B.C.’s thriving mosquito population not a health hazard: Entomologist

While the erratic weather has been atypical across the B.C. Interior this summer, one familiar characteristic has remained and thrived – mosquitoes.

But largely due to our public health infrastructure, mosquitoes remain a nuisance rather than a health hazard, says Sean Rollo, an entomologist with Orkin Canada.

While certain species of mosquitoes are carriers for lethal diseases in many parts of the globe — Africa, Central and South America, and tropical parts of Asia and the Caribbean – Rolle says mosquito-borne illnesses are rarer in Canada due to our climate and prevalent type of native mosquito species.

He recalled that sense of security was rattled beginning in 2002 when the West Nile virus was detected in Canada and would fluctuate up and down over the course of the next decade.

One case was reported in Ontario last week, Rolle noted, but there has yet to be any other reported cases in other provinces this year.

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After its first detection in New York in 1999, West Nile virus quickly spread across the continent, causing an epidemic of human disease and massive bird die-offs.

Today, the virus has become endemic to the United States, where an estimated seven million human infections have occurred, making it the leading mosquito-borne virus infection and the most common cause of viral encephalitis in that country.

He said the lesson from the West Nile virus that applies today to the COVID-19 pandemic, is to not “take our foot off the gas” on preventative public health measures until the virus has completely dissipated.

“That’s where you see those spikes that occur with COVID. The numbers might be low but it’s not wiped out so it can come back,” Rollo said.

“We hope to see that a major disease or virus is not spread by mosquitoes across Canada. If that were to happen, how we deal with controlling their population would change. It would be a daunting challenge because mosquitoes are so effective at reproducing.”

Rolle said it only requires a little more than a thimble of dead water anywhere for females to lay their eggs, which in water evolve from larvae to adults.

“I think people now generally are aware of how stagnant water is an attractant for mosquitoes to lay eggs, but what might surprise people is how little water they require to breed,” he said.

He explained while mosquitoes are an annoyance generally from mid-May until September across B.C.’s Interior, the pesky insects to fulfill a valuable role within the eco-system, providing a food source for bats while playing a minor role in pollination.

“The male mosquitoes feed exclusively on plant pollen, while the females do rely more on blood but will visit pollinating plants as well to a lesser degree. So there is some benefit to them, mainly as a major food source for other animals,” he said.

While wearing light-coloured loose-fitting clothing and chemical repellents, particularly those based on Deet, can be effective, it can be less effective for those who profess to ‘being eaten alive’ by mosquitoes constantly.

“There is a definitive science that shows how mosquitoes are attracted to some people more than others. There are definitive locators or pheromones we give off as individuals that mosquitoes tend to hone in on,” Rolle explained.

“It has nothing to do with body odour, as we all have a unique scent we can’t detect ourselves that other animals with a more sensitive smell can pick up on. Dogs and cats can sense it and so can mosquitoes.”