scholarly journals Delayed Parasite Clearance after Treatment with Dihydroartemisinin-Piperaquine in Plasmodium falciparum Malaria Patients in Central Vietnam

2014 ◽  
Vol 58 (12) ◽  
pp. 7049-7055 ◽  
Author(s):  
Kamala Thriemer ◽  
Nguyen Van Hong ◽  
Anna Rosanas-Urgell ◽  
Bui Quang Phuc ◽  
Do Manh Ha ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Clearance Rate ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Clearance Time ◽  
Sensitivity Testing ◽  
Content Type ◽  
Parasite Clearance Time ◽  
Central Vietnam

ABSTRACTReduced susceptibility ofPlasmodium falciparumtoward artemisinin derivatives has been reported from the Thai-Cambodian and Thai-Myanmar borders. Following increasing reports from central Vietnam of delayed parasite clearance after treatment with dihydroartemisinin-piperaquine (DHA-PPQ), the current first-line treatment, we carried out a study on the efficacy of this treatment. Between September 2012 and February 2013, we conducted a 42-dayin vivoandin vitroefficacy study in Quang Nam Province. Treatment was directly observed, and blood samples were collected twice daily until parasite clearance. In addition, genotyping, quantitative PCR (qPCR), andin vitrosensitivity testing of isolates was performed. The primary endpoints were parasite clearance rate and time. The secondary endpoints included PCR-corrected and uncorrected cure rates, qPCR clearance profiles,in vitrosensitivity results (for chloroquine, dihydroartemisinin, and piperaquine), and genotyping for mutations in the Kelch 13 propeller domain. Out of 672 screened patients, 95 were recruited and 89 available for primary endpoint analyses. The median parasite clearance time (PCT) was 61.7 h (interquartile range [IQR], 47.6 to 83.2 h), and the median parasite clearance rate had a slope half-life of 6.2 h (IQR, 4.4 to 7.5 h). The PCR-corrected efficacy rates were estimated at 100% at day 28 and 97.7% (95% confidence interval, 91.2% to 99.4%) at day 42. At day 3, theP. falciparumprevalence by qPCR was 2.5 times higher than that by microscopy. The 50% inhibitory concentrations (IC50s) of isolates with delayed clearance times (≥72 h) were significantly higher than those with normal clearance times for all three drugs. Delayed parasite clearance (PCT, ≥72 h) was significantly higher among day 0 samples carrying the 543 mutant allele (47.8%) than those carrying the wild-type allele (1.8%;P= 0.048). In central Vietnam, the efficacy of DHA-PPQ is still satisfactory, but the parasite clearance time and rate are indicative of emerging artemisinin resistance. (This study has been registered at ClinicalTrials.gov under registration no. NCT01775592.)

scholarly journals Plasmodium falciparum clearance time in Malawian children with cerebral malaria: a retrospective cohort study

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Alexuse M. Saidi ◽  
Geoffrey Guenther ◽  
Rima Izem ◽  
Xiaojun Chen ◽  
Karl Seydel ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Cohort Study ◽  
Cerebral Malaria ◽  
Retrospective Cohort Study ◽  
Retrospective Cohort ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
First Year ◽  
Clearance Time ◽  
Parasite Clearance Time

