Comparison of surveillance methods applied to a situation of low malaria prevalence at rural sites in The Gambia and Guinea Bissau
Comparison of surveillance methods applied to a situation of low malaria prevalence at rural sites in The Gambia and Guinea Bissau
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DOI：
10.1186/1475-2875-8-274
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发表时间：
2009-12-02
期刊：
影响因子：
3
通讯作者：
Walther, Michael
中科院分区：
文献类型：
--
作者：
Satoguina, Judith;Walther, Brigitte;Walther, Michael
背景：来自非洲多个地区的基于健康记录的观察表明疟疾大幅下降，但有关西非寄生虫流行率的最新信息却很少。本研究旨在分别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 PCR、快速诊断测试 (RDT)、血清学和载玻片显微镜检查在监测方面的有用性。方法：2008 年 1 月/2 月，即年度传播季节结束后不久，对冈比亚和几内亚比绍三个农村地点的 12 个村庄进行了横断面调查。结果：显微镜可检测到的寄生虫流行率出奇地低在冈比亚（法拉芬尼：10.9％，CI95％：8.7-13.1％；巴斯：9.0％，CI95％：7.2-10.8％）和几内亚比绍（Caio：4％，CI95％：2.6-5.4％）检测到寄生虫密度低（几何平均值：104个寄生虫/μl， CI95%：76-143/μl）。相比之下，PCR 检测到的寄生虫携带者比例高出三倍多，这表明它可以灵敏地识别疟疾减少的病灶，而 RDT 的灵敏度非常低。使用年龄血清转化率对感染强度的估计相当于 EIR 约为 1 次传染性叮咬/人/年，明显低于之前的估计。血清流行率概况表明疟疾传播逐渐下降，证实了其在提供有关长期传播趋势信息方面的有用性。所有方法均观察到，同一地点内村庄之间的寄生虫流行率差异大于地点之间的差异。血清学同样捕获了村庄间的变异性，这表明观察到的异质性代表了一种稳定的模式。结论：PCR 和血清学可用作在冈比亚和几内亚比绍等疟疾流行率下降的地区调查疟疾的补充工具。
Background: 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.Methods: 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.Results: 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/mu l, CI95%: 76-143/mu l). 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.Conclusion: 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.