Media Release: WDG Public Health begins mosquito larvicide program to reduce mosquito populations known to carry West Nile virus

May 19, 2022

Wellington-Dufferin-Guelph Public Health has begun its annual mosquito larvicide program which is expected to run until early October. Trained technicians apply larvicide by hand in areas of standing water in and around communities in Wellington and Dufferin counties, helping to reduce or eliminate mosquito populations known to carry West Nile virus.

In 2021, there was one confirmed human case of West Nile virus, and two cases in birds, identified in Wellington-Dufferin-Guelph.

“Mosquitos are more than just a spring and summertime annoyance. Some species may carry the West Nile virus which, if transmitted to humans, may cause flu-like symptoms and in rare cases, inflammation of the brain or spinal column can occur which may result in permanent disability or death,” says Dr. Nicola Mercer, Medical Officer of Health and CEO of Wellington-Dufferin-Guelph Public Health. “By proactively treating areas of standing water on municipal property, we’re helping to prevent these areas from becoming sites for mosquitoes to breed.”

Mosquitoes lay their eggs in standing water, so the first line of defense is eliminating mosquito breeding areas. Larvicide is used in potential larvae breeding sites where standing water cannot be eliminated or is more difficult to control, such as:

  • roadside ditches
  • temporary pools
  • sewage lagoons
  • storm-water retention ponds
  • areas of standing water
  • municipal catch basins

Public Health is also encouraging property owners to remove standing water anywhere it tends to collect. These locations include flowerpots, bird baths, wheelbarrows, eaves troughs, rain barrels and tires. You can reduce the risk of mosquito bites and potential exposure to West Nile virus:

  • wear light-coloured pants and long-sleeved shirts
  • avoid being outside at dawn and dusk when mosquitoes tend to feed
  • use a mosquito repellent with DEET or Icaridin for adults and children over 6 months of age (as recommended by Health Canada)

For information about the products used in the larvicide program, or details on treatment locations, please call the Canadian Centre for Mosquito Management at 1-855-220-7022. If you have a catch basin on your property and would like to have it treated at no cost, call Public Health at 1-800-265-7293 ext. 4753. Visit for more information.

Jessica Anselmini, Communications Specialist
1-800-265-7293 ext. 4377