Abstract Background Standard treatment for both uncomplicated and severe malaria is artemisinin derivatives. Delayed parasite clearance times preceded the appearance of artemisinin treatment failures in Southeast Asia. Most worldwide malaria cases are in sub-Saharan Africa (SSA), where clinically significant artemisinin resistance or treatment failure has not yet been detected. The recent emergence of a resistance-conferring genetic mutation in the Plasmodium falciparum parasite in Africa warrants continued monitoring throughout the continent. Methods An analysis was performed on data from a retrospective cohort study of Malawian children with cerebral malaria admitted between 2010 and 2019 to a public referral hospital, ascertaining parasite clearance times across years. Data were collected from patients treated for severe malaria with quinine or artesunate, an artemisinin derivative. Parasite density was determined at admission and every subsequent 6 h until parasitaemia was below 1000 parasites/µl.The mean parasite clearance time in all children admitted in any one year was compared to the parasite clearance time in 2014, the first year of artesunate use in Malawi. Results The median population parasite clearance time was slower from 2010 to 2013 (quinine-treated patients) compared to 2014, the first year of artesunate use in Malawi (30 h (95% CI: 30–30) vs 18 h (95% CI: 18–24)). After adjustment for admission parasite count, there was no statistically significant difference in the median population parasite clearance time when comparing 2014 with any subsequent year. Conclusion Malaria parasite clearance times in Malawian children with cerebral malaria remained constant between 2014 and 2019, arguing against evolving artemisinin resistance in parasites in this region.

scholarly journals Laboratory Detection of Artemisinin-Resistant Plasmodium falciparum

2014 ◽  
Vol 58 (6) ◽  
pp. 3157-3161 ◽  
Author(s):  
Kesinee Chotivanich ◽  
Rupam Tripura ◽  
Debashish Das ◽  
Poravuth Yi ◽  
Nicholas P. J. Day ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Parasite Clearance ◽  
Ring Stage ◽  
Clearance Time ◽  
Content Type ◽  
Reduced Ring ◽  
Susceptibility Tests ◽  
Low Sensitivity

ABSTRACTConventional 48-hin vitrosusceptibility tests have low sensitivity in identifying artemisinin-resistantPlasmodium falciparum, defined phenotypically by lowin vivoparasite clearance rates. We hypothesized originally that this discrepancy was explained by a loss of ring-stage susceptibility and so developed a simple field-adapted 24-h trophozoite maturation inhibition (TMI) assay focusing on the ring stage and compared it to the standard 48-h schizont maturation inhibition (WHO) test. In Pailin, western Cambodia, where artemisinin-resistantP. falciparumis prevalent, the TMI test mean (95% confidence interval) 50% inhibitory concentration (IC50) for artesunate was 6.8 (5.2 to 8.3) ng/ml compared with 1.5 (1.2 to 1.8) ng/ml for the standard 48-h WHO test (P= 0.001). TMI IC50s correlated significantly with thein vivoresponses to artesunate (parasite clearance time [r= 0.44,P= 0.001] and parasite clearance half-life [r= 0.46,P= 0.001]), whereas the standard 48-h test values did not. On continuous culture of two resistant isolates, the artemisinin-resistant phenotype was lost after 6 weeks (IC50s fell from 10 and 12 ng/ml to 2.7 and 3 ng/ml, respectively). Slow parasite clearance in falciparum malaria in western Cambodia results from reduced ring-stage susceptibility.

scholarly journals K13 Propeller Mutations in Plasmodium falciparum Populations in Regions of Malaria Endemicity in Vietnam from 2009 to 2016

2017 ◽  
Vol 61 (4) ◽  
Author(s):  
Nguyen Thuy-Nhien ◽  
Nguyen Kim Tuyen ◽  
Nguyen Thanh Tong ◽  
Nguyen Tuong Vy ◽  
Ngo Viet Thanh ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Single Strain ◽  
Content Type ◽  
Reduced Ring ◽  
Resistance Markers ◽  
Multiple Strains

