1
|
Falade CO, Orimadegun AE, Olusola FI, Michael OS, Anjorin OE, Funwei RI, Adedapo AD, Olusanya AL, Orimadegun BE, Mokuolu OA. Efficacy and safety of pyronaridine-artesunate versus artemether-lumefantrine in the treatment of acute uncomplicated malaria in children in South-West Nigeria: an open-labelled randomized controlled trial. Malar J 2023; 22:154. [PMID: 37179349 PMCID: PMC10182553 DOI: 10.1186/s12936-023-04574-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 04/24/2023] [Indexed: 05/15/2023] Open
Abstract
BACKGROUND In Nigeria, declining responsiveness to artemether-lumefantrine (AL), the artemisinin-based combination therapy (ACT) of choice since 2005, has been reported. Pyronaridine-artesunate (PA) is a newer fixed-dose ACT recently prequalified by the WHO for the treatment of uncomplicated falciparum malaria. However, PA data from the Nigerian pediatric population is scarce. Therefore, the efficacy and safety of PA and AL using the WHO 28-day anti-malarial therapeutic efficacy study protocol in Ibadan, southwest Nigeria, were compared. METHODS In an open-labelled, randomized, controlled clinical trial, 172 children aged 3-144 months with a history of fever and microscopically confirmed uncomplicated Plasmodium falciparum malaria were enrolled in southwest Nigeria. Enrollees were randomly assigned to receive PA or AL at standard dosages according to body weight for 3 days. Venous blood was obtained for hematology, blood chemistry, and liver function tests on days 0, 3, 7, and 28 as part of the safety evaluation. RESULTS 165 (95.9%) of the enrolled individuals completed the study. About half (52.3%; 90/172) of enrollees were male. Eighty-seven (50.6%) received AL, while 85 (49.4%) received PA. Day 28, adequate clinical and parasitological response for PA was 92.7% [(76/82) 95% CI 83.1, 95.9] and 71.1% [(59/83) 95% CI 60.4, 79.9] for AL (0.001). Fever and parasite clearance were similar in both groups. Two of six and eight of 24 parasite recurrences were observed among PA- and AL-treated children, respectively. PCR-corrected Day-28 cure rates for PA were 97.4% (76/78) and 88.1% (59/67) for AL (= 0.04) in the per-protocol population after new infections were censored. Hematological recovery at day 28 was significantly better among PA-treated patients (34.9% 2.8) compared to those treated with AL (33.1% 3.0) (0.002). Adverse events in both treatment arms were mild and similar to the symptoms of malaria infection. Blood chemistry and liver function tests were mostly within normal limits, with an occasional marginal rise. CONCLUSION PA and AL were well-tolerated. PA was significantly more efficacious than AL in both the PCR-uncorrected and PCR-corrected per-protocol populations during this study. The results of this study support the inclusion of PA in the anti-malarial treatment guidelines in Nigeria. RETROSPECTIVE TRIAL REGISTRATION Clinicaltrials.gov: NCT05192265.
Collapse
Affiliation(s)
- Catherine O Falade
- Department of Pharmacology and Therapeutics, College of Medicine, University of Ibadan, Ibadan, Nigeria.
- Institute for Advanced Medical Research and Training, College of Medicine, University of Ibadan, Ibadan, Nigeria.
| | - Adebola E Orimadegun
- Institute of Child Health, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Fiyinfoluwa I Olusola
- Department of Pharmacology and Therapeutics, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Obaro S Michael
- Department of Pharmacology and Therapeutics, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Oluwafunmibi E Anjorin
- Department of Accident and Emergency, Obafemi Awolowo University Teaching, Hospital, Ile-Ife, Nigeria
| | - Roland I Funwei
- Department of Pharmacology, Babcock University, Ilisan, Remo, Ogun State, Nigeria
| | - Aduragbenro D Adedapo
- Department of Pharmacology and Therapeutics, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Abiola L Olusanya
- Institute for Advanced Medical Research and Training, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Bose E Orimadegun
- Department of Chemical Pathology, College of Medicine, University of Ibadan, Ibadan, Nigeria
| | - Olugbenga A Mokuolu
- Department of Paediatrics, University of Ilorin Teaching Hospital, Ilorin, Nigeria
| |
Collapse
|
2
|
A Novel Ex Vivo Drug Assay for Assessing the Transmission-Blocking Activity of Compounds on Field-Isolated Plasmodium falciparum Gametocytes. Antimicrob Agents Chemother 2022; 66:e0100122. [PMID: 36321830 PMCID: PMC9764978 DOI: 10.1128/aac.01001-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The discovery and development of transmission-blocking therapies challenge malaria elimination and necessitate standard and reproducible bioassays to measure the blocking properties of antimalarial drugs and candidate compounds. Most of the current bioassays evaluating the transmission-blocking activity of compounds rely on laboratory-adapted Plasmodium strains. Transmission-blocking data from clinical gametocyte isolates could help select novel transmission-blocking candidates for further development. Using freshly collected Plasmodium falciparum gametocytes from asymptomatic individuals, we first optimized ex vivo culture conditions to improve gametocyte viability and infectiousness by testing several culture parameters. We next pre-exposed ex vivo field-isolated gametocytes to chloroquine, dihydroartemisinin, primaquine, KDU691, GNF179, and oryzalin for 48 h prior to direct membrane feeding. We measured the activity of the drug on the ability of gametocytes to resume the sexual life cycle in Anopheles after drug exposure. Using 57 blood samples collected from Malian volunteers aged 6 to 15 years, we demonstrate that the infectivity of freshly collected field gametocytes can be preserved and improved ex vivo in a culture medium supplemented with 10% horse serum at 4% hematocrit for 48 h. Moreover, our optimized drug assay displays the weak transmission-blocking activity of chloroquine and dihydroartemisinin, while primaquine and oryzalin exhibited a transmission-blocking activity of ~50% at 1 μM. KDU691 and GNF179 both interrupted Plasmodium transmission at 1 μM and 5 nM, respectively. This new approach, if implemented, has the potential to accelerate the screening of compounds with transmission-blocking activity.
Collapse
|
3
|
Omorou R, Bin Sa'id I, Delves M, Severini C, Kouakou YI, Bienvenu AL, Picot S. Protocols for Plasmodium gametocyte production in vitro: an integrative review and analysis. Parasit Vectors 2022; 15:451. [PMID: 36471426 PMCID: PMC9720971 DOI: 10.1186/s13071-022-05566-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 11/02/2022] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The production of Plasmodium gametocytes in vitro is a real challenge. Many protocols have been described, but few have resulted in the production of viable and infectious gametocytes in sufficient quantities to conduct research on-but not limited to-transmission-blocking drug and vaccine development. The aim of this review was to identify and discuss gametocyte production protocols that have been developed over the last two decades. METHODS We analyzed the original gametocyte production protocols published from 2000 onwards based on a literature search and a thorough review. A systematic review was performed of relevant articles identified in the PubMed, Web of Sciences and ScienceDirect databases. RESULTS A total 23 studies on the production of Plasmodium gametocytes were identified, 19 involving in vitro Plasmodium falciparum, one involving Plasmodium knowlesi and three involving ex vivo Plasmodium vivax. Of the in vitro studies, 90% used environmental stressors to trigger gametocytogenesis. Mature gametocytemia of up to 4% was reported. CONCLUSIONS Several biological parameters contribute to an optimal production in vitro of viable and infectious mature gametocytes. The knowledge gained from this systematic review on the molecular mechanisms involved in gametocytogenesis enables reproducible gametocyte protocols with transgenic parasite lines to be set up. This review highlights the need for additional gametocyte production protocols for Plasmodium species other than P. falciparum.
