West Nile Virus is spread to people by a few different species of mosquitoes only after they have fed on the blood of infected birds. It first appeared in North America in 1999. In Canada, the virus has been found in Quebec, Ontario, Manitoba, Saskatchewan, and Alberta.

Where it occurs, the risk of contracting West Nile Virus is highest during the mosquito season (mid-April through September); however the risk of becoming infected is very low. Most people that do contract West Nile Virus show no symptoms at all, while 20% will develop flu-like symptoms, and, in very rare cases (1%), the virus can cause severe illness. The best way to protect yourself and your family is to avoid mosquito bites if you are in a region where West Nile has been reported.

As part of the monitoring process, please report dead birds on the West Nile website.

Many of the mosquitoes around us come from small sources of standing water around the home, and some mosquitoes even breed in the upper intertidal areas along our coast, so preventing mosquitoes from biting you is the most effective strategy.

Suggestions to protect yourself:

• Avoid the outdoors at dawn and dusk when mosquitoes are most active.
• Protect yourself by wearing clothing to cover your arms and legs and wear a hat.
• Wear light coloured clothes because mosquitoes are attracted to dark clothing.
• Ensure door and window screens are effective in keeping mosquitoes outdoors.
• Use insect repellents when outdoors.

Reduce mosquito breeding areas around your home:

Mosquitoes require standing water to lay their eggs in, and under ideal conditions, some mosquitoes can develop into adults in les than a week. Even a small amount of standing water can provide breeding areas.

• Empty standing water from things such as pool covers, saucers under gardening pots, buckets, recycling bins and garbage cans.
• Clear your property of unused items that could collect water (such as old tires).
• Change water twice a week in items such as bird baths, pet bowls, wading pools and livestock watering tanks.
• Use screens to cover rain barrels.
• Clean eave troughs regularly to avoid standing water.
• Do not overwater lawns or wash cars in driveway - the water goes into the catch basins on your street, providing breeding habitat.

What do I do if I have a pond?

A healthy wetland with native aquatic plants and insects will produce very few mosquitoes, so nothing should be done to upset the balance. If you have a small pond, or a pond that is not a balanced ecosystem, there are still a few options available.

• Purchase an aerator or pump that will keep the surface water moving, making the pond unsuitable for egg-laying by mosquitoes and unwelcoming to mosquito larvae.
• Attract mosquito predators to your yard such as bats, swallows, or dragonflies.

If your wetland is natural, or is connected to a natural waterway such as a creek or lake, it is illegal to put fish in it. Be sure to contact the proper authorities for advice before introducing fish.

Can I use pesticides?

For the health of the environment and your family, pesticide use is not recommended. As a first step, you should try to eliminate all standing water on your property, and allow your ponds to reach a natural state of balance. You can do a search for evidence of breeding mosquitoes, as the larvae are very easy to spot. Look for small aquatic insects that suspend themselves just under the surface of your pond, and wiggle below if you disturb them (image). Many of your mosquitoes may be coming from off-site, especially if you live near the ocean, so be sure to first check your ponds for the tell-tale larvae and remember that natural wetlands have very few mosquitoes.

Concerns over the use of pesticides are that they effect non-target organisms, and can possibly create new, and sometimes more-hospitable, breeding habitat. Mosquitoes may also develop a resistance to the pesticides in use.

Pesticide control for mosquitoes targets the immature life-stages, which are confined to water. This can be done manually or by using bacterial or chemical larvicides. Adult flying mosquitoes cannot be controlled. To manually remove mosquito larvae we suggest using a small gauge aquarium net to scoop the wriggling insects at the water’s surface, or you can also temporarily drain the water source, but remember that mosquitoes are very quick to re-colonize an area.

What can a homeowner do?

Commercial pesticides can only be applied by certified pesticide applicators. If you find water containing mosquito larvae on your property, and you can’t empty or strain the area, there are some options for the homeowner. Biological larvicides are available from your local home-and-garden centre. These contain naturally occurring bacteria (Bacillus thuringiensis israelensis) which target all species of aquatic flies. Using a pesticide of any type in a pond or wetland disrupts the normal balance of predators and prey (the web of life), so it should not be used in healthy ecosystems. Fully 10% of all flies are aquatic in their larval stage, and many of them are food for other animals such as dragonflies, birds, amphibians, fish and bats. Some flies are even predators of mosquitoes.

What is Bti?

Bacillus thuringiensis israelensis (Bti) is a naturally occurring soil bacterium that is being applied as a biological pest control agent to areas of standing water where mosquitoes breed. Bti produces a protein crystal that, once ingested by the feeding larvae, kills all flies by damaging their digestive system so that they can’t feed and they die within days. Bti has been used since 1982, and Health Canada has determined that it poses little threat to human health, and it only affects aquatic flies.

The weight of scientific evidence indicates that Bti is non-infectious and non-toxic to humans and other mammals, and poses little risk at dosage levels permitted in insect control programs. It should be noted however, that mosquitoes can develop resistance to it over time, and when used on a healthy wetland ecosystem the effect can be the opposite of what you would like by creating a predator-free environment that new mosquitoes can colonize. As with all pesticides, Bti should be used with caution.

For more information visit the Health Canada fact sheet

Saanich's Response to West Nile Virus

Since 2003, Saanich has been preparing for the potential arrival of west Nile Virus by surveying and mapping the breeding grounds of mosquito species that can carry the virus. A West Nile Virus Response Plan was completed in 2007.

Information

To register mosquito breeding areas located on public property in Saanich:

Adriane Pollard, Manager
Saanich Environmental Services

Related Web Sites:
BC Centre for Disease Control
Health Canada Surveillance
Canadian Cooperative Wildlife Centre
Van Island Health Authority (VIHA)