LINCOLN, Neb. (DTN) -- Wisconsin's first known case of highly pathogenic avian influenza in dairy cattle was confirmed as part of the routine National Milk Testing Strategy testing, USDA's Animal and Plant Health Inspection Service announced on Dec. 14, 2025.

"APHIS will complete genetic sequencing and announce final results as soon as they are available," USDA said in a news release.

HPAI mostly affects dairy cows that are in late-stage lactation. Clinical signs include a decrease in food consumption, clear nasal discharge, drop in milk production, tacky or loose feces, lethargy, dehydration, fever, and thicker, concentrated milk.

"While dairy cattle in a total of 18 states have been infected since the start of the outbreak in March 2024, APHIS has seen cases in only a small number of states this year," USDA said.

APHIS said it was "working closely" with the Wisconsin Department of Agriculture, Trade, and Consumer Protection to conduct additional on-farm investigations, diagnostic testing, and epidemiological data collection to better understand the detection and prevent further disease spread.

"The affected farm has been quarantined, and any cattle exhibiting signs of illness will be separated for further treatment," the state agency said in a news release.

Wisconsin law requires all livestock owners to register where their animals are kept. Registration helps animal health officials communicate with owners during disease outbreaks.

USDA said the latest detection "does not change" the agency's HPAI eradication strategy.

"Biosecurity is still key to mitigating the risk of disease introduction or spread between premises," USDA said.

APHIS said it recommends enhanced biosecurity measures for all dairy farms. Producers should immediately report any livestock with clinical signs, or any unusual sick or dead wildlife, to their state veterinarian.

"This detection does not pose a risk to consumer health or affect the safety of the commercial milk supply," USDA said.

"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."

USDA said dairies are required to send only milk from healthy animals into processing for human consumption; milk from impacted animals is being diverted from the commercial milk tank or destroyed so that it does not enter the human food supply.

According to the U.S. Centers for Disease Control and Prevention, HPAI viruses circulating in birds and U.S. dairy cattle pose a low risk to the general public in the United States.

However, people who have job-related or recreational exposures to infected birds or mammals are at higher risk of infection and should take appropriate precautions outlined in CDC guidance.

Read more on DTN:

"USDA Says Avian Flu in NE Dairy Herd," https://www.dtnpf.com/…

Todd Neeley can be reached at todd.neeley@dtn.com

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