Collapse
Affiliation(s)
- Roukayatou Omorou
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.
| | - Ibrahim Bin Sa'id
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.,Institut Agama Islam Negeri (IAIN) Kediri, 64127, Kota Kediri, Jawa Timur, Indonesia
| | - Michael Delves
- Department of Infection Biology, Faculty of Infectious Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1A 7HT, UK
| | - Carlo Severini
- Dipartimento Di Malattie Infettive, Istituto Superiore Di Sanità, Rome, Italy
| | - Yobouet Ines Kouakou
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France
| | - Anne-Lise Bienvenu
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.,Service Pharmacie, Groupement Hospitalier Nord, Hospices Civils de Lyon, Lyon, France
| | - Stephane Picot
- Malaria Research Unit, UMR 5246 CNRS-INSA-CPE-University Lyon1, University of Lyon, 69100, Villeurbanne, France.,Institut de Parasitologie Et Mycologie Médicale, Groupement Hospitalier Nord, Hospices Civils de Lyon, Lyon, France
| |
Collapse
|
4
|
Yaméogo KB, Yerbanga RS, Ouattara SB, Yao FA, Lefèvre T, Zongo I, Nikièma F, Compaoré YD, Tinto H, Chandramohan D, Greenwood B, Belem AMG, Cohuet A, Ouédraogo JB. Effect of seasonal malaria chemoprevention plus azithromycin on Plasmodium falciparum transmission: gametocyte infectivity and mosquito fitness. Malar J 2021; 20:326. [PMID: 34315475 PMCID: PMC8314489 DOI: 10.1186/s12936-021-03855-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 07/16/2021] [Indexed: 11/24/2022] Open
Abstract
Background Seasonal malaria chemoprevention (SMC) consists of administration of sulfadoxine-pyrimethamine (SP) + amodiaquine (AQ) at monthly intervals to children during the malaria transmission period. Whether the addition of azithromycin (AZ) to SMC could potentiate the benefit of the intervention was tested through a double-blind, randomized, placebo-controlled trial. The effect of SMC and the addition of AZ, on malaria transmission and on the life history traits of Anopheles gambiae mosquitoes have been investigated. Methods The study included 438 children randomly selected from among participants in the SMC + AZ trial and 198 children from the same area who did not receive chemoprevention. For each participant in the SMC + AZ trial, blood was collected 14 to 21 days post treatment, examined for the presence of malaria sexual and asexual stages and provided as a blood meal to An. gambiae females using a direct membrane-feeding assay. Results The SMC treatment, with or without AZ, significantly reduced the prevalence of asexual Plasmodium falciparum (LRT X22 = 69, P < 0.0001) and the gametocyte prevalence (LRT X22 = 54, P < 0.0001). In addition, the proportion of infectious feeds (LRT X22 = 61, P < 0.0001) and the prevalence of oocysts among exposed mosquitoes (LRT X22 = 22.8, P < 0.001) was reduced when mosquitoes were fed on blood from treated children compared to untreated controls. The addition of AZ to SPAQ was associated with an increased proportion of infectious feeds (LRT X21 = 5.2, P = 0.02), suggesting a significant effect of AZ on gametocyte infectivity. There was a slight negative effect of SPAQ and SPAQ + AZ on mosquito survival compared to mosquitoes fed with blood from control children (LRTX22 = 330, P < 0.0001). Conclusion This study demonstrates that SMC may contribute to a reduction in human to mosquito transmission of P. falciparum, and the reduced mosquito longevity observed for females fed on treated blood may increase the benefit of this intervention in control of malaria. The addition of AZ to SPAQ in SMC appeared to enhance the infectivity of gametocytes providing further evidence that this combination is not an appropriate intervention.
Collapse
Affiliation(s)
- Koudraogo Bienvenue Yaméogo
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso. .,Université Nazi Boni, Bobo-Dioulasso, Burkina Faso.
| | - Rakiswendé Serge Yerbanga
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Institut des Sciences et Techniques (INSTech Bobo), BP2779, Bobo-Dioulasso, Burkina Faso
| | | | - Franck A Yao
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | - Thierry Lefèvre
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France.,Laboratoire Mixte International Sur Les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso.,Centre de Recherche en Écologie et Évolution de la Santé (CREES), Montpellier, France
| | - Issaka Zongo
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | - Frederic Nikièma
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso
| | | | - Halidou Tinto
- Institut de Recherche en Sciences de la Santé, Nanoro, Burkina Faso
| | | | | | | | - Anna Cohuet
- MIVEGEC, University of Montpellier, IRD, CNRS, Montpellier, France.,Laboratoire Mixte International Sur Les Vecteurs (LAMIVECT), Bobo Dioulasso, Burkina Faso
| | - Jean Bosco Ouédraogo
- Institut de Recherche en Sciences de la Santé, Bobo-Dioulasso, Burkina Faso.,Institut des Sciences et Techniques (INSTech Bobo), BP2779, Bobo-Dioulasso, Burkina Faso
| |
Collapse
|
5
|
Roberds A, Ferraro E, Luckhart S, Stewart VA. HIV-1 Impact on Malaria Transmission: A Complex and Relevant Global Health Concern. Front Cell Infect Microbiol 2021; 11:656938. [PMID: 33912477 PMCID: PMC8071860 DOI: 10.3389/fcimb.2021.656938] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Accepted: 03/18/2021] [Indexed: 02/05/2023] Open
Abstract
Malaria/HIV-1 co-infection has become a significant public health problem in the tropics where there is geographical overlap of the two diseases. It is well described that co-infection impacts clinical progression of both diseases; however, less is known about the impact of co-infection on disease transmission. Malaria transmission is dependent upon multiple critical factors, one of which is the presence and viability of the sexual-stage gametocyte. In this review, we summarize evidence surrounding gametocyte production in Plasmodium falciparum and the development factors and the consequential impact that HIV-1 has on malaria parasite transmission. Epidemiological and clinical evidence surrounding anemia, immune dysregulation, and chemotherapy as it pertains to co-infection and gametocyte transmission are reviewed. We discuss significant gaps in understanding that are often due to the biological complexities of both diseases as well as the lack of entomological data necessary to define transmission success. In particular, we highlight special epidemiological populations, such as co-infected asymptomatic gametocyte carriers, and the unique role these populations have in a future focused on malaria elimination and eradication.
Collapse
Affiliation(s)
- Ashleigh Roberds
- Department of Preventive Medicine and Biostatistics, Division of Tropical Public Health, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Emily Ferraro
- Department of Preventive Medicine and Biostatistics, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Shirley Luckhart
- Department of Entomology, Plant Pathology and Nematology, Department of Biological Sciences, College of Agricultural and Life Sciences, University of Idaho, Moscow, ID, United States
| | - V Ann Stewart
- Department of Preventive Medicine and Biostatistics, Division of Tropical Public Health, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| |
Collapse
|
6
|
Villa M, Buysse M, Berthomieu A, Rivero A. The transmission-blocking effects of antimalarial drugs revisited: fitness costs and sporontocidal effects of artesunate and sulfadoxine-pyrimethamine. Int J Parasitol 2021; 51:279-289. [PMID: 33508331 DOI: 10.1016/j.ijpara.2020.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 09/22/2020] [Accepted: 09/23/2020] [Indexed: 12/31/2022]
Abstract
Assays used to evaluate the transmission-blocking activity of antimalarial drugs are largely focused on their potential to inhibit or reduce the infectivity of gametocytes, the blood stages of the parasite that are responsible for the onward transmission to the mosquito vector. For this purpose, the drug is administered concomitantly with gametocyte-infected blood, and the results are evaluated as the percentage of reduction in the number of oocysts in the mosquito midgut. We report the results of a series of experiments that explore the transmission-blocking potential of two key antimalarial drugs, artesunate and sulfadoxine-pyrimethamine, when administered to mosquitoes already infected from a previous blood meal. For this purpose, uninfected mosquitoes and mosquitoes carrying a 6 day old Plasmodium relictum infection (early oocyst stages) were allowed to feed either on a drug-treated or an untreated host in a fully factorial experiment. This protocol allowed us to bypass the gametocyte stages and establish whether the drugs have a sporontocidal effect, i.e. whether they are able to arrest the ongoing development of oocysts and sporozoites, as would be the case when a mosquito takes a post-infection treated blood meal. In a separate experiment, we also explored whether a drug-treated blood meal impacted key life history traits of the mosquito relevant for transmission, and if this depended on their infection status. Our results showed that feeding on an artesunate- or sulfadoxine-pyrimethamine-treated hosts has no epidemiologically relevant effects on the fitness of infected or uninfected mosquitoes. In contrast, when infected mosquitoes fed on an sulfadoxine-pyrimethamine-treated host, we observed both a significant increase in the number of oocysts in the midgut, and a drastic decrease in both sporozoite prevalence (-30%) and burden (-80%) compared with the untreated controls. We discuss the potential mechanisms underlying these seemingly contradictory results and contend that, provided the results are translatable to human malaria, the potential epidemiological and evolutionary consequences of the current preventive use of sulfadoxine-pyrimethamine in malaria-endemic countries could be substantial.
