By Rachel Cramer
Bird flu has infected dairy cows in a dozen states since the first confirmed case in March. But testing for the virus is largely voluntary and varies state-by-state, unless cows are crossing state borders.
The virus can spread from dairy cows to poultry, and vice versa. Unlike flocks, most dairy cattle recover a few weeks after an infection, but producers are required to discard milk from sick cows.
“Producers are concerned and being active to prevent infections,” said Zelmar Rodriguez, a veterinarian and assistant professor at Michigan State University. “The ones who have been affected know that it's a big economic hit.”
In late April, the U.S. Department of Agriculture issued a federal order that requires milk-producing dairy cows to test negative for the virus before crossing state lines. That includes sampling raw milk, which has been found to contain a high concentration of the virus.
The USDA also rolled out a voluntary program in late May to help gather more information and give another testing option to producers. Samples come from a bulk milk tank that represents the whole herd, rather than individual cows. Herds from six states – including Kansas, Nebraska, Ohio and Texas – have enrolled so far.
Iowa and Michigan, both states with high case numbers in the Midwest, have opted for more requirements.
States with more testing
Soon after Iowa’s first confirmed bird flu infection at a dairy in June, the state’s agriculture department announced it was requiring testing at dairies within a 12-mile radius of infected poultry sites.
“This has resulted in and will continue to result in more information, which will hopefully help us to learn more about the origin, the spread and the impact of the virus, and to hopefully help to contain its further spread,” said Grant Menke, the state’s deputy secretary of agriculture, during a recent webinar hosted by Iowa State University Extension.
Dairy producers within the testing zone work with their vets to collect samples from a minimum of five sick cows and bulk milk tanks. Samples go to the Iowa State University Veterinary Diagnostic Lab for analysis and then to the USDA’s National Veterinary Services Laboratories for confirmation.
If bird flu is confirmed, state officials coordinate with USDA epidemiologists to lead on-site investigations. They meet with producers and try to uncover how the virus was introduced, potential ties to other cases and clues about how it’s spreading.
Michigan, one of the states with the most cases in the U.S., does not have mandatory surveillance testing like Iowa. But it’s taken a more direct approach to boosting biosecurity.
A ‘developing field’
Some states may be more proactive due to a history of economic pain from bird flu, said Christine Petersen, the director of the Center for Emerging Infectious Diseases at the University of Iowa. Bird flu took a $1.2 billion toll on Iowa, the top egg producing state in the U.S., in 2015.
But not every state has a veterinary college and diagnostic lab, like Iowa, to run tests. And active disease surveillance – random sampling in a specific population or area – is expensive, Petersen said.
Bird flu testing is a “developing field” for dairy cattle, said Pat Gordon, a professor of veterinary medicine at Iowa State University, during the webinar with Menke.
“As of March 22 of this year, we didn't even realize that this virus was able to infect dairy cattle,” Gordon said. “And we've not seen influenza in cattle much throughout my career, which spans over 30 years.”
Gordon said the best diagnostic tool for milk-producing dairy cows at this time is a PCR test, which can detect trace amounts of genetic material in milk. However, it doesn’t reveal whether the virus is intact and infectious.
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