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Contrasting Transmission Dynamics of Co-endemic Plasmodium vivax and P. falciparum: Implications for Malaria Control and Elimination. PLoS Negl Trop Dis 2015; 9:e0003739. [PMID: 25951184 PMCID: PMC4423885 DOI: 10.1371/journal.pntd.0003739] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 04/05/2015] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Outside of Africa, P. falciparum and P. vivax usually coexist. In such co-endemic regions, successful malaria control programs have a greater impact on reducing falciparum malaria, resulting in P. vivax becoming the predominant species of infection. Adding to the challenges of elimination, the dormant liver stage complicates efforts to monitor the impact of ongoing interventions against P. vivax. We investigated molecular approaches to inform the respective transmission dynamics of P. falciparum and P. vivax and how these could help to prioritize public health interventions. METHODOLOGY/PRINCIPAL FINDINGS Genotype data generated at 8 and 9 microsatellite loci were analysed in 168 P. falciparum and 166 P. vivax isolates, respectively, from four co-endemic sites in Indonesia (Bangka, Kalimantan, Sumba and West Timor). Measures of diversity, linkage disequilibrium (LD) and population structure were used to gauge the transmission dynamics of each species in each setting. Marked differences were observed in the diversity and population structure of P. vivax versus P. falciparum. In Bangka, Kalimantan and Timor, P. falciparum diversity was low, and LD patterns were consistent with unstable, epidemic transmission, amenable to targeted intervention. In contrast, P. vivax diversity was higher and transmission appeared more stable. Population differentiation was lower in P. vivax versus P. falciparum, suggesting that the hypnozoite reservoir might play an important role in sustaining local transmission and facilitating the spread of P. vivax infections in different endemic settings. P. vivax polyclonality varied with local endemicity, demonstrating potential utility in informing on transmission intensity in this species. CONCLUSIONS/SIGNIFICANCE Molecular approaches can provide important information on malaria transmission that is not readily available from traditional epidemiological measures. Elucidation of the transmission dynamics circulating in a given setting will have a major role in prioritising malaria control strategies, particularly against the relatively neglected non-falciparum species.
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252
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Lin JW, Spaccapelo R, Schwarzer E, Sajid M, Annoura T, Deroost K, Ravelli RBG, Aime E, Capuccini B, Mommaas-Kienhuis AM, O'Toole T, Prins F, Franke-Fayard BMD, Ramesar J, Chevalley-Maurel S, Kroeze H, Koster AJ, Tanke HJ, Crisanti A, Langhorne J, Arese P, Van den Steen PE, Janse CJ, Khan SM. Replication of Plasmodium in reticulocytes can occur without hemozoin formation, resulting in chloroquine resistance. ACTA ACUST UNITED AC 2015; 212:893-903. [PMID: 25941254 PMCID: PMC4451122 DOI: 10.1084/jem.20141731] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Accepted: 04/08/2015] [Indexed: 01/03/2023]
Abstract
Lin et al. generate Plasmodium berghei mutants lacking enzymes critical to hemoglobin digestion. A double gene deletion mutant lacking enzymes involved in the initial steps of hemoglobin proteolysis is able to replicate inside reticulocytes of infected mice with limited hemoglobin degradation and no hemozoin formation, and moreover, is resistant to the antimalarial drug chloroquine. Most studies on malaria-parasite digestion of hemoglobin (Hb) have been performed using P. falciparum maintained in mature erythrocytes, in vitro. In this study, we examine Plasmodium Hb degradation in vivo in mice, using the parasite P. berghei, and show that it is possible to create mutant parasites lacking enzymes involved in the initial steps of Hb proteolysis. These mutants only complete development in reticulocytes and mature into both schizonts and gametocytes. Hb degradation is severely impaired and large amounts of undigested Hb remains in the reticulocyte cytoplasm and in vesicles in the parasite. The mutants produce little or no hemozoin (Hz), the detoxification by-product of Hb degradation. Further, they are resistant to chloroquine, an antimalarial drug that interferes with Hz formation, but their sensitivity to artesunate, also thought to be dependent on Hb degradation, is retained. Survival in reticulocytes with reduced or absent Hb digestion may imply a novel mechanism of drug resistance. These findings have implications for drug development against human-malaria parasites, such as P. vivax and P. ovale, which develop inside reticulocytes.
