Mosquito Population Surveillance
Adult mosquito population densities and diversity change markedly in response to water availability, temperature, and effectiveness of control. These populations have to be monitored on a weekly basis to determine these changes. We accomplish this by using three different types of traps: the Encephalitis Virus Surveillance trap, Faye trap, and Gravid trap.
Faye Trap
EVS/Faye Traps
These traps collect host seeking female mosquitoes. Dry ice (~6-8
lbs.) placed within a plastic paint can serves as the attractant for
host seeking females. As female mosquitoes approach the carbon dioxide
plume (produced by the sublimation of the dry ice), they are drawn into
a cage by a down draft fan. This trap will collect all species of
mosquitoes; however, those captured are usually young mosquitoes looking
for their first bloodmeal. This reduces the probability that the
collected mosquitoes will be infected with virus. These traps are placed
overnight in registered locations. We currently monitor 66 trap
locations.
Gravid Traps
This trap was developed by Reiter in 1983 and collects gravid female
mosquitoes seeking a place to lay eggs. The attractant used with this
trap is a water and hay infusion. This trap is very beneficial because
it collects mostly female that have digested a blood meal and are ready
to lay eggs; therefore, they have a greater probability of being
infected with viruses. Female mosquitoes laying their eggs are drawn
into a cage by a vacuum. This trap is very useful in collecting Cx.
pipien mosquitoes, a known vector of WNV. These traps are placed
overnight in registered locations. We currently monitor 10 trap
locations.
Sentinel Chicken Flocks
The district maintains one flock of chickens from April to
November. A blood sample is taken bi-weekly and tested in-house for the
viral antibodies of West Nile Virus (WNV), St. Louis Encephalitis (SLE),
and Western Equine Encephalomyelitis (WEE).