Evidence shows mosquitoes capable of carrying Zika virus may have colony in Ontario

Two adult Aedes albopictus mosquitoes, also known as the Asian tiger mosquito, were recently trapped in the area. The insects could have been transported by cross-border traffic or may have established a colony and survived the mild winter.

The insects tested negative for both the Zika and West Nile virus

This 2006 file photo provided by the Centers for Disease Control and Prevention shows a female Aedes aegypti mosquito in the process of acquiring a blood meal from a human host. The Aedes aegypti mosquito is behind the large outbreaks of Zika virus in Latin America and the Caribbean. (James Gathany/Centers for Disease Control and Prevention/Associated Press)

A mosquito species capable of transmitting the Zika virus and other tropical diseases may have established a colony in southwestern Ontario, a development that could mean changes for Canadian healthcare providers.

Two adult Aedes albopictus mosquitoes, also known as the Asian tiger mosquito, were recently trapped in Windsor-Essex, following the 17 found last year, according to the area's health unit.

Staff are not sure how the insects arrived in Ontario, but the region's acting medical officer of health said evidence suggests the mosquitoes may have hatched in the Windsor area.

"Seeing them this early, we're more concerned about an established population here," said Dr. Wajid Ahmed, explaining that last year the insects were found in mid-October. "This time around it's mid-August, which is more suggestive that they just became adults here in this region."

It's also possible the insects were carried from the United States in a shipping container or by other cross-border traffic.

Species can carry dengue fever

The two mosquitoes tested negative for both the Zika and West Nile virus, just like those captured in Windsor-Essex last year.

Ahmed said climate change bringing warmer temperatures to Windsor might help explain why mosquitoes are moving north.

"Once they establish themselves here it would be more difficult to control and maybe we'll see some diseases we haven't seen before," he said, adding the species can also transmit dengue fever and chikungunya — both of which can cause fevers, and headaches along with muscle and joint pain.

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"Our immune systems are not prepared for that," Ahmed added. "Some of these tropical symptoms are way behind on our list of differential diagnosis so I think that would require some understanding and education from the healthcare provider perspective that these are also a possibility now."

Asian tiger mosquitoes are 'aggressive' biters

The species is described as "aggressive daytime biters," but the health unit notes the insects feed on both people and animals, meaning it's less likely they'll be the primary mosquito to spread the Zika virus.

"For Zika virus transmission to occur, the Aedes albopictus mosquito would need to feed on an infected person then feed upon another susceptible person," according to the health unit.

South America, the Caribbean and Florida remain the areas with the greatest risk for contracting the virus.

Only one in five people infected with Zika show symptoms, which typically include fever, rash, headache, muscle and joint pain, but the virus has also been linked to microcephaly — a birth defect where a baby's head is smaller than expected.

The health unit is planning to conduct a deeper investigation into the area where the two mosquitoes were found in order to root out the insects.

"We've had West Nile since 2003 and we just try to manage it, so we don't want to be in that situation again," said Ahmed. "We want to do everything we can to prevent them from establishing a permanent site here."