Prof. Andrew Peregrine

Dog owners in Ontario may need to do something our New England neighbours to the southeast have been doing for years: checking themselves and their pets for ticks when they come back from a walk in the woods.

Why? Because blacklegged ticks (sometimes called deer ticks) are now more frequently found in southern and eastern Ontario, and because these ticks can carry Lyme disease.

“It’s not a huge problem in most of the province yet,” says pathobiology professor Andrew Peregrine, “but there are some ‘hot spots’ for blacklegged ticks such as the Kingston-Thousand Islands area and a small number of parks or naturalized areas on the northern shores of Lake Erie and Lake Ontario.” That’s thanks, in part, to climate change, which has allowed the ticks to migrate north. They live one stage of their life cycle predominantly on small mammals like mice, squirrels and shrews, and another stage on white-tailed deer.

Peregrine teaches clinical parasitology and says blacklegged ticks are small arachnids, which need to feed on blood before they can reproduce. Their bites are painless, but they stay attached for a number of days, expanding to several times their original size. While deer are their natural source of blood as adults, ticks are happy to latch on to dogs or humans if those happen to pass by where they are waiting.

While the numbers are still low in most of the province, they have increased significantly, especially in those areas Peregrine describes as “hot spots.” Profs. Claire Jardine and Lisa Werden, also in the Department of Pathobiology, have shown that the number of ticks in the Thousand Islands, for example, almost quadrupled in some areas between 2009 and 2011.

Not only are there more ticks in the province, but a higher percentage of them are carrying Lyme disease: in 2012 approximately 17 per cent of ticks gathered across Ontario and submitted for testing to Robbin Lindsay in the Public Health Agency of Canada were infected with the agent of Lyme disease. In the Long Point area, more than 60 per cent are infected.

At certain times of the year Peregrine receives three to five calls daily from veterinarians asking about ticks and tick-borne diseases. “It varies across the province,” he adds. “I talk to vets in Toronto who have rarely seen a tick, but there are vets in Kingston who tell me that at times up to half their work seems to revolve around ticks.”

Awareness of Lyme disease in dogs has also increased, thanks to a simple test for infection that has been added to heartworm test kits by the manufacturer at little or no extra cost. Vets who had previously tested dogs for heartworm alone now find it simple to include the test for Lyme disease.

However, Peregrine points out that approximately 95 per cent of the dogs that test positive for Lyme disease will never develop clinical signs and, therefore, typically don’t require treatment.

In some parts of Ontario, blacklegged ticks carry Lyme disease bacteria.

Pet owners shouldn’t panic if they find a tick on their dogs, either. The tick waits on long grass or brush and then latches onto an animal (or human) leg or body as they pass by. “The ticks don’t go hunting for you,” says Peregrine. Only after the approximately 36 hours of feeding time is the Lyme disease bacteria – assuming the tick is carrying it – passed on to the animal or person. If you discover the tick early enough and remove it, the risk of infection is very low.

What should pet owners do? “Talk to your vet about it,” advises Peregrine. “Vets know if ticks are a problem in their area and can give clients the right advice. If you are going to be travelling with your dog, ask the vet about risks in that area.”

The advice for avoiding ticks is based on common sense. If you are walking out in the woods with your dog, wear long pants and tuck the pant legs into your socks. When you get home, check your dog for ticks. If you find one, use tweezers to remove it, gripping with the tweezers as close to the skin as possible. You don’t want to squish the tick’s body, which could cause the Lyme disease bacteria to be released onto skin and, if damaged, could potentially result in infection.

If you’re feeling squeamish, Peregrine suggests taking the dog to a veterinarian who will have the tools to make removal easier and can also identify the type of tick. Identification is important as more than one type of tick occurs in Ontario, but only blacklegged ticks transmit the agent that causes Lyme disease.

“If your dog has acquired a tick, you might be at risk too from other ticks in the same environment” Peregrine adds. So be sure to check yourself as well.

While there is a new need for awareness of ticks and tick-borne diseases in Ontario, the risk is still low in most parts of the province. Nevertheless, knowing the situation before you head out for a walk with your dog can help you make sure you’re taking the right precautions.