Veterinarians across the country say they're seeing an increase in the number of dogs falling ill after ingesting marijuana, a trend they only expect to continue as Canada prepares to legalize the drug.

Saanich resident Karen Heimlich said it's a nightmare she had to deal with when her dachshund, Pixel, started exhibiting bizarre behaviour after going on a walk last July.

"She was twitching like she was having a seizure or something, and then when I tried to put my hands on her face, her eyes go really wide," said Heimlich. "She was quite paranoid."

The family didn't find out until hours later, at an emergency veterinary clinic, that the symptoms were the result of the dog eating pot.

"I was very, very worried," she said.

It's an incident that has become more common on Vancouver Island and beyond.

Dr. Chris Milligan of Central Island Veterinary Emergency Hospital in Nanaimo said his clinic sees roughly four to five cases of pot-sickened pets per week.

"Probably the most common way that we see it here is people who have been out walking on trails in and around the town, all over the island really, they'll pick it up after it's been discarded," said Milligan.

Heimlich said she suspects that's exactly how Pixel ended up ingesting the drug, and she'll be supervising her pet much more closely on future outings.

"When I heard what it was, I was so shocked and angry too, because you know we're about to legalize pot and it's just going to get worse," she said.

THC, the psychoactive ingredient in marijuana, doesn't make dogs high like it does humans, but veterinarians say it can induce symptoms like wobbling, crying and urinating uncontrollably – and depending on the amount taken and size of the pet, it can be lethal.

"Always contact your veterinarian," said Milligan. "They'll be able to advise you as to what we need to do next. Typical treatment would involve decontamination therapy, and that usually involves inducing patients to vomit."

For Pixel's family, the bill didn't come cheap. The family was hit with a $500 bill for the dog's frightening stay that lasted hours.

Veterinarians in Fredericton, N.B., are calling for the federal government to mount a public awareness campaign on the dangers marijuana can pose to pets as it prepares to legalize the drug this summer.

Colorado, which legalized marijuana in 2012, reported a four-fold increase in cases of marijuana toxicity in dogs between 2010 and 2014. 

With files from The Canadian Press.