Irritability and repellency of synthetic pyrethroids on an Aedes aegypti population from Thailand.

The main objective of this study was to find the optimal dosage of deltamethrin, cyphenothrin, D-tetramethrin, and tetramethrin that would elicit repellency and irritability responses of Aedes aegypti. The F1-F3 generations of field mosquitoes collected from Pu Teuy Village, Sai-Yok District, Kanchanaburi Province, Thailand, were tested with four pyrethroids to determine the LC(25), LC(50), and LC(99). These concentrations were 0.010%, 0.020%, and 0.055%, respectively, for deltamethrin; 0.113%, 0.167%, and 0.353%, respectively, for cyphenothrin; 2.091%, 2.770%, and 5.114%, respectively, for d-tetramethrin; and 2.377%, 4.251%, and 10.715%, respectively, for tetramethrin. All dosages were tested in the excito-repellency system. Survival analysis was used to compare each chamber of the test. It was found that cyphenothrin had a stronger repellent effect than the other pyrethroids, while the contact irritant effect was similar among compounds tested. The LC(50) of each pyrethroid was found to be the optimal dose for repelling Ae. aegypti. There was no significant difference in LC(99) values for either non-contact or contact trials for each pyrethroid.