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West Nile virus and Mosquitoes

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West Nile virus (WNV) is a virus that is found in wild birds and carried by mosquitoes.

What is West Nile virus?

  • West Nile virus (WNV) is a virus that is found in wild birds and carried by mosquitoes. It was first identified in the province of West Nile, Uganda in 1937. Since then it has been identified in Egypt, Asia, Israel, South Africa, parts of Europe and Australia.
  • In 1999, it was found in the United States for the first time, and in the summer of 2001 was discovered in birds in southern Ontario, including Halton.
  • In 2002, human cases were first identified in Canada, including Halton.

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How is West Nile virus spread?

  • Mosquitoes become infected with West Nile virus when they feed on the blood of infected birds.
  • The virus is carried in the mosquito’s salivary glands.
  • An infected mosquito can then transmit WNV to humans and animals, when it takes a blood meal.
  • The virus is not known to spread from person-to-person through contact such as touching, kissing, or caring for someone who is infected.
  • Other modes of transmission are being investigated.

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Do all mosquitoes bite humans?

  • No, only adult female mosquitoes bite humans.
  • Male mosquitoes feed on plant juices.
  • Most female mosquitoes feed on humans, birds and other animals to get sufficient blood to develop eggs.

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Do all mosquitoes transmit West Nile virus ?

  • While there are many species of mosquitoes, the adult Culex pipiens mosquito (the common house mosquito) is the one most commonly associated with the West Nile virus.

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Why are some people bitten more than others?

  • There are many reasons. Cologne, perfumes and scented body lotions can attract mosquitoes. Dark coloured clothing is also more attractive to mosquitoes.
  • During evenings until early morning mosquitoes are most active and looking for a blood meal, so people outdoors during that time are more likely to be bitten.
  • Finally, everyone's body is different, and some people produce odours that are attractive to mosquitoes.

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Where do mosquitoes live?

  • The Culex pipiens mosquito (the common house mosquito) lays its eggs in standing water around the home.
  • Weeds, tall grass, and bushes provide an outdoor home for the adult Culex pipiens mosquito.

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How far can mosquitoes travel?

  • Depending on the species, adult mosquitoes may fly several miles with help from the wind.
  • Culex pipiens , the species most commonly associated with West Nile virus, has a travel range of 2 - 3 miles.

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How long do adult mosquitoes live?

  • Generally, adult female mosquitoes have a life span of 2 weeks to a month while adult male mosquitoes only live a week.

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The life cycle of a mosquito.

Mosquitoes pass through four developmental stages during their life cycle:

  • the egg
  • larval
  • pupal and
  • adult stages

What is the life cycle of a mosquito?

  • A mosquito goes through four distinct stages: egg, larva, pupa and adult.
  • This life cycle, from birth to death, is generally 4 - 6 weeks long.

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What is the egg phase of a mosquito?

  • Eggs are laid in clusters and float on the surface of the water.
  • They can be stuck together in rafts of hundreds of eggs.
  • Most eggs hatch into larvae within 48 hours.
  • Adult female mosquitoes can lay eggs every 10 - 14 days. Females lay their eggs from spring to fall.

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What is the larvae stage of a mosquito?

  • Mosquito larvae live in water from 4 -14 days depending on the water temperature. They come to the surface frequently to obtain air.
  • They feed on algae and small organisms living in the water. Under ideal conditions, the larva becomes a pupa in 7 - 14 days.

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What is the pupa stage of a mosquito?

  • The pupa stage is a resting, non-feeding stage.
  • This is where the mosquito turns into an adult.
  • In the spring the process takes 2 - 4 days, and 2 - 3 days in the summer.

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What is the adult stage of a mosquito?

  • The new adult mosquito rests on the surface of the water for a short time to dry and allow its wings to spread out and dry properly.
  • If nothing eats or kills it, the female adult can live for several weeks, the male only a week.

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