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Affiliation(s)
- Jing-Wen Lin
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands Division of Parasitology, MRC National Institute for Medical Research, London NW7 1AA, England, UK
| | - Roberta Spaccapelo
- Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy
| | - Evelin Schwarzer
- Department of Oncology, University of Torino, 10124 Torino, Italy
| | - Mohammed Sajid
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Takeshi Annoura
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Katrien Deroost
- Laboratory of Immunobiology, Rega Institute for Medical Research, KU Leuven - University of Leuven, 3000 Leuven, Belgium
| | - Raimond B G Ravelli
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Elena Aime
- Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy
| | - Barbara Capuccini
- Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy Division of Parasitology, MRC National Institute for Medical Research, London NW7 1AA, England, UK
| | - Anna M Mommaas-Kienhuis
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Tom O'Toole
- Department of Molecular Cell Biology and Immunology, Vrije University Medical Center, 1007 MB Amsterdam, Netherlands
| | - Frans Prins
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Blandine M D Franke-Fayard
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Jai Ramesar
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Séverine Chevalley-Maurel
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Hans Kroeze
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Abraham J Koster
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Hans J Tanke
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Andrea Crisanti
- Department of Experimental Medicine, University of Perugia, Piazzale Gambuli, 06132 Perugia, Italy Department of Biological Sciences, Imperial College London, South Kensington Campus, SAF, London SW7 2AZ, England, UK
| | - Jean Langhorne
- Division of Parasitology, MRC National Institute for Medical Research, London NW7 1AA, England, UK
| | - Paolo Arese
- Department of Oncology, University of Torino, 10124 Torino, Italy
| | - Philippe E Van den Steen
- Laboratory of Immunobiology, Rega Institute for Medical Research, KU Leuven - University of Leuven, 3000 Leuven, Belgium
| | - Chris J Janse
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
| | - Shahid M Khan
- Leiden Malaria Research Group, Department of Parasitology, Department of Molecular Cell Biology, and Department of Pathology, Leiden University Medical Centre, 2333 ZA Leiden, Netherlands
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253
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Campo B, Vandal O, Wesche DL, Burrows JN. Killing the hypnozoite--drug discovery approaches to prevent relapse in Plasmodium vivax. Pathog Glob Health 2015; 109:107-22. [PMID: 25891812 PMCID: PMC4455353 DOI: 10.1179/2047773215y.0000000013] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The eradication of malaria will only be possible if effective, well-tolerated medicines kill hypnozoites in vivax and ovale malaria, and thus prevent relapses in patients. Despite progress in the 8-aminoquinoline series, with tafenoquine in Phase III showing clear benefits over primaquine, the drug discovery challenge to identify hypnozoiticidal or hypnozoite-activating compounds has been hampered by the dearth of biological tools and assays, which in turn has been limited by the immense scientific and logistical challenges associated with accessing relevant human tissue and sporozoites. This review summarises the existing drug discovery series and approaches concerning the goal to block relapse.
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Affiliation(s)
- Brice Campo
- Medicines for Malaria Venture, Geneva, Switzerland
| | - Omar Vandal
- The Bill and Melinda Gates Foundation, Seattle, WA, USA
| | - David L. Wesche
- The Bill and Melinda Gates Foundation, Seattle, WA, USA
- Great Lakes Drug Development/Certara, Princeton, NJ, USA
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254
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Baird K. Origins and implications of neglect of G6PD deficiency and primaquine toxicity in Plasmodium vivax malaria. Pathog Glob Health 2015; 109:93-106. [PMID: 25943156 PMCID: PMC4455359 DOI: 10.1179/2047773215y.0000000016] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Most of the tens of millions of clinical attacks caused by Plasmodium vivax each year likely originate from dormant liver forms called hypnozoites. We do not systematically attack that reservoir because the only drug available, primaquine, is poorly suited to doing so. Primaquine was licenced for anti-relapse therapy in 1952 and became available despite threatening patients having an inborn deficiency of glucose-6-phosphate dehydrogenase (G6PD) with acute haemolytic anaemia. The standard method for screening G6PD deficiency, the fluorescent spot test, has proved impractical where most malaria patients live. The blind administration of daily primaquine is dangerous, but so too are the relapses invited by withholding treatment. Absent G6PD screening, providers must choose between risking harm by the parasite or its treatment. How did this dilemma escape redress in science, clinical medicine and public health? This review offers critical historic reflection on the neglect of this serious problem in the chemotherapy of P. vivax.
