Pascal Ringwald

World Health Organization WHO, Genève, Geneva, Switzerland

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Publications (189)1003.15 Total impact

  • Christopher V Plowe · Pascal Ringwald
    The Lancet Infectious Diseases 09/2015; 15(9):1001-2. DOI:10.1016/S1473-3099(15)00232-7 · 22.43 Impact Factor
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    ABSTRACT: Primaquine is used to prevent Plasmodium vivax relapse; however, it is not implemented in many malaria-endemic countries, including Cambodia, for fear of precipitating primaquine-induced acute haemolytic anaemia in patients with glucose-6-phosphate dehydrogenase deficiency (G6PDd). Reluctance to use primaquine is reinforced by a lack of quality safety data. This study was conducted to assess the tolerability of a primaquine regimen in Cambodian severely deficient G6PD variants to ascertain whether a weekly primaquine could be given without testing for G6PDd. From January 2013 to January 2014, Cambodians with acute vivax malaria were treated with dihydroartemisinin/piperaquine on days (D) 0, 1 and 2 with weekly doses of primaquine 0.75 mg/kg for 8 weeks (starting on D0, last dose on D49), and followed until D56. Participants' G6PD status was confirmed by G6PD genotype and measured G6PD activity. The primary outcome was treatment completion without primaquine toxicity defined as any one of: (1) severe anaemia (haemoglobin [Hb] <7 g/dL), (2) a >25 % fractional fall in Hb from D0, (3) the need for a blood transfusion, (4) haemoglobinuria, (5) acute kidney injury (an increase in baseline serum creatinine >50 %) or (6) methaemoglobinaemia >20 %. We enrolled 75 patients with a median age of 24 years (range 5-63); 63 patients (84 %) were male. Eighteen patients were G6PDd (17/18 had the Viangchan variant) and had D0 G6PD activity ranging from 0.1 to 1.5 U/g Hb (median 0.85 U/g Hb). In the 57 patients with normal G6PD (G6PDn), D0 G6PD activity ranged from 6.9 to 18.5 U/g Hb (median 12 U/g Hb). Median D0 Hb concentrations were similar (P = 0.46) between G6PDd (13 g/dL, range 9.6-16) and G6PDn (13.5 g/dL, range 9-16.3) and reached a nadir on D2 in both groups: 10.8 g/dL (8.2-15.3) versus 12.4 g/dL (8.8-15.2) (P = 0.006), respectively. By D7, five G6PDd patients (27.7 %) had a >25 % fall in Hb, compared to 0 G6PDn patients (P = 0.00049). One of these G6PDd patients required a blood transfusion (D0-D5 Hb, 10.0-7.2 g/dL). No patients developed severe anaemia, haemoglobinuria, a methaemoglobin concentration >4.9 %, or acute kidney injury. Vivax-infected G6PDd Cambodian patients demonstrated significant, mostly transient, falls in Hb and one received a blood transfusion. Weekly primaquine in G6PDd patients mandates medical supervision and pre-treatment screening for G6PD status. The feasibility of implementing a package of G6PDd testing and supervised primaquine should be explored. The trial was registered on 3/1/2013 and the registration number is ACTRN12613000003774 .
