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When packing your bags for the cottage or campground this weekend, do not forget to bring light long sleeved clothing – and a truck or two of insect repellent.
Spring has come and gone, so welcome to the mosquito season.
How much we enjoy summer in North America depends a lot on the number of mosquitoes waiting for us outside. Their bites cause itching and their drone is annoying, but there is also concern that mosquitoes carrying dangerous diseases will knock on our door.
So what makes some years worse than others?
Is this a good year for mosquitoes?
You do not need to be an entomologist (that is, a scientific insect) to notice that the size of the mosquito population can vary from year to year. other and from one place to another.
Last June, I could not set foot in front of my home in Ottawa without being bitten. Meanwhile, Winnipeg knew its lowest number of mosquitoes in four decades.
This year is far from being free of mosquitoes, but I can at least enjoy peace for about 10 minutes before I find myself.
What is inflating and shrinking mosquito populations? In short, it's a combination of weather and climate – mosquitoes are very sensitive to their environment.
Temperature and precipitation are two major predictors of mosquito abundance, and for good reason: These two factors have a significant effect on their survival and reproductive capacity.
How much does it rain at a given moment, when it rains, how long a cold or heat episode lasts, and when it all happens, when it is time to predict what kind of mosquito season is looming.
Mosquitoes like it hot and humid
Mosquitoes, like most insects, are cold-blooded, or ectothermic. Unlike us, their body temperature closely matches the temperature of the environment (air or water) around them. If it's cold outside, they're cold. If it's hot outside, they are hot. Any time spent outside their comfort zone can slow down or stop their development or even hurt them and die.
For most mosquito larvae to grow, temperatures must be above a threshold, which varies by species, but is usually between 7 and 16 degrees Celsius.
Since the larvae are entirely aquatic, they also need a stagnant water source (like your flowerpot) that will remain until they are ready to emerge as a watering hole. # 39; adults.
This means that cold or dry conditions at the right time during larval development in the spring or summer can significantly reduce the number of adult mosquitoes looking for a meal a week or two later.
Human hunters, disease spreaders
We love to hate mosquitoes, but the vast majority of mosquito species do not have a direct impact on our lives.
Mosquitoes, like most insects, are outrageously diverse: There are more than 3,000 species of mosquitoes buzzing on this planet, and only a handful of these species actively hunt humans.
And even then, only female mosquitoes feed on blood. Much more reasonable males drink the flower nectar instead.
Unfortunately, some of these mosquito species are far from being a slight inconvenience because they can carry dangerous diseases. In Canada and the United States, we often hear about the threat of West Nile virus, which is transmitted by local mosquito species and can lead to serious complications such as coma and paralysis in a minority of cases.
One of the best predictors of West Nile virus infection rates in Ontario is the minimum temperature reached in February. If the coldest temperatures in February are warmer than usual, more people are infected with West Nile virus during the summer months.
In the tropics, people face malaria, yellow fever, dengue fever, chikungunya and Zika virus. These viruses are all spread by mosquitoes, are severely debilitating and cause hundreds of thousands of deaths each year.
When Hurricane Harvey hit Texas in September 2017, flooding increased mosquito breeding habitat. Thus, the state sprayed 240,000 hectares around Houston to help prevent an increase in mosquito-borne diseases.
Read more: Viruses can cause global pandemics, but where does the first virus come from?
The fact that mosquitoes carry these diseases, rather than the mosquitoes themselves, has led the Gates Foundation to label mosquitoes the deadliest animals on the planet.
Two of the worst authors of the spread of the disease are the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus), which generally live in tropical and subtropical regions where it remains hot and humid. The range of these mosquitoes also extends to the continental United States, especially in the southern and eastern states. However, they simply can not survive the northern climates with long, cold winters.
Tinkering with the climate
Low winter temperatures usually prevent tropical and subtropical insect species from establishing permanently in areas closer to the poles where winters are cold. However, in recent decades, climate change has resulted in documented changes in patterns of distribution of insects, including the collapse of the southern range boundaries of drones and the shift to the north. many areas of insects.
As winters become milder, the northern boundaries of mosquito ranges may also change. The displacement of the northern boundaries is thought to occur because milder winters allow species that can not usually hack into the cold to creak in winter, to breed and to settle in a new place.
Mosquito trapping programs are active around the world, precisely because surveillance and response to mosquito populations is critical to global health. In recent years (2016-2018), adult yellow fever mosquito and Asian tiger mosquito have been found in Windsor, Ontario. (near the southernmost point of Canada), suggesting that these dangerous vectors could be a serious health problem in northern climates in the future.
Fortunately, none of the mosquitoes caught in Windsor have been tested positive for a virus.
In the era of climate change, it is becoming increasingly important that we understand what environmental factors determine where insects can and will live, and to what extent they do. Understanding how insects react to climate is absolutely critical to our food security and global health.
It is only when we are armed with this information that we can accurately predict the spread of invasive agricultural pests or disease vectors, such as blood-sucking mosquitoes that even entomologists despise.
Originally published by The Conversation, an independent, non-profit source of news, analysis and commentary from academic experts.
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