Anopheles Culicifacies (Diptera: Culicidae): Ddt Resistance in Sri Lanka Prior to and after Cessation of Ddt Spraying

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Abstract
Insecticide susceptibility tests on Anopheles culicifacies, the only known vector of malaria in Sri Lanka, using 4% DDT with 1–h exposure indicated that there is a polymorphism for the DDT-resistance gene in all the populations sampled; the frequency of this gene seems to be relatively stable over many years and from population to population. The data include tests taken 3–5 years before and 1–4 years after DDT spraying of houses was halted. There were no significant differences in the mortality rates at one village before and after DDT spraying was halted, although there was some significant variation from month to month in each year. These data from Sri Lanka are compared with more recent tests in India to assess their significance for the evolution of insecticide resistance.