Zhou Guofa, Afrane Yaw A, Malla Sameer, Githeko Andrew K, Yan Guiyun
Program in Public Health, University of California, Irvine, CA92697, USA.
Central for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.
Malar J. 2015 Jan 28;14:41. doi: 10.1186/s12936-015-0551-4.
Epidemiological characteristics of clinical malaria may differ from asymptomatic infections, thus both cross-sectional parasite screening and longitudinal clinical case surveillance are necessary for malaria transmission monitoring and control.
In order to monitor malaria transmission, surveillance of clinical malaria from two years of active case surveillance in three cohorts of 6,750 individuals, asymptomatic parasitaemia cases of 5,300 individuals and clinical cases in three study areas were carried out in the western Kenyan highlands in 2009 and 2010. Age distribution, seasonality and spatial clustering were analysed.
The results revealed a significant difference in the age distribution of clinical cases between passive and active case surveillance, and between clinical case rate and asymptomatic parasite rate. The number of reported cases from health facilities significantly underestimated clinical malaria incidence. The increase in asymptomatic parasite prevalence from low to high transmission seasons was significantly higher for infants (<two years) and adults (≥15 years) (500% increase) than that for children (two to 14 years, 65%), but the increase in clinical incidence rates was significantly higher for children (700%) than that for adults (300%). Hotspot of asymptomatic infections remained unchanged over time, whereas new clusters of clinical malaria cases emerged in the uphill areas during the peak season.
Different surveillance methods revealed different characteristics of malaria infections. The new transmission hotspots identified during the peak season with only active case surveillance is an important observation with clear implications in the context of malaria elimination. Both mass parasite screening and active case surveillance are essential for malaria transmission monitoring and control.
临床疟疾的流行病学特征可能与无症状感染有所不同，因此横断面寄生虫筛查和纵向临床病例监测对于疟疾传播监测和控制均必不可少。
为监测疟疾传播，2009年和2010年在肯尼亚西部高地对三个队列的6750名个体进行了为期两年的临床疟疾主动病例监测，对5300名个体进行了无症状寄生虫血症病例监测，并对三个研究区域的临床病例进行了监测。分析了年龄分布、季节性和空间聚集性。
结果显示，被动和主动病例监测之间的临床病例年龄分布、临床病例率和无症状寄生虫率之间存在显著差异。卫生设施报告的病例数严重低估了临床疟疾发病率。从低传播季节到高传播季节，婴儿（<2岁）和成人（≥15岁）无症状寄生虫感染率的增幅（增加500%）显著高于儿童（2至14岁，增加65%），但儿童临床发病率的增幅（增加700%）显著高于成人（增加300%）。无症状感染的热点地区随时间保持不变，而在高峰期，上坡地区出现了新的临床疟疾病例聚集区。
不同的监测方法揭示了疟疾感染的不同特征。仅通过主动病例监测在高峰期发现的新传播热点是一项重要观察结果，在疟疾消除背景下具有明确意义。大规模寄生虫筛查和主动病例监测对于疟疾传播监测和控制均至关重要。
