Chad National Malaria Control Programme, N'Djamena, Chad.
School of Public Health and Community Medicine, University of Gothenburg, Gothenburg, Sweden.
Malar J. 2023 Aug 23;22(1):240. doi: 10.1186/s12936-023-04644-w.
Artesunate-amodiaquine (AS-AQ) and artemether-lumefantrine (AL) are the currently recommended first-and second-line therapies for uncomplicated Plasmodium falciparum infections in Chad. This study assessed the efficacy of these artemisinin-based combinations, proportion of day 3 positive patients, proportions of molecular markers associated with P. falciparum resistance to anti-malarial drugs and variable performance of HRP2-based malaria rapid diagnostic tests (RDTs).
A single-arm prospective study assessing the efficacy of AS-AQ and AL at three sites (Doba, Kelo and Koyom) was conducted between November 2020 to January 2021. Febrile children aged 6 to 59 months with confirmed uncomplicated P. falciparum infection were enrolled sequentially first to AS-AQ and then AL at each site and followed up for 28 days. The primary endpoint was PCR-adjusted adequate clinical and parasitological response (ACPR). Samples collected on day 0 were analysed for mutations in pfkelch13, pfcrt, pfmdr-1, pfdhfr, pfdhps genes and deletions in pfhrp2/pfhrp3 genes.
By the end of 28-day follow-up, per-protocol PCR corrected ACPR of 97.8% (CI 95% 88.2-100) in Kelo and 100% in Doba and Kayoma were observed among AL treated patients. For ASAQ, 100% ACPR was found in all sites. All, but one patient, did not have parasites detected on day 3. Out of the 215 day 0 samples, 96.7% showed pfkelch13 wild type allele. Seven isolates carried nonsynonymous mutations not known to be associated artemisinin partial resistance (ART-R). Most of samples had a pfcrt wild type allele (79% to 89%). The most prevalent pfmdr-1 allele detected was the single mutant 184F (51.2%). For pfdhfr and pfdhps mutations, the quintuple mutant allele N51I/C59R/S108N + G437A/540E responsible for SP treatment failures in adults and children was not detected. Single deletion in the pfhrp2 and pfhrp3 gene were detected in 10/215 (4.7%) and 2/215 (0.9%), respectively. Dual pfhrp2/pfhrp3 deletions, potentially threatening the efficacy of HRP2-based RDTs, were observed in 5/215 (2.3%) isolates.
The results of this study confirm that AS-AQ and AL treatments are highly efficacious in study areas in Chad. The absence of known pfkelch13 mutations in the study sites and the high parasite clearance rate at day 3 suggest the absence of ART-R. The absence of pfdhfr/pfdhps quintuple or sextuple (quintuple + 581G) mutant supports the continued use of SP for IPTp during pregnancy. The presence of parasites with dual pfhrp2/pfhrp3 deletions, potentially threatening the efficacy of HRP2-based RDTs, warrants the continued surveillance. Trial registration ACTRN12622001476729.
青蒿琥酯-阿莫地喹（AS-AQ）和青蒿素-哌喹（AL）是目前在乍得治疗无并发症恶性疟原虫感染的一线和二线推荐疗法。本研究评估了这两种基于青蒿素的联合疗法的疗效、第 3 天阳性患者的比例、与抗疟药物耐药性相关的疟原虫分子标志物的比例以及基于 HRP2 的疟疾快速诊断检测（RDT）的不同表现。
2020 年 11 月至 2021 年 1 月，在乍得的多巴、凯洛和科约姆三个地点进行了一项评估 AS-AQ 和 AL 疗效的单臂前瞻性研究。招募了年龄在 6 至 59 个月之间、患有确诊为无并发症恶性疟原虫感染的发热儿童，先在每个地点按序接受 AS-AQ 治疗，然后接受 AL 治疗，并在 28 天内进行随访。主要终点是聚合酶链反应校正的充分临床和寄生虫学反应（ACPR）。在第 0 天收集的样本用于分析 pfkelch13、pfcrt、pfmdr-1、pfdhfr、pfdhps 基因的突变以及 pfhrp2/pfhrp3 基因的缺失。
在 28 天随访结束时，在接受 AL 治疗的患者中，Kelo 的按方案 PCR 校正 ACPR 为 97.8%（95%置信区间 88.2-100），Doba 和 Kayoma 的 ACPR 为 100%。在所有地点，ASAQ 的 ACPR 均为 100%。所有患者（除 1 例外）在第 3 天均未检测到寄生虫。在 215 份第 0 天的样本中，96.7%显示 pfkelch13 野生型等位基因。有 7 个分离株携带与青蒿素部分耐药性（ART-R）无关的非同义突变。大多数样本具有野生型 pfcrt 等位基因（79%-89%）。检测到的最常见 pfmdr-1 等位基因是单突变 184F（51.2%）。对于 pfdhfr 和 pfdhps 突变，未检测到导致成人和儿童 SP 治疗失败的五重突变等位基因 N51I/C59R/S108N + G437A/540E。在 215 份样本中，分别有 10/215（4.7%）和 2/215（0.9%）检测到 pfhrp2 和 pfhrp3 基因的单个缺失。在 5/215（2.3%）分离株中观察到潜在威胁 HRP2 基于 RDT 疗效的双 pfhrp2/pfhrp3 缺失。
本研究结果证实 AS-AQ 和 AL 治疗在乍得的研究地区非常有效。研究地点缺乏已知的 pfkelch13 突变以及第 3 天的高寄生虫清除率提示不存在 ART-R。pfdhfr/pfdhps 五重或六重（五重+581G）突变的缺失支持继续在怀孕期间使用 SP 进行 IPTp。存在具有双 pfhrp2/pfhrp3 缺失的寄生虫，可能威胁基于 HRP2 的 RDT 的疗效，需要持续监测。试验注册 ACTRN12622001476729。
