A recent University of Calgary study shows many coyotes in Calgary are infected with a tiny tapeworm that lives in the gut.
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Echinococcus multilocularis is relatively harmless to its canine hosts, but it is potentially fatal for people if untreated.
When ingested, the parasite may cause serious disease when its larvae multiply in the liver. The result in the body is similar to cancer.
Spread of infection unknown
University of Calgary wildlife biologist Alessandro Massolo told the CBC's Calgary Eyeopener the infection is extremely rare in North American people.
There are 18,000 to 19,000 cases per year worldwide, with 95 per cent of those in China.
Biologists don't know whether transmission of the parasite is happening between coyotes and humans, but high infection rates in coyotes found in Calgary parks are raising concerns that people could be at risk.
Biologists also don't know whether the parasite is spreading, because there are no baseline data to compare.
Calgary coyote infection rates high
Massolo says rates change from year to year and season to season. The researchers determined the infection rates by collecting dead coyotes and fecal samples.
- Calgary's Bowmont Park: 80-90 per cent.
- Calgary's Nose Hill Park: 20-30 per cent.
- Calgary's Fish Creek Provincial Park: Very few positive samples were found in the study.
- Edmonton: Up to 50 per cent.
- Rural Alberta: 40 per cent.
How humans could become infected
Echinococcus multilocularis is a food-borne parasite that can be ingested by humans eating vegetables or low-growing berries from areas where the parasite is present.
Humans can also become infected by petting dogs who are shedding the parasite's microscopically small eggs through their feces.
Dogs would not likely pick up the parasite directly from coyotes. They would have to eat an infected rodent because the tapeworm circulates between dog family species — like coyotes and foxes — and small mammal species, mostly rodents.
Prevention of infection
To prevent the spread of the parasite, and minimize the health risk to humans, Massolo advises people to thoroughly wash any raw produce found in infected areas before eating it — especially low-growing berries.
He says the owners of Calgary's roughly 125,000 dogs should watch their pets when off-leash, and make sure to pick up after them.
If their dogs are preying on rodents, owners should take them to the vet to be checked and de-wormed regularly.