St. Clair Region Conservation Authority crews have been on the road applying the first of three rounds of mosquito larvicide in road drainage catch basins across Lambton County as part of the annual effort to control the spread of West Nile virus.
They travel in marked vehicles with flashing yellow rooftop lights other drivers are asked to watch for since the crews make frequent stops to apply larvicide pellets in catch basins.
Lambton Public Health has contracted the conservation authority to apply the larvicide under a permit from the Ontario Ministry of Environment, Conservation and Parks. The conservation authority also carries out larval surveillance for the public health agency.
When mosquito larvae are exposed to methoprene, the larvicide used in the pellets, their life cycle is disrupted so they’re prevented from reaching maturity and reproducing, according to the Ontario Ministry of Agriculture, Food and Rural Affairs website.
The larvicide will be applied to road catch basins three times over the summer, said Lori Lucas, a supervisor of health protection with Lambton Public Health.
“It usually takes about two weeks to get through the county to do all of the catch basins” for each application, she said.
Larvicide is applied to roughly 16,500 catch basins in Lambton.
West Nile virus is spread through the bite of an infected female mosquito.
Lucas said there were no confirmed human cases of the virus in Lambton last year, but there have been cases in the past, including one in 2020.
A recent report by Lambton Public Health said there have been seven lab-confirmed cases locally since 2010.
“A case pops up, here and there,” Lucas said. “The thing about West Nile virus is that most people, when they’re infected, they don’t get sick or they might have mild flu-like symptoms – fever, headache, rash, muscle ache, that sort of thing.
They may not feel ill enough to go to a health provider and be tested for the virus.
“It’s sort of less than one per cent of the population that gets really sick and can get seriously ill,” Lucas said.
Applying larvicide to catch basins is only one measure for controlling the virus, and local residents have a role to play, public health agency officials say.
“It’s all about trying to control those areas where mosquitoes like to breed,” Lucas said. “They like to stay in standing and stagnant water.”
Residents are asked to drain water from areas around their property, including items that can hold water like old tires, pails, toys and wheelbarrows.
Water in bird baths should be replaced at least weekly and eaves should be kept clear so water doesn’t pool there.
The county has a bylaw regulating standing water on all local properties between April and October. Last year, three complaints were investigated under that bylaw.
Public health also recommends residents take steps to avoid being bitten by mosquitos, including using insect repellent containing DEET or Icaridin when outside during peak hours at dawn and dusk, or in locations where mosquitoes are most active.
The agency has a mosquito trapping program in the county that runs for 12 weeks with traps set up weekly at locations around the community
“The traps basically attract mosquitoes and then we send them away to the lab,” Lucas said.
Last year, two traps on Walpole Island had mosquitoes that tested positive for the virus.
“At one time, we used to monitor dead birds as an indicator but we do know that West Nile is established in Ontario now” and bird monitoring is not as useful a measure, Lucas said.
Dead birds are no longer collected as part of the West Nile virus surveillance effort.
“We’re just encouraging residents to go ahead and dispose of any bird they might find on their property,” she said.
Lambton public health has a West Nile virus information phone line that can be reached at 519-383-3824, or toll-free 1-800-667-1839 ext. 3824. Information is also available online at lambtonpublichealth.ca.