Laboratory and field evaluation of deet, CIC-4, and AI3-37220 against Anopheles dirus (Diptera: Culicidae) in Thailand.

Laboratory and field tests of the repellents diethyl methylbenzamide (deet), 1-(3-Cyclohexen-1-yl-carbonyl)-2-methylpiperidine (AI3-37220), and (2-hydroxymethylcyclohexyl) acetic acid lactone (CIC-4) were conducted against Anopheles dirus Peyton & Harrison, the principal malaria vector in Thailand. In the laboratory, An. dirus was more sensitive to CIC-4 than either AI3-37220 or deet. The duration of protection provided by each repellent in laboratory tests increased with higher concentrations of repellents and when exposed in cages containing fewer mosquitoes. A field study in Chanthaburi Province, southeastern Thailand, during November 1993 tested 25% (wt:wt) ethanol solutions of each repellent against An. dirus. In contrast to the laboratory experiments, protection provided by AI3-37220 was significantly better than either deet or CIC-4 and there was no significant difference between deet and CIC-4. Protection provided by deet and CIC-4 fell to below 95% 2 h after repellent application, whereas AI3-37220 provided > 95% protection for 4 h. The protection provided by all repellents fell to < or = 65% 7 h after repellent application.