Mosquitoes rise up with warmer temperatures
How climate change is creating an environment for mosquitoes to multiply in Canada
April 7 marks the annual World Health Day. The campaign’s 2022 slogan is “our planet, our health” emphasizing that combating climate change and protecting the planet is vital to our health.
Climate change has many impacts, both direct and indirect, on our health. One indirect impact is through a small insect that can either leave you with a small itchy bump or a life-threatening disease.
Many animals, insects and plant species are on the endangered species list as rising temperatures have resulted in habitat loss. But for mosquitoes, climate change is creating a productive environment for them to thrive. Climate change provides mosquitoes with a longer breeding season, shortens the life-cycle reproduction rate and increases the replication process of the pathogens they carry inside them.
Prolonged mosquito season
In the last two decades, mosquito-related diseases have increased by 10 per cent in Canada. The increased temperature and humidity are the main drivers that contribute to higher mosquito numbers. There has been a steady temperature increase in the past 70 years, leading to at least a 1.5 °C increase during all seasons. In Canada, mosquitoes are present starting in May until early September. Warmer temperatures could mean the potential for prolonged mosquito seasons is on the horizon.
Mosquito development changes
Temperature can influence mosquito physiology and life cycle. The life cycle of a mosquito begins as an egg, which hatches when exposed to water. While still in the wet environment, within two days, the egg becomes a larva, then the larva skin splits and the pupa develops. The pupa is an immature transition phase where it does not feed on blood but can move in the water. Only once it develops into an adult, the mosquito becomes an active flying insect that can feed on blood. Depending on the mosquito species and environmental conditions, the average life cycle of a mosquito from egg to adult can range between six to ten days.
The larvae and pupae stages are a critical time for survival. The typical temperature range for survival is from 16°C to 38°C. It has been documented that as temperature increases, the immature stages of development decrease and the adult stage comes quicker. For example, the Aedes aegypti speciestakes about 40 days to grow from egg to adult at 15°C, but only takes 7.2 days at 35°C.
As adults, some mosquito species fly better at certain temperatures, between 15 to 32°C, which helps them to find food and reproduce. Temperature directly influences when the mosquitoes have the first blood after growing out of the pupae stage. Mosquitoes living in a higher temperature environment have their first blood meal within 48 hours and will begin to lay eggs sooner.
Virus inside benefit
The insatiable itch and tingling sensation on an area of your skin is the least of your worries after being bitten by a mosquito. Some mosquito species are deadly and can spread life-threatening diseases including West Nile, Zika or Lyme disease. Mosquitoes can pick up vector-borne diseases when injecting the proboscis, or mouthpart that pierces the skin and sucks the blood of infected victims. The viruses that are contained within their bodies can replicate as the mosquitoes’ numbers increase.
Virus copies increase with temperature as well, and transmission of the viruses also increases with increased viral copies. Foreign mosquito diseases may emerge over time as climate change can lead to the geographic expansion of these viruses across the globe. The migration of humans, animals or changes to the physical environment due to climate change will expand the landscape of viruses.
Our Planet, Our Health
The reality is that humans live on the same planet that mosquitoes do. As the climate change crisis worsens, the mosquito population will steadily rise. They will continue to feed on humans and wildlife. With every bite, there is a chance of spreading some life-threatening diseases.
The change in the mosquito ecosystem is one example of how climate change is negatively impacting human health. Changes to the earth and its creatures will reveal how deeply human and ecological health are interconnected.
Rebecca is an interdisciplinary researcher and science communicator. She has a diverse research background ranging from pedagogy, medical education and cardiology.
Currently, she is a research assistant in the Department of Medicine at McMaster University. In her spare time, she enjoys writing blogs and creating digital content.