Cows in three dairy herds in California’s Central Valley have tested positive for highly pathogen avian influenza, marking the state’s first cases in dairy cows and prompting quarantines of the farms, the state Department of Food and Agriculture has confirmed.

The dairy herds started showing symptoms around Aug. 25, prompting the dairy owners and their veterinarians to submit samples to the California Animal Health and Food Safety laboratory network. The samples were then sent to the National Veterinary Services Laboratory, where the test results were confirmed Aug. 30.

“We have been preparing for this possibility since earlier this year when HPAI detections were confirmed at dairy farms in other states,” state Food and Agriculture Secretary Karen Ross said. “Our extensive experience with HPAI in poultry has given us ample preparation and expertise to address this incident, with workers’ health and public health as our top priorities.

“This is a tough time for our dairy farmers given the economic challenges they’re facing in a dynamic market, so I want to assure them that we are approaching this incident with the utmost urgency,” she said.

The latest detections come as HPAI, which has caused the loss of more than 43 million egg-laying hens in the U.S. since 2022, had infected 197 dairy cattle herds in 14 states as of Aug. 30, according to the USDA. In the West, infected herds have been reported in Colorado (64 cases), Idaho (31 cases), New Mexico (9 cases) and Wyoming (one case), according to the agency.

Related:Colo. requires HPAI testing of commercial dairies

Fourteen human infections have also been reported, including four following exposure to dairy cows and 10 who were exposed to poultry, according to the U.S. Centers for Disease Control and Prevention. State and federal health officials say the threat of the disease in humans remains low, and consuming pasteurized milk and properly cooked meat is safe.

Economic impact

However, the economic impact of the disease in dairy herds can be significant.

A Michigan producer estimated earlier this year that his total losses for his 500-herd dairy operation were between $30,000 and $40,000 during the first 15 days of an infection in his herd. The losses were caused by a decrease in milk production and added costs for medical supplies and labor, Michigan State University reported.

State ag departments have universally urged biosecurity measures to curb the spread of avian flu, and some states have begun to impose mandatory testing. Colorado, which leads the nation in cases involving dairy cows, recently began requiring testing in the commercial dairy industry after several “spillover events” from dairy operations into commercial poultry operations resulted in the death and depopulation of more than 3.2 million domestic chickens in July, state ag officials said.

Related:HPAI prompts new rules for Ore. livestock shows

Oregon in July issued emergency rules for fairs and livestock expositions, requiring extra record-keeping and the availability of a veterinarian, even though the Beaver State has yet to record any cases of bird flu in dairy cattle.

“The progression we’ve been seeing of avian influenza in dairy cattle had us concerned,” Oregon state veterinarian Ryan Scholz told Farm Press during the state fair in Salem in late August.

Avian flu has affected more than 20 million domesticated birds in the West, including more than 7 million birds from 41 commercial flocks and 26 backyard flocks in California, the USDA reports. Earlier this summer, California’s Department of Public Health handed out protective equipment for dairy farmworkers and others handling raw dairy products, as well as for slaughterhouse and commercial poultry farmworkers.

Enhanced biosecurity measures are in place at the affected dairies, which were not identified. Sick cows are isolated and are being treated at the dairies, while healthy cows have been cleared to continue shipping milk for pasteurization, according to the CDFA.