Canadian mosquito tests for Zika virus transmission begin

A Canadian insect scientist is now growing Zika virus in a university containment lab to test if homegrown mosquitoes could be affected.

Medical entomologist Fiona Hunter of Brock University in St. Catharines, Ont. has received a sample of the virus from the National Microbiology Lab in Winnipeg this week.

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Hunter's team will initially test the virus, originally from Thailand, on a dozen species of mosquitoes at a high-level containment lab to see whether Canadian mosquitoes are able to become infected and transmit the Zika virus by bite or if females pass it on to their eggs.

"We don't have to wait until some traveller comes back to Canada with Zika virus and gets bitten by a local mosquito and wait on tenterhooks to see whether or not there will be local transmission," Hunter told a media briefing Friday.

On Tuesday, Public Health Ontario received positive test results for Zika virus for an individual who had travelled to South America, Dr. David Williams, Ontario's chief medical officer of health, said in a statement Friday. 

It's the province's first confirmed case of Zika virus infection. A total of nine travel-related cases have been reported across Canada.

In Latin America, the Aedes aegypti mosquito carries the Zika virus as well as other troublesome infections such as dengue.

Aedes aegypti mosquitoes can't survive Canadian winters.

"We know from the literature that there are at least 20 other species that have tested positive to Zika in addition to Aedes egpyti and we just don't know if some of our species might be able to transmit it as well," Hunter said in an interview.

Another mosquito species, the Asian tiger mosquito or Aedes albopictus, is a potential vector or carrier of Zika virus, Hunter said, and it's a priority to check.

That's because the Asian tiger mosquito is thought to be adapting to temperate climates, said University of Manitoba entomologist Kateryn Rochon.

So far, the Asian tiger mosquito has been established in southern New York State, New Jersey and Pennsylvania.

Hunter's hypothesis is it will be able to transmit by bite in Ontario. 

If it spreads here, an Aedes albopictus mosquito would first have to get it by biting a traveller with high enough levels of the virus in their blood.

In Italy, Aedes albopictus transmitted another virus, chikungunya, after someone returned from India.

"That's the sort of scenario we have to watch out for," Hunter said. 

Hunter's team will also test the Asian bush mosquito, Aedes japonicus, that first arrived in Ontario in 2001.

"That's a species that is definitely not supposed to be here. As the name suggests, it's originally from Japan and yet it does extremely well here and out competes species that we have."

For Rochon, one of the lessons of West Nile virus, which still causes hundreds of cases in humans each year in Canada, is to check if viruses can be transmitted as Hunter is now doing.

"One thing we should have learned is that we really should be looking at viruses that are potentially coming to our country and if they can be transmitted by our local insect fauna," Rochon said. "Some of that is now beginning. I guess Zika wasn't at the top of the list. Other viruses were being looked at instead."

For Latin America's outbreak, the priority should be to manage the pest in many different ways, Rochon said. These include reducing habitat for mosquito larvae, using pesticides appropriately and at the right time, educating people about how to protect themselves from bites and using tools such as sterile insects.