Research from the University of Guelph has found that a quarter of foxes and coyotes in southern Ontario have a tapeworm that can be fatal to dogs and their owners.

Nearly one in four coyotes and foxes in the area from Windsor to Ottawa tested positive for the Echinococcus multilocularis tapeworm, which has only been found in Western Canada so far.

Prof. Andrew Peregrine, the reports lead researcher at the Ontario Veterinary College at the University of Guelph, said the findings suggest the tapeworm is now well established and has been present even longer than indicated by the study.

Over two winters, the research team collected the carcasses of 460 foxes and coyotes, which belong to the wild canid family, and examined their intestines. They found 23 per cent of them tested positive for E. multilocularis. The first case was identified in 2012 in five dogs, as well as three other species in southern Ontario.

"In fact, when we first showed the data to those we were working with in Sweden, they said two things: Youve had it a lot longer than you think, and its most likely come in from the U.S.," Peregrine said.

The E. multilocularis parasite is spread by coyotes and foxes that eat infected rodents, such as field mice, the report found. For reasons that are not yet known, the wild animals dont become sick, but dogs that eat coyote or fox feces containing parasite eggs — or dogs that hunt and eat infected rodents — can develop a severe infection called alveolar echinococcosis, or AE.

Humans can become infected immediately if these eggs find a way into their system. Pet owners are likely to acquire them from their dogs, not from direct contact with the poop of foxes and coyotes, Peregrine said. Its when owners let their pets sleep in their beds that theyre more likely to get the microscopic tapeworm: If a dogs lower end is covered with the parasites, they can be transferred to the dog owners bed and ingested that way.

The parasite goes largely undetected and can produce no signs or symptoms in dogs or humans. Both can carry the infection for years, but, over time, it aggressively attacks the liver, becoming potentially fatal.

For dog owners, the infection can cause devastating loss.

Megan MacLusky often let her dog Bauer off-leash during their walks in the fields and woods around Guelph, Ont., where she lives, and the two travelled to Alberta in 2012.

Two years later, Bauer developed a large mass on his side, which turned out to be an enlarged liver and a cyst. After a series of tests and vet visits, his veterinarian concluded that the liver was enlarged due to the AE infection, and the cyst contained the parasites.

MacLusky put Bauer on antiparasitic medication. When that didnt work, he underwent surgery, but the cyst could not be fully removed.

"Bauer actually went almost back to normal for about a year, but, eventually, more cysts formed," she said.

Preventive treatment

Peregrine says the parasite is present in both rural and urban areas, and its important for dog owners to talk to their veterinarians about their pets exercise habits.

"The vets now know where this parasite is, and where in the province the greatest risk is," he said.

"If your dog is known to eat rodents, or hunt, there is a drug [it can take] to stop it from developing intestinal infections, so that eliminates any concerns about infections in people in the household."

But not every dog needs the treatment. If your dog never goes off-leash, either in an urban or rural area, its unlikely to be eating rodents. The risk is higher for dogs who are often off-leash, Peregrine said.

https://www.cbc.ca/news/science/tapeworm-southern-ontario-1.5093511