Western Manitoba lab tracks SARS-CoV-2 in white-tailed deer with help from hunters

In a small laboratory in Dauphin's industrial district, deer heads thaw on the floor.

Those heads are submitted as part of the provincial surveillance program for chronic wasting disease in deer, but for the past couple years, technicians in the western Manitoba city have been probing the inside of the deer's nostrils and throats to test for SARS-CoV-2.

Richard Davis, a biologist with Manitoba Conservation and the province's wildlife health program manager, is in charge of the program for preventing disease from impacting wildlife populations in Manitoba.

He said after a U.S. jurisdiction started testing for the virus that causes COVID-19 in white-tailed deer samples, Environment and Climate Change Canada initiated a study across the country asking agencies like the one in Manitoba to start testing deer for the virus.

Davis said his team sent in 300 swabs last year, and three confirmed SARS-CoV-2 for a positivity rate of one per cent.

"It's surprising because ... the type of COVID that was in the deer was the alpha variant, delta variant and a third variant that was only seen in the UK," Davis said.

"Scientists and researchers are really wondering what's going on there, and of course the concern is if it becomes endemic in the deer, are they going to pass it people."

About 50 SARS-CoV-2 infections have been detected in deer across the country since October 2020, with Ontario, Alberta and British Columbia leading the way.

These infections could potentially have repercussions for humans, so researchers are taking advantage of the hunting season to monitor the situation. That includes Jennifer Provencher, a research scientist with Environment and Climate Change Canada, who is based at the National Wildlife Research Centre in Ottawa. 

"I think just emphasizing the contribution and the collaboration with those hunters ... for these programs to ensure that deer are healthy and accessible, I think is just really an important point," she said.

Earlier in the COVID-19 pandemic, animals such as cats and dogs contracted the virus from their family homes and other people they came into contact with, Provencher said.

That data pushed Environment and Climate Change Canada — along with provincial and territorial partners — into thinking about which other species the virus causing COVID-19 could also be transferred to.

"Can it get into deer? Can it get into birds? This was work that we undertook a lot with partners who were on the ground, catching and trapping and tagging animals for other management purposes," Provencher said.

The highest risk to getting or being exposed to SARS CoV-2 two is still from human-to-human interaction, but there are many animals that have interactions with humans. That's where Provencher started to look at animals in the wild.

She says biologists like Davis have tested white-tailed deer, mule deer, elk and moose, and they've found that white-tailed deer and mule deer have been shown to be exposed or have SARS-CoV-2 matching what Provencher's colleagues in the U.S. have found. 

The positivity rate is less than five per cent in most areas, she said, but that is over a sampling period of two to three years.

In Manitoba, the western border accounts for most of the sampling because it's part of a screening program to see if chronic wasting disease is entering the province.

"It's representative probably of that region. It's probably not representative of the whole province," Provencher said.

And just because SARS-CoV-2 doesn't appear to have any negative effects on deer, it doesn't mean it's not having an effect, she said.

"There's still potential ways it could be reducing survival. It could be reducing fertility. There's lots of reasons why a disease can actually affect an animal," Provencher said.

Viruses that circulate in animals can also act as a reservoir, and there is the possibility the virus continues to evolve.

"That's still a big question mark for us. And so we don't know if deer, in particular in North America, will continue to have this virus actually circulate and become a pool of viruses that could spill back into humans," she said.

"There's a spill back in humans that can actually change the disease dynamics against humans. We don't see that yet, but by tracking the deer population in their SARS-CoV-2, we can see if that's happening."