ABSTRACT
Artemisinin-based combination therapies (ACTs) were introduced as the standard of care for uncomplicated malaria in Africa almost two decades ago. Recent studies in East Africa have reported a gradual increase in kelch13 (k13) mutant parasites associated with reduced artesunate efficacy. As part of the Community Access to Rectal Artesunate for Malaria project, we collected blood samples from 697 children with signs of severe malaria in northern Uganda between 2018 and 2020, before and after the introduction of rectal artesunate (RAS) in 2019. K13 polymorphisms were assessed, and parasite editing and phenotyping were performed to assess the impact of mutations on parasite resistance. Whole-genome sequencing was performed, and haplotype networks were constructed to determine the geographic origin of k13 mutations. Of the 697 children, 540 were positive for Plasmodium falciparum malaria by PCR and were treated with either RAS or injectable artesunate monotherapy followed in most cases by ACT. The most common k13 mutation was C469Y (6.7%), which was detected more frequently in samples collected after RAS introduction. Genome editing confirmed reduced in vitro susceptibility to artemisinin in C469Y-harboring parasites compared to wild-type controls (P < 0.001). The haplotypic network showed that flanking regions of the C469Y mutation shared the same African genetic background, suggesting a single and indigenous origin of the mutation. Our data provide evidence of selection for the artemisinin-resistant C469Y mutation. The realistic threat of multiresistant parasites emerging in Africa should encourage careful monitoring of the efficacy of artemisinin derivatives and strict adherence to ACT treatment regimens.
Subject(s)
Antimalarials , Artemisinins , Drug Resistance , Malaria, Falciparum , Plasmodium falciparum , Protozoan Proteins , Plasmodium falciparum/drug effects , Plasmodium falciparum/genetics , Uganda , Artemisinins/therapeutic use , Artemisinins/pharmacology , Humans , Antimalarials/therapeutic use , Antimalarials/pharmacology , Malaria, Falciparum/drug therapy , Malaria, Falciparum/parasitology , Drug Resistance/genetics , Protozoan Proteins/genetics , Mutation , Artesunate/therapeutic use , Artesunate/pharmacology , Child, Preschool , Child , Male , FemaleABSTRACT
BACKGROUND: Mutations in the Plasmodium falciparum dhfr gene confer resistance to pyrimethamine, which is widely used for malaria chemoprevention in Africa. We aimed to evaluate the frequency and evolution of dhfr mutations in Plasmodium ovale spp in Africa and their functional consequences, which are incompletely characterised. METHODS: We analysed dhfr mutations and their frequencies in P ovale spp isolates collected between Feb 1, 2004, and Aug 31, 2023, from the French National Malaria Reference Centre collection and from field studies in Benin, Gabon, and Kenya. Genetic patterns of positive selection were investigated. Full-length recombinant wild-type and mutant DHFR enzymes from both P ovale curtisi and P ovale wallikeri were expressed in bacteria to test whether the most common mutations reduced pyrimethamine susceptibility. FINDINGS: We included 518 P ovale spp samples (314 P ovale curtisi and 204 P ovale wallikeri). In P ovale curtisi, Ala15Ser-Ser58Arg was the most common dhfr mutation (39%; 124 of 314 samples). In P ovale wallikeri, dhfr mutations were less frequent, with Phe57Leu-Ser58Arg reaching 17% (34 of 204 samples). These two mutants were the most prevalent in central and east Africa and were fixed in Kenyan isolates. We detected six and four other non-synonymous mutations, representing 8% (24 isolates) and 2% (five isolates) of the P ovale curtisi and P ovale wallikeri isolates, respectively. Whole-genome sequencing and microsatellite analyses revealed reduced genetic diversity around the mutant pocdhfr and powdhfr genes. The mutant DHFR proteins showed structural changes at the pyrimethamine binding site in-silico, confirmed by a 4-times increase in pyrimethamine half-maximal inhibitory concentration in an Escherichia coli growth assay for the Phe57Leu-Ser58Arg mutant and 50-times increase for the Ala15Ser-Ser58Arg mutant, compared with the wild-type counterparts. INTERPRETATION: The widespread use of sulfadoxine-pyrimethamine for malaria chemoprevention might have exerted fortuitous selection pressure for dhfr mutations in P ovale spp. This calls for closer monitoring of dhfr and dhps mutations in P ovale spp. FUNDING: French Ministry of Health, Agence Nationale de la Recherche, and Global Emerging Infections Surveillance branch of the Armed Forces Health Surveillance Division.
