Dose20:22Why should I worry about mosquitoes?
Melanie Klimkowski, a teacher from Belle River, Ontario, never worried about mosquitoes because they didn’t seem interested in biting her.
She says that after learning more about insects at a special workshop for eighth-grade students, she always carries a small amount of mosquito repellent with her to make sure the arthropods stay away.
“Like hand sanitizer, I keep a little bit of oil in my purse just in case,” Klimkowski said.
Experts say mosquito-borne disease infection rates in Canada are very lowHowever, changing environmental factors — including climate change — are altering the way mosquitoes live and reproduce, and creating additional opportunities for infected mosquitoes to bite humans and increase the risk of disease.
A Closer Look at Mosquitoes in Canada
According to Brock University entomologist Fiona Hunter, Canada is home to more than 80 different species of mosquitoes. They can be found in every province and territory.
Not every mosquito carries diseases that infect humans. Mosquitoes Culex, Culiseta, Anopheles AND Ochlerotatus are among the most common species of mosquitoes in Canada.
The typical mosquito breeding season lasts from April to September, although Hunter says some mosquitoes can survive the winter.
This this process is known as diapause —similar to hibernation in mammals—these animals find hiding places like sewers or subway systems to slow down their development.
Adult mosquitoes are capable of surviving the winter, but according to Hunter, they are more likely to overwinter their eggs, or survive the winter, than the adult insects.
“If you have a wood stove and all of a sudden mosquitoes start flying around, they’ve actually spent the winter in your wood pile,” Hunter said.
Mosquitoes tend to breed in standing water, so experts advise emptying unused buckets in garages or even emptying saucers under flower pots in yards to avoid providing the insects with a place to breed.
Of many mosquito-borne diseases Hunter says West Nile virus, eastern equine encephalomyelitis (EEE) and the California serogroup are most prevalent in Canada but are still rare.
West Nile virus is the most common mosquito-borne disease in Canada, spread by mosquitoes of the genus Culex type.
Public health authorities report between 40 and 200 human cases each year, according to infectious disease specialist Dr. Sumon Chakrabarti. That number is comparable to numbers in other parts of the world, where the disease circulates more often because of tropical climates, Chakrabarti says.
“In 2007 in particular, we had 2,400 cases across Canada,” he said. Dose host Dr. Brian Goldman.
Chakrabarti said weather conditions, a higher number of infected birds and heavier rainfall last year likely contributed to the higher than usual number of cases.
By comparison, as of August 26, there have been 13 confirmed human cases of West Nile virus infection in Canada in 2024.
Provinces and territories are also monitoring mosquitoes for infection by testing mosquito traps in pools set up by public health units. This year over 260 pools in Canada they were diagnosed with West Nile virus.
The type of mosquito that carries West Nile virus, Culex pipiens, thrives in standing water in cities. It has been shown that they can survive prairie winters as well.
Eastern equine encephalomyelitis (EEE) is less common in Canada than West Nile virus; Hunter estimates there has been one reported human case in the past two decades.
According to US data, approximately 11 cases of EEE are reported in humans each year. Centers for Disease Control and Prevention.
Mosquitoes spread disease by feeding on the blood of infected animals, such as horses, sheep, and birds. As the virus develops in the insect, it is transmitted through the mosquito’s saliva when it bites uninfected hosts, including humans.
Chakrabarti says it’s not entirely clear why some people are magnets for mosquitoes while others are less likely to get bitten.
“Part of it is pheromones, the composition of the bacteria on the skin and body heat,” he said, adding that body weight may also play a role.
“People who are usually a little bigger give more of themselves [carbon dioxide]“- he said, because female mosquitoes have receptors that detect the gas we exhale.
Mild symptoms resemble colds and flu.
People infected with West Nile virus They usually show flu-like symptoms such as rashes or muscle pain, Chakrabarti says.
“When you see this in the hospital, it’s often people who come in with high fevers and, in particular, headaches,” he said.
Chakrabarti says many people who have mild illness with West Nile virus usually recover.
The animals we share our cities with could be moving because of climate change. A new Canadian study says pests like ticks and mosquitoes could become more common, and creatures like the blue jay could become less common.
“It doesn’t change the fact that we should be aware of it,” he said.
There are no specific treatments or vaccines for West Nile virus. There is no approved vaccine for EEE.
“It’s something that’s typically monitored and treated supportively,” Chakrabarti said, including managing fever and muscle aches, as well as seizures that can occur with more serious infections.
Climate change means longer breeding seasons
Hunter says that despite low infection rates, climate change is causing changes in Canada’s mosquito population and the introduction of new species.
She cited the tiger mosquito as an example of a tropical species that was recently spotted in the Windsor-Essex region of Ontario, adding that it is a potent vector for transmitting more dangerous diseases, such as the Zika virus.
This mosquito was first identified in Windsor-Essex in 2016. according to the Public Health Agency of Canadaand was regularly recorded in the region between 2018 and 2023.
The Zika virus spreads when a mosquito bites an infected person and then transmits the virus to an uninfected person through another bite.
Hunter says public health units have not found positive Zika cases among humans or mosquitoes in Windsor-Essex because “those mosquitoes were not biting people who already have Zika.”
However, if a tiger mosquito bites someone who has unknowingly brought the Zika virus from abroad, it could lead to an increase in infections.
“But it’s not a big risk,” Hunter explained.
How to protect yourself
Chakrabarti recommends wearing long-sleeved shirts and pants, avoiding brightly colored clothing that attracts mosquitoes, and using insect repellent to ward off these pesky insects.
Longer spring and fall seasons due to human-induced climate change also mean mosquitoes have more time to breed. At the same time, warmer weather leading to more precipitation means mosquitoes are more comfortable in Canada, despite cold winters.
“Climate change has led to the heavy rainfall that we’ve had, and when that happens, the populations of species that have always been here just explode,” Hunter said.
Hunter adds that flood mosquitoes Mosquitoes can bite during the day, as well as at dawn and dusk, when other mosquito species are typically more active.
“Of course the whole public message is: stay protected at dusk and dawn,” she said.
“You should also protect yourself from that little mosquito carrying flood water in a year where it’s hot and you have so many floods.”
