Canada can expect a steady increase in the distribution of ticks that can transmit Lyme disease this year, tick monitoring and surveillance by Canadian researchers have shown.
Manisha Kulkarni, an associate professor in the School of Epidemiology and Public Health at the University of Ottawa, said tick populations, especially the black-legged ticks that can transmit Lyme disease, have been increasing in recent years.
“This year, it looks like the ticks are already out in large numbers and the tick population is steady or increasing in many areas,” said Kulkarni.
Between 2009 and 2021, provincial public health units reported a total of 14,616 human cases of Lyme disease across Canada, according to Health Canada’s tick monitoring webpage.
In 2021, the country saw an estimated 2,851 Lyme disease cases, a 76.5 per cent increase from the 1,615 cases reported in 2020.
Kulkarni said climate change is one of the driving forces behind the expansion of tick territory.
“As we have warmer temperatures over time, the ticks are able to survive at higher latitudes and move further north into new areas,” said Kulkarni.
“We can expect them to continue to spread and establish in new locations due to warming temperatures associated with climate change, especially where there is suitable tick habitat.”
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Where in Canada are ticks most prevalent?
According to the Public Health Agency of Canada (PHAC), the five major Lyme disease risk areas are Southern Manitoba, Western Ontario, Southern Ontario, Southeastern Ontario, Southern Quebec, Maritime provinces and Southern British Columbia.
A report from PHAC’s webpage in 2021 also stated the majority of locally-acquired infections were mainly reported from Ontario, Nova Scotia and Québec in the summer.
Kulkarni said ticks are easily affected by humidity and by temperature. They favour higher levels of humidity because they’re prone to drying out quickly.
“Their behaviour in terms of looking for a host tends to peak at around 25 C,” said Kulkarni, adding that ticks’ activity decreases if the weather gets too much hotter or colder than that.
“Ticks don’t live everywhere in our environment,” said Kulkarni. Ticks are confined to deciduous woodland— areas with lots of maple trees, oak trees and mixed forest areas with cedar trees, Kulkarni said.
To prevent tick encounters, Kulkarni advised taking precautions such as staying on the trail when in a wooded area.
However, anyone who does encounter ticks and fails to remove them immediately might be exposed to a tick-borne disease such as Lyme disease, which is the most common infectious disease ticks can carry.
What are the symptoms of Lyme disease?
The most common early sign of Lyme disease is an expanding skin rash caused by a tick bite, according to Health Canada.
This rash, known as erythema migrans rash, would slowly grow to more than five cm in diameter over several days.
Patients could also experience symptoms such as fever, chills, fatigue, headache, swollen lymph nodes and muscle and joint aches.
Robbin Lindsay, a research scientist at the National Microbiology Laboratory, said the key to tick-borne disease prevention is the quick discovery and removal of ticks.
“For a lot of the disease-causing agents, the ticks have to remain attached for at least 24 hours,” said Lindsay. “You can actually be bitten by an infected tick and not be infected yourself if you promptly remove them.”
“The most important thing people need to do when they’re going out is to check themselves. Check the clothing and remove any ticks that are attached and that’s the best approach to limiting your exposure to tick-borne diseases.”
People are most likely to get infected through the bite of immature blacklegged ticks called nymphs. Nymphs are about the size of a poppy seed.
Adult ticks are about the size of a sesame seed and can also transmit Lyme disease.
As species of ticks vary, not all ticks carry diseases that can be transmitted to humans, said Susan Cork, a professor at The Faculty of Veterinary Medicine at the University of Calgary.
Cork said most ticks that people are likely to come across in Western Canada don’t necessarily carry human infectious diseases.
Other tick-borne diseases include anaplasmosis, babesiosis, powassan virus and borrelia miyamotoi disease, known as hard tick relapsing fever, a 2019 PHAC report stated.
“But it’s still a good idea to get checked out to prevent transmitted diseases like Lyme disease,” Cork added. “We don’t have too many here currently in Alberta, but certainly people that are walking their dogs will be interested in checking their dogs to protect them.”
According to a PHAC pamphlet, even though pets can’t spread Lyme disease directly to humans, they can carry infected ticks into the home or yard.
“Regular tick checks and prompt tick removal are just as important for pets as for people,” it reads.
Cork said different provinces will put out alerts through their veterinary help societies about what to look for in both domestic animals and wildlife when encountering ticks.
She added that it is best to have professional recommendations from a veterinarian before purchasing tick control for pets, as some can irritate the animal.
Why is tick surveillance important?
Lindsay said there are continuous potential threats of other species of ticks from the southern U.S. finding a home in Canada.
“The ones that we’re most concerned about are Lone Star ticks,” said Lindsay. “We do see small numbers of those things coming into the country each year. But as far as we know, we don’t have populations.”
A bite from a Lone Star tick could spark an allergy to red meat as a sugar in the tick’s saliva triggers an immune response in humans according to a 2017 Global New article.
Lindsay said there is also the Asian long-horned tick established in several areas in certain northern states in the U.S., and they can cause both veterinarian and human health implications.
“To date, Canada we have not even seen any specimens of that particular tick,” said Lindsay. “But we need this surveillance network in order to keep tabs on those emerging tick-borne threats.”
Lindsay said there is a healthy population of American dog ticks throughout Manitoba and Saskatchewan, which has helped residents know how to deal with ticks. However, he said other parts of the country might have less experience with the parasites.
“I think using something like eTick will help you to educate yourself about what ticks are or where they are located,” he said.
eTick is an online public platform for image-based identification and population monitoring of ticks in Canada.
Lindsay said many different fact sheets and information are also available to the public on PHAC’s website.
“I think it’s most important that people arm themselves with education – they are aware of what makes ticks exist and where they’re found, how they (survive) and how you can prevent them – that’s going make you feel better when you go out,” he said.
“When many people find ticks on their children, they’re very concerned. There’s no reason to be overly concerned. There are ways to mitigate potential disease, but you have to know what to do.”