Mosquitoes are quiet in Edmonton this summer, but one invasive species has grown
Edmonton is seeing fewer mosquitoes prowl the city this summer. But experts say a new species that harbours the West Nile virus has been creeping its way into the province in recent years.
"We actually have fairly low numbers of mosquitoes," Mike Jenkins, a senior scientist with the City of Edmonton, told CBC.
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"We had very little snowfall that turned into development habitat for the mosquitoes, and then that resulted in very low numbers for the early spring and even into May."
Jenkins said that even with the city seeing rainfall in June, it did not do so in large enough amounts that would create habitats for mosquitoes.
"A lot of the rain that did fall got absorbed by the thirsty ground and the thirsty plants."
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The new kid on the block: Culex pipiens
Edmonton has about 30 different species of mosquitoes.
Culex pipiens has made its way to Alberta in recent years and was detected in Edmonton in 2018.
The species is the primary vector of West Nile virus in North America, Jenkins says.
"We're doing monitoring programs specifically targeting Culex pipiens and figuring out exactly where those are developing," Jenkins said.
"Their population is more driven, actually, by heat than by precipitation, and we have been seeing an increase in the numbers of both Culex pipiens and Culex tarsalis, another heat-loving mosquito species following our summer heat numbers."
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The City of Edmonton has a ground control program that targets roadside ditches and other ground habitats where mosquito larvae can develop.
The program specifically targets larvae to minimize the impact on the ecosystem to ensure adult mosquitoes can remain as a food source option for other insects and animals.
John Soghigian is an assistant professor and veterinary entomologist who focuses on mosquitoes at the University of Calgary.
Soghigian said mosquito numbers are tied heavily to local weather conditions with Calgary seeing increased numbers in July with rain.
Culex pipiens, which is an invasive species, thrives in urban environments with drought conditions.
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"It hasn't been here long enough for us to know exactly what it could do to West Nile transmission," Soghigian said.
"West Nile seasonally in Alberta generally, will get relatively low numbers of cases. And then every five to 10 years there'll be a relatively high spike."
The last big spike was in 2018, which saw 437 human cases of West Nile virus in Canada with about 50 cases in Alberta.
Nine cases of the virus were detected in the province in 2023 according to Alberta Health Services.
"We're a little bit concerned that we could be seeing another uptick this year, but it's too early for us to say, because West Nile transmission usually doesn't occur to mammals until later in the season," Soghigian said.
Further complicating matters is climate change, Soghigian said.
"West Nile is a disease we expect to get worse under climate change scenarios," Soghigian said, referencing the growing prominence of droughts.
"We do, unfortunately, expect that with ... climate changes, we'll see more West Nile and certain mosquito species becoming more abundant, too."
Thumbnail courtesy of francok35/Pixabay.
The story was originally written by Mrinali Anchan and published for CBC News.