Subject(s)
Antimalarials , Drug Resistance , Malaria , Mutation , Plasmodium ovale , Pyrimethamine , Tetrahydrofolate Dehydrogenase , Tetrahydrofolate Dehydrogenase/genetics , Tetrahydrofolate Dehydrogenase/metabolism , Pyrimethamine/pharmacology , Pyrimethamine/therapeutic use , Drug Resistance/genetics , Antimalarials/pharmacology , Antimalarials/therapeutic use , Plasmodium ovale/genetics , Plasmodium ovale/drug effects , Humans , Malaria/epidemiology , Retrospective Studies , Africa South of the Sahara/epidemiology , Protozoan Proteins/genetics , Kenya/epidemiologyABSTRACT
INTRODUCTION: The World Health Organization recommends regular monitoring of the efficacy of nationally recommended antimalarial drugs. We present the results of studies on the efficacy of recommended antimalarials and molecular markers of artemisinin and partner resistance in Afghanistan, Pakistan, Somalia, Sudan and Yemen. METHODS: Single-arm prospective studies were conducted to evaluate the efficacy of artesunate-sulfadoxine-pyrimethamine (ASSP) in Afghanistan and Pakistan, artemether-lumefantrine (AL) in all countries, or dihydroartemisinin-piperaquine (DP) in Sudan for the treatment of Plasmodium falciparum. The efficacy of chloroquine (CQ) and AL for the treatment of Plasmodium vivax was evaluated in Afghanistan and Somalia, respectively. Patients were treated and monitored for 28 (CQ, ASSP and AL) or 42 (DP) days. Polymerase chain reaction (PCR)-corrected cure rate and parasite positivity rate at Day 3 were estimated. Mutations in the P. falciparum kelch 13 (Pfk13) gene and amplifications of plasmepsin (Pfpm2) and multidrug resistance-1 (Pfmdr-1) genes were also studied. RESULTS: A total of 1680 (249 for ASSP, 1079 for AL and 352 for DP) falciparum cases were successfully assessed. A PCR-adjusted ASSP cure rate of 100% was observed in Afghanistan and Pakistan. For AL, the cure rate was 100% in all but four sites in Sudan, where cure rates ranged from 92.1% to 98.8%. All but one patient were parasite-free at Day 3. For P. vivax, cure rates were 98.2% for CQ and 100% for AL. None of the samples from Afghanistan, Pakistan and Yemen had a Pfk13 mutation known to be associated with artemisinin resistance. In Sudan, the validated Pfk13 R622I mutation accounted for 53.8% (14/26) of the detected non-synonymous Pfk13 mutations, most of which were repeatedly detected in Gadaref. A prevalence of 2.7% and 9.3% of Pfmdr1 amplification was observed in Pakistan and Yemen, respectively. CONCLUSION: High efficacy of ASSP, AL and DP in the treatment of uncomplicated falciparum infection and of CQ and AL in the treatment of P. vivax was observed in the respective countries. The repeated detection of a relatively high rate of Pfk13 R622I mutation in Sudan underscores the need for close monitoring of the efficacy of recommended ACTs, parasite clearance rates and Pfk13 mutations in Sudan and beyond. Registration numbers of the trials: ACTRN12622000944730 and ACTRN12622000873729 for Afghanistan, ACTRN12620000426987 and ACTRN12617001025325 for Pakistan, ACTRN12618001224213 for Somalia, ACTRN12617000276358, ACTRN12622000930785 and ACTRN12618001800213 for Sudan and ACTRN12617000283370 for Yemen.
Subject(s)
Antimalarials , Artemisinins , Malaria, Falciparum , Malaria, Vivax , Malaria , Humans , Antimalarials/therapeutic use , Antimalarials/pharmacology , Prospective Studies , Artemether, Lumefantrine Drug Combination/therapeutic use , Artemether/therapeutic use , Artemisinins/therapeutic use , Malaria/drug therapy , Malaria, Falciparum/drug therapy , Malaria, Falciparum/epidemiology , Malaria, Falciparum/parasitology , Chloroquine/therapeutic use , Artesunate/therapeutic use , Plasmodium falciparum/genetics , Drug Combinations , Malaria, Vivax/drug therapy , Malaria, Vivax/epidemiology , Drug Resistance/geneticsABSTRACT
BACKGROUND: In early 2016, in Preah Vihear, Northern Cambodia, artesunate/mefloquine was used to cope with dihydroartemisinin/piperaquine-resistant Plasmodium falciparum parasites. Following this policy, P. falciparum strains harbouring molecular markers associated with artemisinin, piperaquine and mefloquine resistance have emerged. However, the lack of a viable alternative led Cambodia to adopt artesunate/mefloquine countrywide, raising concerns about a surge of triple-resistant P. falciparum strains. OBJECTIVES: To assess the prevalence of triple-resistant parasites after artesunate/mefloquine implementation countrywide in Cambodia and to characterize their phenotype. METHODS: For this multicentric study, 846 samples were collected from 2016 to 2019. Genotyping of molecular markers associated with artemisinin, piperaquine and mefloquine resistance was coupled with phenotypic analyses. RESULTS: Only four triple-resistant P. falciparum isolates (0.47%) were identified during the study period. These parasites combined the pfk13 polymorphism with pfmdr1 amplification, pfpm2 amplification and/or pfcrt mutations. They showed significantly higher tolerance to artemisinin, piperaquine and mefloquine and also to the mefloquine and piperaquine combination. CONCLUSIONS: The use of artesunate/mefloquine countrywide in Cambodia has not led to a massive increase of triple-resistant P. falciparum parasites. However, these parasites circulate in the population, and exhibit clear resistance to piperaquine, mefloquine and their combination in vitro. This study demonstrates that P. falciparum can adapt to more complex drug associations, which should be considered in future therapeutic designs.
