Molecular methods for tracking residual Plasmodium falciparum transmission in a close-to-elimination setting in Zanzibar
Molecular methods for tracking residual Plasmodium falciparum transmission in a close-to-elimination setting in Zanzibar
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DOI：
10.1186/s12936-020-3127-x
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发表时间：
2020-01-29
期刊：
影响因子：
3
通讯作者：
Felger, Ingrid
中科院分区：
文献类型：
--
作者：
Grossenbacher, Benjamin;Holzschuh, Aurel;Felger, Ingrid
低密度恶性疟原虫感染的分子检测对于在接近消灭的环境中为疟疾控制策略提供信息的监测研究至关重要。残留疟疾感染的分子监测通常需要大规模的研究，因此采样和诊断过程需要经济并优化以实现高通量。进行了方法比较，以确定最有效的诊断程序，以最佳的测试灵敏度，简单性和最低的成本处理大量的社区样本。方法在桑给巴尔进行的反应性病例检测研究中，通过针对每个寄生虫基因组多个var基因拷贝的高灵敏度定量（q）PCR对4590名所有年龄段的个体的寄生虫血症进行了研究。为了降低成本，第一轮阳性筛选是在来自五个个体的干血斑池上进行的。直接在滤纸穿孔上进行10个循环的预PCR，然后进行qPCR。在第二轮中，通过pre-PCR和qPCR单独分析阳性合并样本。结果4590例指示病例的家庭成员和邻居的感染率为1.7%（78/4590），寄生虫密度几何平均数为58只/亩血。以qPCR为金标准，快速诊断试验（RDTs）的诊断敏感性为37%（29/78）。qPCR呈阳性但RDT呈阴性的感染的平均密度为15个寄生虫/μ l血液。结论预筛选反应性病例检测样本的方法在5个池中是理想的低患病率设置，如在桑给巴尔。在滤纸打孔器上进行直接PCR可以节省大量时间，并证明适合直接从全血中扩增DNA的聚合酶的成本较高是合理的。社区样本的分子监测提供了更准确的感染流行情况，因为它确定了RDT在很大程度上错过的潜在感染库。已开发的用于筛选大型样本集的基于qPCR的方法主要是一种研究工具，应能为制定消除疟疾战略提供信息。它也可能被证明有益于监测反应活动中的诊断任务。
Background Molecular detection of low-density Plasmodium falciparum infections is essential for surveillance studies conducted to inform malaria control strategies in close-to-elimination settings. Molecular monitoring of residual malaria infections usually requires a large study size, therefore sampling and diagnostic processes need to be economical and optimized for high-throughput. A method comparison was undertaken to identify the most efficient diagnostic procedure for processing large collections of community samples with optimal test sensitivity, simplicity, and minimal costs. Methods In a reactive case detection study conducted on Zanzibar, parasitaemia of 4590 individuals of all ages was investigated by a highly sensitive quantitative (q) PCR that targets multiple var gene copies per parasite genome. To reduce cost, a first round of positivity screening was performed on pools of dried blood spots from five individuals. Ten cycles of a pre-PCR were performed directly on the filter paper punches, followed by qPCR. In a second round, samples of positive pools were individually analysed by pre-PCR and qPCR. Results Prevalence in household members and neighbors of index cases was 1.7% (78/4590) with a geometric mean parasite density of 58 parasites/mu l blood. Using qPCR as gold standard, diagnostic sensitivity of rapid diagnostic tests (RDTs) was 37% (29/78). Infections positive by qPCR but negative by RDT had mean densities of 15 parasites/mu l blood. Conclusion The approach of pre-screening reactive case detection samples in pools of five was ideal for a low prevalence setting such as in Zanzibar. Performing direct PCR on filter paper punches saves substantial time and justifies the higher cost for a polymerase suitable for amplifying DNA directly from whole blood. Molecular monitoring in community samples provided a more accurate picture of infection prevalence, as it identified a potential reservoir of infection that was largely missed by RDT. The developed qPCR-based methodology for screening large sample sets represents primarily a research tool that should inform the design of malaria elimination strategies. It may also prove beneficial for diagnostic tasks in surveillance-response activities.