RESUMO
We present evidence that a parasite with characteristics of Plasmodium vivax is being transmitted among Duffy blood group-negative inhabitants of Kenya. Thirty-two of 4,901 Anopheles gambiae and An. funestus (0.65%) collected in Nyanza Province were ELISA positive for the P. vivax circumsporozoite protein VK 247. All positives were found late in the rainy season, when An. funestus predominated, and disproportionately many were found at a single village. A P. vivax specific sequence of the SSU rRNA gene was amplified from three of six ELISA-positive mosquitoes. Erythrocytes from 31 children, including 9 microscopically diagnosed as infected with P. vivax, were negative by flow cytometry for the Fy3 or Fy6 epitopes, which indicate Duffy blood group expression. A DNA fragment specific for the C terminus of the gene for P. vivax merozoite surface protein 1 (MSP-1) was amplified from the blood of four of these children and subsequently sequenced from two.
Assuntos
Anopheles/parasitologia , Sistema do Grupo Sanguíneo Duffy , Insetos Vetores/parasitologia , Malária Vivax/transmissão , Plasmodium vivax/isolamento & purificação , Sequência de Aminoácidos , Animais , Criança , DNA de Protozoário/análise , Sistema do Grupo Sanguíneo Duffy/sangue , Sistema do Grupo Sanguíneo Duffy/genética , Sistema do Grupo Sanguíneo Duffy/imunologia , Ensaio de Imunoadsorção Enzimática , Eritrócitos/imunologia , Eritrócitos/parasitologia , Humanos , Quênia , Malária Vivax/sangue , Malária Vivax/genética , Proteína 1 de Superfície de Merozoito/química , Proteína 1 de Superfície de Merozoito/genética , Dados de Sequência Molecular , Proteínas de Protozoários/análise , Receptores de Superfície Celular/sangue , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/imunologiaRESUMO
We studied the impact of Plasmodium falciparum on nutritional status in a longitudinal cohort of 147 young men in western Kenya, where malaria transmission is intense and perennial. All volunteers received treatment to eradicate parasitemia and then provided weekly blood smears during a 16-week transmission season. We measured body mass index (BMI), pubertal development, frequency and density of parasitemia, and tumor necrosis factor (TNF)-alpha production by peripheral blood mononuclear cells. During early puberty, mean parasite density had a strong negative effect on the natural increase in BMI. Among older individuals, TNF-alpha production in response to malarial antigen predicted a significantly lower BMI (P<.03), equal to 4.6 kg for a man of average height. Our data indicate that burden of parasitemia has a detrimental effect on the nutritional status of early adolescents and that malaria may continue to influence nutritional status among older adolescents and adults via host elaboration of proinflammatory cytokines. These effects of malaria may have pervasive health and socioeconomic consequences in areas where malaria is endemic.