VERTICAL TRANSMISSION OF WEST NILE VIRUS BY CULEX AND AEDES SPECIES MOSQUITOS

Experiments were conducted to determine whether West Nile (WN) virus w as transmitted vertically by colonized strains of Aedes albopictus, Ae . aegypti, and Culex tritaeniorhynchus. Female mosquitoes were infecte d by intrathoracic inoculation with WN virus, and the F1 progeny were tested for virus by the fluorescence antibody technique and the newbor n mouse assay. Each of the three mosquito species transmitted WN virus to F1 adults derived from immature forms reared at 26-degrees-C. The minimal filial infection rate (MFIR) ranged from 1:124 to 1:138 for Ae . albopictus, from 1:62 to 1:172 for Ae. aegypti, and from 1:325 to 1: 859 for Cx. tritaeniorhynchus. The MFIR for Cx. tritaeniorhynchus rear ed at 20-degrees-C was 1:213 for larvae and 1:390 for pupae, and 1:208 for larvae and 1:554 for pupae reared at 26-degrees-C. These data are the first reported evidence of vertical transmission of WN virus by m osquitoes, and therefore warrant further studies to determine whether vertical transmission occurs among WN viral-infected mosquitoes in nat ure.