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255
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Daniels RF, Rice BL, Daniels NM, Volkman SK, Hartl DL. The utility of genomic data for Plasmodium vivax population surveillance. Pathog Glob Health 2015; 109:153-61. [PMID: 25892032 DOI: 10.1179/2047773215y.0000000014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Genetic polymorphisms identified from genomic sequencing can be used to track changes in parasite populations through time. Such tracking is particularly informative when applying control strategies and evaluating their effectiveness. Using genomic approaches may also enable improved ability to categorise populations and to stratify them according to the likely effectiveness of intervention. Clinical applications of genomic approaches also allow relapses to be classified according to reinfection or recrudescence. These tools can be used not only to assess the effectiveness of malaria interventions but also to appraise the strategies for malaria elimination.
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256
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Waheed AA, Ghanchi NK, Rehman KA, Raza A, Mahmood SF, Beg MA. Vivax malaria and chloroquine resistance: a neglected disease as an emerging threat. Malar J 2015; 14:146. [PMID: 25889875 PMCID: PMC4392755 DOI: 10.1186/s12936-015-0660-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 03/20/2015] [Indexed: 11/21/2022] Open
Abstract
In Pakistan, Plasmodium vivax contributes to major malaria burden. In this case, a pregnant woman presented with P. vivax infection and which was not cleared by chloroquine, despite adequate treatment. This is probably the first confirmed case of chloroquine-resistant vivax from Pakistan, where severe malaria due to P. vivax is already an emerging problem.
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Affiliation(s)
- Anam A Waheed
- Medical College, Aga Khan University, Karachi, Pakistan.
| | - Najia K Ghanchi
- Department of Pathology and Laboratory Medicine, Aga Khan University, Stadium Road, PO Box 3500, Karachi, 74800, Pakistan.
| | - Karim A Rehman
- Medical College, Aga Khan University, Karachi, Pakistan.
| | - Afsheen Raza
- Department of Pathology and Laboratory Medicine, Aga Khan University, Stadium Road, PO Box 3500, Karachi, 74800, Pakistan.
| | - Syed F Mahmood
- Section of Adult Infectious Diseases, Department of Medicine, Aga Khan University, Stadium Road, PO Box 3500, Karachi, 74800, Pakistan.
| | - Mohammad A Beg
- Department of Pathology and Laboratory Medicine, Aga Khan University, Stadium Road, PO Box 3500, Karachi, 74800, Pakistan.
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257
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von Seidlein L, Dondorp A. Fighting fire with fire: mass antimalarial drug administrations in an era of antimalarial resistance. Expert Rev Anti Infect Ther 2015; 13:715-30. [PMID: 25831482 DOI: 10.1586/14787210.2015.1031744] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The emergence and spread of antimalarial resistance has been a major liability for malaria control. The spread of chloroquine-resistant Plasmodium falciparum strains had catastrophic consequences for people in malaria-endemic regions, particularly in sub-Saharan Africa. The recent emergence of artemisinin-resistant P. falciparum strains is of highest concern. Current efforts to contain artemisinin resistance have yet to show success. In the absence of more promising plans, it has been suggested to eliminate falciparum malaria from foci of artemisinin resistance using a multipronged approach, including mass drug administrations. The use of mass drug administrations is controversial as it increases drug pressure. Based on current knowledge it is difficult to conceptualize how targeted malaria elimination could contribute to artemisinin resistance, provided a full treatment course is ensured.
