Canadian dairy farmers brace for bird flu after a year of American outbreaks

Something was spreading through the dairy herds of Texas and Kansas in the spring of 2024.

The cows had spiked a fever; they weren’t eating. Some had stopped producing much milk, and what did come out was lumpy and clotted. Officials took samples of their milk and sent it for testing.

Then, on March 25, several American health authorities made an announcement: the cattle had bird flu.

Since last spring, avian influenza has spread to more than 950 dairy farms in the United States. And although it has yet to be found on dairy farms elsewhere in the world, farmers in Canada—and especially border communities like the Fraser Valley—are preparing for what will happen if the virus eventually arrives.

An American outbreak

Last week, dairy farmer Sarah Sache left her 150-cow farm in Rosedale to meet with fellow farmers in Ottawa. They discussed domestic politics, the impact of national elections, the threat of international tariffs—and perhaps the fastest-evolving worry in the dairy world, avian influenza.

“The concern is definitely growing,” Sache said in a phone call to The Current, just a few hours after a presentation on avian influenza.

As its name would suggest, avian influenza historically only posed a major risk to birds. Variants of the virus have swept through poultry farms for decades, though recent outbreaks have been particularly frequent and severe. In recent years, the virus has also been sneaking its way into mammal populations: bears in Quebec, elephant seals in Argentina, as well as cats, people, and other animals often in close contact with infected poultry. (One 13-year-old girl in Richmond was hospitalized for nearly two months after contracting the virus—details on the particular strain she caught can be found further down.)

But the virus’s infection of cattle is something new.

Think of a virus like a book. Each page represents a different part of the virus’s genetic code. One common way for viruses to mutate is for single letters in the book to change during replication. The mutations take time to accumulate. But sometimes, when different influenza viruses infect the same cell, they can swap entire pages of their genetic code in their progeny—a process called “reassortment.”

“If we’re unlucky, we can get reassortment where a virus that was previously infecting primarily wild birds gets a sub unit from another virus that’s very good at infecting poultry,” Theresa Burns, BC’s chief veterinarian told The Current. When that happens, it’s possible for a virus to get more dangerous.

In late 2023, scientists found a newly reassorted virus in wild birds. They plotted it onto the avian influenza family tree, and named B3.13—standard practice for documenting a new variant. But the virus, instead of staying in ducks and geese as one might expect, moved over to cattle.

Although officials first found the virus in cattle last March, scientists believe the virus had been circulating undetected for at least four months prior. It quickly spread across the country, with new cases found on farms in Michigan and Idaho just days after the initial announcement. By the start of the summer, bird flu had been found on nearly 140 farms.

Today, there have been more than 960 infected farms across the United States.

Most of the farms with infected cattle are in California, where two-thirds of dairy operations have been affected. The state supplies around a fifth of America’s milk, and its dairy farms are huge, with an average of 15,600 cows on each site.

The scale of the outbreak has been overwhelming, California veterinarians told Sache and other Canadian farmers. The vets have been coming to British Columbia to share their insights on the virus with local farmers, to help them prepare for future outbreaks here.

“Their farms are much, much larger than ours, obviously, but once the cows start to get sick, then they get sick for quite a while,” she said. “We’re trying to educate ourselves so that should it show up, we’ll know what it looks like, and we’ll be prepared to watch for those signs and take necessary action if something should happen.”

The threat south of the border continues to evolve and grow. Just last week, a new variant of the virus was found in cattle herds in Nevada. That virus was related to the variant most commonly found in wild waterfowl.

So far, the cattle-focused B3.13 has not been found in Washington State. That gives local farmers a bit of a buffer, Jeremy Dunn—the general manager of BC Dairy, the non-profit representative for dairy farmers—said. But not a big one.

“It’s definitely a concern for dairy farmers, and we’re taking every measure we can to keep it out of our country.”

The health of the cow

Avian influenza is a death sentence for birds. In commercial poultry farms, a single infection results in the mass euthanization of entire barns of birds, to prevent its spread both inside and outside the farm.

Cows, however, can struggle through.

In cattle, avian influenza begins as a high fever. The cattle lose their appetite and in general just act unwell. (Much like a toddler sitting listlessly on the couch rather than playing on the floor.) Then, their milk production slows or stops completely. In serious cases, cows pump out milk that is thick and clotted—”not something like we’ve seen before in dairy cattle,” Sache said.