Collapse
Affiliation(s)
- M Villa
- MIVEGEC (CNRS - IRD - Université de Montpellier), France.
| | - M Buysse
- MIVEGEC (CNRS - IRD - Université de Montpellier), France
| | - A Berthomieu
- MIVEGEC (CNRS - IRD - Université de Montpellier), France; CREES (Centre d'Écologie et Évolution de la Santé, Montpellier), 911 avenue Agropolis, 34394 Montpellier, France
| | - A Rivero
- MIVEGEC (CNRS - IRD - Université de Montpellier), France; CREES (Centre d'Écologie et Évolution de la Santé, Montpellier), 911 avenue Agropolis, 34394 Montpellier, France
| |
Collapse
|
7
|
Batra N, Rajendran V, Wadi I, Lathwal A, Dutta RK, Ghosh PC, Gupta RD, Nath M. Synthesis, characterization, and antiplasmodial efficacy of sulfonamide‐appended [1,2,3]‐triazoles. J Heterocycl Chem 2020. [DOI: 10.1002/jhet.3888] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Neha Batra
- Department of ChemistryUniversity of Delhi Delhi 110 007 India
| | - Vinoth Rajendran
- Department of BiochemistryUniversity of Delhi South Campus New Delhi India
| | - Ishan Wadi
- Department of ChemistryUniversity of Delhi Delhi 110 007 India
| | - Ankit Lathwal
- Department of ChemistryUniversity of Delhi Delhi 110 007 India
| | - Roshan Kumar Dutta
- Faculty of Life Sciences and BiotechnologySouth Asian University New Delhi India
| | - Prahlad C. Ghosh
- Department of BiochemistryUniversity of Delhi South Campus New Delhi India
| | - Rinkoo D. Gupta
- Faculty of Life Sciences and BiotechnologySouth Asian University New Delhi India
| | - Mahendra Nath
- Department of ChemistryUniversity of Delhi Delhi 110 007 India
| |
Collapse
|
8
|
Abstract
The scientific community worldwide has realized that malaria elimination will not be possible without development of safe and effective transmission-blocking interventions. Primaquine, the only WHO recommended transmission-blocking drug, is not extensively utilized because of the toxicity issues in G6PD deficient individuals. Therefore, there is an urgent need to develop novel therapeutic interventions that can target malaria parasites and effectively block transmission. But at first, it is imperative to unravel the existing portfolio of transmission-blocking drugs. This review highlights transmission-blocking potential of current antimalarial drugs and drugs that are in various stages of clinical development. The collective analysis of the relationships between the structure and the activity of transmission-blocking drugs is expected to help in the design of new transmission-blocking antimalarials.
Collapse
|
9
|
Ouologuem DT, Kone CO, Fofana B, Sidibe B, Togo AH, Dembele D, Toure S, Koumare S, Toure O, Sagara I, Toure A, Dao A, Doumbo OK, Djimde AA. Differential infectivity of gametocytes after artemisinin-based combination therapy of uncomplicated falciparum malaria. Afr J Lab Med 2018; 7:784. [PMID: 30568901 PMCID: PMC6295776 DOI: 10.4102/ajlm.v7i2.784] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Accepted: 09/30/2018] [Indexed: 11/01/2022] Open
Abstract
Background Most malaria-endemic countries use artemisinin-based combination therapy (ACT) as their first-line treatment. ACTs are known to be highly effective on asexual stages of the malaria parasite. Malaria transmission and the spread of resistant parasites depend on the infectivity of gametocytes. The effect of the current ACT regimens on gametocyte infectivity is unclear. Objectives This study aimed to determine the infectivity of gametocytes to Anopheles gambiae following ACT treatment in the field. Methods During a randomised controlled trial in Bougoula-Hameau, Mali, conducted from July 2005 to July 2007, volunteers with uncomplicated malaria were randomised to receive artemether-lumefantrine, artesunate-amodiaquine, or artesunate-sulfadoxine/pyrimethamine. Volunteers were followed for 28 days, and gametocyte carriage was assessed. Direct skin feeding assays were performed on gametocyte carriers before and after ACT administration. Results Following artemether-lumefantrine treatment, gametocyte carriage decreased steadily from Day 0 to Day 21 post-treatment initiation. In contrast, for the artesunate-amodiaquine and artesunate-sulfadoxine/pyrimethamine arms, gametocyte carriage increased on Day 3 and remained constant until Day 7 before decreasing afterward. Mosquito feeding assays showed that artemether-lumefantrine and artesunate-amodiaquine significantly increased gametocyte infectivity to Anopheles gambiae sensu lato (s.l.) (p < 10-4), whereas artesunate-sulfadoxine/pyrimethamine decreased gametocyte infectivity in this setting (p = 0.03). Conclusion Different ACT regimens could lead to gametocyte populations with different capacity to infect the Anopheles vector. Frequent assessment of the effect of antimalarials on gametocytogenesis and gametocyte infectivity may be required for the full assessment of treatment efficacy, the potential for spread of drug resistance and malaria transmission in the field.
Collapse
Affiliation(s)
- Dinkorma T Ouologuem
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Cheick O Kone
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Bakary Fofana
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Bakary Sidibe
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Amadou H Togo
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Demba Dembele
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Sekou Toure
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Sekou Koumare
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Ousmane Toure
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Issaka Sagara
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Abdoulaye Toure
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Adama Dao
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Ogobara K Doumbo
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| | - Abdoulaye A Djimde
- Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, University of Science, Techniques and Technologies of Bamako, Bamako, Mali
| |
Collapse
|
10
|
Koepfli C, Yan G. Plasmodium Gametocytes in Field Studies: Do We Measure Commitment to Transmission or Detectability? Trends Parasitol 2018; 34:378-387. [PMID: 29544966 DOI: 10.1016/j.pt.2018.02.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 02/07/2018] [Accepted: 02/21/2018] [Indexed: 01/05/2023]
Abstract
The proportion of Plasmodium spp. infections carrying gametocytes, and gametocyte densities, are often reported as surrogate markers for transmission potential. It remains unclear whether parasites under natural conditions adjust commitment to transmission depending on external factors. Population-based surveys comprising mostly asymptomatic low-density infections are always impacted by the sensitivity of the assays used to diagnose infections and detect gametocytes. Asexual parasite density is an important predictor for the probability of detecting gametocytes, and in many cases it can explain patterns in gametocyte carriage without the need for an adjustment of the gametocyte conversion rate. When reporting gametocyte data, quantification of blood-stage parasitemia and its inclusion as a confounder in multivariable analyses is essential.
