A Prospective Study of the Effects of Ultralow Volume (ULV) Aerial Application of Malathion on Epidemic Plasmodium falciparum Malaria

A large-scale prospective study was designed to test the effects of aerial ultralow volume (ULV) application of malathion on epidemic Plasmodium falciparum malaria. The study was conducted during 1972 to 1973, in the Miragoane Valley of Haiti, an area having annual anticipated outbreaks of malaria, which allowed prospective assessment. Spraying of malathion at a dosage of 4.5 fluid ounces per acre reduced populations of adult Anopheles albimanus to less than 1% of prespray levels and interrupted epidemic transmission of P. falciparum malaria. No change was measured in susceptibility of the vector mosquito to malathion after six applications of spray during a period of 50 days. Ecologic study revealed no significant impact on nontarget vertebrates. Factors that contributed to the success of this method in Haiti were: 1) a susceptible population of mosquitoes; 2) suitable topography and climate conditions for spraying; and 3) treatment of an area sufficiently large to minimize the influence of immigration of mosquitoes from unsprayed areas.