Evaluation of Toxorhynchites Splendens (Diptera: Culicidae) as a Bioassay Host for Dengue Viruses1

Toxorhynchites splendens, a nonhematophagous mosquito, was evaluated as a bioassay host for the detection and propagation of dengue viruses. All dengue virus serotypes and strains attained titers in Tx. splendens comparable to those observed for 2 strains of Aedes aegypti. Peak virus titers occurred in Tx. splendens approximately 6 days postinoculation; however, specific fluorescence for all viruses was not observed in 100% of mosquito heads until 12 days postinoculation. A 100% correlation was noted between specific fluorescence in Tx. splendens heads and the recovery of virus from corresponding thoraxabdomens. The volume of inoculum tolerated by Tx. splendens was approximately 5 times greater than that injected into Ae. aegypti. Thus, for a given volume of inoculum, the number of Tx. splendens required for virus assays was appreciably less than that needed for Ae. aegypti. The overall survival rate for Tx. splendens following intrathoracic inoculation with dengue viruses was 92%, compared to 41 and 42% for 2 strains of male Ae. aegypti. These findings imply that Tx. splendens would be more efficient than Ae. aegypti as a laboratory assay host for detecting dengue viruses in blood of infected patients and for use in experimental investigations.