Department of Biochemistry and Molecular Biology, University of Buea, Buea, Cameroon.
Department of Chemical and Biological Engineering, The University of Bamenda, Bambili, Cameroon.
BMC Infect Dis. 2024 Sep 30;24(1):1080. doi: 10.1186/s12879-024-09935-4.
False negative rapid diagnostic tests (RDTs) accruing to the non-detection of Plasmodium falciparum histidine-rich protein 2/3 (Pfhrp2/3) is threatening the diagnosis and management of malaria. Although regular monitoring is necessary to gauge the level of efficacy of the tool, studies in Cameroon remain limited. This study assessed Plasmodium spp. prevalence and Pfhrp2/3 gene deletions across ecological and transmission zones in Cameroon.
This is a cross-sectional, multi-site, community- and hospital- based study, in 21 health facilities and 14 communities covering all five ecological settings in low seasonal (LS) and intense perennial (IPT) malaria transmission zones between 2019 and 2021. Participants were screened for malaria parasite using Pfhrp2 RDT and light microscopic examination of thick peripheral blood smears. DNA was extracted from dried blood spot using chelex-100 and P. falciparum confirmed using varATS real-time quantitative Polymerase Chain Reaction (qPCR), P. malariae and P. ovale by real-time qPCR of Plasmepsin gene, and P. vivax using a commercial kit. Isolates with amplified Pfcsp and Pfama-1 genes were assayed for Pfhrp 2/3 gene deletions by conventional PCR.
A total of 3,373 participants enrolled, 1,786 Plasmodium spp. infected, with 77.4% P. falciparum. Discordant RDT and qPCR results (False negatives) were reported in 191 (15.7%) P. falciparum mono-infected samples from LS (29%, 42) and IPT (13.9%, 149). The Pfhrp2+/Pfhrp3 + genotype was most frequent, similar between LS (5.5%, 8/145) and IPT (6.0%, 65/1,076). Single Pfhrp2 and Pfhrp3 gene deletions occurred in LS (0.7%, 1/145 each) and IPT (3.6%, 39/1,076 vs. 2.9%, 31/1,076), respectively. Whilst a single sample harboured Pfhrp2-/Pfhrp3- genotype in LS, 2.4% (26/1,076) were double deleted at IPT. Pfhrp2+/Pfhrp3- (0.3%, 3/1,076) and Pfhrp2-/Pfhrp3+ (1.2%, 13/1,076) genotypes were only observed in IPT. Pfhrp2, Pfhrp3 deletions and Pfhrp2-/Pfhrp3- genotype accounted for 78.8% (26), 69.7% (23) and 63.6% (21) RDT false negatives, respectively.
Plasmodium falciparum remains the most dominant and widely distributed Plasmodium species across transmission and ecological zones in Cameroon. Although the low prevalence of Pfhrp2/3 gene deletions supports the continued use of HRP2-based RDTs for routine malaria diagnosis, the high proportion of false-negatives due to gene deleted parasites necessitates continued surveillance to inform control and elimination efforts.
快速诊断检测（RDT）未能检测到恶性疟原虫高变区 2/3 （Pfhrp2/3），这对疟疾的诊断和管理构成了威胁。尽管需要定期监测来评估该工具的效果水平，但喀麦隆的研究仍然有限。本研究评估了 across ecological and transmission zones 中恶性疟原虫的流行情况和 Pfhrp2/3 基因缺失。
这是一项在 2019 年至 2021 年间，在五个低季节性（LS）和高强度常年（IPT）疟疾传播区的 21 个卫生机构和 14 个社区进行的横断面、多地点、社区和医院为基础的研究。使用 Pfhrp2 RDT 和厚外周血涂片的显微镜检查对参与者进行疟疾寄生虫筛查。使用 chelex-100 从干血斑中提取 DNA，并使用 varATS 实时定量聚合酶链反应（qPCR）确认恶性疟原虫，使用 Plasmepsin 基因的实时 qPCR 确认疟原虫、疟原虫和疟原虫，使用商业试剂盒确认疟原虫。使用扩增的 Pfcsp 和 Pfama-1 基因的分离物通过常规 PCR 检测 Pfhrp 2/3 基因缺失。
共纳入 3373 名参与者，1786 名感染疟原虫，其中 77.4%为恶性疟原虫。在 LS（29%，42）和 IPT（13.9%，149）中，191 例恶性疟原虫单感染样本的 RDT 和 qPCR 结果（假阴性）不一致。Pfhrp2+/Pfhrp3+基因型最为常见，在 LS（5.5%，8/145）和 IPT（6.0%，65/1076）中相似。LS（0.7%，1/145）和 IPT（3.6%，39/1076）分别发生单个 Pfhrp2 和 Pfhrp3 基因缺失。虽然 LS 中有一个样本携带 Pfhrp2-/Pfhrp3-基因型，但 IPT 中有 2.4%（26/1076）的样本为双重缺失。Pfhrp2+/Pfhrp3-（0.3%，3/1076）和 Pfhrp2-/Pfhrp3+（1.2%，13/1076）基因型仅在 IPT 中观察到。Pfhrp2、Pfhrp3 缺失和 Pfhrp2-/Pfhrp3-基因型分别占 RDT 假阴性的 78.8%（26）、69.7%（23）和 63.6%（21）。
恶性疟原虫仍然是喀麦隆 across transmission and ecological zones 中最主要和分布最广的疟原虫。尽管 Pfhrp2/3 基因缺失的低流行率支持继续使用基于 HRP2 的 RDT 进行常规疟疾诊断，但由于基因缺失寄生虫导致的高比例假阴性结果需要持续监测，以告知控制和消除努力。
