Rabies hitched a ride to Canada in dogs flown from Iran. Scientists caught the spread just in time

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When two dogs imported to Canada from Iran on separate occasions in 2021 developed deadly canine rabies, alarm bells rang loudly for public health officials. They scrambled to trace dozens of people who may have been in contact with the animals' saliva to give preventive treatment before it was too late.

The quick action staved off what could have become a fatal disease in at least 60 people, including the dogs' foster and adopted families, their friends, as well as staff at several veterinary clinics across Ontario.

For epidemiologists, cases such as those underscore the importance of surveillance for new strains of viruses and bacteria coming into Canada by way of animals, a subject highlighted in a review paper published in Science Translational Medicine last week. 

"It's pretty concerning for individuals when they're told that a dog you came in contact with had rabies," said Dr. Tasha Epp, a veterinarian and epidemiologist at the University of Saskatchewan in Saskatoon tracking diseases that can be transmitted between animals and humans. 

Epp is among several researchers on the lookout for more dog rabies in North America. The authors of the review paper apply the same principles to other illnesses originating in wild and domestic animals. 

While wild animals act as carriers for rabies in Canada, human cases are extremely rare. Still, doctors recommend staying clear of wildlife and seeking treatment if bitten.

Canada has been free of the canine form of rabies for decades, which federal public health officials say is thanks to excellent prevention and control programs.

But the recent scare has them looking at precautions and tightening cross-border rules.

The challenge comes from how long the rabies virus can incubate in a dog before it starts changing its behaviour, such as becoming uncharacteristically aggressive.

Rabies is typically transmitted to people from the bite of a rabid animal through direct contact with its saliva (such as through broken skin or membranes in our eyes, nose or mouth). It affects nerves. People can first feel tingling around the wound or scratch, then weakness, fever or headache. Muscles can become paralyzed followed by coma and eventually death.

In the first of the two 2021 cases of dog rabies, the three-month-old puppy that arrived from Iran didn't need to be quarantined because it was a personal pet.

The pup had no known exposure to wildlife carriers in Canada.

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