ISU research identifies possible point of entry for avian flu in cattle

Iowa State University researchers have identified receptors for the avian flu on dairy cattle mammary glands. (Photo courtesy of the U.S. Department of Agriculture)

As avian influenza is being detected in more and more dairy herds across the U.S., Iowa State University researchers have found a possible “why” connection to the virus being found in raw milk.

A study published this month by a team in ISU’s College of Veterinary Medicine found that bovine mammary gland tissue held receptors for the avian influenza virus, offering a potential explanation for how cattle are being infected.

Todd Bell, a professor of veterinary pathology and co-author of the study, said the idea to look at mammary glands as a potential entry point for the virus came after it was identified in raw milk. Two ISU alums in the spring identified an illness impacting cattle in Texas as avian flu , and ever since different teams at the university and in partnerships with other organizations have been working to tackle the virus and its spread from different angles.

“They really answered the ‘what,’ what was actually going on, what was making these cattle sick, which is a new and novel finding, and then our job, really, at that point as researchers was to understand the ‘why,’” Bell said. “We’ve never seen this before. Why is this happening?”

To understand the concept, Bell suggested thinking of viruses as like keys, and receptors are like locks to cells. In order for the avian flu virus to enter a cell and reproduce, it needs the right receptor. The research team found that receptor on cattle mammary glands.

Another receptor they found is connected to human influenza, Bell said, which is important because it opens up the possibility of a cell being infected by both viruses, potentially causing the creation of a new virus.

“To our knowledge, that hasn’t happened yet in this particular outbreak, but we wanted to look for those receptors to understand what might be possible and hopefully stop the transmission and stop that from happening,” Bell said.

The team also looked at the respiratory system to try and identify evidence of the bird flu, but found little there, narrowing down the possibilities of how cattle are being infected.

According to the American Veterinary Medical Association , as of July 12 the avian influenza had been detected in dairy herds in 12 states, including 13 herds in Iowa. While the virus is being detected in raw milk, the pasteurization process ensures it is safe to be consumed.

Research may inform preventative policies

While Bell and his colleague’s work is still very much focused on the “why” of avian flu in dairy herds and its spread, he said the hope is that their research will help inform regulators in making decisions on testing and biosecurity measures to try and stop the spread of the virus. He said there is some literature that states the virus can live on milking machines for a few hours after an infected cow is hooked up to them, offering one potential method of spread.

“We hope that what we find will help them make those types of decisions, specifically if we can find it in mammary tissue, then how do we stop it from getting to that mammary tissue in the first place,” Bell said.

Next steps for Bell and his colleagues include looking at the milk and mammary glands of other domestic animals, like sheep and goats, to see if they also carry receptors for the avian flu. Bell said they will also look at their respiratory systems and gastrointestinal tracts to see if the flu could have other points of entry, like if a wild bird with the virus defecates into a water supply and farm animals drink the infected water.

Iowa Secretary of Agriculture Mike Naig said during “ Iowa Press ” last week that longitudinal studies are also being conducted on farms to test every single animal housed there in order to track how the virus moves and determine how it exits the herd.

“Because it will, it will eventually exit that herd and you want to be able to track those things and have an expectation of how long does that last,” he said during the program.

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