Discrimination of Aedes aegypti (Diptera: Culicidae) laboratory lines based on wing geometry.

Recent techniques of geometric morphometrics were applied to the study of four Thailand laboratory lines of the dengue vector Aedes aegypti. These lines differed by their geographic origin and the number of generations spent in the laboratory. Using a phase contrast microscope, a set of sixteen landmarks of the wings could be identified. A subsequent Procrustean superposition analysis produced the corresponding size and shape variables which were statistically analyzed. Size showed a significant decrease with the number of generations spent in the laboratory. Shape allowed an almost perfect reclassification of the specimens. This tool is able to accurately distinguish different laboratory lines and will be useful in field studies related to entomological surveillance and vector control.

Susceptibility and transovarial transmission of dengue virus in Aedes aegypti: a preliminary study of morphological variations.

Two types of morphological variants, the dark form and the pale form of Aedes aegypti were selected from wild-caught mosquitos. Ascertaining any differences between the two forms for susceptibility to dengue type 2 virus was performed by oral feeding. Transovarial transmission was further determined from the progenies of infected mosquitos by tracing them to the third generation. Significant differences in oral infection were not observed between these two forms of mosquitos. Transovarial transmission was found in the progenies of infected females of both forms, and the filial infection rates (FIRs) were also similar. However, there was a trend of declining FIR in the later generation. In order to achieve an accurate result, more tests are currently underway to obtain a larger number of progeny. Although the FIR was low in the present study under laboratory conditions, higher rates might occur under field conditions, which could have a significant impact on the maintenance of dengue viruses in nature.