A program to control Aedes aegypti was initiated in 1968 at the onset of an outbreak of dengue hemorrhagic fever on the island of Koh Samui in the Gulf of Thailand. About 90% of the domestic-water containers on the island, the principal source of A. aegypti breeding, were treated with the organophosphate Abate® (0,0,0′,0′-tetramethyl-0-0′-thiodi-p-phenylene phosphorothioate), and ground-applied malathion fogs were dispersed to kill adult mosquitoes in all the villages on Koh Samui. An island-wide reduction in both the larval and adult populations of A. aegypti was observed after this program. The duration of pronounced A. aegypti suppression varied from 2 to 8 weeks, according to area under surveillance and the monitoring techniques used. The Abate treatments were also effective in controlling the breeding of A. albopictus in artificial containers inside and around houses, and A. albopictus adults were temporarily suppressed in those areas where malathion fogs were applied. The control measures, however, had little apparent effect upon the A. albopictus populations outside the villages. There was no indication that the temporary reduction in the A. aegypti population on Koh Samui resulted in any significant invasion of domestic habitats of that species by A. albopictus.
Present address: School of Public Health, University of Texas, P.O. Box 20186 Astrodome Station, Houston, Texas 77025.
Present address: Preventive Medicine Division, Office of the Surgeon General, Department of the Army, Washington, D.C. 20314.
Alternate address: SEATO Medical Project, U.S. Component, APO San Francisco, California 96346.