Epidemiology and Clinical Research Unit, Institut Pasteur de Madagascar, Antananarivo, Madagascar.
IRD, Sorbonne Université, UMMISCO, 93143, Bondy, France.
Malar J. 2022 Aug 21;21(1):242. doi: 10.1186/s12936-022-04260-0.
Targeted research on residual malaria transmission is important to improve strategies in settings pursuing elimination, where transmission reductions prove challenging. This study aimed to detect and characterize spatial heterogeneity and factors associated with Plasmodium falciparum infections and exposure, P. falciparum apical membrane antigen 1 (PfAMA1) antibody (Ab) response, in the Central Highlands of Madagascar (CHL).
From May to July 2014, a cross-sectional school-based survey was carried out in 182 fokontany (villages) within 7 health districts of the CHL. Rapid diagnostic tests (RDTs) and a bead-based immunoassay including PfAMA1 antigen biomarker were used to estimate malaria prevalence and seroprevalence, respectively. Local Moran's I index was used to detect spatial "hotspots". Remotely sensed environmental data-temperature, vegetation indices, land covers, and elevation-were used in multivariable mixed-effects logistic regression models to characterize factors associated with malaria infection and cumulative exposure.
Among 6,293 school-children ages 2-14 years surveyed, RDT prevalence was low at 0.8% (95% CI 0.6-1.1%), while PfAMA1 Ab seroprevalence was 7.0% (95% CI 6.4-7.7%). Hotspots of PfAMA1 Ab seroprevalence were observed in two districts (Ankazobe and Mandoto). Seroprevalence increased for children living > 5 km from a health centre (adjusted odds ratio (OR) = 1.6, 95% CI 1.2-2.2), and for those experiencing a fever episode in the previous 2 weeks (OR 1.7, 95% CI 1.2-2.4), but decreased at higher elevation (for each 100-m increase, OR = 0.7, 95% CI 0.6-0.8). A clear age pattern was observed whereby children 9-10 years old had an OR of 1.8 (95% CI 1.2-2.4), children 11-12 years an OR of 3.7 (95% CI 2.8-5.0), and children 13-14 years an OR of 5.7 (95% CI 4.0-8.0) for seropositivity, compared with younger children (2-8 years).
The use of serology in this study provided a better understanding of malaria hotspots and associated factors, revealing a pattern of higher transmission linked to geographical barriers in health care access. The integration of antibody-assays into existing surveillance activities could improve exposure assessment, and may help to monitor the effectiveness of malaria control efforts and adapt elimination interventions.
针对残留疟疾传播的靶向研究对于改善消除环境中的策略非常重要，因为在这些环境中，传播的减少极具挑战性。本研究旨在检测和描述马达加斯加中央高地（CHL）中空间异质性和与恶性疟原虫感染和暴露、恶性疟原虫顶膜抗原 1（PfAMA1）抗体（Ab）反应相关的因素，这些因素与恶性疟原虫感染和暴露相关。
2014 年 5 月至 7 月，在 CHL 的 7 个卫生区的 182 个 fokontany（村庄）进行了一项基于学校的横断面调查。使用快速诊断测试（RDT）和基于珠的免疫分析，包括 PfAMA1 抗原生物标志物，分别估计疟疾患病率和血清阳性率。局部 Moran's I 指数用于检测空间“热点”。多变量混合效应逻辑回归模型中使用遥感环境数据-温度、植被指数、土地覆盖和海拔-来描述与疟疾感染和累积暴露相关的因素。
在所调查的 6293 名 2-14 岁的学龄儿童中，RDT 患病率较低，为 0.8%（95%置信区间 0.6-1.1%），而 PfAMA1 Ab 血清阳性率为 7.0%（95%置信区间 6.4-7.7%）。在两个区（Ankazobe 和 Mandoto）观察到 PfAMA1 Ab 血清阳性率的热点。对于距离卫生中心>5 公里的儿童（调整后的优势比（OR）为 1.6，95%置信区间 1.2-2.2），以及在前 2 周经历过发热的儿童（OR 为 1.7，95%置信区间 1.2-2.4），血清阳性率增加，但在较高海拔地区（每增加 100 米，OR 为 0.7，95%置信区间 0.6-0.8）降低。观察到了明显的年龄模式，与年龄较小的儿童（2-8 岁）相比，9-10 岁的儿童的 OR 为 1.8（95%置信区间 1.2-2.4），11-12 岁的儿童的 OR 为 3.7（95%置信区间 2.8-5.0），13-14 岁的儿童的 OR 为 5.7（95%置信区间 4.0-8.0）。
本研究中血清学的使用提供了对疟疾热点和相关因素的更好理解，揭示了与获得医疗保健的地理障碍相关的更高传播模式。将抗体检测纳入现有的监测活动中，可以提高暴露评估水平，并有助于监测疟疾控制工作的有效性和适应消除干预措施。
