MOSQUITO PRODUCTIVITY AND SURVEILLANCE FOR ST-LOUIS ENCEPHALITIS-VIRUS IN CHICAGO DURING 1993

The City of Chicago's Department of Health monitors weekly deposition of egg rafts of Culex species, prevalence of St. Louis encephalitis (S LE) virus-specific antibodies in feral birds, and prevalence of the vi rus in mosquito pools. The total number of Cuter egg rafts collected i n 1993 (4,623) was 2-fold greater than for the 1992 mosquito season. V irtually all of the early summer egg rafts were identified as Culex re stuans. After the week of July 18, Culex pipiens accounted for 20-70% of the total rafts collected weekly. The prevalences for SLE viral ant ibodies (avian) and RNA (mosquitoes) were 0.2% and 0.02%, respectively . Both values were about 25-fold less than normally occur in epidemic years. It is important for practical considerations to continue this s urveillance in order to recommend time- and site-specific mosquito aba tement.