    BMC Medicine 08/2015; 13(1):203. DOI:10.1186/s12916-015-0441-1 · 7.25 Impact Factor
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    Pascal Ringwald · Arjen M. Dondorp
    Emerging infectious diseases 07/2015; 21(7). DOI:10.3201/eid2107.141448 · 6.75 Impact Factor
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    ABSTRACT: Western Cambodia is recognized as the epicentre of Plasmodium falciparum multidrug resistance. Recent reports of dihydroartemisinin-piperaquine efficacy, the latest generation of ACTs recommended by the WHO, prompted further investigations. Clinical efficacy of dihydroartemisinin-piperaquine in uncomplicated falciparum malaria was assessed in western and eastern Cambodia over 42 days. Day 7 piperaquine plasma concentrations were measured and day 0 isolates tested for in vitro susceptibilities to piperaquine and mefloquine, polymorphisms in the K13 gene and copy number of the mdr-1 gene (ACTRN12614000344695). 425 patients were recruited in 2011-2013. The proportion of patients with recrudescent infections was significantly higher in western (15.4%) compared to eastern Cambodia (2.5%, p<10(-3)). Day 7 PP plasma concentrations and PP median IC50 were independent of treatment outcomes, contrarily to mefloquine median IC50 which was found lower in recrudescent patient isolates (18.7 vs. 39.7 nM, p=0.005). The most significant risk factor associated with DHA-PP treatment failure was patients infected by parasites carrying the K13 mutant allele (OR=17.5, 95% CI: 1-308, p=0.04). Our data support evidence of falciparum PP resistance in western Cambodia, an area of widespread artemisinin resistance. New therapeutic strategies are needed urgently and must be tested such as the use of triple ACTs. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Antimicrobial Agents and Chemotherapy 05/2015; 59(8). DOI:10.1128/AAC.00835-15 · 4.48 Impact Factor
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    ABSTRACT: Background: Artemisinin resistance in Plasmodium falciparum has emerged in Southeast Asia and poses a threat to malaria control and elimination. Mutations in a P. falciparum gene encoding a kelch protein on chromosome 13 have been associated with delayed parasite clearance following artemisinin treatment elsewhere in the region, but not yet in China. Methods: Therapeutic efficacy studies of artesunate and dihydroartemisinin-piperaquine were conducted from 2009 to 2012 in the Yunnan Province of China near the border with Myanmar. K13 mutations were genotyped by capillary sequencing of DNA extracted from dried blood spots collected in these clinical trials and in routine surveillance. Associations between K13 mutations and delayed parasite clearance were tested using regression models. Results: Parasite clearance half-lives were prolonged after artemisinin treatment, with 44% of infections having half-lives >5 hours (n = 109). Fourteen mutations in K13 were observed, with an overall prevalence of 47.7% (n = 329). A single mutation, F446I, predominated, with a prevalence of 36.5%. Infections with F446I were significantly associated with parasitemia on day 3 following artemisinin treatment and with longer clearance half-lives. Conclusions: Plasmodium falciparum infections in southern China displayed markedly delayed clearance following artemisinin treatment. F446I was the predominant K13 mutation and was associated with delayed parasite clearance.
    The Journal of Infectious Diseases 04/2015; DOI:10.1093/infdis/jiv249 · 6.00 Impact Factor
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    ABSTRACT: Background In 2006, the Mauritanian Ministry of Health adopted a new therapeutic strategy based on the systematic use of artemisinin-based combination therapy (ACT), artesunate-amodiaquine and artemether-lumefantrine, for the first- and second-line treatment of uncomplicated malaria, respectively, regardless of Plasmodium spp. In the Saharan zone of the country, recent studies have shown that Plasmodium vivax largely predominates over Plasmodium falciparum. Anti-malarial drug response of P. vivax has not been evaluated in Mauritania. The aim of the present study was to evaluate the clinical efficacy and tolerance of chloroquine to treat P. vivax malaria in Mauritanian patients.Methods Plasmodium vivax-infected patients aged¿>¿6 months old were enrolled in Nouakchott and Atar in September¿October 2013. Chloroquine was administered at the standard dose of 25 mg base/kg body weight over three days. Patients were followed until day 28, according to the standard 2009 World Health Organization protocol.ResultsA total of 128 patients (67 in Nouakchott and 61 in Atar) were enrolled in the study. Seven patients (5.5%) were either excluded or lost to follow-up. Based on the per protocol analysis, chloroquine efficacy (adequate clinical and parasitological response) was 100%. Treatment was well-tolerated. One patient was excluded on day 1 due to urticaria and treated with artesunate-amodiaquine.Conclusions Although the current national treatment guideline recommends artesunate-amodiaquine for the first-line treatment of uncomplicated malaria, including P. vivax malaria, chloroquine may still have an important role to play in anti-malarial chemotherapy in Mauritania. Further epidemiological studies are required to map the distribution of P. vivax and P. falciparum in the country.
