Mosquito Surveillance > Mosquito Control > Integrated Pest Management > Programs | San Joaquin County Mosquito & Vector Control District

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, Gravid trap, and New Jersey Light traps.

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 69 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 9 trap locations.

New Jersey Light Trap

New Jersey Traps
The New Jersey light trap (created by Mulhern in 1942) was introduced to California Mosquito Control Districts in 1953 to enhance their mosquito surveillance. This trap collects phototactic (mosquitoes attracted to light) species. Once mosquitoes get near the trap a fan creating a down draft pulls the mosquitoes into a collection chamber. Because a light bulb is used as the attractant for this trap, many insects beside mosquitoes are attracted to this trap. These traps operate continuously from dawn to dusk and are collected on a weekly basis. We currently operate 21 traps.

Sentinel Chicken Flocks
The district maintains two flocks 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).