www.thelancet.com/infection Vol 21 April 2021 e82 Review Spatial and molecular mapping of Pfelch13 gene polymorphism in Africa in the era of emerging Plasmodium falciparum resistance to artemisinin: a systematic review Nadine K Kayiba, Doudou M Yobi, Evariste Tshibangu-Kabamba, Vo P Tuan, Yoshio Yamaoka, Brecht Devleesschauwer, Dieudonné M Mvumbi, Emile Okitolonda Wemakoy, Patrick De Mol, Georges L Mvumbi, Marie-Pierre Hayette, Angel Rosas-Aguirre, Niko Speybroeck The spread of Plasmodium falciparum isolates carrying mutations in the kelch13 (Pfkelch13) gene associated with artemisinin resistance (PfART-R) in southeast Asia threatens malaria control and elimination eforts. Emergence of PfART-R in Africa would result in a major public health problem. In this systematic review, we investigate the frequency and spatial distribution of Pfkelch13 mutants in Africa, including mutants linked to PfART-R in southeast Asia. Seven databases were searched (PubMed, Embase, Scopus, African Journal Online, African Index Medicus, Bioline, and Web of Science) for relevant articles about polymorphisms of the Pfkelch13 gene in Africa before January, 2019. Following PRISMA guidelines, 53 studies that sequenced the Pfkelch13 gene of 23 100 sample isolates in 41 sub-Saharan African countries were included. The Pfkelch13 sequence was highly polymorphic (292 alleles, including 255 in the Pfkelch13-propeller domain) but with mutations occurring at very low relative frequencies. Non- synonymous mutations were found in only 626 isolates (2·7%) from west, central, and east Africa. According to WHO, nine diferent mutations linked to PfART-R in southeast Asia (Phe446Ile, Cys469Tyr, Met476Ile, Arg515Lys, Ser522Cys, Pro553Leu, Val568Gly, Pro574Leu, and Ala675Val) were detected, mainly in east Africa. Several other Pfkelch13 mutations, such as those structurally similar to southeast Asia PfART-R mutations, were also identifed, but their relevance for drug resistance is still unknown. This systematic review shows that Africa, thought to not have established PfART-R, reported resistance-related mutants in the past 5 years. Surveillance using PfART-R molecular markers can provide valuable decision-making information to sustain the efectiveness of artemisinin in Africa. Lancet Infect Dis 2021; 21: e82–92 Published Online October 27, 2020 https://doi.org/10.1016/ S1473-3099(20)30493-X Institute of Health and Society, Université catholique de Louvain, Brussels, Belgium (N K Kayiba MPH, A Rosas-Aguirre PhD, Prof N Speybroeck PhD); Department of Public Health (N K Kayiba) and Department of Basic Sciences, University of Mbujimayi, Mbujimayi, DR Congo (E Tshibangu-Kabamba PhD); Department of Epidemiology and Biostatistics (N K Kayiba, Prof E Okitolonda Wemakoy PhD) and Department of Basic Sciences (DM Yobi MSc, D M Mvumbi PhD, Prof G L Mvumbi PhD), University of Kinshasa, Kinshasa, DR Congo; Department of Endoscopy, Cho Ray Hospital, Ho Chi Minh, Vietnam (V P Tuan PhD); Department of Environmental and Preventive Medicine, Oita University, Yufu, Japan (V P Tuan, E Tshibangu-Kabamba, Prof Y Yamaoka PhD); Department of Epidemiology and Public Health, Sciensano, Brussels, Belgium (B Devleesschauwer PhD); Department of Veterinary Public Health and Food Safety, Ghent University, Merelbeke, Belgium (B Devleesschauwer); and Department of Parasitology and Mycology, University Hospital of Liège, Liège, Belgium (Prof P De Mol PhD, Prof M-P Hayette PhD) Correspondence to: Prof Niko Speybroeck, Institute of Health and Society, Faculty of Public Health, Université catholique de Louvain, Brussels 1200, Belgium niko.speybroeck@uclouvain.be Introduction An estimated 219 million new malaria cases and 435 000 deaths occurred globally in 2017, with more than 75% of these cases coming from Africa. 1 In the absence of an efective vaccine, reducing the burden of Plasmodium falciparum malaria relies on the efectiveness of arte- misinin-based combination therapies (ACTs). 1,2 ACTs combine the rapid antimalarial action (but short half- life) of artemisinin or its derivatives with the slower action (but longer half-life) of partner drugs. 3 However, one major challenge for malaria control and elimination eforts is the emergence and spread of P falciparum artemisinin resistance (PfART-R) from the Greater Mekong subregion in southeast Asia over the past decade. 4–6 A reverse migration of PfART-R resistance towards Africa (by comparison with the evolutionary origin and spread of the parasite) 7 is a troubling scenario that could have severe consequences on the burden of malaria because alternative therapies are few. 8–10 As this resistance is not yet established in Africa, monitoring PfART-R on the continent is necessary from a global health perspective. 9 Therapeutic efcacy trials are the standard method for assessing PfART-R; however, insufcient funding restricts these studies in African countries. 3,11,12 The delayed parasite clearance obtained in clinical trials and the in-vitro ring-stage (trophozoite) survival assay are also useful for tracking the emergence of artemisinin resistance. 5,13–15 The association of specifc single nucleotide poly- morphisms (SNPs) in the P falciparum kelch 13 gene (Pfkelch13) with delayed parasite clearance has raised the potential of molecular markers for the surveillance of PfART-R. 14,16,17 More than 100 Pfkelch13 mutations have been reported in Africa, but there is still little evidence of PfART-R mutants circulating in the continent. 9,18 In this systematic review, we examine studies reporting Pfkelch13 SNPs across diferent African countries to determine the relative frequencies and spatial distri- bution of parasites carrying mutations currently con- sidered to be PfART-R markers. Methods Search strategy and selection criteria Our systematic review follows the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. 19,20 Seven electronic medical databases (Pub- Med, Embase, Scopus, African Journal Online, African Index Medicus, Bioline, and Web of Science) were searched for peer-reviewed articles published before January, 2019, that have the relevant population, inter- vention, comparator, outcomes, and study design (PICOS) framework (appendix p 2). A predetermined search strategy used French and English versions of keyword terms of the Medical Subject Headings 2018 database and free terms, such as (“malaria” OR “falciparum” OR “paludisme”) AND (“marqueur moléculaire” OR “molecular marker” OR See Online for appendix