An evaluation of the residual lifespan of DDT in malaria control.
The insecticide lifespan of DDT was assessed in huts sprayed for malaria control. The age of the spray deposits ranged from 3 up to 22 months. Blood-fed female Anopheles arabiensis were either released into the huts or exposed on sprayed surfaces by a bioassay technique. Mosquitoes released were recovered in exit traps fitted on windows or dead on the floor. Only 50% or less of mosquitoes released in sprayed huts were recovered. Mortality figures for recovered mosquitoes ranged from 94% at 3 months, declining to 19% for huts sprayed 18 months previously. Of the recovered mosquitoes, 60% or more attempted to escape from sprayed huts within two hours postrelease up to 15 months postspray. Bioassays gave average mortalities of 95 and 76% on thatch and mud walls, respectively. Analysis of mud samples from test huts showed that target dose of 2 g AI/m2 of DDT was not being achieved. The results support the need for an annual spraying cycle.
Mpofu
S M
SM
Blair Research Laboratory, Causeway, Harare, Zimbabwe.
Taylor
P
P
Govere
J
J
D000818:Animals; D000852:Anopheles; D001681:Biological Assay; D003634:DDT / Q000032:analysis*; D005260:Female; D006801:Humans; D007303:Insect Vectors; D008288:Malaria / Q000517:prevention & control*; D009032:Mosquito Control / Q000379:methods*; D010573:Pesticide Residues / Q000032:analysis*; D013997:Time Factors
D010573:Pesticide Residues; D003634:DDT