A video recently emerged showing several cows lying dead on roadsides in California’s Central Valley amid an avian influenza outbreak across the U.S., sparking biosafety concerns.
The dead cows were close together with swarms of flies buzzing around them, video shows. Dr. Crystal Heath, a veterinary doctor with the Berkeley, California-based nonprofit Our Honor, took the video Oct. 8 and shared it on Twitter on Oct. 17. The dead livestock were in front of Mendonsa Farms and Land O’Lakes Borges Dairy, both in Tulare County, Heath said. There were no visible warning signs of potential biosafety risk that the exposed carcasses posed to the public at the time, Heath added.
On October 8th, I visited Tulare County, California, where I found dead cows that had succumbed to H5N1 avian influenza lying on the side of the road. This was the first published footage of avian influenza-infected cows, and the story was published in Newsweek and on the local… pic.twitter.com/mt2bhhsk2l
— Crystal Heath DVM (@drcrystalheath) October 17, 2024
The highly pathogenic avian influenza (HPAI) caused by H5N1 viruses first hit a poultry farm Oct. 8, 2022, according to the U.S. Department of Agriculture (USDA). It then jumped to dairy farms in March, with 333 confirmed cases among dairy cows across 14 states so far. Some 133 dairy livestock in California have been infected as of Oct. 17, making California the state with the highest number of confirmed cases. Ninety-nine of the 133 cases occurred over the past 30 days.
More than half of the barn cats fed raw milk at the first dairy farm to report positive cases in Texas died after drinking the milk, according to U.S. News & World Reports.
“[D]isturbingly, the first sign that a facility is infected is when the barn cats die after drinking the avian influenza-infected milk,” Heath said in the video.
“To date, CDC has confirmed 13 farm workers have been infected with H5N1 bird flu in California,” the Centers for Disease Control and Prevention (CDC) said. (RELATED: WHO Confirms First Human Death From H5N2 Bird Flu In Mexico)
Washington became the sixth state to report human H5N1 cases, as four poultry workers in Franklin County are presumed positive, the state’s Department of Health said Sunday.
California was the largest producer of cow milk as of 2023, according to the USDA. It has 1,710 dairy cows, the highest number in any state, 2024 data from Statista shows. Some 30% of California’s dairy cows are in Tulare County, a February news release from the University of California–Davis shows.
The USDA, Food and Drug Administration (FDA), CDC and state veterinary and public health officials are all investigating the outbreak. CDC staff are on the ground in California to try to stem the spread, the CDC said.
The disease appears underreported in various other states, with both the infectiousness of the H5N1 virus and California’s mandatory testing being the reasons for California’s high number of confirmed cases, dairy market expert Nathaniel Donnay told the Los Angeles Times.
Prognosis appears grim, with 600 cases projected to occur in the next few weeks, Nathaniel Donnay added.
The projection is not unrealistic, retired USDA veterinarian epidemiologist John Korslund told the LA Times.
If it does become a reality, “I would estimate that the California dairy outbreak is the most serious and widespread infectious animal disease outbreak in history,” he added.
