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Surveillance of molecular markers of antimalarial drug resistance in Plasmodium falciparum and Plasmodium vivax in Federally Administered Tribal Area (FATA), Pakistan.

ABSTRACT: This molecular epidemiological study was designed to determine the antimalarial drug resistance pattern, and the genetic diversity of malaria isolates collected from a war-altered Federally Administered Tribal Area (FATA), in Pakistan. Clinical isolates were collected from Bajaur, Mohmand, Khyber, Orakzai and Kurram agencies of FATA region between May 2017 and May 2018, and they underwent DNA extraction and amplification. The investigation of gene polymorphisms in drug resistance genes (dhfr, dhps, crt, and mdr1) of Plasmodium falciparum and Plasmodium vivax was carried out by pyrosequencing and Sanger sequencing, respectively. Out of 679 PCR-confirmed malaria samples, 523 (77%) were P. vivax, 121 (18%) P. falciparum, and 35 (5%) had mixed-species infections. All P. falciparum isolates had pfdhfr double mutants (C59R+S108N), while pfdhfr/pfdhps triple mutants (C59R+S108N+A437G) were detected in 11.5% of the samples. About 97.4% of P. falciparum isolates contained pfcrt K76T mutation, while pfmdr1 N86Y and Y184F mutations were present in 18.2% and 10.2% of the samples. P. vivax pvdhfr S58R mutation was present in 24.9% of isolates and the S117N mutation in 36.2%, while no mutation in the pvdhps gene was found. Pvmdr1 F1076L mutation was found in nearly all samples, as it was observed in 98.9% of isolates. No significant anti-folate and chloroquine resistance was observed in P. vivax; however, mutations associated with antifolate-resistance were found, and the chloroquine-resistant gene has been observed in 100% of P. falciparum isolates. Chloroquine and sulphadoxine-pyrimethamine resistance were found to be high in P. falciparum and low in P. vivax. Chloroquine could still be used for P. vivax infection but need to be tested in vivo, whereas a replacement of the artemisinin combination therapy for P. falciparum appears to be justified.

SUBMITTER: Nadeem MF

PROVIDER: S-EPMC8323834 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Malaria continues to be an important health problem in Honduras despite major progress achieved reducing its incidence in the last two decades. In a context of case reduction, continuing surveillance of parasite diversity and drug resistance is an important component to assist effective malaria control strategies and support risk assessments. In this study, we employed next generation sequencing on collected Plasmodium vivax and P. falciparum samples from the Hospital Escuela (University Hospital) in Honduras between 2005 and 2017. Hospital Escuela is the main public health hospital in Honduras and receives suspected malaria cases from endemic regions within the country. The resulting sequencing data was used to assess complexity of infections, parasite population structure, parasite diversity and drug resistance profiling. All P. vivax samples and all autochtonous P. falciparum samples were monoclonal and presented a low intra population diversity (π = 0.25 and 0.07, respectively). Genotyping of drug resistance markers showed that three P. falciparum samples presented the chloroquine resistant haplotype SVMNT on pfcrtr (positions 72-76). Epidemiological data suggested that two of these samples were imported cases from Africa whereas the third one was a local case. Three suspected imported cases (two of which were also pfcrt mutants) presented the pfmdr1 86Y mutation that further enhances the CQ resistant genotype. No evidence was found for kelch13 artemisinin resistance associated mutations nor parasite genetic background mutations. Discriminant analysis of principal components and phylogenetic analysis showed two P. vivax and two P. falciparum parasite sub-populations with limited recombination between them. It also confirmed the closer relationship of the three imported cases with African strains. Our findings showed that local Honduras P. falciparum strains do not hold CQ resistance polymorphisms which aligns with clinical data reported by the country and supports the continuity of CQ based treatment in Honduras. In addition, our findings highlight the need of using genomic approaches to provide key information about parasite biology including drug resistance, population structure and HRP2/HRP3 deletions which are becoming relevant as the country move towards elimination.

