspection Service, the virus identified was H5 clade 2.3.4.4b. While HPAI detections in dairy cattle were widespread in 2024, activity in cattle has been relatively limited in 2025, making this Wisconsin case notable as the state’s first.
Wisconsin State Veterinarian Darlene Konkle, DVM, noted that the Dodge County herd did not show obvious signs of illness and that no cattle had recently been moved onto the farm. “The farmer did not have a reason to suspect highly pathogenic avian influenza on the farm,” Konkle said, adding that there was no appreciable increase in sickness or death within the herd.
The DATCP is advising and encouraging all livestock and poultry farmers to be vigilant and take all biosecurity precautions,” said a statement by APLU Rural Affairs Director Tom Philbert.
Symptoms of HPAI infection in dairy cattle may include a decrease in feed intake, a decrease in rumen motility, a decrease in milk production or a change in conductivity, or a change in feces consistency. Farmers are advised by DATCP to be suspicious of any unusual occurrences of disease and notify DATCP immediately if they experience such scenarios
The agency is also reminding producers of the need for registration of livestock premises, which is required by law at the state level. This assists veterinary surveillance personnel in quickly informing producers when there is an outbreak. USDA also still has a federal order requiring producers’ compliance for testing dairy cattle for interstate movement as well as reporting positive Influenza A virus tests.
This is the first reported incident in dairy cows in the state of Wisconsin, but authorities were keen to emphasize the importance of surveillance, bio-security, and inter-agency cooperation in the provision of a secured food supply to the nation.
