Canadian scientists launch early warning system to spot traces of H5N1 bird flu in milk

It all started with a few text messages in late April.

Several well-known Canadian scientists — Toronto-based infectious diseases specialist Dr. Isaac Bogoch, Saskatoon-based virologist Angela Rasmussen and Winnipeg-based microbiologist Jason Kindrachuk — were all chatting about the unprecedented outbreak of H5N1 bird flu in U.S. dairy cows.

By then, American officials had tracked cow cases for roughly a month, and harmless viral particles were showing up in processed, pasteurized milk. 

But on this side of the border, the Canadian Food Inspection Agency (CFIA) was clear its team wasn’t yet undertaking milk testing.

The trio of Canadian academic researchers saw a missed opportunity.

“I think we all were thinking independently: Why aren’t we doing milk testing?” recalled Kindrachuk, an associate professor at the University of Manitoba. “If we can simply get milk off the shelves and [run tests], this would seem like a great initiative for us to undertake.”

Rather than waiting for the government to launch that kind of surveillance, the scientists spearheaded a coast-to-coast initiative to watch for H5N1 in Canadian milk. 

“Within the span of about two minutes … we had a flurry of emails out to partners and collaborators across all the provinces,” Kindrachuk said.

The result, unveiled through an unpublished preprint paper shared online on Wednesday, is what the team dubbed the Pan-Canadian Milk Network. Eighteen scientists in total worked on the findings, from universities throughout Canada. The researchers say the goal is to continue to test milk to spot any fragments of this virus showing up in the Canadian milk supply. 

That outcome wouldn’t pose a risk to consumers — as testing shows pasteurization ensures milk is safe to drink — but it would signal infections in Canadian dairy cows. (Cases of bird flu in U.S. cows have led to high fevers, severe dehydration, aborted calves and a substantial drop in milk production, while exposing a rising number of farm workers to this virus.

A colourized transmission electron micrograph shows Avian influenza A H5N1 viruses (seen in gold) grown in MDCK cells (seen in green). The U.S. is dealing with an avian flu outbreak in dairy cattle, with the virus showing up in close to 70 herds across nine states so far. In Canada, no H5N1 viral fragments have been found in milk. (Cynthia Goldsmith, Jacqueline Katz, Sherif R. Zaki/CDC)

No viral fragments found to date

“Our network and testing will act as an early warning system which will enable rapid responses necessary to contain an outbreak should any samples test positive,” the team wrote.

As of May 24, the researchers have tested 18 retail milk samples from five provinces (Newfoundland, New Brunswick, Quebec, Manitoba and Alberta) and all came back negative for influenza A, the virus family of which H5N1 is a member.

Though government officials initially opted not to pursue milk testing, the CFIA announced its inclusion in surveillance efforts in early May, as CBC News previously reported.

The CFIA also beat the independent team to public results, releasing their preliminary data in mid-May. Full results of their first testing round — looking at roughly 300 retail milk samples from across Canada — were published online a week later. 

None found any H5N1 viral fragments.

Milk testing top priority during migration

What’s not clear yet is whether the CFIA will keep up that work. Next steps will be decided “as part of further discussions with partners,” the agency said.

A member of Kindrachuk’s lab team, virologist and postdoctoral candidate Hannah Wallace, was the lead author on the Pan-Canadian Milk Network’s first preprint paper. She stressed that ongoing milk testing has to be a top priority. 

“Especially because there will be another big bird migration in the fall, and that’s when influenza testing and influenza rates in wild birds are at their highest levels,” Wallace explained.

“So if there was a time for something to happen, it would probably be then.”

WATCH | Food inspection agency testing more milk over bird flu concerns: 

CFIA testing more of the milk supply over avian flu concerns

A decision by the Canadian Food Inspection Agency to bolster testing of the milk supply is the right move as the U.S. deals with an avian flu outbreak in dairy cattle, infectious disease specialists say, because it adds a layer of safety on top of pasteurization of milk sold in stores.

More samples from other provinces are expected soon, Wallace noted.

The team is scanning milk first for the influenza virus more broadly, but has the necessary equipment to spot H5N1 specifically as well. Any positive finds would then be reported to the CFIA.

The team’s next step is looking for anti-influenza antibodies in cows’ milk to see if any Canadian dairy cows were previously exposed to influenza, suggesting prior infections that may have flown under-the-radar, Wallace said.

The CFIA also has additional surveillance efforts underway, including requiring negative test results for lactating dairy cattle being imported from the United States to Canada and helping to facilitate voluntary testing of cows that aren’t presenting with any symptoms.

Cows across 9 U.S. states have confirmed infections

Those scaled-up efforts, both from the Canadian government and independent researchers, come as the U.S. dairy cow outbreak keeps growing.

The virus has shown up in close to 70 herds across nine states so far. There have also been two human infections linked to the outbreak, high rates of death among farm cats exposed to contaminated raw milk, and yet another jump to a new species — alpaca on a farm in Idaho.

Veterinarian and researcher Dr. Scott Weese, with the University of Guelph, stressed that at this point, “more eyes on the problem is good.”

He said milk testing needs to remain part of a multifaceted surveillance program including testing on both sick and healthy cows, farm cats, and continued tests on imported cattle.

“It’s just one piece of the puzzle as far as surveillance is concerned,” echoed Dr. Samira Mubareka, a microbiologist and clinical scientist at the Sunnybrook Health Sciences Centre in Toronto. Looking at various sample types, over time, across a wide geographic range, are all factors research teams need to consider, she said.

WATCH | What does bird flu in cattle mean for humans? 

Bird flu is spreading in cows. Are humans at risk? | About That

For the first time ever, avian influenza, or H5N1 bird flu, was detected in roughly a dozen dairy cow herds across the U.S. About That producer Lauren Bird explores why scientists and public health officials are concerned about the cross-species transmission and whether humans are now at higher risk.

When it comes to milk, “it would be ideal to have a centralized and co-ordinated approach as there are ways to much more efficiently get a large number of milk samples, through milk processors,” Weese said in an email exchange with CBC News. “Retail milk, though, is a simple and relevant indicator.”

It also sidesteps any hesitation that may emerge at the farm level, since it doesn’t require sampling on any individual premises — and offers an anonymous way to get results.

“That can help with some of the concerns that farmers have,” Weese said. It isn’t yet clear what kind of regulations would be needed on farms if tests came back positive, he noted, so there would “likely be barriers to on-farm sampling.”

While the new network’s data is rather general for privacy reasons, Wallace said the team does have the ability to trace samples back to specific sources. “We would be able to provide CFIA with all of the information like the lot number, the batch, where the milk was bought, what company it was from.”

The hope now, Kindrachuk says, is that Canada will have a leg up on a dangerous virus that keeps catching the world off guard.

“We can’t be behind the eight ball,” he said.

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