The first mechanistic explanation for H5N1 bird flu’s unusual presentation in dairy cattle—causing severe mastitis instead of respiratory infection—has been published in Science Advances by researchers at the University of Pittsburgh School of Public Health.
A specific type of receptor in cattle determines which tissues the virus infects, offering a new predictive framework for screening susceptibility across species.
Background
The disease first appeared in dairy cattle in the Texas Panhandle in early 2024, presenting as severe necrotizing mastitis. Initial diagnosis was difficult because the virus affected the udders instead of the lungs, allowing it to spread between herds before being identified.
Mechanism
The study used multimodal approaches, including binding experiments, staining, and ultra-high-resolution imaging. Researchers found that only N-linked sialic acid receptors can bind H5N1. These receptors are virtually absent in cow airway tissue but are prevalent in the udders, explaining the virus’s tissue tropism.
Implications for Transmission and Safety
- Infected cows shed large amounts of virus into milk, posing occupational risks to farm workers and risk to pets fed raw milk.
- Pasteurization effectively kills the virus.
Predictive Framework
The research provides a framework to screen different species and tissues for susceptibility to H5N1. This may allow prediction of symptoms—such as respiratory, mastitis, or neurological disease—in potential new hosts.
Methodology and Contributors
- Senior author: Suresh Kuchipudi, Ph.D., chair of Infectious Diseases and Microbiology at Pitt Public Health.
- Collaborator: Lauren E. Pepi, Ph.D., Harvard Medical School, expert in glycomics.
- Additional collaboration included scientists from Pennsylvania State University and North Dakota State University.
- Funding: Pitt Public Health and USDA National Institute of Food and Agriculture.