MOSQUITO AND ARBOVIRUS SURVEILLANCE IN CONNECTICUT, 1991-1992

A surveillance program for mosquito-borne arboviruses was conducted in Connecticut following an epizootic of eastern equine encephalitis (EE E) in horses and domestic birds during 1990. Mosquito trapping was don e weekly using CO2-baited miniature light traps at 12 freshwater swamp sites that were located mostly in the southeastern portion of the sta te. Trapping was conducted from June 27 to October 11, 1991 and from J une 2 to September 30, 1992. Totals of 7,435 (1991) and 13,912 (1992) adult female mosquitoes representing 21 species in 7 genera were colle cted and assayed for arboviruses. Virus isolates were identified by EL ISA using reference antibody of California encephalitis, EEE, Highland s J (HJ), Jamestown Canyon (JC), LaCrosse, and St. Louis encephalitis viruses. Culiseta melanura was the most common species trapped each ye ar, followed by Aedes canadensis, Aedes cinereus, and Coquillettidia p erturbans. The most abundant univoltine snowmelt species was Aedes abs erratus. Three isolates positive for JC virus were obtained from Ae. a bserratus, Ae. canadensis (new state record), and Ae. cinereus (new st ate record) that were collected from 2 different sites in June (1992) and July (1991 and 1992). Six isolates positive for HJ virus were made from Cs. melanura and one isolate from Ae. cinereus (new host record) collected in mid- to late September, 1992 from 3 locations. Based on repeated virus isolations in this and other studies, high field infect ion rates, and its relative abundance, Ae. abserratus appears to be a principal vector of JC in Connecticut. However, the prevalence and imp ortance of JC as a human disease in the state are unknown. Culiseta me lanura populations were abundant throughout the summer and early fall, and the availability of this potential mosquito vector does not appea r to be a limiting factor for enzootic maintenance and subsequent ampl ification of EEE virus in presumed foci in southeastern Connecticut.