[Exceptional resistance of Malagasy plague-transmitting fleas to insecticides]

Two plague transmitting malagasy fleas S. fonquerniei and X. cheopis, caugh in the cities of Tananarive, Antsirabe-Betafo and Ampefy were tested in conformity with WHO standards. These two fleas were resistant to DDT, dieldrin and malathion, Moreover, X. cheopis from the cities of Tananarive and Antsirabe-Betafo were resistant fenitrothion and propoxur. It seems to be first description of simultaneous resistance to organochlorinated, organophosphorylated and carbamylated products. The authors discuss the causes of this exceptional phenomenon, and make some suggestions in order to obtain a better knowledge and understanding of this phenomenon.