ABSTRACT The spread of artemisinin-resistant Plasmodium falciparum compromises the therapeutic efficacy of artemisinin combination therapies (ACTs) and is considered the greatest threat to current global initiatives to control and eliminate malaria. This is particularly relevant in Vietnam, where dihydroartemisinin-piperaquine (DP) is the recommended ACT for P. falciparum infection. The propeller domain gene of K13, a molecular marker of artemisinin resistance, was successfully sequenced in 1,060 P. falciparum isolates collected at 3 malaria hot spots in Vietnam between 2009 and 2016. Eight K13 propeller mutations (Thr474Ile, Tyr493His, Arg539Thr, Ile543Thr, Pro553Leu, Val568Gly, Pro574Leu, and Cys580Tyr), including several that have been validated to be artemisinin resistance markers, were found. The prevalences of K13 mutations were 29% (222/767), 6% (11/188), and 43% (45/105) in the Binh Phuoc, Ninh Thuan, and Gia Lai Provinces of Vietnam, respectively. Cys580Tyr became the dominant genotype in recent years, with 79.1% (34/43) of isolates in Binh Phuoc Province and 63% (17/27) of isolates in Gia Lai Province carrying this mutation. K13 mutations were associated with reduced ring-stage susceptibility to dihydroartemisinin (DHA) in vitro and prolonged parasite clearance in vivo. An analysis of haplotypes flanking K13 suggested the presence of multiple strains with the Cys580Tyr mutation rather than a single strain expanding across the three sites.

scholarly journals Emergence and Spread of kelch13 Mutations Associated with Artemisinin Resistance in Plasmodium falciparum Parasites in 12 Thai Provinces from 2007 to 2016

2018 ◽  
Vol 62 (4) ◽  
Author(s):  
Theerayot Kobasa ◽  
Eldin Talundzic ◽  
Rungniran Sug-aram ◽  
Patcharida Boondat ◽  
Ira F. Goldman ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Gene Mutations ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Resistance Mutations ◽  
Content Type ◽  
Artemisinin Derivatives ◽  
Reduced Ring ◽  
Control And Prevention ◽  
Greater Mekong Subregion

ABSTRACT Artemisinin-based combination therapy (ACT) is the most effective and widely used treatment for uncomplicated Plasmodium falciparum malaria and is a cornerstone for malaria control and prevention globally. Resistance to artemisinin derivatives has been confirmed in the Greater Mekong Subregion (GMS) and manifests as slow parasite clearance in patients and reduced ring stage susceptibility to artemisinins in survival assays. The P. falciparum kelch13 gene mutations associated with artemisinin-resistant parasites are now widespread in the GMS. We genotyped 277 samples collected during an observational study from 2012 to 2016 from eight provinces in Thailand to identify P. falciparum kelch13 mutations. The results were combined with previously reported genotyping results from Thailand to construct a map illustrating the evolution of P. falciparum kelch13 mutations from 2007 to 2016 in that country. Different mutant alleles were found in strains with different geographical origins. The artemisinin resistance-conferring Y493H and R539T mutations were detected mainly in eastern Thailand (bordering Cambodia), while P574L was found only in western Thailand and R561H only in northwestern Thailand. The C580Y mutation was found across the entire country and was nearing fixation along the Thai-Cambodia border. Overall, the prevalence of artemisinin resistance mutations increased over the last 10 years across Thailand, especially along the Thai-Cambodia border. Molecular surveillance and therapeutic efficacy monitoring should be intensified in the region to further assess the extent and spread of artemisinin resistance.

scholarly journals Mutation in Plasmodium falciparum BTB/POZ domain of K13 protein confers artemisinin resistance

2021 ◽  
Author(s):  
Lucie Paloque ◽  
Romain Coppée ◽  
Barbara H. Stokes ◽  
Nina F. Gnädig ◽  
Karamoko Niaré ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
West African ◽  
Whole Genome Sequence ◽  
Drug Pressure ◽  
Synonymous Mutations ◽  
Survival Assay ◽  
One Year

Partial artemisinin resistance, defined in patients as a delayed parasite clearance following artemisinin-based treatment, is conferred by non-synonymous mutations in the Kelch beta-propeller domain of the Plasmodium falciparum k13 ( pfk13 ) gene. Here, we carried out in vitro selection over a one-year period on a West African P. falciparum strain isolated from Kolle (Mali) under a dose-escalating artemisinin regimen. After 18 cycles of sequential drug pressure, the selected parasites exhibited enhanced survival to dihydroartemisinin in the ring-stage survival assay (RSA 0-3h = 9.2%). Sanger and whole-genome sequence analyses identified the PfK13 P413A mutation, localized in the BTB/POZ domain, upstream of the propeller domain. This mutation was sufficient to confer in vitro artemisinin resistance when introduced into the PfK13 coding sequence of the parasite strain Dd2 by CRISPR/Cas9 gene editing. These results together with structural studies of the protein demonstrate that the propeller domain is not the sole in vitro mediator of PfK13-mediated artemisinin resistance, and highlight the importance of monitoring for mutations throughout PfK13.