    Malaria Journal 01/2015; 14(1):39. DOI:10.1186/s12936-015-0563-0 · 3.11 Impact Factor
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    ABSTRACT: We report a large multicenter genome-wide association study of Plasmodium falciparum resistance to artemisinin, the frontline antimalarial drug. Across 15 locations in Southeast Asia, we identified at least 20 mutations in kelch13 (PF3D7_1343700) affecting the encoded propeller and BTB/POZ domains, which were associated with a slow parasite clearance rate after treatment with artemisinin derivatives. Nonsynonymous polymorphisms in fd (ferredoxin), arps10 (apicoplast ribosomal protein S10), mdr2 (multidrug resistance protein 2) and crt (chloroquine resistance transporter) also showed strong associations with artemisinin resistance. Analysis of the fine structure of the parasite population showed that the fd, arps10, mdr2 and crt polymorphisms are markers of a genetic background on which kelch13 mutations are particularly likely to arise and that they correlate with the contemporary geographical boundaries and population frequencies of artemisinin resistance. These findings indicate that the risk of new resistance-causing mutations emerging is determined by specific predisposing genetic factors in the underlying parasite population.
    Nature Genetics 01/2015; 47(3). DOI:10.1038/ng.3189 · 29.35 Impact Factor
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    ABSTRACT: Background: The emergence of artemisinin-resistant Plasmodium falciparum in Southeast Asia threatens malaria treatment efficacy. Mutations in a kelch protein encoded on P. falciparum chromosome 13 (K13) have been associated with resistance in vitro and in field samples from Cambodia. Methods: P. falciparum infections from artesunate efficacy trials in Bangladesh, Cambodia, Laos, Myanmar, and Vietnam were genotyped at 33 716 genome-wide single-nucleotide polymorphisms (SNPs). Linear mixed models were used to test associations between parasite genotypes and parasite clearance half-lives following artesunate treatment. K13 mutations were tested for association with artemisinin resistance, and extended haplotypes on chromosome 13 were examined to determine whether mutations arose focally and spread or whether they emerged independently. Results: The presence of nonreference K13 alleles was associated with prolonged parasite clearance half-life (P = 1.97 × 10(-12)). Parasites with a mutation in any of the K13 kelch domains displayed longer parasite clearance half-lives than parasites with wild-type alleles. Haplotype analysis revealed both population-specific emergence of mutations and independent emergence of the same mutation in different geographic areas. Conclusions: K13 appears to be a major determinant of artemisinin resistance throughout Southeast Asia. While we found some evidence of spreading resistance, there was no evidence of resistance moving westward from Cambodia into Myanmar.
    The Journal of Infectious Diseases 09/2014; 211(5). DOI:10.1093/infdis/jiu491 · 6.00 Impact Factor
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    The Lancet Infectious Diseases 08/2014; 14(8):668–670. DOI:10.1016/S1473-3099(14)70826-6 · 22.43 Impact Factor
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    ABSTRACT: Background Delayed clearance of Plasmodium falciparum parasites is used as an operational indicator of potential artemisinin resistance. Effective community-based systems to detect P. falciparum cases remaining positive 72 hours after initiating treatment would be valuable for guiding case follow-up in areas of known resistance risk and for detecting areas of emerging resistance. Methods Systems incorporating existing networks of village malaria workers (VMWs) to monitor day three-positive P. falciparum cases were piloted in three provinces in western Cambodia. Quantitative and qualitative data were used to evaluate the wider feasibility and sustainability of community-based surveillance of day three-positive P. falciparum cases. Results Of 294 day-3 blood slides obtained across all sites (from 297 day-0 positives), 63 were positive for P. falciparum, an overall day-3 positivity rate of 21%. There were significant variations in the systems implemented by different partners. Full engagement of VMWs and health centre staff is critical. VMWs are responsible for a range of individual tasks including preparing blood slides on day-0, completing forms, administering directly observed therapy (DOT) on days 0–2, obtaining follow-up slides on day-3 and transporting slides and paperwork to their supervising health centre. When suitably motivated, unsalaried VMWs are willing and able to produce good quality blood smears and achieve very high rates of DOT and day-3 follow-up. Conclusions Community-based surveillance of day-3 P. falciparum cases is feasible, but highly intensive, and as such needs strong and continuous support, particularly supervision and training. The purpose and role of community-based day-3 surveillance should be assessed in the light of resource requirements; scaling-up would need to be systematic and targeted, based on clearly defined epidemiological criteria. To be truly comprehensive, the system would need to be extended beyond VMWs to other public and private health providers.
