Studies on filariasis transmission in Kwale, a Tanzanian coastal village, and the results of mosquito control measures.

The main vectors of bancroftian filariasis in Kwale, Tanzania, were Anopheles gambiae complex and Culex p. quinquefasciatus. After vector control by the insecticides Dursban (chlorpyrifos) or Abate (temephos), the number of all man-biting mosquitoes was reduced by 94.8%, and that of house-resting mosquitoes by 95.3%. Anopheles gambiae complex were highly exophilic, possibly due to a high proportion of Anopheles merus in this village. The infection rate of A. gambiae complex rose significantly in the post-control samples (P less than 0.05), but nevertheless the overall reduction in filariasis transmission was 87.2%. The infection rate of A. gambiae complex caught off human bait was significantly higher than that of the spray-caught sample (P less than 0.05). It was suggested that the former sample contained a higher proportion of A. merus. This species may be a better vector of filariasis than freshwater forms.