Collapse
Affiliation(s)
- Cristian Koepfli
- Program in Public Health, University of California, Irvine, CA, 92697, USA.
| | - Guiyun Yan
- Program in Public Health, University of California, Irvine, CA, 92697, USA
| |
Collapse
|
11
|
Gonçalves BP, Walker PG, Cairns M, Tiono AB, Bousema T, Drakeley C. Pregnant Women: An Overlooked Asset to Plasmodium falciparum Malaria Elimination Campaigns? Trends Parasitol 2017; 33:510-518. [DOI: 10.1016/j.pt.2017.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 01/20/2017] [Accepted: 03/01/2017] [Indexed: 01/28/2023]
|
12
|
Assessing Gametocyte Carriage in Treated Asymptomatic Falciparum Carriers in Africa. EBioMedicine 2016; 14:5-6. [PMID: 27865765 PMCID: PMC5161435 DOI: 10.1016/j.ebiom.2016.11.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 11/11/2016] [Indexed: 11/24/2022] Open
|
13
|
Utilizing direct skin feeding assays for development of vaccines that interrupt malaria transmission: A systematic review of methods and case study. Vaccine 2016; 34:5863-5870. [PMID: 27789147 DOI: 10.1016/j.vaccine.2016.10.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 09/23/2016] [Accepted: 10/11/2016] [Indexed: 01/29/2023]
Abstract
Shifting the malaria priorities from a paradigm of control and elimination to a goal of global eradication calls for renewed attention to the interruption of malaria transmission. Sustained progress toward eradication will require both improved understanding of infectious reservoirs and efficient development of novel transmission-blocking interventions, such as rapidly acting and highly efficacious therapeutics and vaccines. Here, we review the direct skin feeding assay (DSF), which has been proposed as a valuable tool for measuring the in natura transmission of malaria parasites from human hosts to mosquito vectors across heterogeneous populations. To capture the methodological breadth of this assay's use, we first systematically review and qualitatively synthesize previously published investigations using DSFs to study malaria transmission in humans. Then, using a recent Phase 1 trial in Mali of the Pfs25H-EPA/Alhydrogel® vaccine candidate (NCT01867463) designed to interrupt Plasmodium falciparum transmission as a case study, we describe the potential opportunities and current limitations of utilizing the endpoints measured by DSF in making early clinical decisions for individually randomized transmission-interrupting intervention candidates. Using simulations based on the data collected in the clinical trial, we demonstrate that the capacity of the DSF to serve as an evaluative tool is limited by the statistical power constraints of the "effective sample size" (i.e. the number of subjects that are capable of transmitting at the time of feeding). Altogether, our findings suggest DSFs have great potential utility for assessing the public health impacts of emerging antimalarial tools, but additional research is needed to address issues of scalability and to establish correlation with community-wide clinical endpoints as well as complementary in vitro measures, such as standard membrane feeding assays.
Collapse
|
14
|
Karl S, Laman M, Moore BR, Benjamin JM, Salib M, Lorry L, Maripal S, Siba P, Robinson LJ, Mueller I, Davis TME. Risk factors for Plasmodium falciparum and Plasmodium vivax gametocyte carriage in Papua New Guinean children with uncomplicated malaria. Acta Trop 2016; 160:1-8. [PMID: 27056132 DOI: 10.1016/j.actatropica.2016.04.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 04/01/2016] [Accepted: 04/02/2016] [Indexed: 01/06/2023]
Abstract
There are limited data on gametocytaemia risk factors before/after treatment with artemisinin combination therapy in children from areas with transmission of multiple Plasmodium species. We utilised data from a randomised trial comparing artemether-lumefantrine (AL) and artemisinin-naphthoquine (AN) in 230 Papua New Guinean children aged 0.5-5 years with uncomplicated malaria in whom determinants of gametocytaemia by light microscopy were assessed at baseline using logistic regression and during follow-up using multilevel mixed effects modelling. Seventy-four (32%) and 18 (8%) children presented with P. falciparum and P. vivax gametocytaemia, respectively. Baseline P. falciparum gametocytaemia was associated with Hackett spleen grade 1 (odds ratio (95% CI) 4.01 (1.60-10.05) vs grade 0; P<0.001) and haemoglobin (0.95 (0.92-0.97) per 1g/L increase; P<0.001), and P. falciparum asexual parasitaemia in slide-positive cases (0.36 (0.19-0.68) for a 10-fold increase; P=0.002). Baseline P. vivax gametocytaemia was associated with Hackett grade 2 (12.66 (1.31-122.56); P=0.028), mixed P. falciparum/vivax infection (0.16 (0.03-1.00); P=0.050), P. vivax asexual parasitaemia (5.68 (0.98-33.04); P=0.053) and haemoglobin (0.94 (0.88-1.00); P=0.056). For post-treatment P. falciparum gametocytaemia, independent predictors were AN vs AL treatment (4.09 (1.43-11.65)), haemoglobin (0.95 (0.93-0.97)), presence/absence of P. falciparum asexual forms (3.40 (1.66-0.68)) and day post-treatment (0.086 (0.82-0.90)) (P<0.001). Post-treatment P. vivax gametocytaemia was predicted by presence of P. vivax asexual forms (596 (12-28,433); P<0.001). Consistent with slow P. falciparum gametocyte maturation, low haemoglobin, low asexual parasite density and higher spleen grading, markers of increased prior infection exposure/immunity, were strong associates of pre-treatment gametocyte positivity. The persistent inverse association between P. falciparum gametocytaemia and haemoglobin during follow-up suggests an important role for bone marrow modulation of gametocytogenesis. In P. vivax infections, baseline and post-treatment gametocyte carriage was positively related to the acute parasite burden, reflecting the close association between the development of asexual and sexual forms.
Collapse
Affiliation(s)
- Stephan Karl
- Population Health and Immunity Division, Walter and Eliza Hall Institute, Parkville, Victoria, Australia; Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
| | - Moses Laman
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Brioni R Moore
- School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia, Australia
| | - John M Benjamin
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Mary Salib
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Lina Lorry
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Samuel Maripal
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Peter Siba
- Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Leanne J Robinson
- Population Health and Immunity Division, Walter and Eliza Hall Institute, Parkville, Victoria, Australia; Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia; Papua New Guinea Institute of Medical Research, Madang, Papua New Guinea
| | - Ivo Mueller
- Population Health and Immunity Division, Walter and Eliza Hall Institute, Parkville, Victoria, Australia; Department of Medical Biology, University of Melbourne, Melbourne, Victoria, Australia
| | - Timothy M E Davis
- School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia, Australia.
| |
Collapse
|
15
|
Abstract
There has been increasing interest in the role of malaria drugs in preventing malaria transmission from humans to mosquitoes, which would help augment malaria control and elimination strategies. Nevertheless, only one stage in the malaria parasite life cycle, the gametocyte, is infectious to mosquitoes. The Worldwide Antimalarial Resistance Network (WWARN) have analyzed data from 48,840 patients from 141 clinical trials in order to define the nature and determinants of gametocyte clearance following artemisinin combination treatment (ACT) for symptomatic malaria infections. However, the presence of gametocytes does not always predict their infectivity, meaning that the microscopy-based methods used by the WWARN investigators represent an imperfect surrogate marker of transmissibility. Their findings, that some ACTs clear gametocytes faster than others, should be interpreted in light of these limitations and important gaps in our understanding of the biology and epidemiology of malaria transmission.Please see related article: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-016-0621-7.
Collapse
|
16
|
Gametocyte Clearance Kinetics Determined by Quantitative Magnetic Fractionation in Melanesian Children with Uncomplicated Malaria Treated with Artemisinin Combination Therapy. Antimicrob Agents Chemother 2015; 59:4489-96. [PMID: 25987625 DOI: 10.1128/aac.00136-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 05/09/2015] [Indexed: 12/24/2022] Open
Abstract
Quantitative magnetic fractionation and a published mathematical model were used to characterize between-treatment differences in gametocyte density and prevalence in 70 Papua New Guinean children with uncomplicated Plasmodium falciparum and/or Plasmodium vivax malaria randomized to one of two artemisinin combination therapies (artemether-lumefantrine or artemisinin-naphthoquine) in an intervention trial. There was an initial rise in peripheral P. falciparum gametocyte density with both treatments, but it was more pronounced in the artemisinin-naphthoquine group. Model-derived estimates of the median pretreatment sequestered gametocyte population were 21/μl for artemether-lumefantrine and 61/μl for artemisinin-naphthoquine (P < 0.001). The median time for P. falciparum gametocyte density to fall to <2.5/μl (below which transmission becomes unlikely) was 16 days in the artemether-lumefantrine group and 20 days in artemisinin-naphthoquine group (P < 0.001). Gametocyte prevalence modeling suggested that artemisinin-naphthoquine-treated children became gametocytemic faster (median, 2.2 days) than artemether-lumefantrine-treated children (median, 5.3 days; P < 0.001) and had a longer median P. falciparum gametocyte carriage time per individual (20 versus 13 days; P < 0.001). Clearance of P. vivax gametocytes was rapid (within 3 days) in both groups; however, consistent with the reappearance of asexual forms in the main trial, nearly 40% of children in the artemether-lumefantrine group developed P. vivax gametocytemia between days 28 and 42 compared with 3% of children in the artemisinin-naphthoquine group. These data suggest that artemisinin is less active than artemether against sequestered gametocytes. Greater initial gametocyte release after artemisinin-naphthoquine increases the period of potential P. falciparum transmission by 4 days relative to artemether-lumefantrine, but the longer elimination half-life of naphthoquine than of lumefantrine suppresses P. vivax recurrence and consequent gametocytemia.