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Affiliation(s)
- Lorenz von Seidlein
- Mahidol-Oxford Tropical Medicine Research Unit (MORU) - Faculty of Tropical Medicine, 420/6 Rajvithi Road Bangkok 10400, Thailand
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258
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Al-Bari MAA. Chloroquine analogues in drug discovery: new directions of uses, mechanisms of actions and toxic manifestations from malaria to multifarious diseases. J Antimicrob Chemother 2015; 70:1608-21. [PMID: 25693996 PMCID: PMC7537707 DOI: 10.1093/jac/dkv018] [Citation(s) in RCA: 287] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Antimalarial drugs (e.g. chloroquine and its close structural analogues) were developed primarily to treat malaria; however, they are beneficial for many dermatological, immunological, rheumatological and severe infectious diseases, for which they are used mostly today. Chloroquine and hydroxychloroquine, two of the most fascinating drugs developed in the last 50 years, are increasingly recognized for their effectiveness in myriad non-malarial diseases. In advanced research, chloroquine and hydroxychloroquine have been shown to have various immunomodulatory and immunosuppressive effects, and currently have established roles in the management of rheumatic diseases, lupus erythematosus (different forms) and skin diseases, and in the treatment of different forms of cancer. Recently, chloroquine analogues have also been found to have metabolic, cardiovascular, antithrombotic and antineoplastic effects. This review is concerned with the lysosomotropic, anti-inflammatory and immunomodulatory mechanisms of chloroquine, hydroxychloroquine, quinacrine and related analogues, and the current evidence for both their beneficial effects and potential adverse manifestations in various diseases.
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259
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Therapeutic responses of Plasmodium vivax malaria to chloroquine and primaquine treatment in northeastern Myanmar. Antimicrob Agents Chemother 2014; 59:1230-5. [PMID: 25512415 DOI: 10.1128/aac.04270-14] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Chloroquine-primaquine (CQ-PQ) continues to be the frontline therapy for radical cure of Plasmodium vivax malaria. Emergence of CQ-resistant (CQR) P. vivax parasites requires a shift to artemisinin combination therapies (ACTs), which imposes a significant financial, logistical, and safety burden. Monitoring the therapeutic efficacy of CQ is thus important. Here, we evaluated the therapeutic efficacy of CQ-PQ for P. vivax malaria in northeast Myanmar. We recruited 587 patients with P. vivax monoinfection attending local malaria clinics during 2012 to 2013. These patients received three daily doses of CQ at a total dose of 24 mg of base/kg of body weight and an 8-day PQ treatment (0.375 mg/kg/day) commencing at the same time as the first CQ dose. Of the 401 patients who finished the 28-day follow-up, the cumulative incidence of recurrent parasitemia was 5.20% (95% confidence interval [CI], 3.04% to 7.36%). Among 361 (61%) patients finishing a 42-day follow-up, the cumulative incidence of recurrent blood-stage infection reached 7.98% (95% CI, 5.20% to 10.76%). The cumulative risk of gametocyte carriage at days 28 and 42 was 2.21% (95% CI, 0.78% to 3.64%) and 3.93% (95% CI, 1.94% to 5.92%), respectively. Interestingly, for all 15 patients with recurrent gametocytemia, this was associated with concurrent asexual stages. Genotyping of recurrent parasites at the merozoite surface protein 3α gene locus from 12 patients with recurrent parasitemia within 28 days revealed that 10 of these were the same genotype as at day 0, suggesting recrudescence or relapse. Similar studies in 70 patients in the same area in 2007 showed no recurrent parasitemias within 28 days. The sensitivity to chloroquine of P. vivax in northeastern Myanmar may be deteriorating.