Subject(s)
Antimalarials , Artemisinins , Malaria, Falciparum , Quinolines , Humans , Mefloquine/pharmacology , Mefloquine/therapeutic use , Plasmodium falciparum/genetics , Antimalarials/pharmacology , Antimalarials/therapeutic use , Artesunate , Cambodia/epidemiology , Prevalence , Artemisinins/pharmacology , Artemisinins/therapeutic use , Quinolines/pharmacology , Malaria, Falciparum/drug therapy , Malaria, Falciparum/epidemiology , Malaria, Falciparum/parasitology , Drug Resistance/geneticsABSTRACT
BACKGROUND: Rapid diagnostic tests (RDT) for malaria are the primary tool for malaria diagnosis in sub-Saharan Africa but the utility of the most commonly used histidine-rich protein 2 (HRP2) antigen-based tests is limited in high transmission settings due to the long duration of positivity after successful malaria treatment. HRP2 tests are also threatened by the emergence of Plasmodium that do not carry pfhrp2 or pfhrp 3 genes. Plasmodium lactate dehydrogenase (pLDH)-based tests are promising alternatives, but less available. This study assessed the performances of HRP2 and pLDH(pan) tests under field conditions. METHODS: The study performed a prospective facility-based diagnostic evaluation of two malaria RDTs in Aweil, South Sudan, during the high transmission season. Capillary blood by fingerprick was collected from 800 children under 15 years of age with fever and no signs of severity. SD Bioline HRP2 and CareStart pLDH(pan) RDTs were performed in parallel, thick and thin smears for microscopy were examined, and dried blood was used for PCR testing. RESULTS: Using microscopy as the gold standard, the sensitivity of both tests was estimated at > 99%, but the specificity of each was lower: 55.0% for the pLDH test and 61.7% for the HRP2 test. When using PCR as the gold standard, the sensitivity of both tests was lower than the values assessed using microscopy (97.0% for pLDH and 96.5% for HRP2), but the specificity increased (65.1% for pLDH and 72.9% for HRP2). Performance was similar across different production lots, sex, and age. Specificity of both the pLDH and HRP2 tests was significantly lower in children who reported taking a therapeutic course of anti-malarials in the 2 months prior to enrollment. The prevalence of pfhrp2/3 deletions in the study population was 0.6%. CONCLUSIONS: The low specificity of the pLDH RDT in this setting confirms previous results and suggests a problem with this specific test. The prevalence of pfhrp2/3 deletions in the study area warrants continued monitoring and underscores the relevance of assessing deletion prevalence nationally. Improved malaria RDTs for high-transmission environments are needed.
Subject(s)
Malaria , Plasmodium , Child , Diagnostic Tests, Routine , Histidine , Humans , L-Lactate Dehydrogenase , Prevalence , Prospective Studies , South SudanABSTRACT
BACKGROUND: Dihydroartemisinin/piperaquine is increasingly used for the treatment of uncomplicated Plasmodium falciparum malaria in Africa. The efficacy of this combination in Cameroon is poorly documented, while resistance to dihydroartemisinin/piperaquine readily spreads in Southeast Asia. OBJECTIVES: This study evaluated the clinical efficacy of dihydroartemisinin/piperaquine in Cameroon, as well as the molecular profile and phenotypic susceptibility of collected isolates to dihydroartemisinin and piperaquine. PATIENTS AND METHODS: Dihydroartemisinin/piperaquine efficacy in 42 days was followed-up for 138 patients presenting non-complicated falciparum malaria. Piperaquine concentration was determined at day 7 for 124 patients. kelch13 gene polymorphisms (n = 150) and plasmepsin2 gene amplification (n = 148) were determined as molecular markers of resistance to dihydroartemisinin and piperaquine, respectively. Parasite susceptibility to dihydroartemisinin and piperaquine was determined using validated in vitro survival assays. RESULTS: The efficacy of dihydroartemisinin/piperaquine treatment was 100% after PCR correction. The reinfections were not associated with a variation of piperaquine concentration at day 7. Ninety-six percent (144/150) of the samples presented a WT allele of the kelch13 gene. Two percent (3/150) presented the non-synonymous mutation A578S, which is not associated with resistance to dihydroartemisinin. No duplication of the plasmepsin2 gene was observed (0/148). All the samples tested in vitro by survival assays (n = 87) were susceptible to dihydroartemisinin and piperaquine. CONCLUSIONS: Dihydroartemisinin/piperaquine has demonstrated excellent therapeutic efficacy with no evidence of emerging artemisinin or piperaquine resistance in Yaoundé, Cameroon. This observation suggests that dihydroartemisinin/piperaquine could be a sustainable therapeutic solution for P. falciparum malaria if implemented in areas previously free of artemisinin- and piperaquine-resistant parasites, unlike Southeast Asia.
Subject(s)
Antimalarials , Artemisinins , Malaria, Falciparum , Malaria , Quinolines , Antimalarials/therapeutic use , Artemisinins/therapeutic use , Cameroon , Humans , Malaria/drug therapy , Malaria, Falciparum/drug therapy , Plasmodium falciparum/genetics , Quinolines/therapeutic useABSTRACT
BACKGROUND: Rapid elimination of Plasmodium falciparum malaria in Cambodia is a goal with both national and international significance. Transmission of malaria in Cambodia is limited to forest environments, and the main population at risk consists of forest-goers who rely on forest products for income or sustenance. The ideal interventions to eliminate malaria from this population are unknown. METHODS: In two forested regions of Cambodia, forest-goers were trained to become forest malaria workers (FMWs). In one region, FMWs performed mass screening and treatment, focal screening and treatment, and passive case detection inside the forest. In the other region, FMWs played an observational role for the first year, to inform the choice of intervention for the second year. In both forests, FMWs collected blood samples and questionnaire data from all forest-goers they encountered. Mosquito collections were performed in each forest. RESULTS: Malaria prevalence by PCR was high in the forest, with 2.3-5.0% positive for P. falciparum and 14.6-25.0% positive for Plasmodium vivax among forest-goers in each study site. In vectors, malaria prevalence ranged from 2.1% to 9.6%, but no P. falciparum was observed. Results showed poor performance of mass screening and treatment, with sensitivity of rapid diagnostic tests equal to 9.1% (95% CI 1.1%, 29.2%) for P. falciparum and 4.4% (95% CI 1.6%, 9.2%) for P. vivax. Malaria infections were observed in all demographics and throughout the studied forests, with no clear risk factors emerging. CONCLUSIONS: Malaria prevalence remains high among Cambodian forest-goers, but performance of rapid diagnostic tests is poor. More adapted strategies to this population, such as intermittent preventive treatment of forest goers, should be considered.
