Trials with dichlorvos (DDVP) against malaia vectors in huts in Northern Nigeria

Abstract

The present investigations were undertaken because of the paucity of information on the effect of dichlorvos (2,2-dichlorvinyl dimethyl phosphate) on malaria vectors in village huts in the savannah areas of nigeria and West Africa. The relative efficiencies of 3 different makes of dichlorvos dispensers were compared by bio-assays with blood-fed Aedes (Stegomyia) aegypti (L) in village huts in the Kaduna area of Nigeria. A bio-assay mortality of 70% and over was achieved for the first 9–11 weeks. Field trials conducted with Shell dispensers on normal populations of Anopheles gambiae Giles and A. funestus Giles showed that dichlorvos was strongly repellent to both species, resulting in greatly decreased numbers of vectors in the huts. There was little irritant effect of dichlorvos on mosquitoes inside the huts, as there was little increase in either the numbers of vectors, or in their infed individuals, that left the huts. There was no reduction in the number of vectors resting under the outside eaves of dichlorvos huts and no decrease in feeding in the huts, although fewer bites per man were received in them because of a reduction in the numbers entering them. Mortalities of A. gambiae and A. funestus from dichlorvos huts were low, and it appeared unlikely that the insecticide would achieve any measure of control over malaria vectors in Northern Nigeria.