Potential for Organophosphate Resistance in Aedes aegypti (Diptera: Culicidae) in the Caribbean Area and Neighboring Countries

Populations of Aedes aegypti (L.) from 28 sites in Caribbean islands and neighboring countries were tested during 1983–85 for larval resistance to temephos, malathion, fenthion, and propoxur. Nearly all populations displayed somewhat elevated LC95 values toward temephos. In two cases, Tortola and Antigua, susceptibility to this widely used larvicide was 47.4- and 46.8-fold lower than normal, indicating presence of significant resistance; operational importance of this resistance requires investigation. Fenthion resistance was recorded in most collections but at lower levels than for temephos. Malathion resistance was likewise low and present in only 10 of the sites sampled. Some propoxur resistance was found in nearly all samples, but maximal levels (in Granada) did not exceed 10.8-fold. Selection of a synthetic population of A. aegypti from various countries by temephos pressure in the laboratory produced 104.3-fold resistance within 19 generations, thus indicating that risk for organophosphate resistance in this important vector species requires serious consideration.