Subject(s)
Culicidae/parasitology , Disease Eradication/statistics & numerical data , Forests , Malaria/prevention & control , Mosquito Vectors/parasitology , Animals , Asian People/statistics & numerical data , Cambodia/epidemiology , Disease Eradication/methods , Female , Humans , Malaria/blood , Malaria/diagnosis , Malaria/epidemiology , Malaria, Falciparum/epidemiology , Malaria, Falciparum/prevention & control , Malaria, Vivax/epidemiology , Malaria, Vivax/prevention & control , Mass Screening/statistics & numerical data , Operations Research , Prevalence , Risk FactorsABSTRACT
BACKGROUND: Artesunate-amodiaquine is a potential therapy for uncomplicated malaria in Cambodia. METHODS: Between September 2016 and January 2017, artesunate-amodiaquine efficacy and safety were evaluated in a prospective, open-label, single-arm observational study at health centers in Mondulkiri, Pursat, and Siem Reap Provinces, Cambodia. Adults and children with microscopically confirmed Plasmodium falciparum malaria received oral artesunate-amodiaquine once daily for 3 days plus single-dose primaquine, with follow-up on days 7, 14, 21, and 28. The primary outcome was day-28 polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response (ACPR). An amodiaquine parasite survival assay (AQSA) was developed and applied to whole genome sequencing results to evaluate potential amodiaquine resistance molecular markers. RESULTS: In 63 patients, day-28 PCR-adjusted ACPR was 81.0% (95% confidence interval [CI], 68.9-88.7). Day 3 parasite positivity rate was 44.4% (28/63; 95% CI, 31.9-57.5). All 63 isolates had the K13(C580Y) marker for artemisinin resistance; 79.4% (50/63) had Pfpm2 amplification. The AQSA resistance phenotype (≥45% parasite survival) was expressed in 36.5% (23/63) of isolates and was significantly associated with treatment failure (Pâ =â .0020). Pfmdr1 mutant haplotypes were N86/184F/D1246, and Pfcrt was CVIET or CVIDT at positions 72-76. Additional Pfcrt mutations were not associated with amodiaquine resistance, but the G353V mutant allele was associated with ACPR compared to Pfmdr1 haplotypes harboring F1068L or S784L/R945P mutations (Pâ =â .030 and Pâ =â .0004, respectively). CONCLUSIONS: For uncomplicated falciparum malaria in Cambodia, artesunate-amodiaquine had inadequate efficacy owing to amodiaquine-resistant P. falciparum. Amodiaquine resistance was not associated with previously identified molecular markers.
Subject(s)
Antimalarials , Artemisinins , Malaria, Falciparum , Malaria , Adult , Amodiaquine/pharmacology , Amodiaquine/therapeutic use , Antimalarials/pharmacology , Antimalarials/therapeutic use , Artemisinins/pharmacology , Artemisinins/therapeutic use , Artesunate/therapeutic use , Asia , Cambodia , Child , Humans , Malaria/drug therapy , Malaria, Falciparum/drug therapy , Plasmodium falciparum/genetics , Prospective StudiesABSTRACT
BACKGROUND: After a marked reduction in malaria burden in Cambodia over the last decades, case numbers increased again in 2017-2018. In light of the national goal of malaria elimination by 2025, remaining pockets of high risk need to be well defined and strategies well-tailored to identify and target the persisting burden cost-effectively. This study presents species-specific prevalence estimates and risk stratification for a remote area in Cambodia. METHODS: A cross-sectional survey was conducted in 17 villages in the high-incidence province Mondulkiri in the dry season (December 2017 to April 2018). 4200 randomly selected participants (2-80 years old) were tested for Plasmodium infection by PCR. Risk of infection was associated with questionnaire-derived covariates and spatially stratified based on household GPS coordinates. RESULTS: The prevalence of PCR-detectable Plasmodium infection was 8.3% (349/4200) and was more than twice as high for Plasmodium vivax (6.4%, 268) than for Plasmodium falciparum (3.0%, 125, p < 0.001). 97.8% (262/268) of P. vivax and 92.8% (116/125, p < 0.05) of P. falciparum infections were neither accompanied by symptoms at the time of the interview nor detected by microscopy or RDT. Recent travels to forest sites (aOR 2.17, p < 0.01) and forest work (aOR 2.88, p < 0.001) were particularly strong risk factors and risk profiles for both species were similar. Large village-level differences in prevalence of Plasmodium infection were observed, ranging from 0.6% outside the forest to 40.4% inside. Residing in villages at the forest fringe or inside the forest compared to outside was associated with risk of infection (aOR 2.14 and 12.47, p < 0.001). Villages inside the forest formed spatial hotspots of infection despite adjustment for the other risk factors. CONCLUSIONS: Persisting pockets of high malaria risk were detected in forested areas and in sub-populations engaging in forest-related activities. High levels of asymptomatic infections suggest the need of better case detection plans and the predominance of P. vivax the implementation of radical cure. In villages inside the forest, within-village exposure was indicated in addition to risk due to forest activities. Village-level stratification of targeted interventions based on forest proximity could render the elimination efforts more cost-effective and successful.
