infectious disease risks extend north

Cases of Lyme disease have now increased by more than 1,000% in a decade, as climate change pushes the limits of an array of pathogens and risk factors northward.

Populations of exotic mosquito species that can carry diseases such as dengue and yellow fever have become established in parts of Ontario, researchers say. Scientists also fear that climate change will increase the risks of microbial diseases associated with food contamination and hot weather.

15 years ago, Justin Wood, a student in Ontario, started feeling sick. He said that he took about four or five years to get a diagnosis.

When he arrived, the diagnosis was rare: Lyme disease. At the time, the tick-borne disease was responsible for only a few hundred infections per year in Canada, according to government statistics.

The experience of Mr. Wood has at least one positive point. This set him on a career path, and today he runs a private laboratory in Ontario called Geneticks. His company is dedicated to diagnosing different diseases in ticks.

He said his work allows him to meet many people severely, severely disabled because of Lyme disease. It’s very, very serious and the symptoms can be very, very diverse but very, very debilitating.

Health Canada says symptoms range from rashes and headaches to severe joint pain and memory loss. In rare cases, it can lead to death from heart infection.

Mr. Wood said the number of detections of Borrelia burgdorferi, the bacteria that causes Lyme disease, has recently increased in his lab by about 0.5% to 1% per year.

It doesn’t sound like much, but the range of blacklegged ticks carrying the bacteria is expanding; they become more active and live longer, he said.

This means that more and more ticks are being born every year and the number of ticks in Canada will continue to increaseexplained Mr. Wood.

You have more ticks, you have ticks in new places, you have more ticks carrying dangerous bacteria, and it becomes sort of a growing problem every yeardetailed Mr. Wood.

Mr. Wood’s company is dedicated to analyzing ticks. (Archives) Photo: Oleksandr Yuchynskyi

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

This [augmentation] has occurred in part due to climate change, which has contributed to increases in the abundance and geographic distribution of blacklegged tick populations in central and eastern Canadaspecifies the report, adding that approximately 1% of cases of Lyme disease in Canada were contracted abroad.

Canada’s weather conditions have already served as a barrier against many warm-weather illnesses, such as dengue fever, Zika virus, malaria and yellow fever, all of which are carried by certain species of mosquitoes.

But conditions are changing, said Victoria Ng, senior scientific evaluator at the Public Health Agency of Canada.

With climate change, the weather will be wetter, with more extreme weather events, which could be extreme precipitation, and mosquitoes need water to be able to surviveexplained Ms Ng.

Ms. Ng noted that in Windsor, Ontario, where she lives, there is now a population in small numbers of Aedes albopictus, known as the tiger mosquito, native to tropical and subtropical regions of Asia.

Ontario Public Health announced the detection of the first breeding population of Aedes albopictus in fall 2016 in Windsor. Another exotic species, Aedes aegypti, native to Africa, was also detected for the first time.


The Aedes aegypti mosquito can transmit Zika, as well as dengue and chikungunya. (Archives) Photo: Associated Press/James Gathany

These mosquito species are aggressive biters of humans and potential vectors of dengue, chikungunya, yellow fever and Zika viruses in warmer regions of the worldthe agency said.

At the time, the organization said it did not expect either species to survive the Ontario winter.

However, Ms Ng said scientists not only saw Aedes albopictus returning to the area all year round, but also observed them at different life stages.

We see the eggs of this particular species becoming adults, which means they have a full life cycle and reproduce year after year in this region of Canadasaid Ms Ng.

She said this was an example of a mosquito population, especially those carrying exotic viruseshaving the potential to continue to remain established, but also to expand geographically due to global warming.

Dr. Joe Vipond, an emergency physician and former president of the Canadian Association of Physicians for the Environment, said the number of cases of mosquito-borne illnesses has increased slowly over the last 20 years.

What is worrying is that at some point we will be faced with diseases like dengue or malaria that could spread to Canadasaid Dr. Vipond.

He cited the example of Florida, where dengue fever did not exist in the past. But last year, the U.S. state Department of Health placed two counties under mosquito-borne disease alert after five cases of dengue fever were reported in less than a month.

It would be necessary to radical changes for dengue to become a concern for Canadians, he said, adding that it was not a current concernbut within a few decades.

A 2019 article published in the journal Report of Communicable Diseases in Canada indicated that while there was no evidence of disease spread in Canada via new populations of exotic mosquitoes, the problem required a cautious clinical and public health response.

Although the short-term risk of incursion and establishment of exotic (mosquito-borne) diseases into Canada, facilitated or exacerbated by climate change, is very low, it is feasible.

He said malaria was particularly worrying because the disease was once endemic in Canada.

The concern of foodborne illnesses

A more current threat is foodborne illness associated with hot weather.

As climate change continues and/or intensifies, it will increase the risk of negative impacts on food security in Canada, ranging from an increased burden on public health to the emergence of currently unseen risks in our food chainsaid a 2019 article in the Report of Communicable Diseases in Canadaby scientists from the National Microbiology Laboratory of Guelphin Ontario.

He cites studies showing a strong association between increasing air temperatures and various infections with E. coli bacteria, salmonella and Vibrio bacteria.

>>>>>>Microscope view of E. coli bacteria>>>>>>

The number of E. coli infections could increase. (Archives) Photo: iStock

Growth, survival, abundance and diversity of pathogens will be affected by climate change throughout the food chainthe report says.

Extreme weather events and warming oceans would also complicate the effects on the food chain and ultimately lead to more foodborne illnesses, the report said.

Lyme disease isn’t the only tick-borne pathogen that worries scientists, as climate change expands the range of carriers.

A report released by the British Columbia Center for Disease Control in 2023 indicated that two types of tick-borne parasites, Babesia odocoilei and Babesia microti, were recently emerging pathogens in the province. They cause babesiosis, an illness with flu-like symptoms.

Climate change can be expected to facilitate the presence of these tick-borne diseaseswe can read in the report.



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