Collapse
|
17
|
The relationship between Plasmodium infection, anaemia and nutritional status in asymptomatic children aged under five years living in stable transmission zones in Kinshasa, Democratic Republic of Congo. Malar J 2015; 14:83. [PMID: 25880427 PMCID: PMC4336722 DOI: 10.1186/s12936-015-0595-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 01/30/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria is preventable and treatable when recommended interventions are properly implemented. Thus, diagnosis and treatment focus on symptomatic individuals while asymptomatic Plasmodium infection (PI) plays a role in the sustainability of the transmission and may also have an impact on the morbidity of the disease in terms of anaemia, nutritional status and even cognitive development of children. The objective of this study was to assess PI prevalence and its relationship with known morbidity factors in a vulnerable but asymptomatic stratum of the population. METHODS A simple random sample, household survey in asymptomatic children under the age of five was conducted from April to September 2012 in two health areas of the health zone of Mont Ngafula 1, Kinshasa, Democratic Republic of Congo. RESULTS The PI prevalence were 30.9% (95% CI: 26.5-35.9) and 14.3% (95% CI: 10.5-18.1) in Cité Pumbu and Kindele health areas, respectively, (OR: 2.7; p <0.001). All were Plasmodium falciparum infected and 4% were co-infected with Plasmodium malariae. In Cité Pumbu and Kindele, the prevalence of anaemia (haemoglobin <11 g/dL) was 61.6% (95% CI: 56.6-66.5) and 39.3% (95% CI: 34.0-44.6), respectively, (OR: 2.5; p <0.001). The health area of Cité Pumbu had 32% (95% CI: 27.5-37.0) of chronic malnutrition (HAZ score ≤ -2SD) compared to 5.1% (95% CI: 2.8-7.6) in Kindele. PI was predictor factor for anaemia (aOR: 3.5, p =0.01) and within infected children, there was an inverse relationship between parasite density and haemoglobin level (β = -5*10(-5), p <0.001). Age older than 12 months (aOR: 3.8, p = 0.01), presence of anaemia (aOR: 3.4, p =0.001), chronic malnutrition (aOR: 1.8, p = 0.01), having a single parent/guardian (aOR: 1.6, p =0.04), and the non-use of insecticide-treated nets (aOR: 1.7, p = 0.04) were all predictors for PI in the overall population. CONCLUSION PI in asymptomatic children was correlated with anaemia and chronic malnutrition and was thus a harmful condition in the study population. Malaria control initiatives should not only focus on treatment of symptomatic infections but also take into consideration asymptomatic but infected children.
Collapse
|
18
|
Bolscher JM, Koolen KMJ, van Gemert GJ, van de Vegte-Bolmer MG, Bousema T, Leroy D, Sauerwein RW, Dechering KJ. A combination of new screening assays for prioritization of transmission-blocking antimalarials reveals distinct dynamics of marketed and experimental drugs. J Antimicrob Chemother 2015; 70:1357-66. [PMID: 25667405 DOI: 10.1093/jac/dkv003] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 12/29/2014] [Indexed: 12/23/2022] Open
Abstract
OBJECTIVES The development of drugs to reduce malaria transmission is an important part of malaria eradication plans. We set out to develop and validate a combination of new screening assays for prioritization of transmission-blocking molecules. METHODS We developed high-throughput assays for screening compounds against gametocytes, the parasite stages responsible for onward transmission to mosquitoes. An existing gametocyte parasitic lactate dehydrogenase (pLDH) assay was adapted for use in 384-well plates, and a novel homogeneous immunoassay to monitor the functional transition of female gametocytes into gametes was developed. A collection of 48 marketed and experimental antimalarials was screened and subsequently tested for impact on sporogony in Anopheles mosquitoes, to directly quantify the transmission-blocking properties of antimalarials in relation to their effects on gametocyte pLDH activity or gametogenesis. RESULTS AND CONCLUSIONS The novel screening assays revealed distinct stage-specific kinetics and dynamics of drug effects. Peroxides showed the most potent transmission-blocking effects, with an intermediate speed of action and IC50 values that were 20-40-fold higher than the IC50s against the asexual stages causing clinical malaria. Finally, the novel synthetic peroxide OZ439 appeared to be a promising drug candidate as it exerted gametocytocidal and transmission-blocking effects at clinically relevant concentrations.
Collapse
Affiliation(s)
- J M Bolscher
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands
| | - K M J Koolen
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands
| | - G J van Gemert
- Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | | | - T Bousema
- Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - D Leroy
- Medicines for Malaria Venture, Route de Pré-Bois 20, 1215 Geneva 15, Switzerland
| | - R W Sauerwein
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - K J Dechering
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands
| |
Collapse
|
19
|
White NJ, Ashley EA, Recht J, Delves MJ, Ruecker A, Smithuis FM, Eziefula AC, Bousema T, Drakeley C, Chotivanich K, Imwong M, Pukrittayakamee S, Prachumsri J, Chu C, Andolina C, Bancone G, Hien TT, Mayxay M, Taylor WRJ, von Seidlein L, Price RN, Barnes KI, Djimdé A, ter Kuile F, Gosling R, Chen I, Dhorda MJ, Stepniewska K, Guérin P, Woodrow CJ, Dondorp AM, Day NPJ, Nosten FH. Assessment of therapeutic responses to gametocytocidal drugs in Plasmodium falciparum malaria. Malar J 2014; 13:483. [PMID: 25486998 PMCID: PMC4295364 DOI: 10.1186/1475-2875-13-483] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Accepted: 11/29/2014] [Indexed: 01/10/2023] Open
Abstract
Indirect clinical measures assessing anti-malarial drug transmission-blocking activity in falciparum malaria include measurement of the duration of gametocytaemia, the rate of gametocyte clearance or the area under the gametocytaemia-time curve (AUC). These may provide useful comparative information, but they underestimate dose-response relationships for transmission-blocking activity. Following 8-aminoquinoline administration P. falciparum gametocytes are sterilized within hours, whereas clearance from blood takes days. Gametocytaemia AUC and clearance times are determined predominantly by the more numerous female gametocytes, which are generally less drug sensitive than the minority male gametocytes, whereas transmission-blocking activity and thus infectivity is determined by the more sensitive male forms. In choosing doses of transmission-blocking drugs there is no substitute yet for mosquito-feeding studies.
