June and July brings creepy-crawly, icky, disgusting parasites into focus on our blog here at Caledon Mountain Veterinary Hospital. For the most part, parasites are not a big concern for people living in the western world, unless you child comes home from school with lice. But since our pets go places we don’t go, eat things that we don’t eat, and roll in stuff that we don’t (usually) roll in, they are a different story for our companion animals.

Echinococcus multilocularis is a different story, however, and the story reads a little like horror novel if you ask me. More commonly known as the fox tapeworm, E. multilocularis is an intestinal parasite that lives in wildlife and until recently was restricted to Northern and Western Canada. Like most parasites, the fox tapeworm has a life-cycle that involves multiple hosts and tends to cycle between wild canids (foxes, coyote, wolves) and small mammals. When ingested by a small mammal, the larvae migrate through the animals body and form cysts in the animal’s liver. These cysts break open when that creature is eaten by a wild dog and infect the dog, to be shed in it’s feces and start the cycle again. All of this is typical of a parasite life cycle. The scary part is that in rare situations, this parasite can also migrate through the body of other, longer living hosts and form cysts in their bodies as well. In a wolf, fox or coyote, these can grow over years and form growth that resemble a tumour. This same situation can occur in domestic animals such as cats and dogs if they eat small mammals such as rodents that are carrying the parasite.

This means that a domestic dog that hunts mice could, in theory, be carrying a parasitic cyst growing like a tumour in his liver or elsewhere in his body. At this time, the true risk is unknown but thought to be low. However, a scarier fact may be that that same hunting dog could ingest the fox tapeworm and then shed the parasite’s eggs in his feces. These eggs can infect soil and gardens where the dog poops, and can be ingested by people who come into contact with them. Those same tumour-like cysts formed by the migrating parasite larvae can grow inside people who are infected by the parasite. Yes- your best friend could be giving you more than love when he licks your face.

So, what is the big deal?

This is a problem for people in Northern and Western Canada, not us hiking the hills of Caledon, right? Since 2012, 5 cases have been identified in dogs in Ontario, one as close as Guelph. The true risk is thought to be low for any individual or pet and more details are listed below from the Ontario Animal Health Network Website, but there are precautions that can be taken for this emerging risk. Firstly- wash your hands. This is a good safe practice anyway, but especially to decrease the risk of parasite transmission. Secondly, if your cat or dog is a hunter, bring in a stool sample to their annual wellness examination with your veterinarian and discuss the risk with the animal health team. Lastly, if your pet is at high risk, it may be work considering regular deworming for this parasite; your veterinary team can give you more information.

More information on the fox tapeworm;


Parasites are disgusting. Parasites that can grow inside you are on a whole other level. Talk to your veterinary team for more information, or look at the current research being undertaken by the University of Guelph here: