Pet owners are being asked to be more careful with their dogs after researchers at the University of Guelph made an unsettling discovery.

Nearly 25% of coyotes, wolves and foxes in southern Ontario have tested positive for a tapeworm which they get from eating infected rodents. The animals don’t become sick, but the parasite can be passed to both dogs and humans.

“This is a zoonotic disease,” says veterinarian Renee Fleming of the Guelph Animal Hospital. “That means the parasite can be transmitted from pet to humans, and that’s why it’s a really big concern right now.”

Dogs can pick up the parasite in one of two ways: by eating an infected rodent or eating the droppings of an infected coyote or fox.

If they eat the rodent, dogs won’t get sick, but they can pass the along the parasite.

“Often because we don’t know the dog is infected,” says Fleming, “the eggs that can be shed in the feces are what can infect humans.”

If they eat the dropping of an infected animal like a coyote or fox, they can get sick and, if untreated, the condition can be fatal.

The parasite, which is also known as the Fox Tapeworm, was first found in Ontario in 2012 when six dogs and three lemurs died in the Golden Horseshoe region.

Fleming says the easiest way to prevent the parasite from spreading is by washing your hands after petting your dog or cleaning up their feces.

She also warns against letting your dog sleep in your bed and making sure you visit a vet regularly.