OMAHA (DTN) -- The highly pathogenic avian influenza virus affecting dairy herds around the country may have landed in California's Central Valley as the California Department of Food and Agriculture (CDFA) is investigating a possible outbreak at three dairy farms.
CDFA late Thursday announced the testing of samples from three dairies at the state's laboratory. Any positive tests at the California lab would be considered "presumptive" and submitted to USDA for final test confirmation.
California is the country's largest milk-producing state with more than 1.7 million milking cows and more than 1,300 dairies, according to USDA. The state produced about 20% of the U.S. milk supply.
While confirmed cases of the H5N1 virus in dairy cattle have slowed down, there have been 20 confirmed herd outbreaks over the past 30 days in five states, including 13 herds infected in Colorado alone. The latest confirmed case was reported in a Michigan herd on Aug. 26.
CDFA stated the department has taken steps to reduce the risk of infected dairy cows entering California and is prepared to respond to confirmed cases. "If these cases are confirmed, CDFA will continue working closely with the California Department of Public Health, and local agricultural and public health officials, to understand the extent of the introduction and support animal health and public health activities with the goal of limiting exposure to virus while the impacted herds develop immunity."
State and federal officials have stressed since the outbreak began in early spring that pasteurization is fully effective in deactivating the virus. There are no health concerns for dairy products that have been pasteurized. Still, USDA requires milk from impacted cows to be diverted from the food supply and destroyed.
Since late March, USDA has confirmed infected dairy cattle in 193 farms across 13 states.
Generally, most cattle infected with the influenza virus show mild signs of illness, including decreased lactation, low appetite and other systems. The virus, however, concentrates in a cow's milk glands.
FDA earlier this month reported that testing in June and July showed no live virus among 167 retail dairy products tested nationally but roughly 17% of all products tested showed signs of viral fragments that had been deactivated by pasteurization. FDA continues to highlight that there is a risk of live virus showing up in unpasteurized products, or raw milk.
USDA also now is testing culled dairy cows at processing plants to see if any meat samples test positive for the virus. There were no signs of the virus showing up in meat samples in three earlier studies USDA conducted in laboratories this spring.
A larger concern stressed by the Centers for Disease Control and Prevention is that farmworkers could become infected. At least nine farm workers in Colorado have become infected with the H5N1 virus. The CDC has called for farmworkers to use personal protective equipment while working with dairies and to also get vaccinated for the seasonal flu virus to reduce the risk that the H5N1 and the seasonal flu could combine to become a more dangerous virus.
To educate producers about the virus, USDA announced this month it was sending out QR postcards to more than 20,000 dairy farms nationally, including versions in Spanish to educate farmers about USDA assistance for farms that become infected, as well as biosecurity measures that should be taken.
USDA has said dairy cows were initially infected by wild birds that carry the virus. The virus, however, principally moves from herd to herd through an infected cow being introduced to the herd or contaminated equipment.
Most dairy cows recover within weeks of being infected. USDA's Food Safety and Inspection Service (FSIS) has found culled dairy cows testing positive for the virus when they arrive at processing plants.
On Wednesday, USDA announced the department has authorized at least one company to conduct a vaccine field study for the H5N1 virus for dairy cows. That vaccine work is being overseen by the Center for Veterinary Biologicals out of Ames, Iowa. A spokesperson for USDA told DTN that USDA expects to receive similar requests from other vaccine companies. The field trials are for a bovine vaccine only, though right now the vaccine is not authorized for commercial use.
Chris Clayton can be reached at Chris.Clayton@dtn.com
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