Despite the scare mongering, even the pasteurized milk, from a cow testing positive for bird flu, is safe to drink. Some fear-exaggerated claims could create a pandemic of fear.
COWS VS. BIRD FLU:
Bird flu likely coming to Canada but it rarely kills cattle and pasteurized milk is safe to drink
Nelson Zandbergen
Farmers Forum
ST. ISIDORE — Dead barn cats are the first tell-tale signs of bird flu lurking in their herd. That’s often been the American experience as the H5N1 bird flu virus slowly spreads through a small minority of dairy herds south of the border, according to Theresa Sweeney-Murphy, communications director for the largest milk producer group in the U.S., the National Milk Producers Federation.
The bug has yet to infect any Canadian herds, and producers here hope to keep it that way. While bird flu can kill cats, it rarely kills cows and pasteurized milk is safe to drink.
Addressing Eastern Ontario producers last month in St. Isidore, Sweeney-Murphy noted that cats live on 73 % of the nearly 28,000 dairy farms in the U.S. Of the 972 American dairy herds experiencing an H5N1 outbreak in the last year, dead cats and other dead animals were discovered on the premises 29 % of the time.
“They unfortunately are affected really quickly, and they die really quickly. So usually before the clinical signs will show up in a dairy cow, a lot of farms have already found other dead critters around,” the upstate New York resident said. It’s a sign, she added, “that you should start preparing to call your vet and get your ducks in a row because you’re going to have H5N1 soon.”
She advised the producers to prepare for the virus’s potential arrival on their dairy farms.
“I would suggest that you start thinking about what biosecurity risks are on your farm and start planning for a possible animal health outbreak,” she said. “We know that there are opportunities for transmission from cattle movement, from unpasteurized milk, from people and vehicles (moving between farms), so just start thinking about what the risks are on your farm and some opportunities for ameliorating some of those opportunities.”
She also advised that farmers work “sooner rather than later” with the federal and provincial governments to create a testing and response strategy if H5N1 turns up on Canadian dairy farms.
The current H5N1 flare-up dates back to early 2022 when the virus, carried by migrating waterfowl, began infecting North American poultry farms. Millions of poultry birds have been culled in response. In March 2024, the virus “spilled over” from wild birds into a Texas dairy herd. That single event sparked the bug’s current spread through dairy farms in 16 states. It’s been passing directly between cattle or through cross contamination carried by shared farm employees, cattle trucks and equipment, according to Sweeney-Murphy.
In February, wildlife transmitted a slightly different strain of H5N1 into Nevada dairy cattle. It was the second spillover event since the virus first made the leap into bovines almost a year ago. “We’re not sure yet with the new strain … if it was again a spillover from a migratory waterfowl to a dairy cow or if there was some other host,” she said.
The Americans are routinely testing the raw milk in farmers’ bulk tanks and at processing facilities. It was a test of raw milk taken from a silo at a processing plant that turned up the new strain involving seven farms in Nevada. Pasteurized milk remains safe to drink, and the U.S. dairy industry hasn’t seen a decline in demand for milk, she said.
Most cows survive their bout with H5N1 and typically only 10 to 15 % of cattle in an infected herd will show symptoms, according to Sweeney-Murphy. But it’s still a major headache for dairy operators with the misfortune of seeing their cows catch bird flu.
While bird flu rarely kills cows, 90 % of infected poultry die from the disease.
For some operators, it means “drenching” multiple cows with water and electrolytes through a throat tube to help them recover from fever. Spontaneous abortions occur and some animals simply take too long to recover and have to be culled. Breeding programs may be interrupted. Sickened cows that recover can take up to 45 days to return to their regular milk production.
“Somatic cell count will spike even before cows start showing clinical signs,” she said. “And a lot of farms … have had a really hard time getting their cell count back to what it was before the outbreak — even four, six, eight months later. So it can take a while to run through a herd.”
The milk of hard-hit cows may turn yellow and contain flakes. One or all of their udders’ quarters may abruptly dry off. Nasal discharge can be another symptom.
But the impact varies at each farm.
“One farm may have a fairly favorable outcome and a minimal number of cows that are affected…. There is quite a range of how farms are affected and how cows are affected and we aren’t really sure what determines a more positive outcome, but we’re working on it,” Sweeney-Murphy said.
She also advised dairy farmers to collaborate with their counterparts in the poultry industry, recognizing that the latter sector is uniquely threatened by bird flu. Poultry farmers in the U.S. were frustrated with dairy farmers for their initial response to the virus, she acknowledged, but the groups now meet weekly to coordinate.
