Comparative arboviral susceptibility of female Culex tarsalis (Diptera: Culicidae) collected in CO2-baited traps and reared from field-collected pupae.

Abstract

Female Culex tarsalis mosquitoes reared from field pupae or collected as adults in CDC light traps and lard cans baited with dry ice from the same site in Kern Co., California, USA, were tested simultaneously for susceptibility to oral infection with western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses. Results from 15 paired tests for WEE indicated that the overall ID50's obtained with females collected in CO2-baited traps were significantly higher (P < 0.001) than with females reared from pupae. The ID50's obtained with SLE virus for 6 paired samples were not significantly different. Comparisons of total numbers of infected vs. noninfected females after ingestion of 4 and 5 concentrations of SLE and WEE viruses, respectively, indicated that a significantly higher percentage of “host-seeking” females collected in CO2-baited traps were infected with either WEE or SLE virus than were females reared from pupae. These results demonstrate a need for standardizing the method of collection of female mosquitoes used in comparative vector competence studies.