"Your dog is positive for THC, and she's really high right now."

That's something Jennifer Wright never expected to hear from the on-call veterinarian at the Animal Hospital of Cambridge.

Coco, the Wright family's nine-month-old Yorkie-Havanese cross, had been acting out of sorts that evening.

"She was really lethargic, she picked her head up and it was wobbling," Wright said. "So I picked her up and I tried to set her down on the ground, and that's when I noticed ... her back end was sort of swaying back and forth. She looked like she was going to fall over, and she could not walk, she would not walk."

The family piled into the car and frantically tried to find a clinic that was open in the off-hours.

"I literally thought my dog was having a stroke," Wright recalled.

THC out in the open

Coco wasn't having a stroke, but she was one of a growing number of dogs in Canada falling ill from THC toxicity since cannabis was legalized in October, 2018.

Sometimes, THC toxicity happens when an animal gets into their owners' stash, but like the Wrights experienced, sometimes a dog can get sick from eating as little as a discarded butt from the side of a walkway or in a city park, said Cathy Hrinivich, a small animal emergency care veterinarian at the Animal Hospital of Cambridge.

"We have people come in, particularly seniors, they've walked the same route with their dog for years and years and never had a problem with this before, the dog is sniffing around and gets into something," Hrinivich said.

"And they're just absolutely flabbergasted, just floored that we are diagnosing marijuana toxicity."

756 per cent increase over a decade

The numbers are only anecdotal, right now, said Dr. Shane Bateman, an emergency and critical care clinician at the Ontario Veterinary College, but he said similar trends have been studied in the United States.

The American Society for the Prevention of Cruelty of Animals runs a poison control hotline in the U.S. and has reported a 756 per cent increase in calls related to marijuana or cannabis over the course of the last 10 years, he said.

Washington and Colorado became the first two states to legalize recreational cannabis in 2012. It is now legal in 12, including the District of Columbia, and approved for medical use in 33 states.

"Certainly since the legalization of marijuana products, I think every veterinarian has seen just a dramatic spike in marijuana toxicity dogs, for sure," Hrinivich said.

Hrinivich said the hospital has seen an increase in both calls from worried pet owners and cases presented at the clinic — but said many pet owners are hesitant to bring in their dogs.

A basket muzzle can keep food-motivated dogs from ingesting discarded joints or edibles that are becoming more common along sidewalks and in parks now that cannabis is legal in Canada. (Shutterstock / Ardarel)

"They just want to call for advice and they want us to hear them out," but she said, "we're a no-judgment zone. I think all veterinarians, we all want to be there and help people. So if people can use us and come in — the dog really should have care."

Leash or muzzle your dog

The Ontario Veterinary College hasn't seen much of an increase since legalization, said Bateman, but he believes that's because most cases handled by the OVC are complex cases, referred by veterinarians.

"Most veterinarians are probably likely treating these cases on their own. They're generally fairly simple and straightforward and not very many of them are life-threatening," Bateman said.

Bateman recommends people limit off-leash walks with their pets, while Hrinivich recommends taking it a step further.

"There's some great products like basket muzzles out now that the dogs tolerate really well. I use one on my daughter's dog — she brought home a lab and that dog is like a goat, it eats anything, so I put a basket muzzle on him when I take him out. It protects him, it protects me, it's just a safer way to go," she said.

Wright has said her family is now "hyper-vigilant" when they take Coco for a walk "keeping her on the sidewalk and making sure we're trying to keep everything out of her mouth — which is quite a challenge but we're just glad she's OK."

"I literally thought that day, that my dog was going to die."