The U.S. Department of Agriculture will start testing the national milk supply for bird flu next week.
Under a new federal order, facilities and farms will have to share samples of raw milk to be tested for bird flu. That includes entities with bulk milk transporters or dairy processing facilities that send or hold milk intended for pasteurization.
The virus first appeared in a Texas cattle herd in March and has since infected more than 770 herds in 16 states as of Dec. 10, according to the USDA. It’s also infected nearly 60 humans, mainly through exposure with infected cows or birds. But the public health risk remains low for now, according to the Centers for Disease Control and Prevention.
The testing plan will help to better understand exactly where the virus is and is not present, said Catalina Picasso, a veterinary epidemiologist at Michigan State University working on infectious diseases.
“It's going to take a lot of time and a lot of effort, but the plan is to eradicate the disease, to stop it, which I think is really exciting because it's been spreading a lot, and we need to change the approach,” Picasso said.
Until now, testing has been mostly voluntary. Some states, like Colorado and Massachusetts, have implemented required testing, but others have been dependent on farmers reporting sick cows.
A previous federal mandate that went into effect in April still requires the testing of lactating dairy cows crossing state lines, according to the federal order’s release. It also requires all privately-owned labs and state veterinarians report positive results connected to those tests,
Instead of relying on testing cattle, the new order will implement testing along the dairy supply chain, Picasso said.
“It’s more trying to catch a larger number of farms that are integrated in one silo, or something like that,” Picasso said. “With less testing, we will be able to understand more areas of spread of the disease.”
The strategy
The USDA outlines five stages in its National Milk Testing Strategy:
- Stage 1: Dairy regulators and inspectors will test milk silos at dairy processing facilities across the country in an effort to identify in which states the virus is present.
- Stage 2: States can choose to create bulk milk tank sampling programs to determine whether the state is affected.
- Stage 3: If the virus is present, states will work to identify specific cases and enhance biosecurity, movement controls and contact tracing.
- Stage 4: Once a state tests negative, it will move to an unaffected status. Regular testing of samples from farms’ bulk tanks will continue, but will gradually decrease frequency with negative results. A state will return to Stage 3 if a herd becomes affected.
- Stage 5: Once all states move past Stage 4, the department will continue to test samples periodically to ensure the disease remains absent.
The steps aren’t linear, and states don’t have to move through each stage, said Julie Gauthier of the Animal and Plant Health Inspection Service in a release.
The department said it will start testing in six states: California, Colorado, Michigan, Mississippi, Oregon and Pennsylvania. The latter three have not reported any cases of bird flu in dairy cattle, according to the USDA.
Bird flu in cows
It’s still unclear exactly how bird flu is spreading between cows and nearby herds, said Phillip Jardon, the extension dairy veterinarian at Iowa State University. But he said that when the virus is traveling long distances, it's mainly through cattle.
“It's pretty clear that when it jumped from Texas to Michigan, and Texas to the states to the north, that that was through animals,” Jardon said. “Originally we thought it would be through birds, the wildlife, but that doesn't seem to be the case.”
When a cow is infected, the virus often shows up in its milk, Jardon said.
“We can't find it anywhere but the milk frequently,” he said.
Pasteurization – the process of heating milk to kill off bacteria before it’s sold – effectively kills bird flu, according to the U.S. Food and Drug Administration. The agency warns against drinking raw milk, which does not undergo this process.
Earlier this month, a large California raw milk farm, Raw Farm, voluntarily recalled its products due to possible bird flu contamination.
There’s still demand for raw milk, and Midwest raw milk producers said this summer that they were closely watching their herds for signs of bird flu. The exact risks of contracting the virus from consuming raw milk are still unclear, but health experts say it’s possible.
“We still don't know exactly how much [it] affects the health in terms of transmission, but the virus is there,” Picasso said. “We don't want to drink the virus, definitely. So pasteurization is the tool that we have to fight this disease.”
Human infections
Nearly all of the confirmed cases of bird flu in humans have been connected to exposure to sick cows or birds. And many have been workers on dairy or poultry farms.
Recent research found that bird flu is one mutation away from more easily binding to humans.
But the virus has been around for decades in birds and has infected humans before, said Dr. Dana Hawkinson, who’s an infectious disease physician and medical director of infection prevention and control at the University of Kansas Health System.
“I think some of the experts would say it certainly is a concern, and we need to be doing our due diligence in monitoring it, but also doing the research and monitoring for any changes,” he said. “But more concern would be some virus that we don't even know of right now that jumps out of nowhere and causes a new pandemic or epidemic.”
He said one concern would be the virus combining with another in a cow or a pig and creating a new type of virus that can more easily infect humans.
It’s possible to contract bird flu when enough of it gets into a person’s eyes, nose, mouth or is inhaled, according to the CDC. The virus has typically presented itself as conjunctivitis, Hawkinson said.
Personal protective equipment, like a face mask or goggles, and washing hands frequently can help guard against the virus, especially for dairy and poultry workers, he said.
“I would just caution the general public to not be too anxious or worried about it,” Hawkinson said. “But the flip side of that is we need to be able to have the science to be able to do those investigations and do those studies.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest. It reports on food systems, agriculture and rural issues.
