You may think the end of summer heralds the ends of tick season, but one expert says that’s “definitely a myth” she’d like to break. In fact, Katie Clow says fall is the prime season for adult black legged ticks — feared for their ability to carry Lyme disease.
“October into November, sometimes in December, if you have a nice warm fall, is peak adult time,” explained Clow, an assistant professor in the department of population medicine at the Ontario Veterinary College at the University of Guelph.
That’s because the adult black legged tick is “very reliant on humid conditions” and struggles in hot and dry weather during the summer, said Clow. “If it gets too dry, it can die.”
Each kind of tick prefers a different environment, she explained. But because of its draw to humidity, the black legged tick is often found in forested areas, where there’s a layer of “leaf litter” on the ground to hid in when they aren’t feeding, and a plethora of hosts — like white mice for nymphs and white tailed deer for adults — to attach to.
And although people are more likely to cover up with long sleeves and pants in the fall, Clow said people should still conduct “tick checks” after spending time outdoors.
“Think about sort of the line where our socks meet our pants, or our wrist line, where ticks can crawl up. We don’t really feel ticks, unless they’re particularly large, they’re kind of sneaky that way, ” said Clow. “It’s really easy for them to go unnoticed. That’s why doing a good tick check is important.”
Range of black legged tick expanding
Meanwhile, as the temperature warms up, black legged ticks are being found further and further north.
“We’ve seen range expansion … which has been associated with climate change,” said Clow.
A tick needs to feed before growing to the next stage of its life cycle: from larva to nymph, from nymph to adult, and then on to reproduction. But, as Clow explained, the black legged tick can’t develop fast enough in the cold, and will run out of its energy stores.
“Previously, in more northern areas, the climate was never warm enough to allow that tick to develop from life stage to the next, before it starved.”
Before the 1990s, Clow said there was a population of black legged ticks at Long Point Provincial Park.
New populations were found on the north shores of Lake Erie and Lake Ontario, and in recent years Clow said there’d been rapid spread of the black legged tick in parts of eastern Ontario, Toronto, Niagara, Hamilton, and as far north as Penetanguishene, Kenora, and Rainy River.
More than 200 ticks submitted for testing
According to the Region of Waterloo Public Health, people submitted 282 tick and tick queries between January 1 and August 31.
Of those ticks submitted, 185 were dog ticks and 33 were black legged ticks — six of which tested positive for Lyme disease but a health unit spokesperson said only one of those came from the area.
In that time frame, one lone star tick and one ground hog tick were also submitted for testing, however the lone star tick also did not originate in the area.
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Toronto is considered a risk area for Lyme disease.
Check out Public Health’s map of risk areas in Ontario. It’s not the kind of map any city wants to be on, but the deer tick has been found in sufficient numbers in parts of Toronto, to put us on it. Comparing the maps for 2016 through 2019, you can see that ticks continue to expand their feeding grounds. They’re now in Hamilton, York region, Kenora & near Orillia where they weren’t established previously. Ticks expand their territories at a rate of about 46 km/year. And where there’s a black-legged (deer) tick, there’s the potential for that tick to carry the bacterium (Borrelia burgdorferi) that causes Lyme disease. (Click on the 2019 map to see a larger version of it.)
Interested in how Toronto is faring where ticks are concerned? Click here for more information about the city’s tick surveillance program: Backlegged tick surveillance – City of Toronto. This website includes a link to the map shown below as well as data on the number of ticks found in different parts of Toronto. In 2018, about 35% of backlegged ticks in the Rouge Valley tested positive for Borellia burgdorferi (the causative agent of Lyme disease).
By the way, you’re invited to be a citizen scientist & help Dr. Scott Weese of the University of Guelph with his tick surveillance efforts by submitting information about ticks you find on your pet here: https://uoguelph.eu.qualtrics.com/jfe/form/SV_8J12G5SXPBX4dTL. There’s lots of other useful information at this website as well, including some of the latest research on the subject.
Note: It’s still the case that nation- & province-wide, about 1 in 5 deer ticks carry Borrelia burgdorferi. But in certain areas where these ticks have been established for a number of years, as many as 40% of them carry Borrelia. (The longer ticks are established in an area, the higher the level of disease in those tick populations. Gananoque, Kenora District, & Wainfleet Bog have some of the highest level of disease in their tick populations.)
As more information becomes available about the numbers of ticks carrying Borrelia in our area, we’ll keep you posted, but in the meantime, you can assume that at least 20% of our deer ticks are carrying the bacterium.
Tick activity is temperature-driven, not seasonal.
Any day it’s 4ºC or higher (or to be on the safe side, let’s say above freezing [0 ºC]), ticks come out of hiding in search of a meal. We’ve been monitoring weather patterns for a number of years now, & it’s become clear that while the weather is unpredictable, you can count on ticks being active through the winter. Take this winter, for example. One day, the temperature went from a balmy 11.8ºC to a frigid -6.9ºC within a week in mid-January. Almost 90% of January saw temperatures above 0 ºC and almost 20% of the month saw temperatures above 4 ºC. The calendar below shows that there was potential for plenty of tick activity — in the dead of winter.
Given that Toronto is on the map as a risk area for Lyme disease, & winter months here continue to see temperatures that support tick activity, we recommend year-round tick protection to ensure your dog is covered during those warm spells that are becoming a norm through the winter.
Dr. Iz Jakubowski
Royal York Animal Hospital