Prevalence of West Nile virus in tree canopy-inhabiting Culex pipiens and associated mosquitoes

Culex pipiens was the dominant mosquito captured in a West Nile virus (WNV) focus in Stratford, Connecticut. More Cx. pipiens were captured in Centers for Disease Control miniature light traps baited with CO,, quail/hamster traps, and mosquito magnet experimental (MMX) traps placed in the tree canopy than in similar traps placed near the ground. Significantly more Cx. pipiens were captured in MMX traps placed in the canopy than in the other traps tested. Ninety-two percent and 85% of the 206 and 68 WNV isolations were from Cx. pipiens in 2002 and 2003, respectively; 5% and 12% were from Cx. salinarius. Eighty-five percent and 87% of the isolates were from mosquitoes captured in the canopy in each of the two years. The significantly larger numbers of WNV isolates from Cx. pipiens captured in the canopy are attributed to the significantly larger numbers of Cx. pipiens captured in the canopy in comparison to those captured in traps near the ground.