Effect of DDT on survival and blood feeding success of Anopheles arabiensis in northern Kwazulu, Republic of South Africa.

The effect of house spraying with DDT on blood-feeding and resting behavior of An. arabiensis in Natal Province, Republic of South Africa, was investigated. Indoor resting occurred in both control (unsprayed) and replastered (DDT on walls covered due to replastering) huts, but was minimal in fully DDT-sprayed huts. The percentage of bloodfed mosquitoes was greater than 50% in both control and replastered huts, but in the latter huts there was a reduction in the percentage of gravid and an increase in the percentage of unfed mosquitoes. Large numbers were collected in exit traps irrespective of the DDT status of the huts. The percentage of catch that was bloodfed was lowest in exit traps fitted on DDT-sprayed houses. The percentage survival of bloodfed mosquitoes caught in exit traps exceeded 72% for all 3 hut types. The survival of unfed mosquitoes was, however, markedly lower. Susceptibility tests showed no physiological tolerance to DDT by the wild An. arabiensis population. Bioassays using colonized An. arabiensis showed the DDT deposits on hut walls to effect 100% kill with 15 minutes of exposure.