Medical Research Council Laboratories, Fajara, PO Box 273 Banjul, The Gambia.
Malar J. 2009 Dec 2;8:274. doi: 10.1186/1475-2875-8-274.
Health record-based observations from several parts of Africa indicate a major decline in malaria, but up-to-date information on parasite prevalence in West-Africa is sparse. This study aims to provide parasite prevalence data from three sites in the Gambia and Guinea Bissau, respectively, and compares the usefulness of PCR, rapid diagnostic tests (RDT), serology and slide-microscopy for surveillance.
Cross-sectional surveys in 12 villages at three rural sites were carried out in the Gambia and Guinea Bissau in January/February 2008, shortly following the annual transmission season.
A surprisingly low microscopically detectable parasite prevalence was detected in the Gambia (Farafenni: 10.9%, CI95%: 8.7-13.1%; Basse: 9.0%, CI95%: 7.2-10.8%), and Guinea Bissau (Caio: 4%, CI95%: 2.6-5.4%), with low parasite densities (geometric mean: 104 parasites/microl, CI95%: 76-143/microl). In comparison, PCR detected a more than three times higher proportion of parasite carriers, indicating its usefulness to sensitively identify foci where malaria declines, whereas the RDT had very low sensitivity. Estimates of force of infection using age sero-conversion rates were equivalent to an EIR of approximately 1 infectious bite/person/year, significantly less than previous estimates. The sero-prevalence profiles suggest a gradual decline of malaria transmission, confirming their usefulness in providing information on longer term trends of transmission. A greater variability in parasite prevalence among villages within a site than between sites was observed with all methods. The fact that serology equally captured the inter-village variability, indicates that the observed heterogeneity represents a stable pattern.
PCR and serology may be used as complementary tools to survey malaria in areas of declining malaria prevalence such as the Gambia and Guinea Bissau.
来自非洲多个地区的健康记录观察表明，疟疾的发病率大幅下降，但有关西非寄生虫流行率的最新信息仍然很少。本研究旨在提供冈比亚和几内亚比绍三个地点的寄生虫流行率数据，并比较聚合酶链反应（PCR）、快速诊断检测（RDT）、血清学和涂片显微镜检查在监测中的实用性。
2008 年 1 月/2 月，在冈比亚和几内亚比绍的三个农村地点的 12 个村庄进行了横断面调查，这是在年度传播季节之后不久进行的。
令人惊讶的是，在冈比亚（法拉芬尼：10.9%，95%置信区间：8.7-13.1%；巴塞：9.0%，95%置信区间：7.2-10.8%）和几内亚比绍（卡约：4%，95%置信区间：2.6-5.4%），显微镜可检测到的寄生虫流行率很低，寄生虫密度也很低（几何平均值：104 个/微升，95%置信区间：76-143/微升）。相比之下，PCR 检测到的寄生虫携带者比例高出三倍以上，表明其在敏感识别疟疾下降的焦点方面很有用，而 RDT 的灵敏度非常低。使用年龄血清转化率估计的感染强度相当于每年每 1 人约有 1 个感染性叮咬，明显低于以前的估计。血清流行率特征表明疟疾传播逐渐下降，证实了它们在提供传播长期趋势信息方面的有用性。所有方法都观察到，一个地点内的村庄之间的寄生虫流行率变化比地点之间的变化更大。血清学同样捕捉到了村庄之间的变异性，这表明观察到的异质性代表了一种稳定的模式。
PCR 和血清学可作为在冈比亚和几内亚比绍等疟疾发病率下降地区进行疟疾调查的补充工具。
