Bird flu outbreak: Avian influenza transmitted in raw cow’s milk
US researchers have shown raw cow’s milk can transmit the highly pathogenic H5N1 avian influenza virus to other mammals.
US researchers have shown avian influenza-infected cows can transmit the virus to other mammals through their unpasteurised milk.
University of Wisconsin-Madison and the Texas A&M Veterinary Medical Diagnostic Laboratory researchers fed raw cow’s milk containing the highly pathogenic avian influenza H5N1 virus to mice, which showed signs of the disease within 24hrs.
“The animals showed signs of illness starting on day one, including ruffled fur and lethargy,” the researchers reported in The New England Journal of Medicine.
The mice were euthanized on day four to test for the virus, which researchers found “in the respiratory organs and moderate virus titers (levels) in several other organs”.
“Detection of virus in the mammary glands of two mice was consistent with the high virus load in the milk of lactating cows, even though these mice were not lactating,” the report stated.
“Collectively, our data indicate that HPAI H5N1 virus in untreated milk can infect susceptible animals that consume it”.
Pasteurisation destroys the virus.
To date two US dairy workers in Michigan and Texas have been infected with avian influenza, with both developing eye infections.
Based on the information available, the US Centre for Disease Control advises the current H5N1 human health risk for the general public is low, but recommends farmers and their workers wear personal protective clothing when close to cows.
Meanwhile the US Department of Agriculture’s Food Safety and Inspection Service has also found HPAI in meat from a culled dairy cow, but has not determined if the virus is viable.
“On May 22, 2024, viral particles were detected in tissue samples, including muscle, from one cow,” the department stated.
“To date, samples from 95 cows have tested negative for viral particles. No meat from these dairy cattle entered the food supply.”
The cattle were not culled from herds that were known to be infected with avian influenza, but due to what the USDA described as “systemic disease”, which was picked up at slaughter.
The USDA was working on tracing the virus back to the farm so it could notify the producer.
The USDA has also conducted testing of ground beef in stores and in cooked meat, but found no viral particles to date.
To date 67 US dairy herds have been infected with the HPAI H5N1 virus across nine states.