Dairy cow testing aimed at slowing bird flu outbreak

To limit the spread of highly pathogenic H5N1 avian influenza in livestock, all lactating dairy cows must test negative for the virus before they can cross state lines under new requirements by the U.S. Department of Agriculture.

The federal order, which took effect Monday, excludes heifers, dry cows and bull calves. Culled cows going to slaughter that do not show signs of illness also are not required to be tested. But they will still need a certificate of veterinary inspection or approval by animal health officials from the state sending the cattle and the state receiving them.

USDA issued the order last week as outbreaks of the disease have spread to 33 dairy herds in eight states—Kansas, Idaho, Michigan, New Mexico, North Carolina, Ohio, South Dakota and Texas.

The U.S. Food and Drug Administration also confirmed last week that fragments of the virus have been detected in one in five samples of retail milk, with a larger proportion of positive results coming from milk in areas with infected herds. Federal officials acknowledged the findings suggest the virus may be more widespread than USDA’s official count.

Despite the revelations, FDA continued to stress the safety of the commercial milk supply, saying that “pasteurization is very likely to effectively inactivate heat-sensitive viruses, like H5N1, in milk from cows and other species.” The agency also said “additional testing is required to determine whether intact pathogen is still present and if it remains infectious, which determines whether there is any risk of illness associated with consuming the product.”

The new testing requirements are meant to help animal health officials better understand the disease and how it is being spread, USDA said.

“This is an evolving situation, and we’re treating it seriously and with urgency,” Michael Watson, USDA administrator of the Animal and Plant Health Inspection Service, said during a conference call last week with the American Farm Bureau Federation and other state Farm Bureaus.

He said information and data collected from the tests “are key to helping us determine how best to bolster farm and facility biosecurity and to protect farmers, the farm and plant workers, as well as farm animals.”

Under the rule, lactating cows must be tested within seven days prior to interstate transport. A certificate of veterinary inspection must also accompany the shipment.

Sick cows are ineligible for interstate movement and may not enter the food supply. Cows from herds that test positive are not allowed to be moved out of state for 30 days and will need to test negative before they can be shipped.

Testing is done through milk samples, which must be submitted to a USDA-approved lab. USDA said it will pay for the cost of testing but not for associated expenses such as veterinary services, supplies, and the collecting and shipping of samples.

The order requires laboratories and state veterinarians to report positive test results to USDA, which will then conduct an epidemiological investigation, including animal movement tracing.

USDA said it is preparing for a surge in testing, noting that samples submitted to its labs are usually returned within one to three days, though positive test results must be confirmed by another USDA lab in Ames, Iowa. The department estimated the turnaround for confirmation at one to two days.

During the AFBF conference call with USDA, several state Farm Bureaus expressed concerns about testing logistics and potential bottlenecks at USDA labs. Braden Jensen of Idaho Farm Bureau said his state doesn’t have an approved lab.

USDA’s Watson said he realizes “every state won’t have all the resources to do everything we’re asking them to do” but that he expects USDA labs “would be able to handle the influx” of test requests. He said the department stands ready to “help fill some of those gaps” if any state “can’t meet the request that we’re making.”

Watson emphasized that even though the federal order focuses specifically on lactating dairy cows, it can be amended as USDA finds additional information. He said USDA has not determined when the federal order will end but noted previous orders have lasted one to two years.

The testing mandate does not apply to beef cattle, and so far, there have been no reports of beef herds affected by the virus. Dairy cows account for nearly 7% of the nation’s total beef supply, according to the Meat Institute, a trade group in Arlington, Virginia, representing meat packers and processors. The organization has called on USDA and CDC to issue additional, specific guidelines for beef processing facilities “to ensure USDA inspectors and meat company workers are protected from infection.”

“It is important to ensure the free flow of healthy animals to slaughter,” Julie Anna Potts, the institute’s president and CEO, said in a statement.

She said federal officials should “anticipate international trade concerns.” However, USDA said the federal order “should not affect U.S. trade,” noting that it has seen “minimal impacts on markets.”

Since 2022, H5N1 has led to the deaths of millions of wild birds and commercial poultry, including in California. The virus has been detected in more than a dozen different wild mammals in the U.S. and was first confirmed in a Texas dairy herd in late March, with the most recent confirmation on April 19 in an Idaho milking herd.

Federal researchers say they believe wild migratory birds are the original source of the virus and that dairy cows became infected after they consumed feed or water contaminated by infected birds. Researchers have since determined the virus has been spreading between cows and between herds as cattle are moved.

However, they said they have yet to find significant concentration of virus in respiratory-related samples, indicating “respiratory transmission is not a primary means of transmission.” They said there’s also evidence the virus has spread from infected dairy herds to nearby poultry farms “through an unknown route.”

In addition, researchers found H5N1 in a lung tissue sample from an asymptomatic culled dairy cow, which did not enter the food supply. USDA said the finding indicates cows can test positive for the virus even though they show no signs of illness.

In affected herds, about 10% to 20% of cows become sick. Symptoms include decreased milk production and feed intake; thick, discolored milk; loose or tacky manure; and nasal discharge, dehydration and fever. Most dairy cows recover after about seven to 10 days, USDA said.

Because the virus is shed in milk at high concentrations, USDA warned that anything that comes in contact with unpasteurized milk may spread the virus. They stressed the importance of biosecurity on farms to prevent transmission.

Federal researchers maintain they have not found changes to the virus that would make it more transmissible to humans and between people.

“There’s a lot of effort being made right now to work closely with our federal colleagues at the CDC, FDA in terms of food supply, in terms of worker safety,” Watson said, adding USDA wants to take an approach that minimizes disease risks without being overbearing to industry while giving federal researchers “as much information as we possibly can as soon as we possibly can.”

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