As per Public Health Ontario, all of Toronto is an established risk area for blacklegged ticks — the ones that carry Lyme disease.
The City of Toronto conducts its own blacklegged tick surveillance program known as “tick dragging” in the fall of each year. The city’s active tick surveillance map is updated in the spring — when ticks actively seek a host — once lab results come back from the National Microbiology Laboratory.
Since the program began 12 years ago, the number of ticks in the city and cases of Lyme disease have been increasing, as per the city’s Associate Medical Officer of Health. However, tick dragging results are not used for forecasting and they’re not predictive of whether this tick season will be better or worse than the ones prior.
“[Tick dragging] is not really about telling us what happened or what’s going to happen. What we’re doing is using it to get a better idea of what areas in the city there are ticks in and how much Lyme disease the ticks carry in those areas. So even though all of Toronto is considered a risk area for Lyme disease, the risk isn’t equally the same [everywhere],” said Dr. Howard Shapiro.
Surveillance is carried out in a number of areas that are wooded or brushy with tall grass and foliage close to the ground. Areas where tick dragging takes place can change year-over-year and the City says locations are selected “based on suitable blacklegged tick habitat or a previous confirmed finding of a blacklegged tick.”
The ticks are then tested for the Borrelia burgdorferi bacteria that causes Lyme disease as well as five other pathogens: Borrelia miyamotoi, Anaplasma phagocytophilum, Babesia odocoilei, Babesia microti and Powassan virus.
In the fall of 2023, tick dragging results showed that 121 blacklegged ticks were tested from the areas surveilled across the city. A total of 43 tested positive for the bacteria that causes Lyme, with five of those testing positive for one or more of the other pathogens as well.
In the fall of 2024, 57 blacklegged ticks were tested from across the city. A total of 25 tested positive for the bacteria that causes Lyme, with two of those testing positive for one or more of the other pathogens as well.
While the total numbers may seem lower this season, Shapiro reiterates that does not mean the risk is any lower as the areas in the city that are surveilled vary every year.
For example, he says it’s been established that ticks are prevalent in ravines in the east of the city, so they might not necessarily surveil those same areas every year to gather comparative data.
“What we’re trying to do is look for new areas in the city where Lyme disease is occurring and occasionally we might go back to the [established] areas to check,” he said.
“We go to other areas like certain ravines or parks where we think there might be ticks but we haven’t found them so far, to try and see if they’re starting to show up.”
He added the tick dragging numbers are only a representative sample and should not be taken at face value.
“We’re only going to a place once for a number of hours — we’re going there one time. So that doesn’t mean that we’ve completely vacuumed up all the ticks in the area — it’s just a sample and it gives us an idea of what’s around,” he said.
“But that doesn’t mean there aren’t ticks there if we didn’t find them. It probably means they’re not there at a high level, but that doesn’t equate to zero ticks [in that area].”
One location that stands out in both 2023 and 2024 for number of ticks found and number of ticks that tested positive for Lyme disease causing bacteria is the Rouge Park area.
However, Shapiro cautions that people should stay vigilant whenever they are in more naturalized areas of the city.
“When you’re in those areas, try to stick in the center of the trail as best you can. Don’t venture off the trail into the woods or the grasses or anything like that, because that’s where the ticks are going to be,” he said.
“You can use an insect repellant that’s approved by Health Canada … it lessens the chance that the ticks will climb on you. You can wear long pants and long sleeve shirts that are light in colour so that way the ticks won’t get on your skin and you’ll be able to see them if [they get on you].”
Another simple preventative is taking a shower as soon as you can if you’ve been in an area where ticks might be present. You should also check yourself thoroughly, especially in areas like behind the knees, groin and around the hairline.
At home, Shapiro suggests keeping the grass trimmed and avoiding the piling up of leaves or grass that might give ticks a place to thrive. Children’s play equipment should be placed on wood chips or gravel which ticks don’t typically inhabit.
If you do find a tick attached to you, Shapiro says the chances of getting Lyme disease are very low if removed within 24 hours.
There is also a preventative treatment that is effective up to 72 hours after you’ve been bitten that can help avoid contracting Lyme disease.
“It is one dose of an antibiotic, and you can get that from a doctor or a pharmacy in Ontario,” he said.
Lyme disease is often characterized by a bulls eye shaped rash around the tick bite mark that tends to spread, although it might not always show up.
“Just because you don’t have a rash, or the rash doesn’t fit that pattern, it still could be Lyme disease,” he said.
Shapiro added that if a physician suspects you have Lyme disease, they will normally treat it regardless of testing for it. When caught early, Lyme disease can be successfully treated with a two week course of oral antibiotics.
“Where it gets more complicated is when it goes unrecognized and then weeks to months later you get a form of Lyme disease that can affect the nervous system, the heart, your joints — and then the treatment is longer and more complicated.”
Why are the number of ticks in Toronto trending upwards?
Shapiro says just over a decade ago, Toronto was not home to blacklegged ticks known to cause Lyme disease. While the occasional tick may have hitched a ride on a traveller, they were not a self-sustaining population prior to 2013.
However, that changed with the rise in global temperatures, which made the area fertile ground for their growth.
“This has been predicted for a long time by scientists associated with the Public Health Agency of Canada and Health Canada. They were able to look at what the predicted temperatures were and how that affects ticks and Lyme disease and forecast that, while Lyme disease wasn’t here in Toronto and most of Southern Ontario, that it would come here,” he said.
“The reason is that when the climate is warming, that allows the ticks to complete their lifecycle. A longer period when it’s warm allows the ticks to sustain themselves. When we had colder weather, there just wasn’t enough time for the ticks to lay eggs, develop, take a blood meal et. al. in the [short] time period that we had when things were warm enough. And now that things are warmer [overall], they’re able to do that.”
Ticks generally thrive in temperatures of 4 degrees Celsius or higher. In the coming years, Toronto is expected to be hotter and experience more heat events.
“It is projected that by 2040-2050, the city can expect to experience approximately 66 days with maximum temperatures above 30°C,” according to the City of Toronto.
