Avian influenza, commonly known as bird flu, is rapidly spreading through milk on US dairy farms. Since March, the H5N1 virus has infected more than 850 cattle herds across 16 states, and at least 60 people, primarily farmworkers. California is currently the outbreak’s epicenter.
Virus Transmission
Initially, scientists suspected airborne transmission; however, data indicates milk as the primary vector. The H5N1 virus rapidly reproduces in the udders of infected cows, resulting in high pathogen levels in the milk. Infected milk droplets can splash onto workers’ faces, contaminate equipment, and spread the virus to other cows. Although pasteurization neutralizes the virus, traces have been found in retail samples of raw milk in California, raising public health concerns.
Modern Dairy Practices and Risks
The U.S. dairy industry, with over 9 million cows producing 600 million pounds of milk daily, has seen significant consolidation. Large-scale farms now dominate the sector, with 65% of dairy cows residing on farms that house 1,000 or more animals. These large operations milk cows multiple times daily using shared equipment, which can facilitate the spread of viruses.
At Heeg Brothers Dairy in Wisconsin, workers milk 1,050 cows three times a day in a 28-stall parlor. The milking process involves manual stimulation, disinfection, and attaching milking claws. However, milk droplets from infected cows can remain on the equipment and potentially infect other cows. “During milking, the teat end is open, potentially even relaxed,” explained Dr. John Barlow, a veterinary epidemiologist at the University of Vermont.
Could robotic milking systems be a safer alternative?
Technological advancements, such as robotic milking parlors, may help mitigate some risks in dairy farming. At Heeg Brothers Dairy, a newly established robotic barn houses 450 cows. Automated systems handle tasks like disinfecting and milking, thereby reducing direct human contact with udders. Additionally, the robots rinse themselves between cows, which lowers the risk of cross-contamination.
While robots provide economic and safety benefits, they are not without limitations. System malfunctions can occur, and human involvement is still necessary for maintenance and cleaning. Despite these challenges, robotic milking may represent a significant step towards safer dairy farming practices.
The Road Ahead
Bird flu has not yet been detected on dairy farms in Wisconsin, but farmers remain vigilant. Jay Heeg, a third-generation dairy farmer, stated, “I’m not scared of it, but I don’t want it. I think it will be coming.”
As the outbreak progresses, addressing the potential for milk-based transmission will be crucial to protecting both public health and the dairy industry.