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Mosquito species responsible for most Zika cases caught in Ontario

Last Updated Aug 23, 2017 at 7:53 pm EDT

In this Sept. 29, 2016 file photo, Aedes aegypti mosquitoes, responsible for transmitting Zika, sit in a petri dish at the Fiocruz Institute in Recife, Brazil. THE CANADIAN PRESS/AP/Felipe Dana

An adult mosquito belonging to the species of the insect responsible for the majority of Zika cases has been caught in Canada for the first time by a southern Ontario health unit, but the insect captured isn’t carrying the virus.

The Windsor-Essex County Health Unit said one of their mosquito traps recently caught an adult Aedes aegypti mosquito. It noted that the specie’s larvae was also found in the region last year.

Despite the development, the health unit said there’s no reason to worry about an increased risk of Zika virus in the region.

Aedes aegypti mosquitos are capable of carrying the Zika virus as well as a number of other tropical diseases, including dengue fever, chikungunya, and yellow fever.

They are typically found in tropical environments, including the southern United States, but have been known to travel as far north as Michigan.

Public Health Canada says there are currently no reported cases of Zika virus being transmitted by mosquitos in Canada.

Dr. Wajid Ahmed, acting medical officer of health at the health unit, said it isn’t clear exactly how the adult mosquito that was captured made it to the Windsor area. But he said that Aedes aegypti mosquitos have hitched rides into colder climates in shipping containers in the past.

“When you look at the spread of this particular species of mosquitos, that’s how they’re spread in other parts of the world as well,” he said.

Windsor, Ahmed pointed out, is a hub for shipping between Canada and the United States. He added that Windsor also saw the first cases of West Nile virus in Canada.

Windsor’s warm summers, as well as a very mild winter last year, may also be a factor, he said.

“This warmer temperature is definitely one of the reasons that these particular types of mosquitos are finding it much more favourable to grow and survive,” Ahmed said.

Ahmed said that the Windsor-Essex County health unit is consulting with provincial and federal health authorities on how to deal with Aedes-type adults and larvae.

The health unit said local residents should use bug repellent, wear long-sleeved shirts when outside, and ensure that their doors and windows don’t have holes.

Unlike many mosquitos, the Aedes aegypti mosquito bites during the day. The mosquito also doesn’t breed in ponds, puddles or marshes. Instead, the health unit said, it prefers to lay eggs in objects that contain still water, like buckets or vases.

Another mosquito species that’s closely related to Aedes aegypti — called the Aedes albopictus — is also present in the Windsor region, and is also capable of carrying the Zika virus. Last year, the health unit said it captured 17 adults of the species, and Ahmed said more adults were captured this year.

Curtis Russell, a program consultant with Public Health Ontario specializing in mosquito-borne diseases, said the Aedes aegypti mosquito population in Canada is too small for a serious outbreak of Zika.

“It’s very unlikely for this to occur in Windsor or Canada,” he said, noting that Canadians are more at risk of getting Zika if they travel to southern locations where it is more common.

Regions affected by the Zika virus include the Caribbean and South America, as well as parts of west and south Africa and the southern United States.

Most people who contract the infection have no symptoms; those that do get sick experience such ill effects as fever, joint pain, rash and red eyes. The disease usually resolves in about a week.

However, the virus has been potentially linked in Brazil to cases of abnormally small heads in infants born to women who may have been infected while pregnant, as well as cases of Guillain-Barre syndrome, a neurological condition that can cause muscle weakness or even partial paralysis. Researchers are still scrambling to determine if Zika causes both the birth defect — known as microcephaly — and Guillain-Barre.