Number of mosquitoes that can carry West Nile virus expected to rise this summer

The familiar buzz of mosquitoes is never comforting, but the sound could mean something more dangerous this summer.

According to the Ministry of Health, the number of Culex tarsalis mosquitoes — which can carry West Nile virus — could be increasing this season.

“The more warm days that we have, the more likely we are to start to see Culex tarsalis mosquito populations increasing across the province,” said Dr. Julie Kryzanowski, the province’s deputy chief medical health officer.

Although the number of those mosquitoes is expected to increase more than in previous summers, none have been detected yet in the province.

The number of regular nuisance mosquitoes, however, is on a significant rise since 2022. In both Regina and Saskatoon the numbers have skyrocketed since last summer.

“We have seen — I think because of the warmer, wet temperatures — more mosquitoes in and across the province,” said Kryzanowski. “Most of these are what we call in public health nuisance mosquitoes.”

The City of Saskatoon’s website says last week, there was an average of 24 mosquitoes per trap; in 2022 there were 0.82 per trap at this time of year.

In Regina, there was an average of 11 mosquitoes in each trap two weeks ago (not including rural Regina); the 2022 average was one mosquito per trap. The city didn’t have an update for last week.

Saskatoon’s current mosquito numbers. (City of Saskatoon)

Regina’s mosquito numbers as of two weeks ago. (City of Regina)

Updates will soon be up on the Government of Saskatchewan website on Culex tarsalis mosquitoes as well.

“That includes surveillance for Culex tarsalis mosquitoes as well as testing those mosquitoes, once they’re detected, for West Nile virus,” said Kryzanowski.

The surveillance program is starting this week and the weekly surveillance report will be available on the Government of Saskatchewan website starting later this month.

Kryzanowski said West Nile hasn’t been prevalent in Saskatchewan in the past.

During 2019, 2020 and 2022, there wasn’t a single human neuroinvasive case of West Nile virus found in Saskatchewan. In 2021 there was one.

Most people don’t contract a neuroinvasive case, said Kryzanowski, and often don’t feel symptoms at all. Kryzanowski said only a small number of people infected by the virus would see any symptoms at all.

“Twenty per cent of people do experience symptoms,” she said. “It can feel like a flu-like illness with a headache, bodyache, fever (and) generally feeling unwell.”

Kryzanowski suggests limiting exposure to West Nile virus by wearing loose-fitting, light-coloured clothing that covers your arms and legs, reducing any standing water in your yard, and limiting time outdoors at dusk when the Culex tarsalis mosquitoes are the most active.

She is also urging people to remember to use proper mosquito repellent when outside and ensuring all window screens in homes are tight-fitting so no mosquitoes can get inside.

“It is good advice for everyone just to take these measures to reduce your exposure to mosquito bites from any species,” said Kryzanowski.