Investigations on the mechanism of DDT resistance in certain anopheline mosquitos.

DDT resistance, first observed some thirteen years ago in houseflies, is rapidly spreading in an alarming number of other insects of public health importance, particularly mosquitos. But while much has been learned of the mechanism of this resistance in houseflies, little is known as yet of the corresponding mechanism in mosquitos. A WHO-sponsored study was designed to find out primarily whether, as in houseflies, the breakdown of DDT to DDE-a non-toxic metabolite-in vivo is the predominant factor responsible for the development of resistance in anopheline mosquitos.No definite correlation could be established between the detoxication of DDT and resistance in the anophelines tested, but the interesting fact emerged that the detoxication potential was a measure of the ratio of DDE to absorbed DDT rather than of the ratio of DDT recovered. A multiplicity of factors governs the development of resistance in mosquitos, each species possessing a "combination of attributes for resistance" that may differ from that of other species; some of these are discussed.