Unité Epidémiologie, Institut Pasteur, BP 1274, Antananarivo, Madagascar.
BMC Infect Dis. 2010 Jun 16;10:173. doi: 10.1186/1471-2334-10-173.
Previous studies, conducted in the urban of Antananarivo, showed low rate of confirmed malaria cases. We used a geographical and environmental approach to investigate the contribution of environmental factors to urban malaria in Antananarivo.
Remote sensing data were used to locate rice fields, which were considered to be the principal mosquito breeding sites. We carried out supervised classification by the maximum likelihood method. Entomological study allowed vector species determination from collected larval and adult mosquitoes. Mosquito infectivity was studied, to assess the risk of transmission, and the type of mosquito breeding site was determined. Epidemiological data were collected from November 2006 to December 2007, from public health centres, to determine malaria incidence. Polymerase chain reaction was carried out on dried blood spots from patients, to detect cases of malaria. Rapid diagnostic tests were used to confirm malaria cases among febrile school children in a school survey.A geographical information system was constructed for data integration. Altitude, temperature, rainfall, population density and rice field surface area were analysed and the effects of these factors on the occurrence of confirmed malaria cases were studied.
Polymerase chain reaction confirmed malaria in 5.1% of the presumed cases. Entomological studies showed An. arabiensis as potential vector. Rice fields remained to be the principal breeding sites. Travel report was considered as related to the occurrence of P. falciparum malaria cases.
Geographical and environmental factors did not show direct relationship with malaria incidence but they seem ensuring suitability of vector development. Absence of relationship may be due to a lack of statistical power. Despite the presence of An. arabiensis, scarce parasitic reservoir and rapid access to health care do not constitute optimal conditions to a threatening malaria transmission. However, imported malaria case is suggestive to sustain the pocket transmission in Antananarivo.
先前在塔那那利佛市区进行的研究显示确诊疟疾病例的比例较低。我们采用地理和环境方法来研究环境因素对塔那那利佛城市疟疾的影响。
使用遥感数据定位被认为是主要蚊子滋生地的稻田。我们采用最大似然法进行监督分类。通过收集幼虫和成年蚊子来进行蚊虫学研究，以确定媒介种类。对蚊子的感染性进行研究，以评估传播风险，并确定蚊子滋生地的类型。2006 年 11 月至 2007 年 12 月，我们从公共卫生中心收集流行病学数据，以确定疟疾发病率。对患者的干血斑进行聚合酶链反应，以检测疟疾病例。在学校调查中，使用快速诊断测试来确认发热学童中的疟疾病例。构建了一个地理信息系统来整合数据。分析了海拔、温度、降雨量、人口密度和稻田面积，并研究了这些因素对确诊疟疾病例发生的影响。
聚合酶链反应证实，假定病例中有 5.1%患有疟疾。昆虫学研究表明，An. arabiensis 可能是潜在的传播媒介。稻田仍然是主要的滋生地。旅行报告被认为与恶性疟原虫疟疾病例的发生有关。
地理和环境因素与疟疾发病率没有直接关系，但它们似乎确保了媒介的适宜发育。缺乏关系可能是由于统计能力不足。尽管存在 An. arabiensis，但寄生虫储存量稀少且快速获得医疗保健并不构成威胁疟疾传播的最佳条件。然而，输入性疟疾病例表明，在塔那那利佛维持局部传播的可能性。
