Echinococcus in coyotes around Saskatoon

photo: Cam Barlow

photo: Cam Barlow

Recently a small study on the prevalence of Echinococcus sp. infections in coyotes in the Saskatoon area has revealed a high rate of infection, and in some cases, a very high number of parasites in individual animals. This parasite is important because it can be transmitted to humans.

The species was identified as Echinococcus multilocularis, a parasite found throughout the world. Echinococcus multilocularis is a tapeworm with a life cycle involving two hosts. In the coyote, which is the definitive host, the adult stage is found in the intestine. The ribbon-shaped adult stage is relatively small, with a total length of no more than ~8 mm. Other mammalian carnivores such as foxes, lynx, dogs and cats, are also definitive hosts for this parasite. The definitive host sheds eggs which are ingested by an intermediate host which consists of small rodents, such as voles, mice and muskrats. In the intermediate host fluid filled cysts containing larval stages are formed. These cysts continue to grow and bud-off new cysts throughout the life of the animal. Larval stages are found in the liver and in other tissues in the abdomen.


Echinococcus life cycle
Center for Disease Control and Prevention 

Humans become infected by inadvertently ingesting eggs and then act as an intermediate host with cystic larval stages growing in their liver or other tissues. Fortunately, exposure is uncommon and the disease occurs rarely in North America. Trappers and people that use country foods are at highest risks but domestic pets that commonly feed on small rodents can carry Echinococcus multilocularis and pose a risk to people without contact with wildlife, especially small children. Occasionally other species such as dogs and pigs can develop larval stages in their tissues and their occurrence may indicate increased risk to humans.

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