RESUMO
BACKGROUND: Malaria is the direct cause of approximately one million deaths worldwide each year, though it is both preventable and curable. Increasing the understanding of the transmission dynamics of falciparum and vivax malaria and their relationship could suggest improvements for malaria control efforts. Here the weekly number of malaria cases due to Plasmodium falciparum (1994-2006) and Plasmodium vivax (1999-2006) in Perú at different spatial scales in conjunction with associated demographic, geographic and climatological data are analysed. METHODS: Malaria periodicity patterns were analysed through wavelet spectral analysis, studied patterns of persistence as a function of community size and assessed spatial heterogeneity via the Lorenz curve and the summary Gini index. RESULTS: Wavelet time series analyses identified annual cycles in the incidence of both malaria species as the dominant pattern. However, significant spatial heterogeneity was observed across jungle, mountain and coastal regions with slightly higher levels of spatial heterogeneity for P. vivax than P. falciparum. While the incidence of P. falciparum has been declining in recent years across geographic regions, P. vivax incidence has remained relatively steady in jungle and mountain regions with a slight decline in coastal regions. Factors that may be contributing to this decline are discussed. The time series of both malaria species were significantly synchronized in coastal (rho = 0.9, P < 0.0001) and jungle regions (rho = 0.76, P < 0.0001) but not in mountain regions. Community size was significantly associated with malaria persistence due to both species in jungle regions, but not in coastal and mountain regions. CONCLUSION: Overall, findings highlight the importance of highly refined spatial and temporal data on malaria incidence together with demographic and geographic information in improving the understanding of malaria persistence patterns associated with multiple malaria species in human populations, impact of interventions, detection of heterogeneity and generation of hypotheses.
Assuntos
Meio Ambiente , Malária Falciparum/epidemiologia , Malária Vivax/epidemiologia , Plasmodium falciparum/isolamento & purificação , Plasmodium vivax/isolamento & purificação , Animais , Geografia , Humanos , Incidência , Malária Falciparum/transmissão , Malária Vivax/transmissão , Peru/epidemiologia , Estações do Ano , Clima TropicalRESUMO
Diagnosis of Chagas disease is hindered by discordance between screening and confirmatory test results for Trypanosoma cruzi infection. In periurban Arequipa, Peru, spatial analysis revealed that individuals with discordant test results are spatially clustered in hotspots of T. cruzi transmission, suggesting that discordant results likely represent true infections in this setting.
Assuntos
Doença de Chagas/diagnóstico , Doença de Chagas/epidemiologia , Trypanosoma cruzi/isolamento & purificação , Animais , Doença de Chagas/transmissão , Análise por Conglomerados , Simulação por Computador , Ensaio de Imunoadsorção Enzimática , Imunofluorescência , Humanos , Modelos Biológicos , Método de Monte Carlo , Peru/epidemiologia , Ensaio de Radioimunoprecipitação , Fatores de Tempo , Topografia MédicaRESUMO
Two expert research microscopists, each blinded to the other's reports, diagnosed single-species malaria infections in 2,141 adults presenting at outpatient malaria clinics in Tak Province, Thailand, and Iquitos, Peru, in May-August 1998, May-July 1999, and May-June 2001. Plasmodium vivax patients with gametocytemia had higher fever and higher parasitemia than those without gametocytemia; temperature correlated with parasitemia in the patients with gametocytemia. Plasmodium falciparum patients with gametocytemia had lower fever than those without gametocytemia, but similar parasitemia; temperature correlated with parasitemia in the patients without gametocytemia. Hematologic data in Thailand in 2001 showed lower platelet counts in P. vivax patients with gametocytemia than in the P. vivax patients without gametocytemia, whereas P. falciparum patients with gametocytemia had similar platelet counts but lower red blood cell counts, hemoglobin levels, hematocrit levels, and higher lymphocyte counts than patients without gametocytemia.
Assuntos
Doenças Endêmicas , Malária Falciparum/epidemiologia , Malária Vivax/epidemiologia , Parasitemia/epidemiologia , Adulto , Fatores Etários , Animais , Estudos Transversais , Contagem de Eritrócitos , Feminino , Febre , Hematócrito , Hemoglobinas/análise , Humanos , Contagem de Leucócitos , Malária Falciparum/parasitologia , Malária Vivax/parasitologia , Masculino , Parasitemia/parasitologia , Peru/epidemiologia , Tailândia/epidemiologiaRESUMO
Enumeration of parasites by microscopic examination of blood smears is the only method available for quantifying parasitemia in infected blood. However, the sources and scale of error inherent in this technique have not been systematically investigated. Here we use data collected in outpatient clinics in Peru and Thailand to elucidate important sources of variation in parasite density measurements. We show that discrepancies between readings from two independent microscopists and multiple readings from a single microscopist are inversely related to the density of the infection. We present an example of how differences in reader technique, specifically the number of white blood cells counted, can contribute to the differences between readings. We discuss the implications of this analysis for field studies and clinical trials.
Assuntos
Malária Falciparum/diagnóstico , Malária Falciparum/epidemiologia , Malária Vivax/diagnóstico , Malária Vivax/epidemiologia , Microscopia/métodos , Animais , Humanos , Leucócitos/parasitologia , Variações Dependentes do Observador , Peru , TailândiaRESUMO
White blood cells (WBCs) were counted in 4697 individuals who presented to outpatient malaria clinics in Maesod, Tak Province, Thailand, and Iquitos, Peru, between 28 May and 28 August 1998 and between 17 May and 9 July 1999. At each site and in each year, WBC counts in the Plasmodium falciparum-infected patients were lower than those in the Plasmodium vivax-infected patients, which, in turn, were lower than those in the uninfected patients. In Thailand, one-sixth of the P. falciparum-infected patients had WBC counts of <4000 cells/microL. Leukopenia may confound population studies that estimate parasite densities on the basis of an assumed WBC count of 8000 cells/microL. For instance, in the present study, use of this conventional approach would have overestimated average asexual parasite densities in the P. falciparum-infected patients in Thailand by nearly one-third.