September 16, 2024 - By Ching Lee - Three Central Valley dairy herds remain under quarantine after cows in the herds tested positive for highly pathogenic avian influenza.
The positive findings, which the U.S. Department of Agriculture confirmed on Aug. 30, mark the first time highly pathogenic avian influenza, or HPAI, has been detected in California dairy cows. Since March 25, 13 other states have detected HPAI in dairy cows, with a total 197 confirmed cases as of Sept. 9.
“We have been preparing for this possibility since earlier this year when HPAI detections were confirmed at dairy farms in other states,” said California Department of Food and Agriculture Secretary Karen Ross. “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.”
Agriculture officials continue to stress the safety of the nation’s milk supply and dairy products, saying pasteurization remains fully effective at inactivating the virus. Under state and federal requirements, milk from sick cows is not permitted in the public milk supply.
The sick cows have been isolated, CDFA said, and healthy cows have been cleared to continue shipping milk.
CDFA has not disclosed in which county or counties the affected dairy herds are located. But the department said its preliminary investigation has confirmed that cows were moved recently among the three dairies and that the cows began showing clinical signs consistent with HPAI from Aug. 23-25.
State Veterinarian Annette Jones said the cow movements occurred before any of the animals exhibited HPAI symptoms. All three dairies began showing “a spike in clinical signs at about the same time and immediately reported to CDFA,” she said.
Jones said investigation of how the dairy herds became infected is ongoing, but she confirmed that the gene sequence of the virus found in samples from the dairies “supports that the introduction is consistent with the cattle-associated virus found in other U.S. states, not the virus commonly found in migrating birds.”
Anja Raudabaugh, CEO of Western United Dairies, said it is known that the affected dairies had cows purchased from an out-of-state dairy and then moved them to California before they showed clinical signs.
With HPAI showing up in U.S. dairy cows, states initially responded with different protocols for moving cattle across their borders.
In early April, California began requiring dairy cows from states with HPAI-infected cattle to be inspected by a veterinarian seven days before shipment. On April 24, USDA implemented mandatory testing of lactating dairy cows prior to interstate movement.
“Our on-farm biosecurity plans have worked, both in keeping the disease out of California and now in catching it immediately with a rapid response,” Raudabaugh said. “Other biosecurity and quarantine protocols are now in place, and we feel confident that the disease won’t be spreading beyond these dairy farms.”
First identified in Europe in 2020, the current strain of the H5N1 avian influenza virus is widespread around the world.
In the U.S., H5N1 has been detected in wild birds since 2022 and has caused major outbreaks on commercial poultry farms, including in California. Some 48 states have been affected by HPAI, with a total 1,173 reported outbreaks. The outbreaks have led to the loss of millions of egg layers and other poultry, pummeling production.
California poultry flocks have not been affected by the current HPAI detections in dairy cows. The state declared itself free of HPAI in poultry on June 28.
Though the virus remains deadly to poultry, most dairy cows fully recover within a few weeks. Infected cows typically experience a drop in milk production during the illness.
“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,” CDFA Secretary Ross said.
No other countries have reported HPAI cases in cattle to date.
The California HPAI detections come as demand for milk is expected to see its seasonal bump heading into the fall, with schools back in session and more milk flowing to school-lunch programs. Consumption of dairy products such as butter, cream, cheese and eggnog typically rises during autumn months as people do more cooking and baking and go out to eat for the holidays.
“Avian influenza has already taken a hefty toll on U.S. milk output,” said Sarina Sharp, a dairy analyst based in Michigan, in her weekly report for the Milk Producers Council. “If bird flu is indeed cropping up in the San Joaquin Valley, it will threaten dairy product output in the nation’s top milk shed.”
As the country’s leading dairy state, California produces more than 18% of the U.S. milk supply. The Golden State also ranks first in the production of butter, ice cream and nonfat dry milk, and second in cheese and yogurt production.
With the HPAI infections appearing so far in just three of the state’s dairy herds, it’s unclear how significant milk production will be affected. Some dairy producers speculate the July heat wave may deal a bigger blow to the state’s milk production than HPAI.
No human cases of HPAI have been confirmed in California related to the dairy detections. Nationwide, there have been four human cases in dairy workers since April—one each in Texas and Colorado, and two in Michigan, according to the U.S. Center for Disease Control. All have had mild symptoms.
Since 2022, there have been 10 human cases associated with poultry exposure, nine of which occurred this year.
Agriculture officials say they believe waterfowl first introduced the virus to dairy cows in Texas through “a single spillover event” and that subsequent spread to dairies in other states has been linked mostly to interstate and regional cattle movement or contamination by people and equipment.
Colorado, which first detected H5N1 in its dairy cows on April 25, has the most cases, with 64 herds affected, the last one confirmed on Aug. 13. The Centennial State in July began mandatory weekly testing bulk-tank milk samples.
In late May, USDA launched the HPAI Dairy Herd Status Program. The voluntary program allows dairy farmers to move their cows across state lines without having to test them individually so long as they maintain a monitored unaffected herd status, which requires three consecutive weeks of negative test results and weekly bulk-tank sample testing with negative results. As of Sept. 9, 41 U.S. dairy herds have been enrolled, with one in California.
California Farm Bureau President Shannon Douglass said the organization is monitoring the situation and keeping its membership informed.
Douglass said she is confident “in steps being taken by the CDFA, the California Department of Public Health and our local officials in safeguarding agricultural workers and protecting livestock from additional exposure.”
(Ching Lee is an assistant editor of Ag Alert. She may be contacted at clee@cfbf.com.)
The California Farm Bureau Federation works to protect family farms and ranches on behalf of nearly 32,000 members statewide and as part of a nationwide network of more than 5.5 million Farm Bureau members.
Source: Reprinted with permission CFBF