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260
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Ingram RJH, Crenna-Darusallam C, Soebianto S, Noviyanti R, Baird JK. The clinical and public health problem of relapse despite primaquine therapy: case review of repeated relapses of Plasmodium vivax acquired in Papua New Guinea. Malar J 2014; 13:488. [PMID: 25495607 PMCID: PMC4295472 DOI: 10.1186/1475-2875-13-488] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 12/06/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Primaquine is the only drug available for preventing relapse following a primary attack by Plasmodium vivax malaria. This drug imposes several important problems: daily dosing over two weeks; toxicity in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency; partner blood schizontocides possibly impacting primaquine safety and efficacy; cytochrome P-450 abnormalities impairing metabolism and therapeutic activity; and some strains of parasite may be tolerant or resistant to primaquine. There are many possible causes of repeated relapses in a patient treated with primaquine. CASE DESCRIPTION A 56-year-old Caucasian woman from New Zealand traveled to New Ireland, Papua New Guinea for two months in 2012. One month after returning home she stopped daily doxycycline prophylaxis against malaria, and one week later she became acutely ill and hospitalized with a diagnosis of Plasmodium vivax malaria. Over the ensuing year she suffered four more attacks of vivax malaria at approximately two-months intervals despite consuming primaquine daily for 14 days after each of those attacks, except the last. Genotype of the patient's cytochrome P-450 2D6 alleles (*5/*41) corresponded with an intermediate metabolizer phenotype of predicted low activity. DISCUSSION Multiple relapses in patients taking primaquine as prescribed present a serious clinical problem, and understanding the basis of repeated therapeutic failure is a challenging technical problem. This case highlights these issues in a single traveler, but these problems will also arise as endemic nations approach elimination of malaria transmission.
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Affiliation(s)
| | | | | | - Rintis Noviyanti
- />Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - J Kevin Baird
- />Eijkman-Oxford Clinical Research Unit, Jakarta, 10430 Indonesia
- />Centre for Tropical Medicine, Nuffield Department of Medicine, University of Oxford, Oxford, UK
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261
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Visser BJ, Wieten RW, Kroon D, Nagel IM, Bélard S, van Vugt M, Grobusch MP. Efficacy and safety of artemisinin combination therapy (ACT) for non-falciparum malaria: a systematic review. Malar J 2014; 13:463. [PMID: 25428624 PMCID: PMC4258384 DOI: 10.1186/1475-2875-13-463] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 11/18/2014] [Indexed: 01/18/2023] Open
Abstract
Background Artemisinin combination therapy (ACT) is recommended as first-line treatment for uncomplicated Plasmodium falciparum malaria, whereas chloroquine is still commonly used for the treatment of non-falciparum species (Plasmodium vivax, Plasmodium ovale and Plasmodium malariae). A more simplified, more uniform treatment approach across all malaria species is worthwhile to be considered both in endemic areas and for malaria as an imported condition alike. Methods A PROSPERO-registered systematic review to determine the efficacy and safety of ACT for the treatment of non-falciparum malaria was conducted, following PRISMA guidelines. Without language restrictions, Medline/PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Science, LILACS, Biosis Previews and the African Index Medicus were searched for studies published up to November 2014. Results The literature search identified 986 reports; 40 publications were found eligible for inclusion, all of them on non-falciparum malaria in endemic areas. Most evidence was available for P. vivax (n = 35). Five clinical trials in total were identified evaluating ACT for P. ovale, P. malariae and Plasmodium knowlesi. Most ACT presentations have high efficacy against P. vivax parasites; artemisinin-based combinations have shorter parasite and fever clearance times compared to chloroquine. ACT is as effective as chloroquine in preventing recurrent parasitaemia before day 28. Artemisinin-based combinations with long half-lives show significantly fewer recurrent parasitaemia up to day 63. The limited evidence available supports both the use of chloroquine and an ACT for P. ovale and P. malariae. ACT seems to be preferable for optimal treatment of P. knowlesi. Conclusion ACT is at least equivalent to chloroquine in effectively treating non-falciparum malaria. These findings may facilitate development of simplified protocols for treating all forms of malaria with ACT, including returning travellers. Obtaining comprehensive efficacy and safety data on ACT use for non-falciparum species particularly for P. ovale, P. malariae and P. knowlesi should be a research priority. Trial registration CRD42014009103 Electronic supplementary material The online version of this article (doi:10.1186/1475-2875-13-463) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | - Martin P Grobusch
- Department of Infectious Diseases, Division of Internal Medicine, Center of Tropical Medicine and Travel Medicine, Academic Medical Center, University of Amsterdam, Meibergdreef 9, PO Box 22700, 1100 DE Amsterdam, The Netherlands.