“They do eventually kick it and get better,” she said. “But it takes quite a lot of care from those looking after them, and quite a lot of time.”

Although Sache hasn’t seen any infected cattle of her own, she and other local farmers have been learning about how to identify it and treat it.

Farmers need to use what is essentially a cow-pedialyte—a hydrating combination of electrolytes and minerals—to help animals through their fevers. Lactating dairy cows still need to be milked, but that milk must be dumped rather than processed.

Milking the cows, though, can pose a challenge. Raw milk—milk that hasn’t been pasteurized—can contain extremely high levels of the virus. That has allowed the virus to spread among US cattle. If a bit of milk is left on a milking machine from an infected cow, it could pass the virus to the next animal to use the device.

Cleaning milking equipment—and anything else that could get sprayed with milk straight from the udder—is high on farmers’ priority lists. More than a third of BC producers, Sache included, use robotic milkers that automatically sanitize the equipment between cows. Farmers who use more traditional milking methods need to make sure their equipment is thoroughly scrubbed between milking sessions if their farm is ever infected.

Canada’s food inspection agency has repeatedly stated that avian influenza is not considered a food safety risk. (Other research has corroborated this: a study in Nature noted that although infected milk sprayed in someone’s nose could potentially make them sick, milk that was drunk was unlikely to do so.) In Canada, regulations also help keep avian influenza out of the food production chain.

“Milk from sick cattle does not go into the food system at all,” Burns said.

All Canadian milk must also be pasteurized before sale—a process that kills micro-organisms in the milk that can cause all sorts of illnesses, not just bird flu. (There are a few small processors who make cheese out of raw milk: if their supplier’s herd got an infection, the milk from the sick cow would be dumped. The rest would be pasteurized, rather than used raw.)

“Raw milk certainly can spread virus, and we have seen cases of that in the United States,” Burns said. “But in BC, because our pasteurization system is very robust and pasteurization works so well, we have a good system to manage that.”

But there is always risk for the farmworkers who milk the cattle and clean the equipment. Personal protective equipment, including gloves, masks, and glasses, can help make infections less likely. But in the States, it hasn’t been enough to stop the movement of B3.13 into people.

The virus spreads to people

Less than a week after the US reported its first cases of bird flu in dairy cows, a Texas farmworker suffering with red, swollen eyes was diagnosed with avian flu.

“It’s a huge thing that the virus has jumped from birds to mammals, dairy cows in this case, and then to humans,” Steven Presley, the director of a Texas institute involved with investigating the case, said in a press release at the time.

Most of the human illnesses associated with B3.13 have been comparatively mild—the majority are cases of pink eye, doctors noted. At least 40 people in the United States have caught the B3.13 version of avian influenza in the United States, and all recovered on their own.

Cats have also been a casualty of bird flu’s race through cattle herds since B3.13 arrived. According to the US Department of Agriculture, around 80% of dairy farms had cats living on the property—and by June, 2024, half of those farms had sick or dead cats. (The virus is often fatal for cats, with symptoms beginning with fever and eventually resulting in neurological issues like seizures.) In February, the CDC reportedly shared (but later deleted) information on two potential transmissions of avian flu between humans and their cats.

So far, the B3.13 variant has not made its way into Canada—either in cows, cats, or people.

An eye on the border

When cattle began catching avian influenza in the United States last spring, Canada switched into protection mode.

“The science on this virus changes every day,” said Dunn.

In late April, Canada changed its requirements for cattle entering the country. All lactating cattle—the ones who are most likely to transmit the virus—must be tested for avian influenza before arriving in Canada. The Canadian Food Inspection Agency also began widespread testing of both pasteurized and raw milk for the virus.

Burns said her office has administered hundreds of tests for farmers—all of which were negative. (Burns’ labs are based in Abbotsford, at the heart of BC’s dairy industry.) The tests, which are conducted on milk samples, help give farmers’ peace of mind, she said.

“Some people just want to feel confident and comfortable that their herd is negative,” Burns said. “Other people might be thinking about buying new cattle or selling cattle to another farm, and they want to make sure that they’re negative before moving them between farms.”

