Epidemiology of Malaria in the Peruvian and Brazilian Amazon

设在两个疟疾流行国家巴西和秘鲁的机构正在与美国的一个主要研究小组合作，其长期目标是提供科学证据，这些证据可转化为有效的公共卫生干预措施，以在亚马逊地区控制疟疾。为了确定无症状疟原虫携带是否是该地区疟疾传播的主要因素，我们的目标是：(a)估计亚马逊农村地区无症状疟原虫携带的流行率、发病率和危险因素；(b)估计配子体携带的流行率、发生率、平均持续时间和危险因素；(c)比较配子细胞有症状携带者和无症状携带者实验性感染野生本地病媒的能力；(d)前瞻性比较生活在同一社区的无症状寄生虫携带者和未受感染的对照者随后发生临床疟疾的风险，并确定这些事件是由于持续存在的寄生虫谱系还是由于新的感染；(e)测试遗传上不同的寄生虫克隆的宿主内竞争是否有助于增加寄生虫的毒力、增加疾病风险和增加配子体的产生。这些目标将通过人口调查实现，采用统一的临床和实验室协议，在三个流行病学不同的亚马逊环境中：(a)巴西有地方性疟疾传播的典型农业定居点，(b)秘鲁最近接触到流行病疟疾的城郊村庄，以及(c)秘鲁金矿飞地，间日疟原虫导致疟疾爆炸性爆发。实地临床和流行病学分析将辅之以免疫学参数测量、广泛的寄生虫基因分型和通过膜食法对蚊子进行实验感染，为亚马逊盆地无症状寄生虫携带的公共卫生意义提供独特的多学科视角。至关重要的是，基础设施和实地七年积极疟疾监测所产生的数据将为本建议的媒介生物学和发病机制组成部分以及为今后在亚马逊地区开展疟疾疫苗试验奠定基础。

Institutions based in two malaria-endemic countries, Brazil and Peru, are partnering with a leading research group in the USA with the long-term goal of providing scientific evidence that can be translated into effective public health interventions for malaria control in Amazonia. To determine whether asymptomatic parasite carriage is a major contributor to malaria transmission across the region, we aim: (a) to estimate the prevalence, incidence and risk factors for asymptomatic malaria parasite carriage in rural Amazonia; (b) to estimate the prevalence, incidence, average duration and risk factors for gametocyte carriage; (c) to compare the ability of symptomatic and asymptomatic carriers of gametocytes to experimentally infect wild caught local vectors; (d) to compare prospectively the risk of subsequent clinical malaria among asymptomatic parasite carriers and non-infected controls living in the same communities and to determine whether these episodes are due to persistent parasite lineages or to new infections; and (e) to test whether intra-host competition of genetically distinct parasite clones contributes to increased parasite virulence, greater risk of disease, and increased gametocyte production. These aims will be achieved with population based surveys, using uniformized clinical and laboratory protocols, in three epidemiologically diverse Amazonian settings: (a) a typical agricultural settlement with endemic malaria transmission in Brazil, (b) periurban villages in Peru that became recently exposed to epidemic malaria, and (c) gold-mining enclaves in Peru with explosive malaria outbreaks due to P. vivax. The field-based clinical and epidemiological analysis will be complemented with measurements of immunological parameters, extensive parasite genotyping and experimental infections of mosquitoes through membrane-feeding assays, providing a unique multidisciplinary perspective on the public health significance of asymptomatic parasite carriage in the Amazon Basin. Of crucial importance, the infrastructure and the data resulting of seven years of active malaria surveillance in the field sites will establish the bases for the vector biology and pathogenesis components of this proposal and for implementing future malaria vaccine trials in the Amazon region.