Warming Canada Faces Rising Infectious Disease Risks

Canada Faces Rising Infectious Disease Risks – Fifteen years ago, Ontario student Justin Wood began feeling unwell. An avid soccer player, snowboarder, and mountain biker, Wood found himself having to step back from sports and academics due to his mysterious illness.

His condition worsened significantly. “I got really, really sick, and I couldn’t do anything. I couldn’t work, function, or participate in society. It took about four or five years before I received any sort of diagnosis.”

Eventually, he was diagnosed with Lyme disease, a rare condition at the time. Back then, government statistics indicated that this tick-borne illness caused only a few hundred infections annually in Canada.

Lyme disease cases have surged by over 1,000% in a decade as the warming climate extends the range of various pathogens and risk factors northward.

Exotic mosquito species, potentially carrying illnesses like dengue and yellow fever, have established populations in parts of Ontario, according to researchers.

Scientists are also concerned that climate change will heighten the risks of foodborne microbial diseases and warm-weather-related illnesses.

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Justin Wood’s experience had a silver lining: it inspired his career. He now runs Geneticks, a private lab in Ontario that tests ticks for diseases. His work brings him into contact with many individuals severely affected by Lyme disease. “The symptoms are incredibly diverse and debilitating,” Wood said, “leaving many people heavily, heavily disabled.”

Health Canada reports that Lyme disease symptoms range from rashes and headaches to severe joint pain and memory loss. In rare instances, it can be fatal due to heart infections.

Justin Wood noted that detections of Borrelia burgdorferi, the bacteria causing Lyme disease, have been increasing by about 0.5 to 1 percent annually in his lab. This seemingly small increase is significant because the range of black-legged ticks, which carry the bacteria, is expanding. These ticks are becoming more active and living longer.

“This means more ticks are born each year, and the number of ticks in Canada will continue to increase,” Wood explained. He added that between 50 million and 175 million ticks arrive in Canada each spring on migratory songbirds.

“With more ticks, ticks in new places, and more ticks carrying dangerous bacteria, the problem grows every year,” said Wood.

Surveillance data supports his observations. A federal report indicated there were 3,147 reported cases of Lyme disease in Canada in 2021, up from just 266 in 2011.

“This increase occurred partly due to climate changes, which have led to more abundant and widespread black-legged tick populations in central and eastern Canada,” the report states. It adds that only about 1% of Lyme disease cases in Canada are contracted abroad.

Historically, Canada’s weather has acted as a barrier against many warm-weather diseases like dengue, Zika virus, malaria, and yellow fever, which are transmitted by specific mosquito species. However, conditions are changing.

Victoria Ng, a senior scientific evaluator for the Public Health Agency of Canada, explained, “With climate change, it will be wetter, with more extreme weather events, including heavy precipitation, which mosquitoes need to survive.”

Ng highlighted that in Windsor, Ontario, where she lives, there is now a small population of Aedes albopictus, or tiger mosquitoes, which are native to the tropics and subtropics of Asia.

Public Health Ontario announced the first reproducing population of Aedes albopictus in Windsor in the fall of 2016. Another exotic species, Aedes aegypti, originally from Africa, was also detected for the first time.

“These species of mosquitoes are aggressive human biters and potential carriers of dengue, chikungunya, yellow fever, and Zika viruses in warmer regions of the world,” the agency noted. At the time, it did not expect either species to survive the Ontario winter.

However, Victoria Ng explained that scientists have observed Aedes albopictus returning year-round and in various life stages in the region. “We see the eggs of this particular species to adults, indicating they’re completing their full life cycle and reproducing annually in this part of Canada,” Ng said.

This demonstrates how mosquito populations, especially those carrying exotic viruses, have the potential to remain established and expand geographically as the climate warms.

Dr. Joe Vipond, an emergency physician and past president of the Canadian Association of Physicians for the Environment, noted that mosquito-borne disease cases have been “slowly growing” over the past 20 years. “The worry is that at some point, we’ll have diseases like dengue fever or malaria that are able to come all the way up into Canada,” Vipond said.

Dr. Joe Vipond highlighted Florida as an example of the potential for disease spread due to climate change. Dengue fever, once absent in Florida, prompted a mosquito-borne illness alert in two counties last year after five cases were reported in less than a month.

However, Vipond emphasized that significant changes would be necessary for dengue fever to become a concern for Canadians. While it’s not an immediate worry, he suggested it could be a concern in a few decades.

A 2019 article in the Canada Communicable Disease Report journal stressed the need for a cautious clinical and public health response to the issue of exotic mosquitoes potentially spreading diseases in Canada. Although the short-term risk is low, climate change could facilitate the incursion and establishment of mosquito-borne diseases.

Malaria is singled out as a particular concern because it was once endemic in Canada. Historical records show malaria had a temporary presence in southern Ontario during the 18th and 19th centuries, likely brought by refugees from the American War of Independence and transmitted by local mosquitoes.

Another emerging threat is the risk of foodborne diseases associated with warmer weather. A 2019 article in the Canada Communicable Disease Report by scientists from the National Microbiology Laboratory in Guelph warns that climate change could lead to increased public health burdens and the emergence of new risks in Canada’s food chain.

The Canada Communicable Disease Report highlighted studies indicating a “strong association” between rising air temperatures and infections caused by various pathogens like E. coli, salmonella, and vibrio.

According to the report, climate change will impact the growth, survival, abundance, and distribution of pathogens throughout the food chain. Extreme weather events and ocean warming will further complicate these effects, potentially leading to an increase in food-borne diseases.

Lyme disease isn’t the only concern regarding tick-borne illnesses as the climate changes. A 2023 report from the British Columbia Centre for Disease Control identified two tick-borne parasites, Babesia odocoilei and Babesia microti, as emerging pathogens in the province. These parasites cause babesiosis, a disease characterized by flu-like symptoms.

The report emphasized that climate change is expected to facilitate the spread of these tick-borne diseases. Stefan Iwasawa, a vector specialist with the BC Centre for Disease Control, agreed, noting that rising temperatures could create favorable conditions for tick populations to expand.

The longer warm season resulting from increased temperatures could also open up new habitats for ticks as warmer climates move northward.

Stefan Iwasawa pointed out that as warm temperatures extend further north, not only will tick habitats expand, but so will habitats for their hosts, such as mice, deer, and raccoons.

Donna Lugar, a Lyme disease awareness advocate from Nova Scotia who contracted the disease in 2011, expressed concern that Canadians are too complacent about the risks. She fears that rising temperatures will lead to an increase in ticks in the province.

Lugar noted changes in Nova Scotia’s winters over the years, with fewer extreme cold spells that used to freeze everything. Her own experience with Lyme disease involved experiencing dozens of symptoms.

In response to the growing problem, she founded the Nova Scotia Lyme Disease Support Group to raise awareness about tick-borne diseases and prevention measures. However, she acknowledges the challenges of awareness-raising.

Reflecting on the situation, Lugar admitted, “At some point, I might just decide to move to a country where ticks aren’t a concern.”

Source: battlefordsnow.com

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