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Deadly 'fox' tapeworm found in Ontario can kill dogs and humans

A tiny but potentially deadly tapeworm has popped up in Ontario. It's dangerous for dogs and chipmunks but can also kill humans. Veterinarian Andrew Peregrine from the University of Guelph explains why it's dangerous.

Experts don't know for sure, veterinarian says, how the tapeworm got into Ontario

Conrad Collaco · CBC News ·
A red fox bounding through long grass.
The Yukon Wildlife Preserve has raised the money it needs to build an enclosure for the little red fox that was mistaken for a puppy this spring. (Jake Paleczny/Yukon Wildlife Preserve)
0:01Fox Tapeworm
The "fox" tapeworm has been found, for the first time, in Ontario. University of Guelph veterinarian Andrew Peregrine says it can kill dogs and humans.

A tiny but potentially deadly tapeworm has popped up in Ontario. It's dangerous for dogs and chipmunks but can also kill humans.

Veterinarian Andrew Peregrine from the University of Guelph spoke with the CBC's Conrad Collaco about why the tapeworm is so dangerous. He put together a website to help explains to people in Ontario everything we need to know about the creature. You can read an abridged and edited version of the interview below or listen to the full audio interview. 

Veterinarian Andrew Peregrine, University of Guelph

Why is it called a 'fox' tapeworm?
Andrew Peregrine is a veterinarian at the University of Guelph. (University of Guelph)
In Europe it is only found in the intestines of foxes. In North America it occurs in both the intestines of foxes and coyotes. It's a tiny little tape worm. It live in their intestines but it doesn't make them sick. They shed eggs into the environment into their feces and if those eggs are eaten by any type of rodent the parasite migrates to the liver of that rodent and behaves like a really nasty tumour and eventually kills the rodent. Foxes and coyotes get infected when they consume or eat those infected rodents.

How did it get to Ontario?

We don't actually know. For many, many decades we've known it is in wildlife in many U.S. states. The one that is the greatest relevance to us is Michigan. Prior to 2012 this parasite had not been diagnosed in Ontario. We've now seen quite a number of cases. Either it has come in from Michigan, and that is very likely, or there is some evidence that it may have come in from Europe as well with dogs imported into Ontario from central parts of Europe especially Switzerland.

... it causes very significant liver damage in both dogs and in people.- Andrew Peregrine, University of Guelph

How dangerous is this for dogs and other animals?

It causes very nasty disease both in dogs and in people. And just as in the mice I mentioned it causes very significant liver damage in both dogs and in people.

How do humans get infected?

Just one way, by ingesting eggs of the parasite. Theoretically that's possible by eating fox or coyote feces but that's highly unlikely. We think most human infections actually occur by ingestion of eggs passed in the feces of dogs. At the moment we don't know how many human cases there have been in Ontario. That's why it was made, in July, a disease of public health significance in Ontario which means all cases must be reported.

We know there have been at least three human cases since 2014 but going forward now we'll hear about all the human cases. We know, since 2012, there have been six cases in dogs and three cases in lemurs and a case in a chipmunk. All except one of those occurred in the Golden Horseshoe area at the western end of Lake Ontario.

Is it difficult for veterinarians or other doctors to diagnose?    

It was usually not on anyone's radar. Now we're trying to make sure veterinarians and physicians are aware of this parasite. It will in future be included in a list of differentials when physicians or vets are working up cases. 

If you think you or your dog might be ill from this parasite what do you do?

If you have a dog and you have concerns you should go talk to your veterinarian so that you understand the risk in your area of your dog getting exposed. Does your dog do things that increase the risk of exposure? Does it eat fox or coyote feces? Does it eat rodents? If it eats rodents there is a de-wormer than can be given to dogs that works extremely well. If you have concerns about infections in yourself go to your physician or your local public health unit. 

What symptoms might a human experience?

Humans experience symptoms associated with liver damage like pain in the upper abdomen, weight loss and they may become jaundiced. There are many other things that cause liver damage. If you've got any of those critical signs or symptoms it's important to see a physician to make sure they consider all the potential options rather than focusing on one.

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