Researchers have identified why H5N1 bird flu causes severe udder infections in dairy cattle rather than respiratory illness. The discovery, published in Science Advances, centers on specific cell receptors found mainly in mammary tissue.
The outbreak began in early 2024 among U.S. dairy herds in the Texas Panhandle. Infected cows developed necrotizing mastitis while showing little lung involvement, surprising veterinarians who initially suspected bacterial causes.
University of Pittsburgh scientists led by Suresh Kuchipudi mapped glycan receptors in cattle tissues. They found that N-linked sialic acid receptors, which the virus uses to bind, are abundant in udders but nearly absent in airways.
"Mastitis is a classic disease in milk-production animals, and veterinarians were dutifully looking to all the usual suspects," Kuchipudi said. The team noted that infected cows shed high levels of virus in milk, raising risks for farm workers and pets.
Pasteurization destroys the virus. Researchers said the receptor-mapping approach could help identify susceptible tissues in other species before future outbreaks occur.