Hypoendemic Malaria in Rondonia (Brazil, Western Amazon Region): Seasonal Variation and Risk Groups in an Urban Locality

Luis Marcelo Aranha CamargoDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Gloria Maria Duccini Dal CollettoDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Marcelo Urbano FerreiraDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Sergio De Mello GurgelDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Ana Lucia EscobarDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Agostinho MarquesDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Henrique KriegerDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Erney Plessmann CamargoDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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Luiz Hildebrando Pereira Da SilvaDepartmento de Parasitologia, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Unite de Parasitologie Experimentale, Institute Pasteur, Universidade de Rondonia, Fundacao Nacional de Saude Brasilia, Sao Paulo, Brazil

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A longitudinal epidemiologic survey (1989–1991) plus a cross-sectional parasitologic, clinical, and sociodemographic survey (July–October 1990) were conducted in Candeias do Jamary, a village with approximately 7,000 inhabitants in Rondonia, Brazil. Analysis of the results revealed hypoendemic malaria with a complex epidemiology. Plasmodium vivax predominated over P. falciparum infections while infections with P. malariae were absent. Malaria is present throughout the year but was clearly seasonal with epidemic outbreaks in the dry season from June to August. Malaria prevalence was lower in children less than 10 years of age and significantly higher in young adult males, which represent the high-risk group. The incidence of locally acquired infections (autochthonous cases) was significantly lower in the rainy season as compared with the dry season. This is not true with respect to heterotochthonous (imported) malaria cases, that is, malaria acquired elsewhere by Candeias residents, most of whom are male adults working outside the town. In both cases, however, the age and sex distribution of prevalence and its relationship with occupational activities indicate a predominance of outdoor transmission. The results of the cross-sectional survey are in agreement with those of the longitudinal passive survey and, in addition, disclose the absence of asymptomatic infection.

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