Studying Bird Flu to Protect the Dairy Industry

In March 2024, the USDA reported the first known cases of highly pathogenic avian influenza (HPAI) in U.S. dairy cows. At the time, there were multiple unknowns including how animals become infected, how it was passed from animal-to-animal and farm-to-farm, and the length of the infection. 

ARS scientists at the National Animal Disease Center in Ames, IA, rapidly responded with all available resources to conduct studies to better understand the virus and its effect on dairy cattle. The studies showed that the 2024 outbreak was caused by a single spillover event from wild birds into dairy cattle in Texas and then the HPAI virus spread through cattle transport. Early research also showed that exposure to the virus through the respiratory route resulted in mild respiratory illness, but further spread in the animal’s body was not detected.  However, in experiments, lactating cattle directly exposed to the virus through their mammary glands showed similar symptoms as seen in the field such as mammary tissue inflammation, reduced feed and water intake, and a drop in milk production. These were the first studies completed worldwide to provide insights into this unforeseen animal health event. These studies have been used to design challenge methods for testing treatments to protect against HPAI events in the future. 

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