Bird Flu Likely Spreading Through Shared Personnel, Equipment: USDA

A cow at a farm in Ohio, in an undated file photo. Aaron Josefczuk/Reuters

The highly pathogenic avian influenza is likely being spread by people who work on multiple farms, as well as through the sharing of equipment, the U.S. Department of Agriculture (USDA) said on June 13.

Farmers with confirmed cases of the influenza in their cattle who answered USDA surveys said that they had used shared trucks or trailers to transport cattle within 30 days of the cows showing clinical signs of influenza, which is also known as bird flu or H5N1.

Of the farmers who used shared equipment, 28 percent didn’t clean the equipment before using it.

A significant percentage of workers from the dairy farms also hold jobs at an additional farm, have family members who work on another farm, or visited other farms within 30 days of symptoms appearing among cows at their primary workplace, according to the surveys.

A deep dive into the cases in Michigan found evidence to show that H5N1 was introduced to the state from animals from outside of the state. The investigation also found links between farm workers and other farms, numerous instances of shared vehicles being used, and frequent visitors, such as veterinarians and milk haulers, to farms.

“Based on the epidemiological findings, the majority of links between affected dairy premises, and between dairy and poultry premises, are indirect from shared people, vehicles, and equipment,” the USDA said in a statement.

“All of those add up to the bigger picture that implementing enhanced biosecurity at this time is really critical to stop the spread of H5N1 between dairies and from subsequent spillover to domestic poultry and wildlife with that,” Kammy Johnson, a veterinary epidemiologist at the USDA, told reporters on a call.

Authorities are recommending that farmers not move cattle if possible, restricting farm visitors, cleaning and disinfecting vehicles and equipment when they’re moved on and off farms, and requiring workers to use protective equipment such as goggles.

Cases of the bird flu, which typically appear in poultry, began showing up in cattle in the United States earlier this year. Cases among cows have since been confirmed in 92 herds across 12 states, including Colorado, Iowa, and Ohio.

Two people in Michigan and one in Texas have also been sickened. All work on dairy farms, and have since recovered or are recovering.

Historically, some patients who contract H5N1 die.

Monitoring for cases and trying to avoid the spread of the illness can help protect against the evolution of the flu, which so far shows no signs of transmission between people, according to the U.S. Centers for Disease Control and Prevention (CDC).

“Simply put, the more infections there are among cows, the more risk there is for infections to occur among humans,” Dr. Nirav Shah, the CDC’s deputy director, told reporters.

“And the more risk there is for infections to occur among humans, the more risk there is for some sort of change to the virus that could take this from what it is right now—which is a low risk to the general population to something much different—and that’s why public health ... is so engaged with our counterparts at USDA so that we can, working together, quell this virus.”

According to the surveys, most farms with H5N1 cases among cattle have recorded abnormal lactation. More than 90 percent of the farmers who answered the surveys said cows produced thickened or clotted milk.

The death rate among affected herds is less than 10 percent on average, with small numbers of deaths and a higher number of cattle being culled, the farmers said. One percent of second lactation cows and 2 percent of dry cows, for instance, were culled on average, while 1 percent of dry cows died on average.

State officials previously reported bovine deaths in five states, including South Dakota.