Subject(s)
Asymptomatic Infections/epidemiology , Malaria, Falciparum/epidemiology , Malaria, Vivax/epidemiology , Occupational Diseases/epidemiology , Adolescent , Adult , Aged , Cambodia/epidemiology , Child , Child, Preschool , Cluster Analysis , Cross-Sectional Studies , Female , Humans , Infant , Male , Middle Aged , Plasmodium falciparum , Plasmodium vivax , Prevalence , Risk Factors , Spatial Analysis , Young AdultABSTRACT
[This corrects the article DOI: 10.1371/journal.pmed.1003084.].
ABSTRACT
BACKGROUND: The radical cure of Plasmodium vivax and P. ovale requires treatment with primaquine or tafenoquine to clear dormant liver stages. Either drug can induce haemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, necessitating screening. The reference diagnostic method for G6PD activity is ultraviolet (UV) spectrophotometry; however, a universal G6PD activity threshold above which these drugs can be safely administered is not yet defined. Our study aimed to quantify assay-based variation in G6PD spectrophotometry and to explore the diagnostic implications of applying a universal threshold. METHODS AND FINDINGS: Individual-level data were pooled from studies that used G6PD spectrophotometry. Studies were identified via PubMed search (25 April 2018) and unpublished contributions from contacted authors (PROSPERO: CRD42019121414). Studies were excluded if they assessed only individuals with known haematological conditions, were family studies, or had insufficient details. Studies of malaria patients were included but analysed separately. Included studies were assessed for risk of bias using an adapted form of the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Repeatability and intra- and interlaboratory variability in G6PD activity measurements were compared between studies and pooled across the dataset. A universal threshold for G6PD deficiency was derived, and its diagnostic performance was compared to site-specific thresholds. Study participants (n = 15,811) were aged between 0 and 86 years, and 44.4% (7,083) were women. Median (range) activity of G6PD normal (G6PDn) control samples was 10.0 U/g Hb (6.3-14.0) for the Trinity assay and 8.3 U/g Hb (6.8-15.6) for the Randox assay. G6PD activity distributions varied significantly between studies. For the 13 studies that used the Trinity assay, the adjusted male median (AMM; a standardised metric of 100% G6PD activity) varied from 5.7 to 12.6 U/g Hb (p < 0.001). Assay precision varied between laboratories, as assessed by variance in control measurements (from 0.1 to 1.5 U/g Hb; p < 0.001) and study-wise mean coefficient of variation (CV) of replicate measures (from 1.6% to 14.9%; p < 0.001). A universal threshold of 100% G6PD activity was defined as 9.4 U/g Hb, yielding diagnostic thresholds of 6.6 U/g Hb (70% activity) and 2.8 U/g Hb (30% activity). These thresholds diagnosed individuals with less than 30% G6PD activity with study-wise sensitivity from 89% (95% CI: 81%-94%) to 100% (95% CI: 96%-100%) and specificity from 96% (95% CI: 89%-99%) to 100% (100%-100%). However, when considering intermediate deficiency (<70% G6PD activity), sensitivity fell to a minimum of 64% (95% CI: 52%-75%) and specificity to 35% (95% CI: 24%-46%). Our ability to identify underlying factors associated with study-level heterogeneity was limited by the lack of availability of covariate data and diverse study contexts and methodologies. CONCLUSIONS: Our findings indicate that there is substantial variation in G6PD measurements by spectrophotometry between sites. This is likely due to variability in laboratory methods, with possible contribution of unmeasured population factors. While an assay-specific, universal quantitative threshold offers robust diagnosis at the 30% level, inter-study variability impedes performance of universal thresholds at the 70% level. Caution is advised in comparing findings based on absolute G6PD activity measurements across studies. Novel handheld quantitative G6PD diagnostics may allow greater standardisation in the future.
Subject(s)
Glucosephosphate Dehydrogenase Deficiency/diagnosis , Glucosephosphate Dehydrogenase Deficiency/metabolism , Glucosephosphate Dehydrogenase/metabolism , Spectrophotometry , Adolescent , Adult , Aged , Aged, 80 and over , Antimalarials/therapeutic use , Child , Child, Preschool , Female , Glucosephosphate Dehydrogenase Deficiency/drug therapy , Humans , Infant , Infant, Newborn , Malaria/epidemiology , Male , Middle Aged , Young AdultABSTRACT
Since 2012, a single low dose of primaquine (SLDPQ; 0.25 mg/kg of body weight) with artemisinin-based combination therapies has been recommended as the first-line treatment of acute uncomplicated Plasmodium falciparum malaria to interrupt its transmission, especially in low-transmission settings of multidrug resistance, including artemisinin resistance. Policy makers in Cambodia have been reluctant to implement this recommendation due to primaquine safety concerns and a lack of data on its efficacy. In this randomized controlled trial, 109 Cambodians with acute uncomplicated P. falciparum malaria received dihydroartemisinin-piperaquine (DP) alone or combined with SLDPQ on the first treatment day. The transmission-blocking efficacy of SLDPQ was evaluated on days 0, 1, 2, 3, 7, 14, 21, and 28, and recrudescence by reverse transcriptase PCR (RT-PCR) (gametocyte prevalence) and membrane feeding assays with Anopheles minimus mosquitoes (gametocyte infectivity). Without the influence of recrudescent infections, DP-SLDPQ reduced gametocyte carriage 3-fold compared to that achieved with DP. Of 48 patients tested on day 0, only 3 patients were infectious to mosquitoes (â¼6%). Posttreatment, three patients were infectious on day 14 (3.5%, 1/29) and on the 1st and 7th days of recrudescence (8.3%, 1/12 for each); this overall low infectivity precluded our ability to assess its transmission-blocking efficacy. Our study confirms the effective gametocyte clearance of SLDPQ when combined with DP in multidrug-resistant P. falciparum infections and the negative impact of recrudescent infections due to poor DP efficacy. Artesunate-mefloquine (ASMQ) has replaced DP, and ASMQ-SLDPQ has been deployed to treat all patients with symptomatic P. falciparum infections to further support the elimination of multidrug-resistant P. falciparum in Cambodia. (This study has been registered at ClinicalTrials.gov under identifier NCT02434952.).
