H5N1 Bird Flu Mechanism in Cattle Found by Researchers

In early 2024, H5N1 bird flu began infecting cattle in the U.S., but its diagnosis was initially challenging due to the atypical symptoms exhibited by the cows. Instead of affecting the lungs, as seen in other mammals, H5N1 caused severe infections in the udders of the cattle, leading to necrotizing mastitis. This condition, common in dairy animals, was initially attributed to bacterial pathogens until the true cause was identified.

A study published in Science Advances by researchers from the University of Pittsburgh School of Public Health has provided the first mechanistic explanation for this unusual manifestation of the virus. The study reveals that only a specific subtype of glycan receptors, known as N-linked sialic acid receptors, allows the virus to bind and infect the udders. These receptors are prevalent in the udders but nearly absent in the respiratory tract of cows, explaining the lack of lung infections.

Dr. Suresh Kuchipudi, a senior author of the study, highlighted the occupational risks for farm workers due to virus shedding in milk. He emphasized the importance of pasteurization to eliminate the virus and prevent infections. The study also notes instances of domestic cats becoming ill after consuming raw milk from infected cows, suggesting a broader risk to pets.

Kuchipudi, along with colleagues from Harvard Medical School, employed advanced methodologies to map glycan structures comprehensively. Their findings suggest that the virus's ability to infect different species and tissues can be predicted by screening for specific glycan types.

The study involved contributions from several other researchers, including those from Pennsylvania State University and North Dakota State University, and was supported by the U.S. Department of Agriculture's National Institute of Food and Agriculture.