REDFIELD, Iowa (DTN) -- The H5N1 strain of Highly Pathogenic Avian Influenza has continued to spread across dairy herds in the U.S., with California being hit the hardest, leading to a ban on all dairy exhibitions until the risk lowers.

The California exhibition ban was put into effect in January 2025 and remains in place for dairy animals and poultry. As of March 11, 2025, there have been 985 confirmed cases in dairy cattle in 17 states. Of that, 754 of those cases have been in California, with the latest reported on March 7.

Laura Bradley, public information officer and veterinarian for the California Department of Food and Agriculture (CDFA), told DTN the ban will remain in place as long as the risks of viral spread remain high in California dairies. "This is because infected dairy cattle can infect other cattle, poultry farms, and people in close contact with infected animals," she said. "Overall, infections in California are slowing down in both poultry and dairy cattle."

AG DEPARTMENT WILL RE-EVALUATE RISK

The CDFA will re-evaluate the risks monthly and allow exhibitions to resume once the risks are deemed appropriate, at which time the state veterinarian will lift the ban.

Summer 2024, many fairs used a testing protocol for animals going to the exhibitions where they had to test negative for the HPAI virus within seven days of going to the show. California is not taking this approach as they have said the most reliable test for H5N1 is using a milk sample. If a reliable test for non-lactating dairy cattle is developed, they will consider it.

The highest risk class of cattle known to be associated with spreading H5N1 in California has been bred cattle close to parturition, lactating cows and recently dried off cows. However, since almost all classes of dairy cattle are associated with farms in one way or another or co-housed at the same destination, the ban includes replacement heifers, bred heifers and cows, lactating cows and recently dried off adult cows.

SOME ANIMALS ARE NOT INCLUDED IN THE BAN

According to a fact sheet prepared by CDFA, dairy bulls, feeder calves, and steers can be exhibited, as these classes of dairy cattle have not been strongly implicated in spreading H5N1 to dairies and are generally segregated or moved to harvest channels.

The ban also includes the higher risk bird species related to avian influenza, including chickens, turkeys, ducks and upland game birds such as pheasants.

The department is most concerned with minimizing the risk of spreading the virus or exposing outside animals and people to the virus. The 2025 fair season in California started as many farms were infected. This ban, while not seen in other states, is to help decrease the amount of virus spread in the state and will be continued until they see fewer cases and less risk to these animals.

For more information on the California ban, visit www.cdfa.ca.gov.The federal rule on animal movement can be found here: https://www.aphis.usda.gov/…

Jennifer Carrico can be reached at jennifer.carrico@dtn.com

Follow her on social platform X @JennCattleGal

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