Virus-dependent mortality in Rift Valley fever, eastern equine encephalomyelitis, and chikungunya virus-inoculated mosquito (Diptera: Culicidae) larvae.

The effect of inoculation of mosquito larvae with Rift Valley fever (RVF) virus on survival to the adult stage was evaluated in Aedes aegypti (L.), Ae. fowleri (Charmoy), Ae. mcintoshi Huang, Ae. taeniorhynchus (Wiedemann), Ae. triseriatus (Say), Eretmapodites quinquevittatus Theobald, Anopheles albimanus Wiedemann, and Culex pipiens L. Pupation rates were similar for RVF virus-inoculated and diluent-inoculated larvae of all mosquito species tested except Cx. pipiens. However, with the exception of An. albimanus and Ae. triseriatus, virtually all pupae derived from RVF virus-inoculated larvae failed to emerge successfully as adults. In contrast, both pupation and emergence rates were similar for diluent-inoculated and either La Crosse or St. Louis encephalitis virus-inoculated larvae of Ae. taeniorhynchus. There was also poor survival to the adult stage of Ae. taeniorhynchus inoculated with either eastern equine encephalomyelitis (EEE) or chikungunya (CHIK) virus. The high mortality rates observed under laboratory conditions of pupae derived from larvae inoculated with either RVF, EEE, or CHIK virus may be responsible for the lack of laboratory confirmation of vertical transmission of these viruses.