Mosquitoes hatched by high water could create real summer buzz kill
It is likely to be a banner year for mosquitoes as flood waters are expected to hatch eggs that were laid not only last year, but up to a decade ago.
Mosquito-control expert Dirk Lewis said female mosquitoes often lay their eggs in soil that is prone to flooding.
The eggs don’t hatch until they get wet, which happens more easily during high-water years.
“Many areas in the Interior are seeing a peak (in mosquito numbers) now, while the peak is still coming for the Lower Mainland,” said Lewis, a manager with Morrow BioScience, a private company that provides mosquito-control services to municipalities across B.C.
After hatching, the mosquito larvae spend several weeks in the water before becoming flying adults. Only female mosquitoes bite, as they need a “blood meal” to produce eggs.
Most mosquito-control companies use a bacteria that kills the larvae in the water.
Once the blood-sucking bugs become adults, little is done to control the population. Mosquitoes live for about one or two months, so the major swarms are expected to die away by late June or July.
But other mosquito species that lay their eggs in standing water can continue to cause localized problems throughout the summer.
“It’s important for people to get rid of standing water,” explained Lewis.
In the wake of flooding, the Interior Health Authority is advising residents to “drain, overturn, or empty vessels” as the flood waters recede, including dog bowls, cans and small pockets of trapped moisture on plants and trees.
Interior Health medical health officer Kamran Golmohammadi said eliminating mosquito breeding grounds is one part of a solid defence against the nuisance insects. He also advised minimizing exposure to mosquitoes and using a DEET-based repellent.
It is also prudent to wear longsleeved, loose-fitting, light-coloured clothing to avoid being bitten.
Eating garlic has not been proven to help deter the insects, while drinking alcohol can make your scent more attractive to them.
In addition to causing itchy bites, mosquitoes can carry disease, including the West Nile virus. In 2017, two human cases and four horse cases were detected in B.C., according to the B.C. Centre for Disease Control. Surveillance is conducted by testing sick and dead horses and birds, as well as people with symptoms compatible with the virus. Mosquitoes are also trapped and tested.
Golmohammadi said a spike in the number of mosquitoes does not necessarily mean B.C. will see an increase in West Nile cases this summer. West Nile infections are rare, with less than one per cent of known cases resulting in severe symptoms.
“People might assume that an increase in mosquitoes would result in a higher number of cases, but we have not seen that correlation yet,” he said.