Estimates of the infectious reservoir of Plasmodium falciparum malaria in The Gambia and in Tanzania

Separate studies carried out in Farafenni, The Gambia and Ifakara, Tanzania in 1990-94 provided comparative data on population age structure, populati on gametocyte prevalences and gametocyte carrier infectivity. The percentag e of the population estimated to be infective to mosquitoes was 5(.)5% and 3(.)8% in The Gambia and Tanzania, respectively. The age groups 1-4 years, 5-9 years, 10-19 years and 20 years or more comprised 17(.)5%, 21(.)7%, 22( .)2% and 37(.)9%, respectively, of the infectious population in The Gambia; the corresponding figures for Tanzania were 30(.)9%, 25(.)2%, 15(.)7% and 28(.)1%. These figures are in broad agreement with those from other publish ed studies which estimated the infectious reservoir directly and suggest th at adults contribute significantly to the infectious reservoir of malaria, particularly in areas of intense seasonal transmission. Control measures ai med at reduction of transmission may have only a limited effect in areas of moderate seasonal transmission if directed only at children.