Ecology and control of dengue vectors on an island in the Gulf of Thailand.

Entomological observations made on Koh Samui during an epidemic of dengue hemorrhagic fever in 1967 indicated that the densities of the populations of the 2 vector species, Aedes aegypti and Aedes albopictus , were directly related to the amount of rainfall during that period. The incidence of dengue virus infections in man and mosquitoes was also highest during the period of greatest precipitation. On Koh Samui A. aegypti was highly endophilic, while A. albopictus was exophilic, and there was very little overlap between the preferred habitats of the 2 species. Significant numbers of both species were observed to be taking multiple blood meals during their individual gonotrophic cycles. Effective control of the A. aegypti was achieved for a period of approximately 10 weeks in a village on the island by treatment of water storage containers with Abate and by ground applications of malathion fog. The results obtained suggest that such control measures would be effective in preventing dengue transmission by A. aegypti in Thailand.