    Malaria Journal 07/2014; 13(1):282. DOI:10.1186/1475-2875-13-282 · 3.11 Impact Factor
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    ABSTRACT: Background: A regular evaluation of therapeutic efficacy in sentinel sites and a system of surveillance are required to establish treatment guidelines and adapt national anti-malarial drug policy to the rapidly changing epidemiology of drug-resistant malaria. The current anti-malarial treatment guideline in Mauritania, officially recommended since 2006, is based on artemisinin-based combination therapy. The aim of the present study was to evaluate clinical efficacy and tolerance of artesunate-amodiaquine, the first-line treatment for acute uncomplicated malaria, in Mauritanian paediatric and adult patients to validate its continued use in the country. Methods: Plasmodium falciparum-infected symptomatic patients aged > six months were enrolled in Kobeni and Timbedra in southern Mauritania in September to October 2013. Co-formulated artesunate-amodiaquine was administered at the recommended dose over three days. Patients were followed until day 28. Parasitological and clinical response was classified according to the standard 2009 World Health Organization protocol. Results: A total of 130 patients (65 in Kobeni and 65 in Timbedra) were enrolled in the study. Seventeen patients (13.1%) were either excluded (before PCR correction) or lost to follow-up. Based on the per protocol analysis, artesunate-amodiaquine efficacy (i.e., the proportion of adequate clinical and parasitological response) was 96.6% in Kobeni and 98.2% in Timbedra before PCR correction. Late clinical failure was observed in two patients in Kobeni and one patient in Timbedra. After PCR correction, the efficacy rate in the two study sites was 98.2%. On day 3, all patients were afebrile and had negative smears. Treatment was well tolerated. Conclusions: Artesunate-amodiaquine is well tolerated and highly efficacious for the treatment of uncomplicated P. falciparum malaria. In the majority of patients, fever and parasitaemia were rapidly cleared before day 3. The results support the national anti-malarial drug guideline for a continued use of artesunate-amodiaquine as a first-line drug for uncomplicated malaria in southern Mauritania.
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    ABSTRACT: Plasmodium falciparum resistance to artemisinin derivatives in southeast Asia threatens malaria control and elimination activities worldwide. To monitor the spread of artemisinin resistance, a molecular marker is urgently needed. Here, using whole-genome sequencing of an artemisinin-resistant parasite line from Africa and clinical parasite isolates from Cambodia, we associate mutations in the PF3D7_1343700 kelch propeller domain ('K13-propeller') with artemisinin resistance in vitro and in vivo. Mutant K13-propeller alleles cluster in Cambodian provinces where resistance is prevalent, and the increasing frequency of a dominant mutant K13-propeller allele correlates with the recent spread of resistance in western Cambodia. Strong correlations between the presence of a mutant allele, in vitro parasite survival rates and in vivo parasite clearance rates indicate that K13-propeller mutations are important determinants of artemisinin resistance. K13-propeller polymorphism constitutes a useful molecular marker for large-scale surveillance efforts to contain artemisinin resistance in the Greater Mekong Subregion and prevent its global spread.
    Nature 12/2013; 505(7481). DOI:10.1038/nature12876 · 41.46 Impact Factor
  • Arjen M Dondorp · Pascal Ringwald
    Trends in Parasitology 06/2013; 29(8). DOI:10.1016/ · 6.20 Impact Factor
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    ABSTRACT: We describe an analysis of genome variation in 825 P. falciparum samples from Asia and Africa that identifies an unusual pattern of parasite population structure at the epicenter of artemisinin resistance in western Cambodia. Within this relatively small geographic area, we have discovered several distinct but apparently sympatric parasite subpopulations with extremely high levels of genetic differentiation. Of particular interest are three subpopulations, all associated with clinical resistance to artemisinin, which have skewed allele frequency spectra and high levels of haplotype homozygosity, indicative of founder effects and recent population expansion. We provide a catalog of SNPs that show high levels of differentiation in the artemisinin-resistant subpopulations, including codon variants in transporter proteins and DNA mismatch repair proteins. These data provide a population-level genetic framework for investigating the biological origins of artemisinin resistance and for defining molecular markers to assist in its elimination.