Project description:BackgroundArtefenomel (OZ439) is a novel synthetic trioxolane with improved pharmacokinetic properties compared with other antimalarial drugs with the artemisinin pharmacophore. Artefenomel has been generally well tolerated in volunteers at doses up to 1600 mg and is being developed as a partner drug in an antimalarial combination treatment. We investigated the efficacy, tolerability, and pharmacokinetics of artefenomel at different doses in patients with Plasmodium falciparum or Plasmodium vivax malaria.MethodsThis phase 2a exploratory, open-label trial was done at the Hospital for Tropical Diseases, Bangkok, and the Shoklo Malaria Research Unit in Thailand. Adult patients with acute, uncomplicated P falciparum or P vivax malaria received artefenomel in a single oral dose (200 mg, 400 mg, 800 mg, or 1200 mg). The first cohort received 800 mg. Testing of a new dose of artefenomel in a patient cohort was decided on after safety and efficacy assessment of the preceding cohort. The primary endpoint was the natural log parasite reduction per 24 h. Definitive oral treatment was given at 36 h. This trial is registered with ClinicalTrials.gov, number NCT01213966.FindingsBetween Oct 24, 2010, and May 25, 2012, 82 patients were enrolled (20 in each of the 200 mg, 400 mg, and 800 mg cohorts, and 21 in the 1200 mg cohort). One patient withdrew consent (before the administration of artefenomel) but there were no further dropouts. The parasite reduction rates per 24 h ranged from 0·90 to 1·88 for P falciparum, and 2·09 to 2·53 for P vivax. All doses were equally effective in both P falciparum and P vivax malaria, with median parasite clearance half-lives of 4·1 h (range 1·3-6·7) to 5·6 h (2·0-8·5) for P falciparum and 2·3 h (1·2-3·9) to 3·2 h (0·9-15·0) for P vivax. Maximum plasma concentrations, dose-proportional to 800 mg, occurred at 4 h (median). The estimated elimination half-life was 46-62 h. No serious drug-related adverse effects were reported; other adverse effects were generally mild and reversible, with the highest number in the 1200 mg cohort (17 [81%] patients with at least one adverse event). The most frequently reported adverse effect was an asymptomatic increase in plasma creatine phosphokinase concentration (200 mg, n=5; 400 mg, n=3; 800 mg, n=1; 1200 mg, n=3).InterpretationArtefenomel is a new synthetic antimalarial peroxide with a good safety profile that clears parasitaemia rapidly in both P falciparum and P vivax malaria. Its long half-life suggests a possible use in a single-dose treatment in combination with other drugs.FundingBill & Melinda Gates Foundation, Wellcome Trust, and UK Department for International Development.

Project description:KAF156 belongs to a new class of antimalarial agents (imidazolopiperazines), with activity against asexual and sexual blood stages and the preerythrocytic liver stages of malarial parasites.We conducted a phase 2, open-label, two-part study at five centers in Thailand and Vietnam to assess the antimalarial efficacy, safety, and pharmacokinetic profile of KAF156 in adults with acute Plasmodium vivax or P. falciparum malaria. Assessment of parasite clearance rates in cohorts of patients with vivax or falciparum malaria who were treated with multiple doses (400 mg once daily for 3 days) was followed by assessment of the cure rate at 28 days in a separate cohort of patients with falciparum malaria who received a single dose (800 mg).Median parasite clearance times were 45 hours (interquartile range, 42 to 48) in 10 patients with falciparum malaria and 24 hours (interquartile range, 20 to 30) in 10 patients with vivax malaria after treatment with the multiple-dose regimen and 49 hours (interquartile range, 42 to 54) in 21 patients with falciparum malaria after treatment with the single dose. Among the 21 patients who received the single dose and were followed for 28 days, 1 had reinfection and 7 had recrudescent infections (cure rate, 67%; 95% credible interval, 46 to 84). The mean (±SD) KAF156 terminal elimination half-life was 44.1±8.9 hours. There were no serious adverse events in this small study. The most common adverse events included sinus bradycardia, thrombocytopenia, hypokalemia, anemia, and hyperbilirubinemia. Vomiting of grade 2 or higher occurred in 2 patients, 1 of whom discontinued treatment because of repeated vomiting after receiving the single 800-mg dose. More adverse events were reported in the single-dose cohort, which had longer follow-up, than in the multiple-dose cohorts.KAF156 showed antimalarial activity without evident safety concerns in a small number of adults with uncomplicated P. vivax or P. falciparum malaria. (Funded by Novartis and others; ClinicalTrials.gov number, NCT01753323 .).

