In Venezuela malaria has in some areas been responsive, and in others partially refractory, to DDT indoor residual spraying. Eradication has been achieved in the former areas, as for example in the great north-central region (Area I), where indigenous cases have not been found since 1951. The time required for eradication after the beginning of a spraying program depends on the constitution of malaria, that is, the degree of endemicity and epidemicity of the disease peculiar to a given region. In zones of high endemicity and those of high epidemicity, eradication was reached by the fifth year. In zones of low endemicity and low epidemicity, no more cases were observed after three years of spraying.
The time needed for eradication depends mainly on the bionomics of the vector. A. darlingi malaria took five years to disappear whereas A. albimanus malaria required only three. Where both species occurred together in low densities, three years proved sufficient to eliminate malaria.
As Venezuela is at the crossroads of the neotropical anophelines, and most of the important vectors are present in the country, the experience presented here may be useful for the projected continental program of malaria eradication.