Identification of candidate repellents and insecticides for field testing and development

Effective control of vector borne disease requires new types of insecticides and repellents, especially in light of widespread resistance to existing products. Repellency screening of new compounds was conducted in a micro glass tube assay to assess vapor repellency effectiveness in 1 hr exposures to Aedes aegypti or Anopheles gambiae mosquitoes. In this assay, a series of halogenated arylamides has shown repellency greater than or equal to DEET, with GMR189 (2,2,3,3,3-pentafluoro-N-(4-fluorophenyl)propanamide) as the best overall compound with repellent activity about 7-fold more potent. In addition to GMR189, we identified GMR134 (3-phenoxybenzaldehyde) as another spatial repellent with high activity (5.7-fold more potent than DEET), and its chemistry places it as an analog of the natural repellent, benzaldehyde. Other experiments characterized the repellent effects of pyrethroid acids, which are at least as active as DEET, and more importantly display a strong synergistic effect when mixed with other repellents. The best compound in this class was R>,3R)-2,2-dimethyl-3-(2-methylprop-1-en-1-yl)cyclopropane-1-carboxylic acid), abbreviated TCA, which is a component of natural pyrethrins, and synergized both GMR189 (synergism ratio = 56) and GMR134 (synergism ratio = 16). None of these repellents show any kdr-type cross resistance in the Puerto Rico strain of Ae. aegypti. The laboratory performance and planned field experiments with the three finalists, GMR134, GMR189, and TCA, will be discussed.