    Nature Genetics 04/2013; 45(6). DOI:10.1038/ng.2624 · 29.35 Impact Factor
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    ABSTRACT: Plasmodium falciparum resistance to artemisinins, the first line treatment for malaria worldwide, has been reported in western Cambodia. Resistance is characterized by significantly delayed clearance of parasites following artemisinin treatment. Artemisinin resistance has not previously been reported in Myanmar, which has the highest falciparum malaria burden among Southeast Asian countries. A non-randomized, single-arm, open-label clinical trial of artesunate monotherapy (4 mg/kg daily for seven days) was conducted in adults with acute blood-smear positive P. falciparum malaria in Kawthaung, southern Myanmar. Parasite density was measured every 12 hours until two consecutive negative smears were obtained. Participants were followed weekly at the study clinic for three additional weeks. Co-primary endpoints included parasite clearance time (the time required for complete clearance of initial parasitemia), parasite clearance half-life (the time required for parasitemia to decrease by 50% based on the linear portion of the parasite clearance slope), and detectable parasitemia 72 hours after commencement of artesunate treatment. Drug pharmacokinetics were measured to rule out delayed clearance due to suboptimal drug levels. The median (range) parasite clearance half-life and time were 4.8 (2.1-9.7) and 60 (24-96) hours, respectively. The frequency distributions of parasite clearance half-life and time were bimodal, with very slow parasite clearance characteristic of the slowest-clearing Cambodian parasites (half-life longer than 6.2 hours) in approximately 1/3 of infections. Fourteen of 52 participants (26.9%) had a measurable parasitemia 72 hours after initiating artesunate treatment. Parasite clearance was not associated with drug pharmacokinetics. A subset of P. falciparum infections in southern Myanmar displayed markedly delayed clearance following artemisinin treatment, suggesting either emergence of artemisinin resistance in southern Myanmar or spread to this location from its site of origin in western Cambodia. Resistance containment efforts are underway in Myanmar. Australian New Zealand Clinical Trials Registry ACTRN12610000896077.
    PLoS ONE 03/2013; 8(3):e57689. DOI:10.1371/journal.pone.0057689 · 3.23 Impact Factor
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    ABSTRACT: Background. The emergence of Plasmodium falciparum resistance to artemisinins on the Cambodian and Myanmar-Thai borders poses severe threats to malaria control. We investigated whether increasing or splitting the dose of the short-half-life drug artesunate improves parasite clearance in falciparum malaria in the 2 regions. Methods. In Pailin, western Cambodia (from 2008 to 2010), and Wang Pha, northwestern Thailand (2009–2010), patients with uncomplicated falciparum malaria were randomized to oral artesunate 6 mg/kg/d as a once-daily or twice-daily dose for 7 days, or artesunate 8 mg/kg/d as a once-daily or twice-daily dose for 3 days, followed by mefloquine. Parasite clearance and recrudescence for up to 63 days of follow-up were assessed. Results. A total of 159 patients were enrolled. Overall median (interquartile range [IQR]) parasitemia half-life (half-life) was 6.03 (4.89–7.28) hours in Pailin versus 3.42 (2.20–4.85) hours in Wang Pha (P = .0001). Splitting or increasing the artesunate dose did not shorten half-life in either site. Pharmacokinetic profiles of artesunate and dihydroartemisinin were similar between sites and did not correlate with half-life. Recrudescent infections occurred in 4 of 79 patients in Pailin and 5 of 80 in Wang Pha and was not different between treatment arms (P = .68). Conclusions. Increasing the artesunate treatment dose up to 8 mg/kg/d or splitting the dose does not improve parasite clearance in either artemisinin resistant or more sensitive infections with P. falciparum. Clinical Trials Registration. ISRCTN15351875.
