Ticks, mosquitoes and fleas are expanding in Canada

University of Toronto epidemiologist David Fisman explains why


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Ticks carrying Lyme disease are spreading due to warmer temperatures

According to an African proverb (and the Dalai Lama), “If you think you’re too small to make a difference, try sleeping in a closed room with a mosquito.” 

The saying implies that even when we feel insignificant, we can create a buzz. But mosquitoes and other tiny critters can have a huge impact. An insect no bigger than a grain of rice, fortified by climate change, has devastated forests in British Columbia. Warmer winters have allowed the mountain pine beetle to move north and survive and thrive in places where cold temperatures once halted them.

Researchers have found that ticks, fleas and mosquitoes are also moving into new territories, in part because of climate change.

The U.S. Centers for Disease Control and Prevention found vector-borne diseases spread by parasitic insects and arachnids more than tripled in the U.S. over 12 years — from 27,388 cases in 2004 to 96,075 in 2016.

Although the report only looked at disease increases, experts say climate change is a factor. 

University of Toronto epidemiologist David Fisman told E&E News (republished in Scientific American) that black-legged ticks carrying Lyme disease — which can impair motor function and cause memory loss, even death — are showing up in parts of Canada where they haven’t been seen before.

In the past, “They just didn’t have the ability to establish local tick populations because it simply was too cold for them to complete their life cycles,” Fisman said.

A disease-carrying mosquito, Aedes aegypti, is also expanding throughout the continental U.S. and is now common in 38 states. 

Yet another arthropod, the lone star tick, causes a severe lifelong immune response to meat, called “alpha-gal allergy.” When a tick bites, it spreads the alpha-gal sugar molecule through its saliva into the human’s blood. As a Grist article explains, “Then, the molecule essentially rewires the body’s immune system, prompting it to produce an overload of alpha-gal antibodies.” The life-threatening reaction hits infected people several hours after they eat meat.

An article in the Lancet says, “Under current predictions of climate change, mosquitoes such as Aedes aegypti and Aedes albopictus are expected to increase in both distribution and ability to transmit diseases such as dengue, Zika, and yellow fever.”

The article also says increasing cases of dengue and spread and intensity of cholera have been “directly linked to climate change.” 

Parasite and disease proliferation that comes with accelerated global warming is a collective problem we must work together to resolve. 

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David Suzuki is the host of the CBC’s The Nature of Things and author of more than 30 books on ecology. 

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