Collapse
Affiliation(s)
- Nicholas J White
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Elizabeth A Ashley
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Judith Recht
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | | - Andrea Ruecker
- />Department of Life Sciences, Imperial College, London, UK
| | - Frank M Smithuis
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- />Myanmar Oxford Clinical Research Unit, Yangon, Myanmar
| | | | - Teun Bousema
- />London School of Hygiene and Tropical Medicine, London, UK
| | - Chris Drakeley
- />London School of Hygiene and Tropical Medicine, London, UK
| | - Kesinee Chotivanich
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Mallika Imwong
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Sasithon Pukrittayakamee
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Jetsumon Prachumsri
- />Mahidol Vivax Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Cindy Chu
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Chiara Andolina
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Germana Bancone
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| | - Tran T Hien
- />Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
| | - Mayfong Mayxay
- />Lao-Oxford-Mahosot Hospital-Wellcome Trust Research Unit, Microbiology Laboratory, Mahosot Hospital, Vientiane, Lao PDR
| | - Walter RJ Taylor
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Lorenz von Seidlein
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Ric N Price
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT Australia
| | - Karen I Barnes
- />Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Cape Town, South Africa
| | - Abdoulaye Djimdé
- />Malaria Research and Training Centre, Department of Epidemiology of Parasitic Diseases, Faculty of Medicine and Odonto-Stomatogy, University of Sciences, Techniques and Technologies of Bamako, Bamako, Mali
| | | | - Roly Gosling
- />Global Health Group, UCSF Global Health Sciences, San Francisco, CA USA
| | - Ingrid Chen
- />Global Health Group, UCSF Global Health Sciences, San Francisco, CA USA
| | - Mehul J Dhorda
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- />World Wide Antimalarial Resistance Network, Churchill Hospital, Oxford, Headington, UK
| | - Kasia Stepniewska
- />World Wide Antimalarial Resistance Network, Churchill Hospital, Oxford, Headington, UK
| | - Philippe Guérin
- />World Wide Antimalarial Resistance Network, Churchill Hospital, Oxford, Headington, UK
| | - Charles J Woodrow
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Arjen M Dondorp
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Nicholas PJ Day
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Francois H Nosten
- />Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- />Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- />Shoklo Malaria Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Tak, Thailand
| |
Collapse
|
20
|
Strategic use of antimalarial drugs that block falciparum malaria parasite transmission to mosquitoes to achieve local malaria elimination. Parasitol Res 2014; 113:3535-46. [PMID: 25185662 DOI: 10.1007/s00436-014-4091-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 08/25/2014] [Indexed: 01/03/2023]
Abstract
The ultimate aim of malaria chemotherapy is not only to treat symptomatic infection but also to reduce transmission potential. With the absence of clinically proven vaccines, drug-mediated blocking of malaria transmission gains growing interest in the research agenda for malaria control and elimination. In addition to the limited arsenal of antimalarials available, the situation is further complicated by the fact that most commonly used antimalarials are being extensively resisted by the parasite and do not assist in blocking its transmission to vectors. Most antimalarials do not exhibit gametocytocidal and/ or sporontocidal activity against the sexual stages of Plasmodium falciparum but may even enhance gametocytogenesis and gametocyte transmissibility. Artemisinin derivatives and 8-aminoquinolines are useful transmission-blocking antimalarials whose optimal actions are on different stages of gametocytes. Transmission control interventions that include gametocytocides covering the spectrum of gametocyte development should be used to reduce and, if possible, stop transmission and infectivity of gametocytes to mosquitoes. Potent gametocytocidal drugs could also help deter the spread of antimalarial drug resistance. Novel proof-of-concept compounds with gametocytocidal activity, such as trioxaquines, synthetic endoperoxides, and spiroindolone, should be further tested for possible clinical utility before investigating the possibility of integrating them in transmission-reducing interventions. Strategic use of potent gametocytocides at appropriate timing with artemisinin-based combination therapies should be given attention, at least, in the short run. This review highlights the role that antimalarials could play in blocking gametocyte transmission and infectivity to mosquitoes and, hence, in reducing the potential of falciparum malaria transmissibility and drug resistance spread.
Collapse
|
21
|
Andagalu B, Mativo J, Kamau E, Ogutu B. Longitudinal study on Plasmodium falciparum gametocyte carriage following artemether-lumefantrine administration in a cohort of children aged 12-47 months living in Western Kenya, a high transmission area. Malar J 2014; 13:265. [PMID: 25007860 PMCID: PMC4105514 DOI: 10.1186/1475-2875-13-265] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2014] [Accepted: 07/05/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The effects that artemether-lumefantrine (AL) has on gametocyte dynamics in the short-term have recently been described. However there is limited long-term longitudinal data on the effect of AL on gametocyte dynamics in asymptomatic children. METHODS An epidemiological study was conducted in Kombewa, Western Kenya, in which 270 asymptomatic children aged between 12 and 47 months were enrolled. The subjects were randomized to receive either a course of AL or placebo at enrolment. Active follow-up was conducted for one year. RESULTS The gametocyte prevalence and density dynamics throughout the study period mirrored that of the asexual forms. The proportion of initially parasitaemic subjects becoming gametocytaemic was significantly lower in the AL arm for the first 12 weeks following randomization. The geometric mean gametocyte density was lower in the AL arm for 2 weeks following randomization. None of the variables of interest had a statistically significant effect on the duration of gametocytaemia. There is no effect seen in subjects who are not parasitaemic at the time of drug administration. CONCLUSIONS The treatment of asymptomatic parasitaemic subjects with AL results in a significant reduction in the proportion of subjects who become gametocytaemic for at least 12 weeks.
Collapse
Affiliation(s)
| | | | - Edwin Kamau
- Department of Emerging Infectious Diseases-Global Emerging Infections Surveillance and Response System (DEID-GEIS) Program, United States Army Medical Research Unit-Kenya (USAMRU-K), Kenya Medical Research Institute (KEMRI)-Walter Reed Project, P,O, Box 54, Kisumu, 40100, Kenya.
| | | |
Collapse
|
22
|
Johnston GL, Gething PW, Hay SI, Smith DL, Fidock DA. Modeling within-host effects of drugs on Plasmodium falciparum transmission and prospects for malaria elimination. PLoS Comput Biol 2014; 10:e1003434. [PMID: 24465196 PMCID: PMC3900379 DOI: 10.1371/journal.pcbi.1003434] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 11/25/2013] [Indexed: 01/05/2023] Open
Abstract
Achieving a theoretical foundation for malaria elimination will require a detailed understanding of the quantitative relationships between patient treatment-seeking behavior, treatment coverage, and the effects of curative therapies that also block Plasmodium parasite transmission to mosquito vectors. Here, we report a mechanistic, within-host mathematical model that uses pharmacokinetic (PK) and pharmacodynamic (PD) data to simulate the effects of artemisinin-based combination therapies (ACTs) on Plasmodium falciparum transmission. To contextualize this model, we created a set of global maps of the fold reductions that would be necessary to reduce the malaria R C (i.e. its basic reproductive number under control) to below 1 and thus interrupt transmission. This modeling was applied to low-transmission settings, defined as having a R 0<10 based on 2010 data. Our modeling predicts that treating 93-98% of symptomatic infections with an ACT within five days of fever onset would interrupt malaria transmission for ∼91% of the at-risk population of Southeast Asia and ∼74% of the global at-risk population, and lead these populations towards malaria elimination. This level of treatment coverage corresponds to an estimated 81-85% of all infected individuals in these settings. At this coverage level with ACTs, the addition of the gametocytocidal agent primaquine affords no major gains in transmission reduction. Indeed, we estimate that it would require switching ∼180 people from ACTs to ACTs plus primaquine to achieve the same transmission reduction as switching a single individual from untreated to treated with ACTs. Our model thus predicts that the addition of gametocytocidal drugs to treatment regimens provides very small population-wide benefits and that the focus of control efforts in Southeast Asia should be on increasing prompt ACT coverage. Prospects for elimination in much of Sub-Saharan Africa appear far less favorable currently, due to high rates of infection and less frequent and less rapid treatment.
Collapse
Affiliation(s)
- Geoffrey L. Johnston
- Department of Microbiology and Immunology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- School of International and Public Affairs, Columbia University, New York, New York, United States of America
- Bloomberg School of Public Health, John Hopkins University, Baltimore, Maryland, United States of America
| | - Peter W. Gething
- 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
| | - David L. Smith
- Bloomberg School of Public Health, John Hopkins University, Baltimore, Maryland, United States of America
| | - David A. Fidock
- Department of Microbiology and Immunology, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
- Division of Infectious Diseases, Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York, United States of America
| |
Collapse
|
23
|
Hobbs CV, Tanaka TQ, Muratova O, Van Vliet J, Borkowsky W, Williamson KC, Duffy PE. HIV treatments have malaria gametocyte killing and transmission blocking activity. J Infect Dis 2013; 208:139-48. [PMID: 23539746 DOI: 10.1093/infdis/jit132] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Millions of individuals being treated for human immunodeficiency virus (HIV) live in malaria-endemic areas, but the effects of these treatments on malaria transmission are unknown. While drugs like HIV protease inhibitors (PIs) and trimethoprim-sulfamethoxazole (TMP-SMX) have known activity against parasites during liver or asexual blood stages, their effects on transmission stages require further study. METHODS The HIV PIs lopinavir and saquinavir, the nonnucleoside reverse-transcriptase inhibitor nevirapine, and the antibiotic TMP-SMX were assessed for activity against Plasmodium falciparum transmission stages. The alamarBlue assay was used to determine the effects of drugs on gametocyte viability, and exflagellation was assessed to determine the effects of drugs on gametocyte maturation. The effects of drug on transmission were assessed by calculating the mosquito oocyst count as a marker for infectivity, using standard membrane feeding assays. RESULTS Lopinavir and saquinavir have gametocytocidal and transmission blocking activities at or approaching clinically relevant treatment levels, while nevirapine does not. TMP-SMX is not gametocytocidal, but at prophylactic levels it blocks transmission. CONCLUSIONS Specific HIV treatments have gametocyte killing and transmission-blocking effects. Clinical studies are warranted to evaluate these findings and their potential impact on eradication efforts.
