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New parasite in Ontario raises concern

In 2012, OVC student Alicia Skelding was completing an externship at a southern Ontario veterinary clinic when a two-year-old boxer, who had never left the province, was brought in.

During surgery, the veterinarian saw what looked like a large mass in the liver. Although liver masses are common in boxers, Skelding opted to use her “case study” money to have further testing done. The dog was diagnosed with an infection of Echinococcus multilocularis.

“Until that testing was done, we didn’t know this parasite was even in Ontario,” says pathobiology professor Andrew Peregrine. Prior to 2009, the only cases described in dogs in North America were seen in Alaska; the 2009 case was in British Columbia.

Echinococcus multilocularis is a tiny tapeworm usually found in the small intestines of foxes and coyotes. The eggs in the animals’ feces are picked up by rodents, where they develop into an inter­mediate stage and cause alveolar hydatid cysts in the liver that are ultimately fatal. When foxes or coyotes eat these rodents, the adult tapeworm develops and the cycle continues. The parasite can also infect dogs and cats if they eat rodents.

Peregrine says the parasite poses a sig­nificant health risk to humans: if people ingest the parasite’s eggs they may develop the intermediate stage in the liver, which has a high mortality rate if left untreated. Much of the research on this parasite has been done in Switzerland, where it is becoming a significant problem.

The Ontario boxer most likely con­sumed a “massive number of eggs” from coyote or fox feces explains Peregrine. Since then, two more dogs have been diagnosed in southern Ontario. Neither of these dogs had travelled outside the prov­ince. To date, no human cases have been described in Ontario.

“The Swiss researchers who con­firmed the Ontario canine infections have warned us these cases are likely the tip of the iceberg,” says Peregrine. “It takes five to 15 years for clinical signs to develop in humans, so we may have people in Ontario infected with the parasite but not yet diagnosed. To date, all people in contact with the three Ontario dogs have tested negative. Cases in dogs may have been missed because the infection in the liver looks grossly like a tumour.”

Peregrine is urging veterinarians to be aware of this emerging disease. Bayer Canada is assisting veterinarians with diagnostic testing for dogs with suspi­cious abdominal lesions. Peregrine is also working with Public Health Ontario and other groups on further research and prevention strategies.

As seen in the Summer 2015 issue of The Crest.  If you are an OVC alumni you should receive The Crest with your issue of UofG’s Portico.  Need to update you address – you can do that through Alumni Affairs.

Be sure to watch Dr. Peregrine‘s presentation on Echinococcus Multilocularis: Emerging Public Health Issue in Canada? on YouTube.