Bird flu and dairy cow research

One of the early hints that the virus could be spreading through a route other than contact with infected milking machines, Lombard said, was that the virus was spreading through herds quickly, more quickly than would be the case with machine-based spread.

Another clue, he said, came from identifying that antibodies for the virus were first showing up in cattle’s bloodstream prior to detection in the milk. That finding, he said, suggested cattle were being exposed to the virus by a route other than from contact with infected machines.

Lombard is now in the process of collaborating with members of CSU’s Department of Atmospheric Sciences to try to better understand the potential for airborne spread. The researchers are attempting to match wind patterns to dates of infected farms from a recent outbreak in California, which could support the theory that the virus moves through the air. Another possibility, he said, is that the virus is being carried from farm to farm via another species, such as birds.

In addition to learning about how the virus spreads, there have been other initial takeaways from the sampling done by Lombard’s team. Notably, he said, they detected the virus intermittently, which can make the virus more difficult to track because an animal might not test positive one day but might still be shedding the virus. Generally, Lombard said, cattle also appeared to shed the virus for a particularly long period, in some cases more than 10 weeks.

Lombard said the team’s sampling also revealed that cattle could shed the virus up to seven days prior to showing clinical signs — a so-called “subclinical” period similar to how COVID-19 behaves in humans. “By the time you have clinical signs,” Lombard said, “it’s everywhere.” In addition to decreased milk production, the most common clinical signs, he said, have included nasal discharge, decreased feed intake and inflammation of the mammary glands.

Notably, Lombard said, the cattle they tested in Colorado showed a strong antibody response to the virus, suggesting that an avian influenza vaccine could be effective in dairy cattle.

In addition to sampling cattle, Lombard’s team also sampled for the virus on trucks that transport milk from the farm to production facilities. They found a single positive, he said, suggesting milk trucks are not a high risk for spreading the virus.