Life Cycle of Mosquito
All species of mosquitoes need water for their early developmental life stages. Some mosquitoes lay their eggs in standing water where they hatch in a day or two. Other mosquitoes lay their eggs in old tires, tin cans, or other water-holding containers in which they may remain un-hatched for weeks or months until they are covered with water. With both types of mosquitoes, the "wigglers" or larvae grow quickly and turn into "tumblers" or pupae. Soon the skin of the tumbler splits open and out climbs another hungry adult mosquito.
Adult flying mosquitoes frequently rest in grass, shrubbery or other foliage, but they never develop there.
West Nile Virus Transmission Cycle
Role of Mosquitoes in WNV Transmission:
West Nile (WN) virus is amplified during periods of adult mosquito blood-feeding by continuous transmission between mosquito vectors and bird reservoir hosts. Infectious mosquitoes carry virus particles in their salivary glands and infect susceptible bird species during blood-meal feeding.
Role of Birds in WNV Transmission:
Infected mosquitoes bite birds and infect them. Some infected birds transmit the virus to other mosquitoes when bitten again. Birds of some species get ill; others do not show disease symptoms, although infected. Infected migrating birds carry the virus to new places.
Occasionally WNV affects mammals bitten by mosquitoes. Mammals are dead end hosts. The level of virus in mammals is generally too low to transmit the infection back to mosquitoes.