    Clinical Infectious Diseases 03/2013; 56(5):e48-e58. DOI:10.1093/cid/cis958 · 8.89 Impact Factor
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    ABSTRACT: The Malaria Policy Advisory Committee to the World Health Organization met in Geneva, Switzerland from 11 to 13 September, 2012. This article provides a summary of the discussions, conclusions and recommendations from that meeting. Meeting sessions included: updated policy recommendations on the use of sulphadoxinepyrimethamine for Intermittent Preventive Treatment of malaria in pregnancy, as well as the use of single dose primaquine as a Plasmodium falciparum gametocytocide; the need to develop a Global Technical Strategy for Malaria Control and Elimination 2016- 2025 and a global strategy for control of Plasmodium vivax; the Affordable Medicines Facility for malaria independent evaluation and promoting malaria case management in the private sector; updates from the Technical Expert Group on drug resistance and containment and the Evidence Review Group on malaria burden estimation; update on the RTS,S/AS01 malaria vaccine; progress on the policy setting process for malaria vector control; and the process for updating the WHO Guidelines for the Treatment of Malaria. Policy statements, position statements, and guidelines that arise from the MPAC meeting conclusions and recommendations will be formally issued and disseminated to World Health Organization Member States by the World Health Organization Global Malaria Programme.
    Malaria Journal 12/2012; 11(1):424. DOI:10.1186/1475-2875-11-424 · 3.11 Impact Factor
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    ABSTRACT: Recent reports indicate that first cases of genuine artemisinin resistance have already emerged along the Thai-Cambodian border. The main objective of this trial was to track the potential emergence of artemisinin resistance in Bangladesh, which in terms of drug resistance forms a gateway to the Indian subcontinent. We conducted an open-label, randomized, controlled 42-day clinical trial in Southeastern Bangladesh to investigate the potential spread of clinical artemisinin resistance from Southeast Asia. A total of 126 uncomplicated falciparum malaria patients were randomized to one of 3 treatment arms (artesunate monotherapy with 2 or 4 mg/kg/day once daily or quinine plus doxycycline TID for 7 days). Only cases fulfilling a stringent set of criteria were considered as being artemisinin-resistant. The 28-day and 42-day cure rates in the artesunate monotherapy (2 and 4 mg/kg) and quinine/doxycyline arms were 97.8% (95% confidence interval, CI: 87.8-99.8%), 100% (95% CI: 91.1-100%), and 100% (95% CI: 83.4-100%), respectively. One case of re-infection was seen in the artesunate high dose arm, and a single case of recrudescence was observed in the low dose group on day 26. No differences in median parasite and fever clearance times were found between the 2 artesunate arms (29.8 h and 17.9 h vs. 29.5 h and 19.1 h). Not a single case fulfilled our criteria of artemisinin resistance. Parasite clearance times were considerably shorter and ex vivo results indicate significantly higher susceptibility (50% inhibitory concentration for dihydroartemisinin was 1.10 nM; 95% CI: 0.95-1.28 nM) to artemisinins as compared to SE-Asia. There is currently no indication that artemisinin resistance has reached Bangladesh. However, the fact that resistance has recently been reported from nearby Myanmar indicates an urgent need for close monitoring of artemisinin resistance in the region. NCT00639873.
    PLoS ONE 12/2012; 7(12):e52236. DOI:10.1371/journal.pone.0052236 · 3.23 Impact Factor
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    ABSTRACT: The recent emergence of artemisinin-resistant Plasmodium falciparum malaria in western Cambodia could threaten prospects for malaria elimination. Identification of the genetic basis of resistance would provide tools for molecular surveillance, aiding efforts to contain resistance. Clinical trials of artesunate efficacy were conducted in Bangladesh, in northwestern Thailand near the Myanmar border, and at two sites in western Cambodia. Parasites collected from trial participants were genotyped at 8,079 single nucleotide polymorphisms (SNPs) using a P. falciparum-specific SNP array. Parasite genotypes were examined for signatures of recent positive selection and association with parasite clearance phenotypes to identify regions of the genome associated with artemisinin resistance. Four SNPs on chromosomes 10 (one), 13 (two), and 14 (one) were significantly associated with delayed parasite clearance. The two SNPs on chromosome 13 are in a region of the genome that appears to be under strong recent positive selection in Cambodia. The SNPs on chromosomes 10 and 13 lie in or near genes involved in postreplication repair, a DNA damage-tolerance pathway. Replication and validation studies are needed to refine the location of loci responsible for artemisinin resistance and to understand the mechanism behind it; however, two SNPs on chromosomes 10 and 13 may be useful markers of delayed parasite clearance in surveillance for artemisinin resistance in Southeast Asia.
