Vector competence of Culex tarsalis (Diptera : Culicidae) from Iowa for a sympatric strain of western equine encephalomyelitis (WEE-7738) virus

Experiments were designed to evaluate the vector competence of Culex tarsal is Coquillet from an area (Sioux City) where Cx. tarsalis is most abundant in Iowa for western equine encephalomyelitis virus (WEE-7738). WEE-7738 was isolated from Aedes trivittatus (Coquillet) collected in Ames, IA, in 1977 . Infection rate, dissemination rate, multiplication efficiency, and. trans mission rate were determined for this virus in the SC strain of Cx. tarsali s. SC strain of Cx. tarsalis was as susceptible to WEE-7738 as Californian strains of Cx. tarsalis were to BFS1703 strain of WEE; OID50 of SC Cx. tars alis was 2.63 log TCID50 per mosquito and OID50 of Californian strains of C x. tarsalis were 2.0-4.1 log PFU per mosquito. However, transmission of WEE -7738 (4.2%) by the SC strain of Cx. tarsalis was lower than those (10-60%) reported in other studies.