Development of an Orally Effective Insect Repellent

The objective of this program is to develop insect repellents that can be administered systemically, preferably orally. During this year, the testing of compounds for mosquito repellency by the electronic recording method continued, and the results were statistically analyzed for significant differences from control values in a specialized digital computer program. A new electronic bitometer that facilitates the compilation of laboratory repellency data was developed. Work was continued on a hypothesis developed during the course of this work that could explain the physiochemical basis of a mosquitos attraction to warm-blooded hosts. Gamma-aminobutyric acid GABA was found in aqueous extracts of mosquito heads and bodies, and it was hypothesized that the interactions of GABA with carbon dioxide, heat, and water vapor form the basis of mosquitoes attraction to hosts. Evidence supporting the validity of the hypothesis was obtained from chemical studies of the interactions of GABA with carbon dioxide, correct predictions of chemical structures that should repel mosquitoes and direct in vivo physiological investigations.