Federal authorities say it is likely being carried from farm to farm on objects like farm equipment or clothing that has touched a sick cow.
The H5N1 bird flu virus has ripped through more than two-thirds of California’s dairy farms since August, sickening untold numbers of cows and infecting more than 30 farmworkers.
How it has been able to hop so quickly from farm to farm remains a mystery.
Federal authorities say it is likely being carried from farm to farm on objects like farm equipment or clothing that has touched a sick cow.
“That’s why strong biosecurity is critically important in stopping the spread of the virus,” a U.S. Department of Agriculture spokesperson told Barron’s.
That would be good news, if true. Lax biosecurity can be fixed. But experts who study the virus are skeptical. They say H5N1 may be moving in ways that even the most careful farms could never stop.
“That’s what they want us to think, that we can control it,” says Dr. Kay Russo, a veterinarian in Colorado with RSM Consulting, who has been involved in the dairy cow outbreak since it began early this year. “But there are operations that have good biosecurity in this that have still fallen. So that suggests that there’s pieces to this that we’re missing.”
What those pieces are remains an open question, but some theories involve house flies; sick workers infecting cows; or even dust plumes carrying the virus through the air.
If ongoing studies confirm any of those routes of transmission, the implications for the ability to wipe out H5N1 in cattle aren’t good. It is perhaps possible for a careful farm to thoroughly wash each person and truck that comes through the gate. It isn’t possible for even the most vigilant farmer to stop every mouse, fly, or plume of dust.
Experts have been scrambling since H5N1 first appeared in cattle in March to learn how the virus takes hold in bovines, even as it has spread to nearly 900 farms in more than 16 U.S. states.
The situation in California, by far the biggest milk-producing state in the U.S., appears to be particularly serious. As of Monday, the USDA had confirmed cases of the virus on 660 of the state’s 984 dairy farms. What’s more, roughly half of the country’s 65 confirmed cases of humans infected with H5N1 this year have been California dairy workers.
California’s governor, Gavin Newsom, declared a state of emergency due to the outbreak in mid-December.
One reason California has found so many cases is that it is looking harder than other states.
Until this month, there was no federal requirement to test for bird flu unless lactating cows were being moved between states. The USDA only launched an effort to monitor unprocessed milk for signs of the virus in December.
Meanwhile, it has been up to individual states to decide how closely they want to look for infected dairy herds.
California has been conducting surveillance testing on all of its dairy farms. “When you’re testing every dairy, you’re going to find every infection,” Dr. Marie Culhane, a professor at the University of Minnesota College of Veterinary Medicine, told Barron’s.
Colorado also did extensive surveillance testing, and found cases on 64 dairies between April and mid-August, a substantial portion of the state’s dairy operations. There have been no newly confirmed positive herds there in months, in what has been taken as a sign that testing and quarantining may be effective in controlling the virus.
The scale in California, however, is far larger. The California dairy herd produced 40.9 billion pounds of milk in 2023, 18% of the U.S. total. There’s no sign of the California outbreak slowing down.
One issue in California may be that the dairy farms there are concentrated in the state’s Central Valley region, and that milk trucks, calves, and workers move regularly among farms. “The milk is moving every day, twice a day, maybe,” says Culhane. “They’re not taking time out to stop, shower, change the clothes, put on new clothes, wash the truck.”
That speed, Culhane says, is how the industry keeps milk prices low. “That’s why we drink milk for $3 a gallon; because we make a lot of it and we move it fast,” she says. “Something’s got to change.”
The virus could be hitching a ride on milking equipment and clothing, the route of transmission the USDA spokesperson said the agency believes is largely responsible for the virus’s spread.
But experts say that may only be part of the story. Russo said that one possibility that needs to be considered is whether human workers are contracting the virus, and then infecting cows on other farms.
Dr. Jürgen Richt, an avian influenza expert at the Kansas State University College of Veterinary Medicine, said that mice, rats, or even flies might be moving the virus from farm to farm.
“If you go in a barn, there are millions of flies,” Richt says. “And they sit on the milk, right, and then they go on cows. They sit on the udder, they sit on the cow. This could be a culprit. I don’t know, but you have to test it.”
Other scientists have theorized that the virus could be carried through the air. “There could be basically a plume of virus, if you’ve got all these animals shedding,” Russo says. “Ultimately the virus could potentially travel on dust particles, odoriferous compounds, things like that; that can potentially spread it from animal to animal.”
Scientists in California are investigating these and other theories. At a webinar for the dairy industry on Dec. 19, state officials and scientists at the University of California at Davis School of Veterinary Medicine described a long list of ongoing research projects into the California H5N1 outbreak, including a project by the USDA’s Agricultural Research Service to collect and test house flies on infected farms to determine whether flies as a “vector for transmission,” according to slides from the presentation obtained by Barron’s.
Other ongoing projects discussed on the webinar include an examination of “dairy feed rations as a potential source” of H5N1, and “enhanced surveillance” of wildlife by USDA near infected farms “to better understand viral transmission.”
The results of these studies may help the dairy industry, and federal regulators, understand how the virus is spreading, and whether even the most intensive biosecurity measures can stop it.
Meanwhile, the virus continues to spread. The USDA confirmed outbreaks on four new farms in California between Monday and Tuesday, bringing the total to 664.
You can now read the most important #news on #eDairyNews #Whatsapp channels!!!
🇺🇸 eDairy News INGLÊS: https://whatsapp.com/channel/0029VaKsjzGDTkJyIN6hcP1K
