Selection of permethrin resistance in the malaria vector Anopheles stephensi.

The laboratory strain of Anopheles stephensi, a well-known urban malaria vector, was selected with permethrin, a synthetic pyrethroid at LD90 level up to five generations. The selection resulted in the development of resistance in F5 generation to the tune of 13-fold to permethrin and cross-resistance to the tune of 7-fold to cypermethrin, 9-fold to alphamethrin, and 10-fold to deltamethrin. The development of cross-resistance to 4% DDT was also noticed. The susceptibility status against 5% malathion was maintained throughout the five generations. The synergistic effect of piperonyl butoxide with permethrin did not overcome the development of resistance. The development of resistance showed a significant relationship between hatchability and different generations.