Collapse
Affiliation(s)
- Charlotte V Hobbs
- Laboratory of Malaria Vaccinology and Immunology, NIH/NIAID, 12735 Twinbrook Pkwy, Rockville, MD 20852, USA.
| | | | | | | | | | | | | |
Collapse
|
24
|
Sawa P, Shekalaghe SA, Drakeley CJ, Sutherland CJ, Mweresa CK, Baidjoe AY, Manjurano A, Kavishe RA, Beshir KB, Yussuf RU, Omar SA, Hermsen CC, Okell L, Schallig HDFH, Sauerwein RW, Hallett RL, Bousema T. Malaria transmission after artemether-lumefantrine and dihydroartemisinin-piperaquine: a randomized trial. J Infect Dis 2013; 207:1637-45. [PMID: 23468056 DOI: 10.1093/infdis/jit077] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Artemisinin-based combination therapy (ACT) reduces the potential for malaria transmission, compared with non-ACTs. It is unclear whether this effect differs between ACTs. METHODS A total of 298 children (age, 6 months to 10 years) with uncomplicated falciparum malaria were randomized to artemether-lumefantrine (AL; n = 153) or dihydroartemisinin-piperaquine (DP; n = 145) in Mbita, a community in western Kenya. Gametocyte carriage was determined by molecular methods on days 0, 1, 2, 3, 7, 14, 28, and 42 after treatment initiation. The gametocyte infectiousness to mosquitoes was determined by mosquito-feeding assays on day 7 after beginning therapy. RESULTS The cumulative risk of recurrent parasitemia on day 42 after initiation of treatment, unadjusted by polymerase chain reaction findings, was 20.7% (95% confidence interval [CI], 14.4-28.2) for AL, compared with 3.7% (95% CI, 1.2-8.5) for DP (P < .001). The mean duration of gametocyte carriage was 5.5 days (95% CI, 3.6-8.5) for AL and 15.3 days (95% CI, 9.7-24.2) for DP (P = .001). The proportion of mosquitoes that became infected after feeding on blood from AL-treated children was 1.88% (43 of 2293), compared with 3.50% (83 of 2371) for those that fed on blood from DP-treated children (P = .06); the oocyst burden among mosquitoes was lower among those that fed on blood from AL-treated children (P = .005) CONCLUSIONS: While DP was associated with a longer prophylactic time after treatment, gametocyte carriage and malaria transmission to mosquitoes was lower after AL treatment. CLINICAL TRIALS REGISTRATION NCT00868465.
Collapse
Affiliation(s)
- Patrick Sawa
- Human Health Division, International Centre for Insect Physiology and Ecology, Mbita Point, Nairobi, Kenya
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Salcedo-Sora JE, Ward SA. The folate metabolic network of Falciparum malaria. Mol Biochem Parasitol 2013; 188:51-62. [PMID: 23454873 DOI: 10.1016/j.molbiopara.2013.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2012] [Revised: 02/04/2013] [Accepted: 02/11/2013] [Indexed: 01/07/2023]
Abstract
The targeting of key enzymes in the folate pathway continues to be an effective chemotherapeutic approach that has earned antifolate drugs a valuable position in the medical pharmacopoeia. The successful therapeutic use of antifolates as antimalarials has been a catalyst for ongoing research into the biochemistry of folate and pterin biosynthesis in malaria parasites. However, our understanding of the parasites folate metabolism remains partial and patchy, especially in relation to the shikimate pathway, the folate cycle, and folate salvage. A sizeable number of potential folate targets remain to be characterised. Recent reports on the parasite specific transport of folate precursors that would normally be present in the human host awaken previous hypotheses on the salvage of folate precursors or by-products. As the parasite progresses through its life-cycle it encounters very contrasting host cell environments that present radically different metabolic milieus and biochemical challenges. It would seem probable that as the parasite encounters differing environments it would need to modify its biochemistry. This would be reflected in the folate homeostasis in Plasmodium. Recent drug screening efforts and insights into folate membrane transport substantiate the argument that folate metabolism may still offer unexplored opportunities for therapeutic attack.
Collapse
Affiliation(s)
- J Enrique Salcedo-Sora
- Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
| | | |
Collapse
|
26
|
Dechy-Cabaret O, Benoit-Vical F. Effects of Antimalarial Molecules on the Gametocyte Stage of Plasmodium falciparum: The Debate. J Med Chem 2012; 55:10328-44. [DOI: 10.1021/jm3005898] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Odile Dechy-Cabaret
- CNRS, LCC (Laboratoire de Chimie de Coordination), 205 Route de Narbonne, BP
44099, F-31077 Toulouse Cedex 4, France
- Université de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, France
| | - Françoise Benoit-Vical
- CNRS, LCC (Laboratoire de Chimie de Coordination), 205 Route de Narbonne, BP
44099, F-31077 Toulouse Cedex 4, France
- Université de Toulouse, UPS, INPT, F-31077 Toulouse Cedex 4, France
- Service de Parasitologie-Mycologie
and Faculté de Médecine de Rangueil, Centre Hospitalier Universitaire de Toulouse, Toulouse, France
| |
Collapse
|
27
|
|
28
|
Kolaczinski K, Leslie T, Ali I, Durrani N, Lee S, Barends M, Beshir K, Ord R, Hallett R, Rowland M. Defining Plasmodium falciparum treatment in South West Asia: a randomized trial comparing artesunate or primaquine combined with chloroquine or SP. PLoS One 2012; 7:e28957. [PMID: 22303437 PMCID: PMC3269419 DOI: 10.1371/journal.pone.0028957] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 11/17/2011] [Indexed: 11/22/2022] Open
Abstract
INTRODUCTION Antimalarial resistance has led to a global policy of artemisinin-based combination therapy. Despite growing resistance chloroquine (CQ) remained until recently the official first-line treatment for falciparum malaria in Pakistan, with sulfadoxine-pyrimethamine (SP) second-line. Co-treatment with the gametocytocidal primaquine (PQ) is recommended for transmission control in South Asia. The relative effect of artesunate (AS) or primaquine, as partner drugs, on clinical outcomes and gametocyte carriage in this setting were unknown. METHODS A single-blinded, randomized trial among Afghan refugees in Pakistan compared six treatment arms: CQ; CQ+(single-dose)PQ; CQ+(3 d)AS; SP; SP+(single-dose)PQ, and SP+(3 d)AS. The objectives were to compare treatment failure rates and effect on gametocyte carriage, of CQ or SP monotherapy against the respective combinations (PQ or AS). Outcomes included trophozoite and gametocyte clearance (read by light microscopy), and clinical and parasitological failure. FINDINGS A total of 308 (87%) patients completed the trial. Failure rates by day 28 were: CQ 55/68 (81%); CQ+AS 19/67 (28%), SP 4/41 (9.8%), SP+AS 1/41 (2.4%). The addition of PQ to CQ or SP did not affect failure rates (CQ+PQ 49/67 (73%) failed; SP+PQ 5/33 (16%) failed). AS was superior to PQ at clearing gametocytes; gametocytes were seen on d7 in 85% of CQ, 40% of CQ+PQ, 21% of CQ+AS, 91% of SP, 76% of SP+PQ and 23% of SP+AS treated patients. PQ was more effective at clearing older gametocyte infections whereas AS was more effective at preventing emergence of mature gametocytes, except in cases that recrudesced. CONCLUSIONS CQ is no longer appropriate by itself or in combination. These findings influenced the replacement of CQ with SP+AS for first-line treatment of uncomplicated falciparum malaria in the WHO Eastern Mediterranean Region. The threat of SP resistance remains as SP monotherapy is still common. Three day AS was superior to single-dose PQ for reducing gametocyte carriage. TRIAL REGISTRATION ClinicalTrials.gov NCT00959517.
