Mosquito capable of carrying Zika found
Ontario find the first time seen in Canada
The species capable of carrying the Zika virus — a “sneaky” daytime biter — was captured last week in Windsor, Ont., the first known adult mosquito to be found in Canada, the local health unit reported Tuesday.
An adult Aedes aegypti mosquito, commonly known as the yellow fever mosquito and the species responsible for the majority of human cases of Zika virus infections in the Caribbean, South America and Florida, was found in a single mosquito trap somewhere in the city. The Windsor Essex County Health Unit would not reveal the location, but the mosquito tested negative for Zika virus and West Nile virus.
It is the first time that an adult Aedes aegypti mosquito has been captured in Canada, according to the health unit. Last year, Aedes aegypti larvae were found in the region through enhanced mosquito surveillance. The discovery of an adult Aedes aegypti, along with last week’s discovery of the two adult Aedes albopictus, or Asian tiger, mosquitoes indicates that the Aedes species may be starting to become established in the region, the health unit said.
“This is pretty significant from a risk perspective since this mosquito type normally doesn’t prefer our cooler climate,” WindsorEssex Health Unit acting medical officer Dr. Wajid Ahmed said. “It also brings the new risk of diseases. But at this point there really is no increased risk for the Zika virus.”
Ahmed said although the risk is low, the health unit along with the Ministry of Health and Long-Term Care, Public Health Ontario and the Public Health Agency of Canada will be working together to come up with an action plan.
Dr. Robbin Lindsay, a research scientist with the Public Health Agency of Canada, said the latest discovery raises two important questions: Is this an introduction of the Aedes aegypti mosquito into the area and if so, has it resulted in a population of the mosquito?
“Clearly there would be more of a risk if it is already established,” Lindsay said. “We don’t have all the information yet to be able to answer those questions.”
Lindsay said the Aedes aegypti likely will not survive the winter, and the threat of the species growing in this region is remote.
“The capacity for them to survive over winter and establish a population on an ongoing basis seems unlikely,” Lindsay said.
It’s unknown how the mosquitos arrived in Canada, but both Ahmed and Lindsay believe they were transported from the U.S. in shipping containers or cross border vehicle traffic. The mosquitos are container breeders, which means all they need is a little standing water to survive.
“We are trying to be more diligent tracking where these mosquito are and where their colony is because we need to get rid of them before they get established,” Ahmed said. “It would become a lot more challenging to get rid of them once they are established.”
In the U.S., the Aedes aegypti mosquito resides in the southern states, where temperatures are more favourable for its survival.
“We definitely want to find out how they ended up here,” Ahmed said. “The history is they come in through transportation. We may not be able to completely answer the ‘how’ but at this point that’s the hypothesis we are going with.”
Traps have been set up around the city and Essex County. They are monitored and tested weekly. Ahmed said the traps will provide researchers with a good idea of the mosquitos’ preferred location in the community.
He stressed it’s important to get rid of any standing water. The Aedes aegypti doesn’t breed in ponds, puddles or marshes. It is drawn to standing water, whether it be on a pool cover, a bird feeder or inside an old tire.
The biting behaviour of the Aedes aegypti is different from those that transmit West Nile disease. They tend to approach humans from behind and bite them on elbows and ankles.
“They are really active during the daytime,” he said. “People think during the day mosquitos wouldn’t be out, but these ones are. They are sneaky, daytime biters.”
For the Zika virus transmission to occur the mosquito would need to feed on an infected person within the first several days of infection, and then bite another person. The greatest risk still remains for those who have travelled to Zika-risk areas such as South America, the Caribbean and Florida.