GAMETOCYTEMIA AND INFECTIVITY TO MOSQUITOES OF PATIENTS WITH UNCOMPLICATED PLASMODIUM FALCIPARUM MALARIA ATTACKS TREATED WITH CHLOROQUINE OR SULFADOXINE PLUS PYRIMETHAMINE

Abstract. Plasmodium falciparum gametocytemia and its related infectivity for mosquitoes was studied in 115 patients (median age 18 years, range 4–45) with simple malaria attacks who lived in the hypoendemic area of Dakar, Senegal. Patients were included in a 28-day in vivo sensitivity test after treatment with chloroquine (CQ, n 82) or sulfadoxine plus pyrimethamine (SP, n 33). The prevalence of resistant infections was 58.5 % in those treated with CQ and 0 % in those treated with SP. The gametocytemia peaked at day 7 after treatment. The maximal game-tocyte prevalence was 38.2 % in the CQ-sensitive infection group, 89.6 % in the CQ-resistant group, and 97.0 % in those treated with SP. The maximal geometric mean gametocytemia was 2.19/l in the CQ-sensitive infection group, 29.12/l in the CQ-resistant group and 85.55/l in those treated with SP. The period between appearance of the first clinical symptom and treatment was positively related to gametocyte prevalence at days 0 and 2. Experimental infection of wild Anopheles arabiensis using membrane feeders was performed at days 0 and 7, and mosquito infectivity was measured by oocyst detection on the midgut. At day 0, 14.1 % of the patients had infected at least 1 mosquito, and at day 7, this value was 38.5%. The mean percentage of infected mosquitoes was 3.2 % at day 0 and 12.6 % at day 7. At day 7 after treatment with CQ, the relative risk for patients with resistant infections of infecting anophelines was 4.07 higher than in those with sensitive infections. No difference was observed in infectivity for mosquitoes between RI-type resistance and the RII RIII-type resistance. A sporonticidal effect of SP was observe