By Scott Roblin

West Nile Virus risk increasing in August

Aug 28, 2017 | 4:17 PM

MEDICINE HAT, AB – Mosquitoes are a rare sight in Medicine Hat this summer, thanks to sweltering conditions over the last few months.

Superintendent of Parks Dave Genio said it’s been a very quiet year on the mosquito front so far.

“We saw some higher numbers in the first part of the spring due to some of the rainfall we had seen,” said Genio. “But throughout the remainder of the summer, the mosquito numbers have dropped considerably, we’re about just below average.”

Despite the overall number of mosquitoes dropping, the hot and dry conditions continue to raise the risk of West Nile Virus.

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Transmitted through mosquito bites, West Nile can attack the central nervous system and cause seizures, paralysis, and even death in extreme cases.

Around 80% of West Nile cases present little to no symptoms, but can be fatal in less than 1% of cases.

AHS South Zone Medical Officer of Health Dr. Lena Derie-Gillespie said while there are no cases in Alberta this year, it’s always a concern.

“We went a couple of years with no cases and then had a year with five, and it’s important to note that three of those cases were South Zone cases,” said Derie-Gillespie. “So, definitely for us in the South Zone, we always want to keep it on people’s radar.”

Alberta Health uses ‘Degree Days’ to measure heat accumulation in a particular area, which correlates with West Nile risk.

Taken from the province’s website, “it is generally assumed that a total of 109 Degree Days above 14.3 C are required for 50% of mosquitoes to be able to transmit the virus.”

Between the start of June and now, Medicine Hat’s Degree Days have jumped from between 100-150 days to between 500-550.

According to Derie-Gillespie, a major cool down is needed to drop the current West Nile Virus risk.

“Over this time period now, we’re seeing most of our areas in the South Zone have reached those Degree Days that are needed to have the replication,” said Derie-Gillespie. “So, it will be when it starts to cool down, that the risk starts to go away.”

Wearing light coloured clothing, staying indoors during dawn and dusk, and applying insect repellent with DEET are the best ways to avoid bites.

If mosquito populations were to grow over the next few weeks, Genio said the City has additional mosquito control measures.

“We will do dip counts to double-check to see what type of larvae numbers we are getting,” he said. “If we do see an increase in regards to larvae numbers, we will treat with a low-risk, highly effective, environmentally compatible biological larvicide.”

Genio adds there are steps people can take to decrease the numbers even further.

“There is still some mosquito activity out there, you can’t control every single area or puddle that is out there in the city,” he said. “That’s why we usually ask residents to help out with the cause. If there happens to be anything on their property that could be holding water, just kind of be diligent.”

Residents are encouraged to drain the standing water on their properties to keep mosquito populations as low as possible.