Comparative susceptibility to oral infection with dengue viruses among local strains of Aedes aegypti (Diptera: Culicidae) collected at different seasons of the year.

The vector competence of Aedes aegypti (L.) mosquitoes, collected during the hot, rainy and cool seasons from different localities in Thailand, was tested for a correlation with a seasonal cyclic pattern of dengue incidence. Under laboratory conditions, some groups of mosquitoes exhibited differences in susceptibility to oral infection but showed no correlation to dengue cases that peak during the rainy season. Thus, the environmental conditions of each season, although they might affect a temporal change of mosquito vector competence, they might not have any direct effects on virus transmission patterns. Mosquito populations from different parts of Thailand were also likely to be homogeneous in their susceptibility to dengue virus during the study period. Other factors, such as characteristics of the virus, vector density and frequency of host-vector contact, should be considered for seasonal pattern of dengue diseases.