BACKGROUND The World Health Organization (WHO) recommends rapid diagnostic tests (RDTs) as a good alternative malaria-diagnosis method in remote parts of sub-Saharan Africa. The majority of commercial RDTs currently available detect the Plasmodium falciparum protein histidine-rich protein 2 (PfHRP2). There have also been recent reports of pfhrp2 gene deletions being found in parasites collected from several African countries. The WHO has concluded that lacking the pfhrp2 gene must be monitored in Africa. The purpose of the study was to analyse why the samples that were positive by PCR were negative by RDTs and, therefore, to determine whether there have been deletions in the pfhrp2 and/or pfhrp3 genes. METHODS Malaria NM-PCR was carried out on all the samples collected in the field. A group of 128 samples was positive by PCR but negative by RDT; these samples were classified as RDT false-negatives. PCR was carried out for exon2 of pfhrp2 and pfhrp3 genes to detect the presence or absence of these two genes. Frequencies with 95% confidence intervals (CIs) were used for prevalence estimates. Associations were assessed by the Chi square test or Fisher´s exact test. The level of significance was set at p ≤ 0.05. Statistical analyses were performed using the software package SPSSv.15.0. RESULTS After PCR, 81 samples were identified (4.7%, 95% CI 3.8-5.8) which had deletion in both genes, pfhrp2 and pfhrp3. Overall, however, 11 samples (0.6%, 95% CI 0.36-1.14) had deletion only in pfhrp2 but not in pfhrp3, and 15 (0.9%, 95% CI 0.6-1.5) presented with deletion only in pfhrp3 but not in pfhrp2. Considering the pfhrp2 gene separately, within the total of 1724 samples, 92 (5.3%, 95% CI 4.37-6.5) had evidence of deletion. CONCLUSION The present study provides the first evidence of deletion in the pfhrp2 and pfhrp3 genes in P. falciparum isolates from Equatorial Guinea. However, larger studies across different regions within the country and across different seasonal profiles are needed to determine the full extent of pfhrp2 and pfhrp3 deletion. It is strongly recommended to implement an active surveillance programme in order to detect any increases in pfhrp2 and pfhrp3 deletion frequencies.

中文翻译：

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赤道几内亚恶性疟原虫pfhrp2和pfhrp3基因缺失的第一个证据。

背景技术世界卫生组织（WHO）推荐快速诊断测试（RDT）作为撒哈拉以南非洲偏远地区的一种很好的替代性疟疾诊断方法。当前可用的大多数商业RDT可检测出恶性疟原虫蛋白富含组氨酸的蛋白2（PfHRP2）。最近也有报道称在从几个非洲国家收集的寄生虫中发现了pfhrp2基因缺失。世界卫生组织得出结论，必须在非洲监测缺乏pfhrp2基因的情况。这项研究的目的是分析为什么PCR阳性的样品被RDT阴性，因此，确定pfhrp2和/或pfhrp3基因是否存在缺失。方法对野外采集的所有样本进行疟疾NM-PCR。一组128个样品经PCR呈阳性，而RDT呈阴性。这些样本被归类为RDT假阴性。对pfhrp2和pfhrp3基因的外显子2进行PCR以检测这两个基因的存在或不存在。具有95％置信区间（CI）的频率用于患病率估计。通过卡方检验或费舍尔精确检验对关联进行评估。显着性水平设定为p≤0.05。使用软件包SPSSv.15.0进行统计分析。结果PCR后，鉴定出81个样品（4.7％，95％CI 3.8-5.8），两个基因pfhrp2和pfhrp3均缺失。但是，总体而言，有11个样本（0.6％，95％CI 0.36-1.14）仅在pfhrp2中删除，而在pfhrp3中没有删除，而15个样本（0.9％，95％CI 0.6-1.5）仅在pfhrp3中删除而在pfhrp2中没有删除。分别考虑pfhrp2基因，在总共1724个样本中，有92个（5.3％，95％CI 4.37-6。5）有删除的证据。结论本研究提供了赤道几内亚恶性疟原虫分离物中pfhrp2和pfhrp3基因缺失的第一个证据。但是，需要进行全国范围内不同地区和不同季节概况的更大研究，才能确定pfhrp2和pfhrp3缺失的完整程度。强烈建议执行主动监视程序，以检测pfhrp2和pfhrp3删除频率的任何增加。