Project description:Ethiopia is one of the few African countries where Plasmodium vivax is co-endemic with P. falciparum. Malaria transmission is seasonal and transmission intensity varies mainly by landscape and climate. Although the recent emergence of drug resistant parasites presents a major issue to malaria control in Ethiopia, little is known about the transmission pathways of parasite species and prevalence of resistant markers. This study used microsatellites to determine population diversity and gene flow patterns of P. falciparum (N = 226) and P. vivax (N = 205), as well as prevalence of drug resistant markers to infer the impact of gene flow and existing malaria treatment regimes. Plasmodium falciparum indicated a higher rate of polyclonal infections than P. vivax. Both species revealed moderate genetic diversity and similar population structure. Populations in the northern highlands were closely related to the eastern Rift Valley, but slightly distinct from the southern basin area. Gene flow via human migrations between the northern and eastern populations were frequent and mostly bidirectional. Landscape genetic analyses indicated that environmental heterogeneity and geographical distance did not constrain parasite gene flow. This may partly explain similar patterns of resistant marker prevalence. In P. falciparum, a high prevalence of mutant alleles was detected in codons related to chloroquine (pfcrt and pfmdr1) and sulfadoxine-pyrimethamine (pfdhps and pfdhfr) resistance. Over 60% of the samples showed pfmdr1 duplications. Nevertheless, no mutation was detected in pfK13 that relates to artemisinin resistance. In P. vivax, while sequences of pvcrt-o were highly conserved and less than 5% of the samples showed pvmdr duplications, over 50% of the samples had pvmdr1 976F mutation. It remains to be tested if this mutation relates to chloroquine resistance. Monitoring the extent of malaria spread and markers of drug resistance is imperative to inform policy for evidence-based antimalarial choice and interventions. To effectively reduce malaria burden in Ethiopia, control efforts should focus on seasonal migrant populations.

Project description:BACKGROUND:In Vietnam, malaria transmission has been reduced to very low levels over the past 20 years, and as a consequence, the country aims to eliminate malaria by 2030. This study aimed to characterize the dynamics and extent of the parasite reservoir in Central Vietnam, in order to further target elimination strategies and surveillance. METHODS:A 1-year prospective cohort study (n?=?429) was performed in three rural communities in Quang Nam province. Six malaria screenings were conducted between November 2014 and November 2015, including systematic clinical examination and blood sampling for malaria parasite identification, as well as molecular and serological analysis of the study population. Malaria infections were detected by light microscopy (LM) and quantitative real time PCR (qPCR), while exposure to Plasmodium falciparum and Plasmodium vivax was measured in the first and last survey by ELISA for PfAMA1, PfGLURP R2, PvAMA1, and PvMSP1-19. Classification and regression trees were used to define seropositivity and recent exposure. RESULTS:Four malaria infections (2 P. falciparum, 2 P. vivax) were detected in the same village by qPCR and/or LM. No fever cases were attributable to malaria. At the same time, the commune health centre (serving a larger area) reported few cases of confirmed malaria cases. Nevertheless, serological data proved that 13.5% of the surveyed population was exposed to P. falciparum and/or P. vivax parasites during the study period, of which 32.6% were seronegative at the start of the study, indicating ongoing transmission in the area. Risk factor analysis for seroprevalence and exposure to P. falciparum and/or P. vivax identified structural or economic risk factors and activity/behaviour-related factors, as well as spatial heterogeneity at the village level. CONCLUSIONS:Previous studies in Central Vietnam demonstrated high occurrence of asymptomatic and sub-microscopic infections. However, in this study very few asymptomatic infections were detected despite serological evidence of continued transmission. Nonetheless, the factors associated with spatial heterogeneity in transmission could be evaluated using serological classification of recent exposure, which supports the usefulness of serological methods to monitor malaria transmission.

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Surveillance of molecular markers of antimalarial drug resistance in Plasmodium falciparum and Plasmodium vivax in Federally Administered Tribal Area (FATA), Pakistan.

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