Collapse
Affiliation(s)
- Kate Kolaczinski
- London School of Hygiene and Tropical Medicine, London, United Kingdom.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
A sub-microscopic gametocyte reservoir can sustain malaria transmission. PLoS One 2011; 6:e20805. [PMID: 21695129 PMCID: PMC3114851 DOI: 10.1371/journal.pone.0020805] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 05/13/2011] [Indexed: 11/19/2022] Open
Abstract
Background Novel diagnostic tools, including PCR and high field gradient magnetic fractionation (HFGMF), have improved detection of asexual Plasmodium falciparum parasites and especially infectious gametocytes in human blood. These techniques indicate a significant number of people carry gametocyte densities that fall below the conventional threshold of detection achieved by standard light microscopy (LM). Methodology/Principal Findings To determine how low-level gametocytemia may affect transmission in present large-scale efforts for P. falciparum control in endemic areas, we developed a refinement of the classical Ross-Macdonald model of malaria transmission by introducing multiple infective compartments to model the potential impact of highly prevalent, low gametocytaemic reservoirs in the population. Models were calibrated using field-based data and several numerical experiments were conducted to assess the effect of high and low gametocytemia on P. falciparum transmission and control. Special consideration was given to the impact of long-lasting insecticide-treated bed nets (LLIN), presently considered the most efficient way to prevent transmission, and particularly LLIN coverage similar to goals targeted by the Roll Back Malaria and Global Fund malaria control campaigns. Our analyses indicate that models which include only moderate-to-high gametocytemia (detectable by LM) predict finite eradication times after LLIN introduction. Models that include a low gametocytemia reservoir (requiring PCR or HFGMF detection) predict much more stable, persistent transmission. Our modeled outcomes result in significantly different estimates for the level and duration of control needed to achieve malaria elimination if submicroscopic gametocytes are included. Conclusions/Significance It will be very important to complement current methods of surveillance with enhanced diagnostic techniques to detect asexual parasites and gametocytes to more accurately plan, monitor and guide malaria control programs aimed at eliminating malaria.
Collapse
|
30
|
Bousema T, Drakeley C. Epidemiology and infectivity of Plasmodium falciparum and Plasmodium vivax gametocytes in relation to malaria control and elimination. Clin Microbiol Rev 2011; 24:377-410. [PMID: 21482730 PMCID: PMC3122489 DOI: 10.1128/cmr.00051-10] [Citation(s) in RCA: 508] [Impact Index Per Article: 39.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Malaria remains a major cause of morbidity and mortality in the tropics, with Plasmodium falciparum responsible for the majority of the disease burden and P. vivax being the geographically most widely distributed cause of malaria. Gametocytes are the sexual-stage parasites that infect Anopheles mosquitoes and mediate the onward transmission of the disease. Gametocytes are poorly studied despite this crucial role, but with a recent resurgence of interest in malaria elimination, the study of gametocytes is in vogue. This review highlights the current state of knowledge with regard to the development and longevity of P. falciparum and P. vivax gametocytes in the human host and the factors influencing their distribution within endemic populations. The evidence for immune responses, antimalarial drugs, and drug resistance influencing infectiousness to mosquitoes is reviewed. We discuss how the application of molecular techniques has led to the identification of submicroscopic gametocyte carriage and to a reassessment of the human infectious reservoir. These components are drawn together to show how control measures that aim to reduce malaria transmission, such as mass drug administration and a transmission-blocking vaccine, might better be deployed.
Collapse
Affiliation(s)
- Teun Bousema
- Department of Immunology & Infection, London School of Hygiene and Tropical Medicine, London W1CE 7HT, United Kingdom
| | - Chris Drakeley
- Department of Immunology & Infection, London School of Hygiene and Tropical Medicine, London W1CE 7HT, United Kingdom
| |
Collapse
|
31
|
Blocking Plasmodium falciparum Malaria Transmission with Drugs: The Gametocytocidal and Sporontocidal Properties of Current and Prospective Antimalarials. Pharmaceuticals (Basel) 2010. [PMCID: PMC4052541 DOI: 10.3390/ph4010044] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Drugs that kill or inhibit the sexual stages of Plasmodium could potentially amplify or synergize the impact of other interventions by blocking transmission to mosquitoes. Primaquine and other 8-aminoquinolines have long offered such potential, but safety and other concerns have limited their use. Although transmission-blocking properties are not often a priority of drug discovery efforts, a number of interesting gametocytocidal and/or sporontocidal drug candidates have emerged in recent years. Some still bear significant technical and safety concerns, while others have passed clinical trials and are on the verge of entering the antimalarial armamentarium. Recent advances in our knowledge of gametocyte differentiation, gametogenesis and sporogony have also led to the identification of a large array of potential new targets for drugs that might interfere with malaria transmission. This review examines the properties of existing and prospective drugs, mechanisms of action, counter-indications and their potential role in regional malaria elimination efforts.
Collapse
|
32
|
Kone A, van de Vegte-Bolmer M, Siebelink-Stoter R, van Gemert GJ, Dara A, Niangaly H, Luty A, Doumbo OK, Sauerwein R, Djimde AA. Sulfadoxine-pyrimethamine impairs Plasmodium falciparum gametocyte infectivity and Anopheles mosquito survival. Int J Parasitol 2010; 40:1221-8. [PMID: 20515695 DOI: 10.1016/j.ijpara.2010.05.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 05/19/2010] [Accepted: 05/20/2010] [Indexed: 11/26/2022]
Abstract
Sulfadoxine-pyrimethamine (SP) is currently the drug of choice for intermittent preventive treatment of Plasmodium falciparum both in pregnancy and infancy. A prolonged parasite clearance time conferred by dhfr and dhps mutations is believed to be responsible for increased gametocyte prevalence in SP treated individuals. However, using a direct feeding assay in Mali, we showed that gametocytes present in peripheral venous blood post-SP treatment had reduced infectivity for Anopheles gambiae sensu stricto (ss) mosquitoes. We investigated the potential mechanisms involved in the dhfr and dhps quintuple mutant NF-135 and the single dhps 437 mutant NF-54. Concentrations of sulfadoxine (S) and pyrimethamine (P) equivalent to the serum levels of the respective drugs on day 3 (S=61 microg/ml, P=154.7 ng/ml) day 7 (S=33.8 microg/ml, P=66.6 ng/ml) and day 14 (S=14.2 microg/ml, P=15.7 ng/ml) post-SP treatment were used to study the effect on gametocytogenesis, gametocyte maturation and infectivity to Anopheles stephensi mosquitoes fed through an artificial membrane. The drugs readily induced gametocytogenesis in the mutant NF-135 strain but effectively killed the wild-type NF-54. However, both drugs impaired gametocyte maturation yielding odd-shaped non-exflagellating mature gametocytes. The concomitant ingestion of both S and P together with gametocytemic blood-meal significantly reduced the prevalence of oocyst positivity as well as oocyst density when compared to controls (P<0.001). In addition, day 3 concentrations of SP decreased mosquito survival by up to 65% (P<0.001). This study demonstrates that SP is deleterious in vitro for gametocyte infectivity as well as mosquito survival.
Collapse
Affiliation(s)
- Aminatou Kone
- Malaria Research and Training Center (MRTC), Department of Epidemiology of Parasitic Diseases, Faculty of Medicine, Pharmacy and Odonto-Stomatology, University of Bamako, P.O. Box 1805, Point G, Bamako, Mali
| | | | | | | | | | | | | | | | | | | |
Collapse
|