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262
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White MT, Karl S, Battle KE, Hay SI, Mueller I, Ghani AC. Modelling the contribution of the hypnozoite reservoir to Plasmodium vivax transmission. eLife 2014; 3. [PMID: 25406065 PMCID: PMC4270097 DOI: 10.7554/elife.04692] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 11/13/2014] [Indexed: 12/25/2022] Open
Abstract
Plasmodium vivax relapse infections occur following activation of latent liver-stages parasites (hypnozoites) causing new blood-stage infections weeks to months after the initial infection. We develop a within-host mathematical model of liver-stage hypnozoites, and validate it against data from tropical strains of P. vivax. The within-host model is embedded in a P. vivax transmission model to demonstrate the build-up of the hypnozoite reservoir following new infections and its depletion through hypnozoite activation and death. The hypnozoite reservoir is predicted to be over-dispersed with many individuals having few or no hypnozoites, and some having intensely infected livers. Individuals with more hypnozoites are predicted to experience more relapses and contribute more to onwards P. vivax transmission. Incorporating hypnozoite killing drugs such as primaquine into first-line treatment regimens is predicted to cause substantial reductions in P. vivax transmission as individuals with the most hypnozoites are more likely to relapse and be targeted for treatment. DOI:http://dx.doi.org/10.7554/eLife.04692.001 Malaria is one of the world's most deadly infections, causing 100s of 1000s of deaths each year despite being both preventable and curable. Malaria is caused by Plasmodium parasites, which are transmitted between humans by mosquitoes. When a mosquito bites a human, Plasmodium is injected into the bloodstream with the mosquito's saliva. The parasite then travels through the bloodstream to the liver, infects liver cells and multiplies within those cells without causing any noticeable symptoms. After remaining silent in the liver for weeks or months, the now abundant parasite ruptures the host liver cell, re-enters the bloodstream, and begins infecting red blood cells. If another mosquito bites the infected individual and takes a blood meal, the parasite moves into the mosquito and the cycle of transmission continues. There are several species of Plasmodium that are known to cause malaria. The most widely studied species is P. falciparum, which also causes one of the deadliest types of malaria. However, another Plasmodium species called P. vivax is the most widely distributed species and, despite being less virulent than P. falciparum, is particularly dangerous because it causes recurring malaria. In contrast to P. falciparum, P. vivax has the ability to form hypnozoites: a dormant form of the parasite that can remain inside liver cells for long periods of time, sometimes for years. The reservoir of P. vivax hypnozoites can regularly populate the bloodstream with the infectious form of the parasite, triggering relapses of malaria. Even if an individual suffering a relapse receives prompt treatment to clear parasites in the blood, more parasites may emerge from the liver and cause new blood-stage infections. White et al. developed a mathematical model to help understand how P. vivax is transmitted. Unlike many of the established models of malaria transmission, the new model accounts for the reservoir of P. vivax hypnozoites in the liver, and assumes that hypnozoites in the reservoir either die, or are activated and enter the bloodstream, at a constant rate. This produces patterns that closely match how often relapses occur in patients. White et al. go on to predict that although many infected people have few or no hypnozoites in their liver, some have many hypnozoites, and these people are more likely to suffer from malaria relapses. This suggests that if the initial treatments given to malaria sufferers incorporate additional drugs that kill the hypnozoites in the liver, then it may be possible to substantially reduce the extent of P. vivax transmission. DOI:http://dx.doi.org/10.7554/eLife.04692.002
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Affiliation(s)
- Michael T White
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Stephan Karl
- Department of Infection and Immunity, Walter and Eliza Hall Institute, Melbourne, Australia
| | - Katherine E Battle
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Simon I Hay
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Ivo Mueller
- Department of Infection and Immunity, Walter and Eliza Hall Institute, Melbourne, Australia
| | - Azra C Ghani
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
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263
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Ariey F, Paul RE. Antimalarial resistance: is vivax left behind? THE LANCET. INFECTIOUS DISEASES 2014; 14:908-9. [PMID: 25213734 DOI: 10.1016/s1473-3099(14)70921-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Frédéric Ariey
- Genetics and Genomics of Insect Vectors Unit, Institut Pasteur, Paris 75724, France.
| | - Richard E Paul
- Functional Genetics of Infectious Diseases Unit, Institut Pasteur, Paris 75724, France
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