Tick-borne disease is spreading into new parts of Canada. Here’s where you’re at risk

As the weather gets warmer, public health experts are warning about the risk of tick-borne illnesses like lyme disease -- a problem that’s spreading to new parts of the country.

The Public Health Agency of Canada (PHAC) has identified thousands of postal codes across more than 1,100 municipalities it considers “risk areas” for exposure to lyme.

As of the current list, high-risk areas are concentrated in communities along the U.S. border, as well as in major population centres.

In Western Canada, risk areas are concentrated on Vancouver Island, the coastal areas of B.C.’s Lower Mainland and river valleys across that province’s south, as well as nearly all of Manitoba from the north shore of Lake Winnipeg to the U.S. border.

Further east, much of southern Ontario’s Great Lakes coasts, including the entirety of the Greater Toronto Area, are within areas considered high risk by the agency. A corridor of risk areas also exists along the St. Lawrence River from Lake Ontario to the Atlantic coast, including Kingston, Ont., Ottawa and Montreal.

And in Atlantic Canada, nearly all of New Brunswick and Nova Scotia, including Cape Breton Island, are known to be habitats for blacklegged ticks.

Virginie Millien is an associate professor of biology at McGill University who studies the effects of climate change on wildlife such as ticks and their hosts.

“Risk areas are growing,” Millien told CTVNews.ca by phone. “It’s not going to stop anytime soon because it’s really driven by climate warming.”

Millien has been tracking the emergence of Lyme disease in Quebec for over a decade

“The risk is present for people, not just whenever they go far in the woods in remote areas,” Millien cautioned. “It’s also present in some major cities now because there’s large urban parks in these cities.”

Informed by data from provincial and territorial authorities, risk areas are identified by the emergence of new tick populations, as well as human populations “most at risk of lyme disease.”

But PHAC is quick to note that even if you are not located in a high-risk postal code, it’s important to remain vigilant.

“[Ticks] can also spread by travelling on birds and deer. You can sometimes find blacklegged ticks in areas outside of where they’re known to live,” the agency’s lyme-disease monitoring page reads.

“Always take precautions against tick bites when you’re in wooded or grassy areas.”

Ticking upward

PHAC notes that as climate change has increased temperatures across the country, the viable range for lyme-infected ticks has grown, increasing risks of exposure.

“Incidence continues to remain high due to factors such as greater human exposure to risk areas and to risk of infection,” reads a 2022 report on lyme-disease monitoring.

Millien says ticks can be spread by other animals like mice, which are also expanding their range due to climate change.

“The tick needs to be able to survive the winter to become established in a region,” Millien explained. “Winter conditions are going to determine whether the tick is going survive or not, and of course it’s getting warmer, so they can survive each year in more northern localities.”

‘It’s going to get bigger and bigger’

Lyme disease is a life-altering infection caused by the bacteria Borrelia burgdorferi, which can spread to humans via tick bites. There are more than 40 varieties of ticks in Canada, and many are known to carry lyme. The species that are of the biggest concern are the blacklegged tick in Eastern Canada and the western blacklegged tick in B.C.

While early signs of the disease can be fairly mild, including fever, fatigue, swollen lymph nodes and a bullseye-shaped rash near the location of the bite, later stages can cause severe headaches, arthritis, spreading pain throughout the muscles, bones and joints, difficulties with thinking and memory and facial paralysis, among other symptoms.

First tracked nationally in 2009, reported cases of lyme disease have risen greatly in the past quarter-century, to more than 5,000 in last year’s preliminary data from just a few hundred per year in the early 2010s.

“In Canada, there were only a handful of cases only a decade ago,” Millien said. “It’s not a linear relationship, it’s exponential when a disease emerges. So it’s going to get bigger and bigger, and in an exponential way. That’s the expectation.”

PHAC notes that cases are often underreported because they go undetected, possibly even to those infected with the disease. Case counts can vary annually due to underlying weather, trends in outdoor activity among humans and prevention efforts by public health authorities, they say.

Anyone who develops symptoms after a tick bite, or does after visiting a high-risk area for tick-borne lyme, is advised to contact their heath-care provider. Treatment with antibiotics is most effective soon after exposure, posing the best chance of recovery, though symptoms may persist after treatment is complete, PHAC says.

How to remove a tick

George Chaconas is a professor at the University of Calgary’s Cumming School of Medicine who studies the bacteria that causes lyme disease.

“If you’re in an area known to have ticks, protect yourself,” he told CTVNews.ca by phone. “Wear light-coloured clothing, so if you pick up a tick, you can see it. Tuck your pants into your socks. You may look a little bit funny, but if you do that, if a tick gets on your foot and crawls upwards, which is what they do, it’s not going to get under your pants and crawl up to your groin or somewhere else.”

Insect repellants can also help. If bitten, Chaconas says it’s important to quickly but carefully remove a tick by the head without squeezing its body. You can then upload a picture of a tick to eTick.ca to have it identified.

“If it’s been less than 24 hours, then chances of picking up Lyme disease are very low because Lyme is usually not transmitted until 24 to 48 hours after the tick bite,” he added. “If it’s been on for longer than that, you can also usually tell by what the tick looks like. If it’s big and fat and full of blood, then it’s been there for a while.”

Related:

• Camper warning others after being swarmed with ticks at Alberta provincial park
• Lyme disease patient shares harrowing story of the daily impact of the disease
• Are tick populations rising in Ontario?
• Tick lodged in young woman’s ear leads to sudden hearing loss and vertigo
• Nova Scotia warns residents of growing tick population as temperatures rise