Each year, Canadian farmers import hundreds of thousands of cattle from the United States. Most of the cattle are destined to become beef, but a couple thousand cattle make their way to dairy farms.

Farmers import cattle from elsewhere for various reasons—but in the Fraser Valley, a common reason is the sheer expense of raising livestock.

“Not everybody has the land base or the facilities to allow them to raise their own young stock,” Sache explained.

The new regulations around imported cattle have “slowed the trade of dairy milk cows,” Dunn said.

Sache’s 150-cow farm hasn’t been affected. She and her husband raise all their new stock themselves, which is part of the reason she has yet to take advantage of the free avian influenza testing.

“I feel badly saying, ‘No, I’m not testing at the moment,’ but for reasons, including the fact that we’re a completely closed herd, we haven’t felt the need to take on that level of surveillance,” she said.

If—or likely, when—dairy-related bird flu makes its way into Canada, that will change, Sache said.

“It’s not unlikely we will eventually have it in Canada, because we have had it in birds and other animals,” Sache said. “Once it shows up in Canada, we’ll definitely start testing our tank.”

An ounce of Canadian prevention

Most farms have standard and established biosecurity measures: workers and visitors must wash their boots before entering a barn, cattle are vaccinated on schedule, and new animals are segregated before mingling with a herd. But America’s avian influenza outbreak has ramped up dairy farmers’ focus on biosecurity.

On her Rosedale farm, Sache said they are limiting extra visitors to the farm, and ensuring employees keep their work clothes at work and don’t move them between farms.

Elsewhere in BC, Dunn said farmers are reducing large-scale farm tours and ensuring cattle don’t move between farms unnecessarily. They are also increasing the availability of personal protective equipment so no one is unnecessarily exposed to milk spray.

Meanwhile, veterinarians and scientists like Burns and her colleagues at Abbotsford’s Animal Health Centre are further studying avian influenza, and trying to determine exactly what biosecurity measures could be most effective against the virus. (We’ll have more on that in our update on avian influenza in BC poultry next week.)

“The job of people like me is to be well prepared for risks that … could have a serious impact if they were to happen,” Burns said. “Even though there’s no guarantee something will happen, we really try to be prepared to reduce that risk further.”

A look to the future

America’s cow outbreak, which scientists had originally pinned to a single jump from birds into cattle, is not as singular as it was once thought to be.

Last Wednesday, the United States Department of Agriculture announced it had discovered four more herds with avian influenza. But they weren’t infected with B3.13. Instead, it was a relative of the D1.1 strain—the same one affecting wild birds, poultry farms, and one 13-year-old girl in Canada.

According to an analysis from the US government’s Animal and Plant Health Inspection Service, the virus was found before the cattle started to look sick. Many states have mandated bulk milk testing, meaning scientists can take a sample from a vat of milk coming from multiple herds and test it periodically for the virus (similar to the peace-of-mind testing option available for BC dairy farmers today).

The test in Nevada found three silos with the D1.1 virus, although it took almost a month to trace it back to the original farms. By then, the cattle had begun to act sick. There have also been mass die-offs of wild birds near the affected farms, the report said.

As a whole, D1.1 appears to pose more of a danger to people. Around two dozen people in the US have caught the D1.1 variant, which is most common in wild birds and poultry. That strain of the virus first appeared in September of 2024 as a reassortment, and quickly expanded across North America. (Although it is the predominant type of avian influenza virus in wild birds, it only makes up a little more than 6% of all detections.)

Scientists analyzing the genetic material in the D1.1 dairy virus say it did have one genetic change that has not been found in either D1.1 in birds or B3.13 in cattle. That change makes it easier for the virus to replicate in mammal cells, and was found in D1.1 viruses in people as well.

Although people’s understanding of bird flu in dairy cattle has advanced significantly since the first jump happened less than a year ago, there is still more to learn, according to veterinarians like Burns. And Canadian dairy farmers aren’t convinced they’ll escape the outbreak unscathed.

But there is still hope.

“There is the potential we could avoid this, which would be the optimal situation,” Sache said. “There’s definitely risk out there that we need to be alert to, and it just depends on how much time passes, if a vaccine can be developed before we actually have things get worse.

“Until then, we’ll keep working with biosecurity and working with our teams to keep everybody safe and keep the cows healthy, and go from there.”