Sensitivity of Toxorhynchites amboinensis mosquitoes versus chicken embryonic cell cultures for assays of Venezuelan encephalitis virus.

Toxorhynchites amboinensis mosquitoes inoculated intrathoracically with Venezuelan encephalitis virus and tested for infectious virus 12 to 19 days later by inoculation of primary chicken embryonic cell cultures yielded approximately the same titers of virus as did direct inoculation of cultures, with counting of plaques 3 days thereafter. Titers were slightly higher in T. amboinensis for three virus strains, equal for two virus strains, and slightly lower for two virus strains. Comparative titers of four strains were similar, whether virus suspensions came from infectious vertebrate cells or infected invertebrate (T. amboinensis) cells. Each of the seven strains of Venezuelan encephalitis virus reached virus concentrations of 10(4.2) to 10(5.1) plaque-forming units in individual T. amboinensis mosquitoes after extrinsic incubation periods of 12 to 19 days. No temperature-sensitive (29 versus 37 degrees C) virus was detected in T. amboinensis mosquitoes infected by six strains of Venezuelan encephalitis virus.