    Proceedings of the National Academy of Sciences 12/2012; 110(1). DOI:10.1073/pnas.1211205110 · 9.67 Impact Factor
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    ABSTRACT: The declining efficacy of artemisinin derivatives against Plasmodium falciparum in western Cambodia is a major concern. The knowledge gap in the understanding of the mechanisms involved hampers designing monitoring tools. Here, we culture-adapted 20 isolates from Pailin and Ratanakiri (areas of artemisinin resistance and susceptibility in western and eastern Cambodia, respectively) and studied their in vitro response to dihydroartemisinin. No significant difference between the two sets of isolates was observed in the classical isotopic test. However, a 6-h pulse exposure to 700 nM dihydroartemisinin (ring-stage survival assay -RSA]) revealed a clear-cut geographic dichotomy. The survival rate of exposed ring-stage parasites (ring stages) was 17-fold higher in isolates from Pailin (median, 13.5%) than in those from Ratanakiri (median, 0.8%), while exposed mature stages were equally and highly susceptible (0.6% and 0.7%, respectively). Ring stages survived drug exposure by cell cycle arrest and resumed growth upon drug withdrawal. The reduced susceptibility to artemisinin in Pailin appears to be associated with an altered in vitro phenotype of ring stages from Pailin in the RSA.
    Antimicrobial Agents and Chemotherapy 12/2012; 57(2). DOI:10.1128/AAC.01868-12 · 4.48 Impact Factor

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5k Citations
1,003.15 Total Impact Points


  • 2004–2015
    • World Health Organization WHO
      • Global Malaria Programme (GMP)
      Genève, Geneva, Switzerland
    • Institute Of Tropical Medicine
      Antwerpen, Flemish, Belgium
  • 2012
    • National Institute of Malaria Research
      Old Delhi, NCT, India
    • CERN
      Genève, Geneva, Switzerland
  • 2004–2009
    • Mahidol University
      • Faculty of Tropical Medicine
      Bangkok, Bangkok, Thailand
  • 2008
    • IT University of Copenhagen
      København, Capital Region, Denmark
  • 2007
    • Université René Descartes - Paris 5
      Lutetia Parisorum, Île-de-France, France
  • 2003
    • Cambodia National Malaria Center
      Phnum Pénh, Phnom Penh, Cambodia
  • 1998–2003
    • Institute of Research for Development
      Marsiglia, Provence-Alpes-Côte d'Azur, France
  • 2000–2002
    • OCEAC
      Jaúnde, Centre, Cameroon
    • Centre d'Études sur les Ressources Végétales
      N'Tamo, Brazzaville, Republic of the Congo
  • 1996–2001
    • Institute of Agricultural Research for Development
      Jaúnde, Centre, Cameroon
  • 1999–2000
    • International Centre of Medical Research of Franceville
      Franceville, Haut-Ogooué, Gabon
  • 1997–1998
    • French National Centre for Scientific Research
      • Centre of Molecular Genetics
      Lutetia Parisorum, Île-de-France, France
  • 1990–1995
    • Hôpital Bichat - Claude-Bernard (Hôpitaux Universitaires Paris Nord Val de Seine)
      • Service des Maladies Infectieuses et Tropicales
      Lutetia Parisorum, Île-de-France, France
  • 1994
    • Claude Bernard University Lyon 1
      • Faculté de médecine
      Villeurbanne, Rhône-Alpes, France
  • 1993
    • French Institute of Health and Medical Research
      Lutetia Parisorum, Île-de-France, France
  • 1992
    • The Pasteur Institute of Madagascar
      Tananarive, Analamanga, Madagascar