Avian flu probe continues as virus hits South State dairies 

By Ching Lee

As the state continues to investigate the spread of bird flu in Southern California dairies, officials say Gov. Gavin Newsom’s emergency proclamation last month would allow state and local agencies more flexibility to address the outbreak. 

Newsom declared a state of emergency after dairy cows at four Southern California dairies tested positive Dec. 12 for the H5N1 virus. All previous cases of bird flu affecting dairy cows had been in the Central Valley. The new detections in Southern California necessitated “a shift from regional containment to statewide monitoring and response to active cases,” the proclamation said. 

The governor’s action came as the U.S. Department of Agriculture began mandatory testing of bulk tank milk samples nationwide for the virus, with California, Colorado, Michigan, Mississippi, Oregon and Pennsylvania targeted in the first round of testing. 

The governor’s order won’t change California’s overall approach to the outbreak, but it would allow the state to obtain more services and materials and to potentially make more staffing available, said Steven Fenaroli, a California Farm Bureau policy advocacy director.

“The truth is that we were already doing loads of amazing testing,” he said. 

As of Dec. 16, 984 dairies were under surveillance related to bird flu, according to the California Department of Food and Agriculture. Of those, 52 were in the southern region, 110 were along the coast, and 822 were inland dairies. 

With gene sequencing still pending, State Veterinarian Annette Jones said it remains unknown if H5N1 spread to Southern California from the Central Valley. But she noted the strain of bird flu in the Southern California herds is the one detected in bovine, not wild birds, making the transmission “most likely” through “cattle, dirty trailer, contaminated service providers or other slip-up.”

“We are not allowing movement from infected farms to (Southern California) but cannot police everything, and both intentional and unintentional mistakes happen,” Jones said.  

Since Aug. 30, when the state confirmed its first case of bird flu in Central Valley dairy cows, there have been 697 dairy herds confirmed to have been infected as of Dec. 30. Of the total, 56 dairy herds have fully recovered and have been released from quarantine, according to CDFA. 

Tulare County dairy farmer Blake Wilbur, whose cows first tested positive for bird flu in late October, received his first negative test result last month. He needs two more negative results—with each test performed a week apart—to be released from quarantine. CDFA tests infected dairies using unpasteurized milk samples. 

Wilbur said he hopes the emergency declaration will allow the state to conduct more and faster testing, noting how state labs remain backlogged, resulting in delays getting test results. Early on, he opted to send additional milk samples to a private lab at his own expense when he was notified that his dairy was within 2 miles of an infected dairy, making his farm subject to state testing. 

By conducting his own tests, he said he had hoped to “detect when we had bird flu as soon as we possibly could, so we could prepare for it.”

“If the state of emergency helps bring resources to help with that, that’s a huge help in and of itself,” Wilbur said. 

Due to the size of the outbreak, the state has acknowledged its main lab is already at capacity. So are four other out-of-state labs certified to do bird flu testing, with thousands of such tests done each week, including on every negative dairy in the state. 

The labs also test all poultry in disease control zones at least twice a week, the state said. They test quarantined dairies weekly as well, to determine if they can be released from quarantine. In addition, there’s testing for ongoing research and to allow dairy and poultry farms to obtain movement permits.    

Michael Payne, a researcher and specialist at the University of California, Davis, School of Veterinary Medicine, said he thinks CDFA and the California Department of Public Health “have already been responding appropriately and aggressively” to the bird flu outbreak. With the governor’s emergency proclamation, the state can mobilize more resources, he said, which “can elevate and quicken the response.” 

“It makes additional emergency funding available, and it can cut through an enormous amount of red tape,” Payne added. 

Because pasteurization neutralizes the virus, state and federal officials continue to stress the safety of pasteurized milk and dairy products. 

Human infection has occurred almost entirely in dairy workers. As of Dec. 23, there have been 37 confirmed cases in California, with 36 involving people who’ve had direct contact with infected dairy cattle.

Dairy farmer Wilbur said he would like to see more funding and resources for research on bird flu transmission. It remains unclear how the virus spread to his farm, he said, although he said he knew it was “coming” as soon as he learned a neighboring dairy tested positive. 

Researchers believe wild migratory birds are the original source of the virus, but exactly how it spreads between dairies has been harder to pin down. Studies suggest transmission can be through milk, contaminated objects such as equipment, clothing and vehicles, and animal movement.

Due to the quarantine, Wilbur said he has been unable to ship animals, resulting in his farm having an oversupply of replacements, which typically are sold to out-of-state dairies. 

At peak infection, Wilbur estimated his Jersey cows produced 23% less milk, but he said he knows of dairies that had lost more than 50% of their milk production on their worst days. That the virus hit his farm in late October helped, he said, noting dairies that were infected during the late-summer heat wave suffered much harder, with sicker cows and higher mortality. 

Meanwhile, bird flu has also been spreading among the state’s commercial and backyard poultry flocks, all of which must be destroyed because the disease is fatal to poultry. As of Dec. 19, movement restrictions have been placed on Fresno, Kern, Marin, Merced, Monterey, Sacramento, San Joaquin, Stanislaus and Tulare counties where bird flu cases have been confirmed. During the past 30 days, 22 commercial flocks and four backyard flocks have been affected, with more than 7.78 million birds destroyed.

(Ching Lee is an assistant editor of Ag Alert. She may be contacted at clee@cfbf.com.)