Climate change increasing range and number of ticks

It’s not just mosquitoes that people should be on the lookout for this summer.

Tick season is upon us, and a recent report by the Public Health Agency of Canada adds that climate change is increasing the population and spread of the bug.

Robbin Lindsay of the National Microbiology Lab in Winnipeg said overall temperatures are increasing in Canada and that allows ticks to survive more and spread the ranges of their habitats.

“What (climate change) is leading to is in areas where the ticks are present already, that’s increasing their abundance,” said Lindsay, who co-authored the Public Health Agency report released April 4. “It’s also resulting in giving a capacity for them to spread to more northern latitudes.”

The biggest thing that Lindsay warns about is the spread of the black-legged tick, which carries Lyme disease.

Although the black-legged tick is rarely present in Saskatchewan, the spread of its population means it’s not too far off.

“The range change in 20 years has been extremely striking,” said Lindsay, who added that black-legged ticks now exist throughout Northern Ontario, Quebec, New Brunswick, Nova Scotia and into Manitoba.

Twenty years ago the tick only existed in Southern Ontario. Saskatchewan is likely to see the spread of the tick at some point.

“There are certainly areas of Saskatchewan that parallel Manitoba in terms of suitable habitat (and) acceptable climate, so we don’t anticipate that it’s (only) going to happen — it’s just a matter of when,” said Lindsay.

Lyme disease is the most common illness that ticks carry, which Lindsay says poses the greatest risk to humans.

“If a person is bitten by a tick, they’re most likely to be exposed to (Lyme disease),” said Lindsay. “The number of ticks that are infected with Lyme disease vary from location to location and can be as little as 10 per cent in a given location, but once populations become established it can get much higher, in the 50- to 60-per-cent range.”

Lyme disease rates in Saskatchewan are low, mainly because of the low numbers of black-legged ticks. Any rates of infection that have been recorded are due to travel outside of the province.

However, the rate of Lyme disease infections has been increasing dramatically nationwide. 2009 had a probable rate of infection of 144 per 100,000. The latest data from 2016 indicates a rate of 992 per 100,000.

The black-legged tick is not alone in its expansion, however. Lindsay added that the populations of all tick species have been increasing across the country.

Tick species in Saskatchewan are most commonly the American dog tick and the Rocky mountain wood tick.

“A group at the University of Saskatchewan has been studying these ticks and we have seen a range expansion in a northward direction with those populations; we’ve also seen that in Manitoba as well,” added Lindsay. “The American dog tick, for example, has moved into areas it was never found in before.”

With the effects of climate change increasing across the country, Lindsay said he expects to continue to see a range expansion in a number of species, especially into Western Canada, as well as the probable introduction of other exotic tick species.

“As the climate becomes more amenable to species that are used to more temperate climate, and as our climate becomes more temperate, we’ll have an opportunity for ticks like the Lone Star tick or even the Asian longhorn tick to be introduced and maintained within Canada,” Lindsay said.

Lindsay added that ticks are out in any weather that is above 5 C. As a result of climate change, temperatures are generally warmer and therefore expand the time period for which ticks are active.

“At the end of the day, that results in potential exposures to a larger number of individuals across Canada,” said Lindsay, who added the biggest thing is for people to be educated about ticks and the spread of Lyme disease.

Preventative measures include wearing long-sleeved clothing, bug repellent and removing any tick that latches on within 24 hours.

Lindsay added that public health is also doing surveillance to understand what tick species are in what region and working with physicians to be aware of what tick pathogens exist in a local area.