scholarly journals Efficacy of dihydroartemisinin/piperaquine and artesunate monotherapy for the treatment of uncomplicated Plasmodium falciparum malaria in Central Vietnam

2020 ◽  
Author(s):  
Eduard Rovira-Vallbona ◽  
Nguyen Van Hong ◽  
Johanna H Kattenberg ◽  
Ro Mah Huan ◽  
Nguyen Thi Thu Hien ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Falciparum Malaria ◽  
Ex Vivo ◽  
Survival Rates ◽  
Artemisinin Resistance ◽  
Plasmodium Falciparum Malaria ◽  
Parasite Clearance ◽  
Resistance Mutations ◽  
Malaria Burden ◽  
Central Vietnam

Abstract Background Artemisinin-based combination therapies (ACTs) have significantly contributed to reduce Plasmodium falciparum malaria burden in Vietnam, but their efficacy is challenged by treatment failure of dihydroartemisinin/piperaquine ACT in Southern provinces. Objectives To assess the efficacy of dihydroartemisinin/piperaquine for uncomplicated P. falciparum malaria in Gia Lai, Central Vietnam, and determine parasite resistance to artemisinin (ClinicalTrials.gov identifier NCT02604966). Methods Sixty patients received either dihydroartemisinin/piperaquine (4 mg/kg/day, 3 days; n = 33) or artesunate monotherapy (4 mg/kg/day, 3 days; n = 27) followed by dihydroartemisinin/piperaquine (AS + DHA/PPQ). Clinical phenotypes were determined during a 42 day follow-up and analysed together with ex vivo susceptibility to antimalarials and molecular markers of drug resistance. Results Day 3 positivity rate was significantly higher in the AS + DHA/PPQ arm compared with dihydroartemisinin/piperaquine (70.4% versus 39.4%, P = 0.016). Parasite clearance time was 95.2 h (AS + DHA/PPQ) versus 71.9 h (dihydroartemisinin/piperaquine, P = 0.063) and parasite clearance half-life was 7.4 h (AS + DHA/PPQ) versus 7.0 h (dihydroartemisinin/piperaquine, P = 0.140). Adequate clinical and parasitological response at Day 42 was 100% in both arms. By RT–qPCR, 36% (19/53) patients remained positive until Day 7. No recurrences were detected. kelch13 artemisinin resistance mutations were found in 87% (39/45) of isolates and 50% (20/40) were KEL1/C580Y. The piperaquine resistance marker plasmepsin-2 was duplicated in 10.4% (5/48). Isolates from Day 3-positive patients (n = 18) had higher ex vivo survival rates to artemisinin compounds (P < 0.048) and prevalence of kelch13 mutations (P = 0.005) than Day 3-negative patients (n = 5). The WHO definition of artemisinin resistance was fulfilled in 60% (24/40) of cases. Conclusions Although dihydroartemisinin/piperaquine remained effective to treat P. falciparum, the high Day 3 positivity rate and prevalence of KEL1 strains calls for continuous monitoring of dihydroartemisinin/piperaquine efficacy in Central Vietnam.

scholarly journals Plasmodium falciparum Founder Populations in Western Cambodia Have Reduced Artemisinin SensitivityIn Vitro

