University of Wisconsin–Madison

Surveys, trap counts, and test results

West Nile Virus:  Culex mosquitoes are the major vectors for WNV.  Results are for weekly traps maintained by Milwaukee Public Health and Dane County Public Health.

In 2018, Milwaukee will be surveyed with 20 traps that collect the Culex mosquito when it is looking for a place to lay eggs.  These “gravid” traps use a strong smelling watery bait to attract the mosquitoes.  Because these mosquitoes have already taken a blood meal (which they turned into eggs), they are more likely to be positive for West Nile virus than the mosquitoes collected in the light/carbon dioxide traps, which may be host seeking for the first time.   Traps are put out weekly, with collections sent to the Medical Entomology lab for sorting, identification, counting, and testing.

For 2018, Dane County will use 7 trap locations.  At each location, two trap types will be deployed: a light/CO2 trap which collects all types of mosquitoes that are seeking hosts and a gravid trap (collects Culex mosquitoes looking to lay eggs).  The first trap provides indications of the level of nuisance mosquitoes.

Surveys for the Zika Mosquito:  During 2018, we will continue to assess the introduction of the Asian tiger mosquito into Wisconsin with an expanded trap network.  During 2017, locations in 5 Wisconsin counties (Dane, Rock, Milwaukee, Kenosha, La Crosse) were selected for surveys of the Asian tiger mosquitoes (Aedes albopictus) which were found in two counties. The traps are containers which are attractive to female Asian tiger mosquitoes that are looking for a place to lay eggs.  The eggs are sent to the Medical Entomology lab for hatching and identification of the larvae.