Subject(s)
Antimalarials , Artemisinins , Malaria, Falciparum , Animals , Antimalarials/therapeutic use , Artemisinins/therapeutic use , Asian People , Cambodia , Drug Therapy, Combination , Humans , Malaria, Falciparum/drug therapy , Plasmodium falciparum , Primaquine/therapeutic useABSTRACT
Antigenic variation, the capacity to produce a range of variable antigens, is a well-described strategy of Plasmodium and other parasites to evade host immunity. Here, we show that gene amplification is an additional evasion mechanism used by Plasmodium vivax to escape humoral immunity targeting PvDBP, the key ligand involved in reticulocyte invasion. PvDBP gene amplification leads to increased mRNA levels and protects P. vivax in vitro against invasion inhibitory human monoclonal antibodies targeting a conserved binding domain of DBP. Patient samples suggest that parasites with increased pvdbp copy number are able to infect individuals with naturally acquired antibodies highly blocking the binding of PvDBP to the Duffy receptor. These results show that gene copy number variation affect the parasite's ability to evade anti-PvDBP humoral immunity.
Subject(s)
Antigens, Protozoan/genetics , Immune Evasion/genetics , Malaria, Vivax/parasitology , Plasmodium vivax/pathogenicity , Protozoan Proteins/genetics , Receptors, Cell Surface/genetics , Antibodies, Blocking/blood , Antibodies, Blocking/immunology , Antibodies, Protozoan/blood , Antibodies, Protozoan/immunology , Duffy Blood-Group System/genetics , Erythrocytes/parasitology , Gene Dosage , Humans , Immunity, Humoral , Malaria, Vivax/blood , Malaria, Vivax/immunology , Plasmodium vivax/genetics , Plasmodium vivax/immunology , RNA, Messenger/metabolism , RNA, Protozoan/metabolism , Reticulocytes/parasitologyABSTRACT
Proposed interventions for eliminating drug-resistant Plasmodium falciparum malaria include the targeting of asymptomatic carriers through screening and treatment. We report on the diagnostic performance of the recently developed ultrasensitive rapid diagnostic test (uRDT) compared with screening with conventional RDTs (cRDT) and polymerase chain reaction (PCR) under field conditions in Cambodia in a total of 2,729 individuals. The P. falciparum positivity by quantitative PCR (qPCR) was 3.8% (26/678) in those screened during active case detection and 0.5% (10/2,051) in the cross-sectional survey. Compared with qPCR, the sensitivity of the uRDTs was 53.8% (95% CI: 33.4-73.4%) when used in active case detection and 60.0% (95% CI: 26.2-87.8%) in the cross-sectional survey. The uRDTs did not show a significant improvement in diagnostic performance over cRDTs when used for active case detection and for a malaria prevalence survey in the context of this low-transmission setting.
Subject(s)
Diagnostic Tests, Routine/methods , Diagnostic Tests, Routine/standards , Malaria, Falciparum/diagnosis , Plasmodium falciparum , Cambodia/epidemiology , Humans , Malaria, Falciparum/epidemiology , Polymerase Chain Reaction/methods , Sensitivity and Specificity , Thailand/epidemiology , Time FactorsABSTRACT
BACKGROUND: Multidrug-resistant Plasmodium falciparum undermines the efficacy of currently deployed antimalarial therapies in southern Viet Nam. METHODS: Between May 2017 and December 2018, this prospective, open-label, single-arm, observational clinical trial, conducted in Binh Phuoc, Dak Nong, Gia Lai, Khanh Hoa, and Ninh Thuan provinces, evaluated the safety and efficacy of oral pyronaridine-artesunate once daily for 3 consecutive days in adults and children with microscopically confirmed P. falciparum malaria. Patients were treated as inpatients for Days 0-3, with follow-up visits on Days 7, 14, 21, 28, 35, and 42. The primary outcome was the proportion of polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response (ACPR) at Day 42. RESULTS: The cumulative incidence of PCR-adjusted ACPR at Day 42 was 96.1% (95% confidence interval [CI] 91.4-98.2; Kaplan-Meier). In the per-protocol analysis, the proportion of patients with Day 42 PCR-adjusted ACPR was 96.1% (147/153; 95% CI 91.7-98.5). The proportion of patients with parasitemia at Day 3 was 24.0% (40/167; 95% CI 17.7-31.2). The prevalences of the Kelch13 (C580Y) mutation were: in Binh Phuoc, 97.7% (43/44); in Dak Nong, 96.2% (25/26); in Gia Lai, 57.8% (37/64); in Khanh Hoa, 66.6% (6/9); and in Ninh Thuan, 3.6% (1/28). The majority of artemisinin-resistant isolates also had increased plasmepsin2 copy number (75.9%; 85/112). There was 1 isolate (Binh Phuoc) that had Kelch13 (C580Y) plus increased plasmepsin2 and Pfmdr1 copy numbers. Asymptomatic transient increases in alanine transaminase and aspartate transaminase were observed at Day 7, resolving by Day 28. CONCLUSIONS: Pyronaridine-artesunate can be used to diversify antimalarial therapy in areas of artemisinin-resistant P. falciparum in Viet Nam. CLINICAL TRIALS REGISTRATION: ACTRN12618001274268.