2014 ◽  
Vol 58 (8) ◽  
pp. 4935-4937 ◽  
Author(s):  
Chanaki Amaratunga ◽  
Benoit Witkowski ◽  
Dalin Dek ◽  
Vorleak Try ◽  
Nimol Khim ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Parasite Clearance ◽  
Parasite Development ◽  
Ring Stage ◽  
Content Type ◽  
Short Course ◽  
Founder Populations ◽  
Admixed Population ◽  
Survival Assay

ABSTRACTReducedPlasmodium falciparumsensitivity to short-course artemisinin (ART) monotherapy manifests as a long parasite clearance half-life. We recently defined three parasite founder populations with long half-lives in Pursat, western Cambodia, where reduced ART sensitivity is prevalent. Using the ring-stage survival assay, we show that these founder populations have reduced ART sensitivityin vitroat the early ring stage of parasite development and that a genetically admixed population contains subsets of parasites with normal or reduced ART sensitivity.

scholarly journals Plasmodium falciparum K13 mutations in Africa and Asia present varying degrees of artemisinin resistance and an elevated fitness cost in African parasites

2021 ◽  
Author(s):  
Barbara H. Stokes ◽  
Kelly Rubiano ◽  
Satish K. Dhingra ◽  
Sachel Mok ◽  
Judith Straimer ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Southeast Asia ◽  
Survival Rates ◽  
Point Mutations ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Definitive Evidence ◽  
The Impact

AbstractThe emergence of artemisinin (ART) resistance in Plasmodium falciparum parasites has led to increasing rates of treatment failure with first-line ART-based combination therapies (ACTs) in Southeast Asia. In this region, select mutations in K13 can result in delayed parasite clearance rates in vivo and enhanced survival in the ring-stage survival assay (RSA) in vitro. Our genotyping of 3,299 P. falciparum isolates across 11 sub-Saharan countries reveals the continuing dominance of wild-type K13 and confirms the emergence of a K13 R561H variant in Rwanda. Using gene editing, we provide definitive evidence that this mutation, along with M579I and C580Y, can confer variable degrees of in vitro ART resistance in African P. falciparum strains. C580Y and M579I were both associated with substantial fitness costs in African parasites, which may counter-select against their dissemination in high-transmission settings. We also report the impact of multiple K13 mutations, including the predominant variant C580Y, on RSA survival rates and fitness in multiple Southeast Asian strains. No change in ART susceptibility was observed upon editing point mutations in ferrodoxin or mdr2, earlier associated with ART resistance in Southeast Asia. These data point to the lack of an evident biological barrier to mutant K13 mediating ART resistance in Africa, while identifying their detrimental impact on parasite growth.

scholarly journals Continued Sensitivity of Plasmodium falciparum to Artemisinin in Guyana, With Absence of Kelch Propeller Domain Mutant Alleles

2016 ◽  
Vol 3 (3) ◽  
Author(s):  
Reyaud Rahman ◽  
Maria Jesus Sanchez Martin ◽  
Shamdeo Persaud ◽  
Nicolas Ceron ◽  
Dwayne Kellman ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Confidence Interval ◽  
Clearance Rate ◽  
Artemisinin Resistance ◽  
Parasite Clearance ◽  
Wild Type ◽  
Resistance Monitoring ◽  
Mining Areas ◽  
Widespread Availability ◽  
Kelch 13

Abstract Because of concerns about possible emergence of artemisinin resistance strains of Plasmodium falciparum in mining areas of the interior of Guyana, a 7-day artesunate trial was conducted from March to December 2014. The day-3 parasite clearance rate, the efficacy of artesunate at day 28, and polymorphism of Kelch 13 (PfK13)—the marker of artemisinin resistance—were assessed. The study confirmed the continued sensitivity of P falciparum to artemisinin. A 7-day course of artesunate was 100% efficacious with only 2% (95% confidence interval, .1%–10.9%) of enrolled subjects positive at day 3. All day-0 parasite samples were wild type. Continued resistance monitoring is nevertheless recommended, given the widespread availability and uncontrolled use of artemisinin drugs in mining areas of Guyana.

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