Specific and Nonspecific Responses to Plasmodium falciparum Blood-Stage Parasites and Observations on the Gametocytemia in Schoolchildren Living in a Malaria-Endemic Area of Mozambique

B. Hogh Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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R. Thompson Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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C. Hetzel Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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S. L. Fleck Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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N. A. A. Kruse Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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I. Jones Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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M. Dgedge Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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J. Barreto Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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R. E. Sinden Laboratory of Parasitology and Epidemiology Research Unit, Statens Seruminstitut, Department of Blood Parasitology and Department of Immunology, National Institute of Health, Molecular and Cellular Parasitology Group, Department of Biology, Imperial College, Copenhagen, Denmark

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We have observed specific and nonspecific reactivities to the asexual stages and gametocytes of Plasmodium falciparum and examined the effect of chloroquine and Fansidar™ (pyrimethamine/sulfadoxine) on the dynamics of gametocytemia. Schoolchildren peripheral blood films positive for P. falciparum gametocytes were identified in a malaria-endemic area of Mozambique. The children were randomly allocated into two groups to receive chloroquine or pyrimethamine/sulfadoxine, and were followed for 28 days after treatment. In patients harboring drug-sensitive parasites, asexual parasitemias were cleared by day 4, but gametocytes persisted for an additional 17 days. The prevalence of the asexual parasites was 67.6% in the chloroquine-treated group at day 0 and 61.1% at day 28, whereas in the pyrimethamine/sulfadoxine treated group, the initial parasite positive prevalence of 70.7% was reduced to 2.4% at day 28, suggesting a high prevalence of chloroquine-resistant parasites. On day 0, gametocyte prevalence was 59.5% in the chloroquine-treated group and in 68.3% in the pyrimethamine/sulfadoxine-treated group; these values were reduced to 5.6% and 2.4%, respectively, at day 28. Our results suggest strongly that there is no induction of gametocytogenesis by either course of chemotherapy.

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