Acidification can inactivate the Highly Pathogenic Avian Influenza H5N1 (HPAI H5N1) virus, also known as the “bird flu,” in milk, according to a study led by University of California, Davis (UC Davis) researchers published in the Journal of Dairy Science.

The findings are especially pertinent amid the ongoing HPAI H5N1 outbreak sweeping North American dairy herds, with cases confirmed in cattle in 16 states thus far.

Although pasteurization is already proven to be effective at inactivating HPAI H5N1 in dairy products, pasteurization can be expensive. Additionally, fewer than 50 percent of large dairy farms pasteurize waste milk, which includes colostrum, the first milk after calving; milk from cows treated with antibiotics or other drugs; or any other factor that can make milk unsuitable and unsellable for human consumption. Even if it is not sold for human consumption, waste raw (unpasteurized) milk can potentially spread avian influenza.

In laboratory tests, the UC Davis researchers demonstrated that acidifying milk to a pH of 4.1–4.2 with citric acid effectively inactivates HPAI in only six hours. Per the scientists, not only is citric acid inexpensive, but acidified waste milk can be used to feed pre-weaned calves, and it does not require refrigeration.

Next, the UC Davis team will conduct on-farm testing of milk acidification in HPAI-contaminated waste milk, with the goal of developing practical guidance for farmers to implement waste milk acidification.

The study was funded by the U.S. Department of Agriculture (USDA) and the California Department of Food and Agriculture. The study’s authors include Beate Crossley, D.V.M, M.P.V.M., Ph.D. and Daniel Rejmanek, R.N.Dr., Ph.D. from the California Animal Health and Food Safety Lab at UC Davis, along with Richard Van Vleck Pereira, Ph.D.; Craig Miramontes; and Rodrigo Gallardo, Ph.D., D.V.M. with the UC Davis School of Veterinary Medicine.