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Canadian scientists test native mosquitoes for Zika virus transmission

ST. CATHARINES, FEB 19, 2016..MOSQUITO HUNTERâ¶Dr. Fiona Hunter a medical and veterinary entomologist looks at aedes albopictus mosquito larvae used in Zika virus research when the larvae mature into adult mosquitos, (at left) in her lab at Brock University in St.Catharines on Friday February 19, 2016. In March, Hunter an expert on the Zika virus will be travelng to Brazil to study the virusâs epicentre. Glenn Lowson photo for The Globe and Mail

A front line in Canadian efforts to understand the spread of Zika virus is located behind five sealed doors in a lab in St. Catharines, Ont., where vents and drains are fitted with fine mesh to prevent errant insects from escaping if the negative air pressure does not stop them first.

It's there that Fiona Hunter, an entomologist at Brock University, plans to spend the coming months along with her students, infecting about a dozen species of locally collected mosquitoes with a strain of the virus that is spreading rapidly through South and Central America and is raising alarms because of its link to birth defects.

The Brock team is working with researchers at the National Microbiology Laboratory in Winnipeg who will be collecting species found in Western Canada. Together, they are hoping to determine whether any species found in Canada could be a possible carrier of the disease.

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"The fact is, we just don't know," explained Prof. Hunter, who last month shifted the focus of her lab's work from West Nile to Zika virus as the severity of the outbreak became clear. Researchers, she said, were "a bit blindsided" by the fast emergence of the virus in Brazil last year and its link to birth defects in babies born to mothers who were infected with the disease while pregnant. Since then, the researchers have been scrambling to respond to what the World Health Organization has declared as a "public health emergency of international concern."

Mosquitoes are at the heart of the Zika outbreak, specifically a "day biter" variety called Aedes aegypti, which lives off humans and is adept at laying its eggs even in nooks and crannies filled with water.

While the Aedes aegypti lives in tropical and subtropical regions and is not present in Canada, another invasive species that lives as far north as New Jersey and southern New York state has been identified as a possible carrier of Zika, as well.

It is only a matter of time until that mosquito establishes itself in Canada, Prof. Hunter predicts, particularly the Niagara region where Brock is located – an area she calls a "gateway" for invasive species into Canada.

And while most – including the World Health Organization – are not expecting locally transmitted cases of Zika to emerge in Canada, Prof. Hunter says it will take tests on infected, live mosquitoes native to Canada to rule that out.

To do that, Prof. Hunter and the Winnipeg lab will be working this summer to infect local mosquitoes with the virus and painstakingly collect their saliva in tubes. This work on live insects is important, she said, because a mosquito that tests positive for the virus still may not be capable of transmitting it through its bite.

To date, all the cases of Zika reported in Canada have been travel-related. On Friday, Ontario's Chief Medical Officer of Health confirmed the first case in the province in an individual who had travelled to South America.

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The Brock facility and the one in Winnipeg are the only Level 3 containment labs in the country equipped with the safeguards needed to handle infected live insects. That ability, Prof. Hunter said, will allow researchers to be proactive and determine whether precautions need to be taken in Canada, rather than waiting "on tenterhooks" to see whether a case of local transmission from an infected traveller is found.

Her group received a shipment Wednesday of Zika virus that was isolated by the national lab in Winnipeg in 2010 and originated in Thailand. The national lab is now working to isolate the Brazilian strain of the disease, she said.

Once the snow clears and the ice melts, the Brock team will begin collecting mosquitoes from traps set in the region, with collection continuing throughout the summer. Ontario is home to about 67 species of mosquitoes, but the Brock researchers plan to zero in on about 12, giving special attention to "day biters" who might be good vectors.

The Public Health Agency of Canada is recommending that pregnant women and those thinking about becoming pregnant consider postponing travel to areas where Zika virus is circulating. Canadians who have travelled to affected countries are ineligible to give blood for 21 days after their return.

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