Absence of Eastern Equine Encephalitis (EEE) Virus in Immature Coquillettidia perturbans Associated with Equine Cases of EEE.

摘要

During the summer of 1983, 5 fatal equine cases of eastern equine encephalitis (EEE) were confirmed in New Jersey. Hayes et al. indicated that the distance from coastal marshes made it unlikely that the salt marsh mosquito, Aedes sollicitans, served as the vector for EEE virus in these areas. Four of the 1983 cases occurred at a distinct focus in Jackson Township, Ocean County. After the initial case with an onset of July 8, mosquito surveillance was initiated and concentrated on 3 Jackson Township farms within a 5-km radius of each other. The dominant mosquito species collected at these farms was Coquillettidia perturbans. This study of the overwintering stages of Cq perturbans, temporally and spatially associated with equine fatalities of EEE and EEE virus-infected female Cq. perturbans, failed to implicate this species as an overwintering host for EEE virus. With Keystone virus which is transovarially transmitted, the Minimum Field Infection Rate (MFIR) in reared adults approximates that found in larvae. If transovarial transmission was occurring in the virus-vector system we investigated and the 2 EEE virus isolates were the result of transovarial transmission infections, we should have obtained 7 isolates from the Jackson Township collections. Although Cq. perturbans appears to play a major role as an epizootic vector for EEE virus in freshwater habitats, we were not able to detect transovarial or transstadial maintenance of EEE virus in this species.