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Metro Vancouver's Role
About Mosquitoes and West Nile
Protect Yourself and Your Family
Mosquitoes Around Your Home
Managing Mosquito Habitats
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About Mosquitoes and West Nile 

West Nile virus (WNV) is a disease spread to humans through the bite of an infected mosquito. The mosquitoes pick up the virus from feeding on infected birds. Not all mosquitoes or birds carry WNV. The types of birds that are most affected are corvids, which include crows, ravens and jays.

The virus is named after a region in Uganda where it first appeared in 1937. From there, outbreaks were recorded in Europe before the first North American infection was confirmed in New York State in 1999. WNV has since been detected in most American states and Canadian provinces.

So far, there have been no recorded cases of West Nile infection in Metro Vancouver. However, once infection has been recorded, we can expect that the virus is here to stay, and will remain as a monitored health risk in B.C.

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Typical West Nile virus transmission cycle

Mosquitoes around your homeProtecting yourself and your family

Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. Infected mosquitoes can then transmit West Nile virus to humans and animals while biting to take blood. The virus is located in the mosquito's salivary glands. During blood feeding, the virus may be injected into the animal or human, where it may multiply, possibly causing illness.



Mosquito Life Cycle

A mosquito pupa is also found in the water. It floats near the surface and has two tubes on its back for breathing. Mosquito pupae are sometimes called 'tumblers' because they tumble though the water when threatened. Like the caterpillar's cocoon, the pupa is undergoing metamorphosis. When development is complete, the skin splits and an adult mosquito emerges.From the eggs hatch mosquito larvae, also called 'wrigglers.' They are usually found hanging upside down just below the water's surface. This stage of the mosquito eats and grows, much as a caterpillar does. After a series of molts, a larva goes into a transitional stage - the pupa.Female mosquitoes lay eggs in water, either singularly or attached together in 'rafts,' depending on the species. Most eggs will hatch within 48 hours; others may withstand subzero winters before hatching. Regardless, water is a necessary part of their habitat. A single female mosquito is known to lay up to 300 eggs at a time depending on the species.This is the distribution and breeding stage of the mosquito. It leaves the water behind at last and launches into the air. Male and female adult mosquitoes feed mostly on plant juices. It is only when it comes time to lay eggs that the female needs to feed her eggs with the protein of a blood meal. She will draw blood for each batch of eggs she lays. Stimuli that influence biting include: carbon dioxide, temperature, moisture, smell, colour and movement. Mosquito activity varies by species but most are especially active from dusk to dawn. This is the time that you are most likely to be bitten.

Mosquitoes spend three of their four life stages in the water and any sources of standing water are potential mosquito breeding hot spots. It takes seven to ten days for a mosquito egg to hatch and grow into an adult mosquito. By removing any standing water around your home on a weekly basis, you will prevent new eggs from hatching. Roll-over a stage to get more information. More information on controlling mosquitoes around your home.