Culex mosquitoes have been implicated as the primary enzootic vector of West Nile Virus (WNV). CMMCP uses the Reiter-Cummings modified gravid traps to collect adult Culex mosquitoes for viral testing. "Gravid" means pregnant or egg-bearing. The mosquitoes attracted to this trap are female and have already taken at least one bloodmeal and are ready to lay eggs, therefore potentially exposed to WNV and other mosquito-borne pathogens.
This trap type is preferred for this purpose for the following reasons:
- Selection of the specific mosquito species implicated as vectors of WNV;
- Samples that portion of the mosquito population most likely to have been exposed to WNV;
- Cost effective, allowing multiple traps to be placed in a given area.
The CDC light traps selects for mosquito species that the gravid trap may not, and will be used in situations where the collection of these mosquitoes is deemed necessary, i.e. to sample the population density of human-biting mosquito species to help determine risk to the general public in that area. These collections are not as good for viral resting due to the fact the mosquitoes sampled may not have taken a bloodmeal yet, but this is important data when WNV is suspected or confirmed in other mosquito species to allow specific control procedures to be considered.
Additional trap types will be employed as new information is learned about trap efficacy.