Subject(s)
Antimalarials , Artemisinins , Malaria, Falciparum , Adult , Antimalarials/therapeutic use , Artemisinins/therapeutic use , Artesunate/therapeutic use , Child , Drug Combinations , Humans , Malaria, Falciparum/drug therapy , Malaria, Falciparum/epidemiology , Naphthyridines , Plasmodium falciparum/genetics , Prospective Studies , Vietnam/epidemiologyABSTRACT
BACKGROUND: Cambodia is the epicentre of resistance emergence for virtually all antimalarial drugs. Selection and spread of parasites resistant to artemisinin-based combination therapy (ACT) is a major threat for malaria elimination, hence the need to renew the pool of effective treatments. OBJECTIVES: To determine whether ACT resistance haplotypes could have an effect on ferroquine in vitro antimalarial activity. METHODS: In vitro susceptibility to ferroquine was measured for 80 isolates from Cambodia characterized for their molecular resistance profile to artemisinin, piperaquine and mefloquine. RESULTS: Among the 80 isolates tested, the overall median (IQR) IC50 of ferroquine was 10.9 nM (8.7-18.3). The ferroquine median (IQR) IC50 was 8.9 nM (8.1-11.8) for Pfk13 WT parasites and was 12.9 nM (9.5-20.0) for Pfk13 C580Y parasites with no amplification of Pfpm2 and Pfmdr1 genes. The median (IQR) IC50 of ferroquine for Pfk13 C580Y parasites with amplification of the Pfpm2 gene was 17.2 nM (14.5-20.5) versus 9.1 nM (7.9-10.7) for Pfk13 C580Y parasites with amplification of the Pfmdr1 gene. CONCLUSIONS: Ferroquine exerts promising efficacy against ACT-resistant isolates. Whereas Pfpm2 amplification was associated with the highest parasite tolerance to ferroquine, the susceptibility range observed was in accordance with those measured in ACT resistance-free areas. This enables consideration of ferroquine as a relevant therapeutic option against ACT-resistant malaria.
Subject(s)
Aminoquinolines/pharmacology , Antimalarials/pharmacology , Artemisinins/pharmacology , Drug Resistance/genetics , Ferrous Compounds/pharmacology , Metallocenes/pharmacology , Plasmodium falciparum/drug effects , Cambodia , Drug Therapy, Combination , Humans , Inhibitory Concentration 50 , Malaria, Falciparum/parasitology , Parasitic Sensitivity TestsABSTRACT
BACKGROUND: Artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DHA/PPQ) are the recommended first- and second-line treatments, respectively, for uncomplicated falciparum malaria in Somalia. The studies reported here were conducted to assess the efficacy of these artemisinin-based combinations and the mutations in Plasmodium falciparum K13-propeller (Pfk13) domain and amplification in Pfplasmepsin 2 (Pfpm2) gene in Somalia. METHODS: One-arm prospective studies were conducted to assess the clinical and parasitological responses to DHA/PPQ and AL at two sites in 2016 and 2017, respectively, using the standard WHO protocol. The patterns of molecular markers associated with artemisinin and PPQ resistance were investigated for the first time in Somalia. RESULTS: A total of 339 patients were enrolled with 139 for AL and 200 for DHA/PPQ. With AL, no parasite recurrence was observed among patients treated at either site, corresponding to 100% clinical and parasitological responses. For DHA-PPQ, an adequate clinical and parasitological response rate > 97% was observed. All study patients on both treatments at both sites were parasite-free on day 3. Of the 138 samples with interpretable results for the polymorphism in Pfk13, only one (0.7%), from Bosaso, contained a non-synonymous mutation (R622I), which is not one of the known markers of artemisinin resistance. No Pfpm2 amplification was observed among the 135 samples with interpretable results. CONCLUSIONS: AL and DHA/PPQ were highly effective in the treatment of uncomplicated falciparum malaria, and there was no evidence of resistance to artemisinin or PPQ. These two combinations are thus relevant in the chemotherapeutic strategy for malaria control in Somalia. Trial registration ACTRN12616001005448 (Jowhar DP study), ACTRN12616000553471 (Bosaso DP study), ACTRN12617001055392 (AL study in Bosaso and Jowhar).
Subject(s)
Antimalarials/therapeutic use , Artemether, Lumefantrine Drug Combination/therapeutic use , Artemisinins/therapeutic use , Malaria, Falciparum/prevention & control , Plasmodium falciparum/drug effects , Quinolines/therapeutic use , Adolescent , Adult , Child , Child, Preschool , Female , Humans , Infant , Male , Middle Aged , Somalia , Young AdultABSTRACT
This single-arm trial (n = 104) in western Cambodia showed high efficacy for 3-day treatment with pyronaridine-artesunate plus single-dose primaquine in Plasmodium falciparum malaria. Day 42 PCR-adjusted adequate clinical and parasitological response (ACPR) was 98.3% (58/59) (95% confidence interval [CI], 90.9 to 100.0) in Trapeng Chau in Kampong Speu and 100% (41/41) (95% CI, 91.4 to 100) in Veal Veng in Pursat; 80.6% (83/103) of the patients had P. falciparum with drug resistance molecular markers. For Plasmodium vivax malaria, pyronaridine-artesunate day 28 ACPR was 98.3% (59/60) (95% CI, 91.1 to 100) and 100% (60/60) (95% CI, 94.0 to 100), respectively. (This study is registered in the Australian New Zealand Clinical Trials Registry [ANZCTR] under reference no. ACTRN12618001999224.).
