Understanding and Assessing Impacts
Shifting weather patterns, changing seasonality, and increases to average temperature have resulted in changes to the conventional patterns of disease vectors. Vector-borne diseases, such as malaria, dengue, West Nile virus, and Lyme disease, are becoming more prevalent in Canada as a direct result of climate change. Warmer temperatures in Canada have resulted in the expansion of vector-borne diseases transmitted by ticks, mosquitos, and other animals. As Canada’s climate continues to warm and increases in spring, summer, and fall season length has contributed to greater distribution of these species and their life cycles.
Lyme disease, carried by black-legged ticks, is the most common tick-borne disease in Canada. Various hosts for black-legged ticks include white-tailed deer, white-footed mouse, and migratory birds. White-footed mice habitat has been expanding northward at a rate of 10 km per year, and migratory bird patterns have been expanding northward at an accelerated pace due to climate change. This, in conjunction with warmer and more temperate fall seasons has resulted in the expansion of black-legged ticks, and the establishment of populations in places previously too cold to sustain them.
Mosquitos carry a host of VBDs, including West Nile virus, dengue, malaria, chikungunya, and Zika. Of primary concern now is the transmission of West Nile, considered the most health-endangering mosquito-borne illness in Canada. Though largely asymptomatic, severe cases of West Nile can be life threatening, and climate models demonstrate a growing geographic range in the spread of West Nile in Canada. Further, the less common vectors of malaria, dengue, chikungunya, and Zika could become more likely as Canada experiences further warming.
Environmental trends related to warmer temperatures in Canada are predicted to increase the risk of acquiring Lyme and West Nile, as well as other mosquito and tick-borne diseases, and represent a public health concern in Canada, especially in at-risk populations such as those over 70, and childbearing persons.