Dengue vector surveillance and control in Taiwan

In view of possible dengue outbreak due to the rapid development of national tourism to Southeast Asia, the long-neglected Aedes surveillance was resumed since July 1987. After the dengue outbreak was detected in November 1987, the surveillance was greatly intensified, and house mosquitoes were collected for virus isolation. Nine isolates of dengue type one virus were obtained from the female mosquitoes of Aedes aegypti among the 9 species of mosquitoes collected in houses in 1987 and 1988. Health education of the public was enforced by propaganda through newspapers, broadcastings, televisions and public lectures etc. Although the outbreak could be kept under control fairly successfully, the results of Aedes surveys reveal that the achievement in source reduction of Aedes breeding has so far been unsatisfactory. Aedes larval density per 100 houses showed only very gradual lowering each year from 3,010 in 1987 to 1,900, 1,015, 1,373, 604, 570 and 218. Since Ae. aegypti is considered playing an important role in the present outbreak, in 1991 and 1992 residual spray of alphacypermethrin was applied to the interior walls of houses in the area with Breteau index of above 35 for Ae. aegypti. Undoubtedly it contributed much in suppressing the outbreak in recent years.