Subject(s)
Artesunate/adverse effects , Artesunate/therapeutic use , Malaria/drug therapy , Naphthyridines/adverse effects , Naphthyridines/therapeutic use , Primaquine/adverse effects , Primaquine/therapeutic use , Adolescent , Adult , Antimalarials/adverse effects , Antimalarials/therapeutic use , Cambodia , Child , Drug Resistance , Female , Humans , Male , Middle Aged , Plasmodium vivax/drug effects , Plasmodium vivax/pathogenicity , Young AdultABSTRACT
BACKGROUND: Today, the development of new and well-tolerated anti-malarial drugs is strongly justified by the emergence of Plasmodium falciparum resistance. In 2014-2015, a phase 2b clinical study was conducted to evaluate the efficacy of a single oral dose of Artefenomel (OZ439)-piperaquine (PPQ) in Asian and African patients presenting with uncomplicated falciparum malaria. METHODS: Blood samples collected before treatment offered the opportunity to investigate the proportion of multidrug resistant parasite genotypes, including P. falciparum kelch13 mutations and copy number variation of both P. falciparum plasmepsin 2 (Pfpm2) and P. falciparum multidrug resistance 1 (Pfmdr1) genes. RESULTS: Validated kelch13 resistance mutations including C580Y, I543T, P553L and V568G were only detected in parasites from Vietnamese patients. In Africa, isolates with multiple copies of the Pfmdr1 gene were shown to be more frequent than previously reported (21.1%, range from 12.4% in Burkina Faso to 27.4% in Uganda). More strikingly, high proportions of isolates with multiple copies of the Pfpm2 gene, associated with piperaquine (PPQ) resistance, were frequently observed in the African sites, especially in Burkina Faso and Uganda (> 30%). CONCLUSIONS: These findings were considered to sharply contrast with the recent description of increased sensitivity to PPQ of Ugandan parasite isolates. This emphasizes the necessity to investigate in vitro susceptibility profiles to PPQ of African isolates with multiple copies of the Pfpm2 gene and estimate the risk of development of PPQ resistance in Africa. Trial registration Clinicaltrials.gov reference: NCT02083380. Study title: Phase II efficacy study of artefenomel and piperaquine in adults and children with P. falciparum malaria. https://clinicaltrials.gov/ct2/results?cond=&term=NCT02083380&cntry=&state=&city=&dist= . FSFV: 23-Jul-2014; LSLV: 09-Oct-2015.
Subject(s)
Adamantane/analogs & derivatives , Antimalarials/pharmacology , Aspartic Acid Endopeptidases/genetics , Drug Resistance/genetics , Peroxides/pharmacology , Plasmodium falciparum/genetics , Protozoan Proteins/genetics , Quinolines/pharmacology , Adamantane/pharmacology , Adolescent , Adult , Africa , Aged , Aspartic Acid Endopeptidases/metabolism , Biomarkers/analysis , Child , Child, Preschool , DNA Copy Number Variations , Drug Combinations , Female , Genotype , Humans , Infant , Malaria, Falciparum , Male , Middle Aged , Plasmodium falciparum/drug effects , Protozoan Proteins/metabolism , Vietnam , Young AdultABSTRACT
BACKGROUND: The WHO recommends single low-dose primaquine (SLDPQ, 0.25 mg/kg body weight) in falciparum-infected patients to block malaria transmission and contribute to eliminating multidrug resistant Plasmodium falciparum from the Greater Mekong Sub region (GMS). However, the anxiety regarding PQ-induced acute haemolytic anaemia in glucose-6-phosphate dehydrogenase deficiency (G6PDd) has hindered its use. Therefore, we assessed the tolerability of SLDPQ in Cambodia to inform national policy. METHODS: This open randomised trial of dihydroartemisinin-piperaquine (DHAPP) + SLDPQ vs. DHAPP alone recruited Cambodians aged ≥1 year with acute uncomplicated P. falciparum. Randomisation was 4:1 DHAPP+SLDPQ: DHAPP for G6PDd patients and 1:1 for G6PDn patients, according to the results of the qualitative fluorescent spot test. Definitive G6PD status was determined by genotyping. Day (D) 7 haemoglobin (Hb) concentration was the primary outcome measure. RESULTS: One hundred nine patients (88 males, 21 females), aged 4-76 years (median 23) were enrolled; 12 were G6PDd Viangchan (9 hemizygous males, 3 heterozygous females). Mean nadir Hb occurred on D7 [11.6 (range 6.4 â 15.6) g/dL] and was significantly lower (p = 0.040) in G6PDd (n = 9) vs. G6PDn (n = 46) DHAPP+SLDPQ recipients: 10.9 vs. 12.05 g/dL, Δ = -1.15 (95% CI: -2.24 â -0.05) g/dL. Three G6PDn patients had D7 Hb concentrations < 8 g/dL; D7-D0 Hbs were 6.4 â 6.9, 7.4 â 7.4, and 7.5 â 8.2 g/dL. For all patients, mean (range) D7-D0 Hb decline was -1.45 (-4.8 â 2.4) g/dL, associated significantly with higher D0 Hb, higher D0 parasitaemia, and receiving DHAPP; G6PDd was not a factor. No patient required a blood transfusion. CONCLUSIONS: DHAPP+SLDPQ was associated with modest Hb declines in G6PD Viangchan, a moderately severe variant. Our data augment growing evidence that SLDPQ in SE Asia is well tolerated and appears safe in G6PDd patients. Cambodia is now deploying SLDPQ and this should encourage other GMS countries to follow suit. TRIAL REGISTRATION: The clinicaltrials.gov reference number is NCT02434952 .