06/17/2016 02:29 EDT | Updated 06/17/2016 02:59 EDT

Ontario Rabies Outbreak Blamed On Hitchhiking American Raccoon That Picked A Fight With Canadian Dogs

Danita Delimont via Getty Images
The Raccoons (Procyon lotor) are highly adaptable omnivores, predominantly nocturnal. Can become pests in human environments and are known to be rabies carriers
Scientists say they now have evidence suggesting a rabid raccoon hitchhiked more than 500 kilometres into Ontario from southeastern New York state to ignite Ontario's first rabies outbreak in a decade.

Susan Nadin-Davis, a researcher with the Canadian Food Inspection Agency who focuses on rabies research, says she was surprised at the result and had to run tests again to make sure it wasn't a mistake.

A fight between two Hamilton dogs and an aggressive raccoon in the back of an animal control van in December led to the discovery of the first documented case of rabies in a raccoon in the province since 2005.


Renald Ferland, a Quebec trapper, and Marie-Claude Benoit an Animal health technician, walk from the woods during daily rounds with Operation Raccoon in August, 2007 in Saint Angele de Manoir, Que. (Photo: Peter McCabe/AFP/Getty Images)

The Ministry of Natural Resources and Forestry says the outbreak has ballooned to 128 cases of raccoon strain rabies in both the masked creatures and skunks.

Nadin-Davis says her laboratory in Ottawa has genetically analyzed the rabies strain with a new technique and compared the results to a database she has been building for the past several years that helps pinpoint where variants of the virus originate.

She says the virus is closely related to a strain from southeastern New York state, and quite distinct from the strains found closer to the border.

Nadin-Davis had expected the virus had come from "an incursion" from western New York state, where there are active rabies cases in raccoons, and was surprised it came from further afield.

“It was quite a surprise.”

But even with the presence of rabid raccoons closer to the Canadian border, they still would have faced a daunting task to bring the virus into Canada. Ontario has long had a nearly invisible barrier draped across its southern border that is designed to keep rabid raccoons away from their healthy Canadian brethren.

That barrier consists of thousands of edible rabies vaccine baits that have proven incredibly effective.

"I went back and re-analyzed the sample in order to confirm there hadn't been a mixup or cross-contamination," Nadin-Davis said. "The results seem to hold true. It was quite a surprise."

Nadin-Davis said she will use her research techniques to look into the role skunks are playing in the outbreak.

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