651
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Mechanism-based model of parasite growth and dihydroartemisinin pharmacodynamics in murine malaria. Antimicrob Agents Chemother 2012; 57:508-16. [PMID: 23147722 DOI: 10.1128/aac.01463-12] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Murine models are used to study erythrocytic stages of malaria infection, because parasite morphology and development are comparable to those in human malaria infections. Mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) models for antimalarials are scarce, despite their potential to optimize antimalarial combination therapy. The aim of this study was to develop a mechanism-based growth model (MBGM) for Plasmodium berghei and then characterize the parasiticidal effect of dihydroartemisinin (DHA) in murine malaria (MBGM-PK-PD). Stage-specific (ring, early trophozoite, late trophozoite, and schizont) parasite density data from Swiss mice inoculated with Plasmodium berghei were used for model development in S-ADAPT. A single dose of intraperitoneal DHA (10 to 100 mg/kg) or vehicle was administered 56 h postinoculation. The MBGM explicitly reflected all four erythrocytic stages of the 24-hour P. berghei life cycle. Merozoite invasion of erythrocytes was described by a first-order process that declined with increasing parasitemia. An efflux pathway with subsequent return was additionally required to describe the schizont data, thus representing parasite sequestration or trapping in the microvasculature, with a return to circulation. A 1-compartment model with zero-order absorption described the PK of DHA, with an estimated clearance and distribution volume of 1.95 liters h(-1) and 0.851 liter, respectively. Parasite killing was described by a turnover model, with DHA inhibiting the production of physiological intermediates (IC(50), 1.46 ng/ml). Overall, the MBGM-PK-PD described the rise in parasitemia, the nadir following DHA dosing, and subsequent parasite resurgence. This novel model is a promising tool for studying malaria infections, identifying the stage specificity of antimalarials, and providing insight into antimalarial treatment strategies.
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652
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Blanford S, Jenkins NE, Read AF, Thomas MB. Evaluating the lethal and pre-lethal effects of a range of fungi against adult Anopheles stephensi mosquitoes. Malar J 2012; 11:365. [PMID: 23126549 PMCID: PMC3520692 DOI: 10.1186/1475-2875-11-365] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 10/05/2012] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Insecticide resistance is seriously undermining efforts to eliminate malaria. In response, research on alternatives to the use of chemical insecticides against adult mosquito vectors has been increasing. Fungal entomopathogens formulated as biopesticides have received much attention and have shown considerable potential. This research has necessarily focused on relatively few fungal isolates in order to 'prove concept'. Further, most attention has been paid to examining fungal virulence (lethality) and not the other properties of fungal infection that might also contribute to reducing transmission potential. Here, a range of fungal isolates were screened to examine variation in virulence and how this relates to additional pre-lethal reductions in feeding propensity. METHODS The Asian malaria vector, Anopheles stephensi was exposed to 17 different isolates of entomopathogenic fungi belonging to species of Beauveria bassiana, Metarhizium anisopliae, Metarhizium acridum and Isaria farinosus. Each isolate was applied to a test substrate at a standard dose rate of 1×109 spores ml-1 and the mosquitoes exposed for six hours. Subsequently the insects were removed to mesh cages where survival was monitored over the next 14 days. During this incubation period the mosquitoes' propensity to feed was assayed for each isolate by offering a feeding stimulant at the side of the cage and recording the number probing. RESULTS AND CONCLUSIONS Fungal isolates showed a range of virulence to A. stephensi with some causing >80% mortality within 7 days, while others caused little increase in mortality relative to controls over the study period. Similarly, some isolates had a large impact on feeding propensity, causing >50% pre-lethal reductions in feeding rate, whereas other isolates had very little impact. There was clear correlation between fungal virulence and feeding reduction with virulence explaining nearly 70% of the variation in feeding reduction. However, there were some isolates where either feeding decline was not associated with high virulence, or virulence did not automatically prompt large declines in feeding. These results are discussed in the context of choosing optimum fungal isolates for biopesticide development.
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Affiliation(s)
- Simon Blanford
- Center for Infectious Disease Dynamics, Department of Biology, Penn State University Mueller Laboratory, University Park, PA 16802, USA.
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653
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Nkhoma SC, Nair S, Al-Saai S, Ashley E, McGready R, Phyo AP, Nosten F, Anderson TJC. Population genetic correlates of declining transmission in a human pathogen. Mol Ecol 2012; 22:273-85. [PMID: 23121253 PMCID: PMC3537863 DOI: 10.1111/mec.12099] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/14/2012] [Accepted: 09/19/2012] [Indexed: 12/17/2022]
Abstract
Pathogen control programs provide a valuable, but rarely exploited, opportunity to directly examine the relationship between population decline and population genetics. We investigated the impact of an ~12-fold decline in transmission on the population genetics of Plasmodium falciparum infections (n = 1731) sampled from four clinics on the Thai-Burma border over 10 years and genotyped using 96 genome-wide SNPs. The most striking associated genetic change was a reduction in the frequency of infections containing multiple parasite genotypes from 63% in 2001 to 14% in 2010 (P = 3 × 10(-15)). Two measures of the clonal composition of populations (genotypic richness and the β-parameter of the Pareto distribution) declined over time as more people were infected by parasites with identical multilocus genotypes, consistent with increased selfing and a reduction in the rate at which multilocus genotypes are broken apart by recombination. We predicted that the reduction in transmission, multiple clone carriage and outbreeding would be mirrored by an increased influence of genetic drift. However, geographical differentiation and expected heterozygosity remained stable across the sampling period. Furthermore, N(e) estimates derived from allele frequencies fluctuation between years remained high (582 to ∞) and showed no downward trend. These results demonstrate how genetic data can compliment epidemiological assessments of infectious disease control programs. The temporal changes in a single declining population parallel to those seen in comparisons of parasite genetics in regions of differing endemicity, strongly supporting the notion that reduced opportunity for outbreeding is the key driver of these patterns.
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Affiliation(s)
- Standwell C Nkhoma
- Texas Biomedical Research Institute, 7620 NW Loop 410, San Antonio, TX 78227, USA
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654
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Amaratunga C, Sreng S, Suon S, Phelps ES, Stepniewska K, Lim P, Zhou C, Mao S, Anderson JM, Lindegardh N, Jiang H, Song J, Su XZ, White NJ, Dondorp AM, Anderson TJC, Fay MP, Mu J, Duong S, Fairhurst RM. Artemisinin-resistant Plasmodium falciparum in Pursat province, western Cambodia: a parasite clearance rate study. THE LANCET. INFECTIOUS DISEASES 2012; 12:851-8. [PMID: 22940027 PMCID: PMC3786328 DOI: 10.1016/s1473-3099(12)70181-0] [Citation(s) in RCA: 262] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Artemisinin-resistant Plasmodium falciparum has been reported in Pailin, western Cambodia, detected as a slow parasite clearance rate in vivo. Emergence of this phenotype in western Thailand and possibly elsewhere threatens to compromise the effectiveness of all artemisinin-based combination therapies. Parasite genetics is associated with parasite clearance rate but does not account for all variation. We investigated contributions of both parasite genetics and host factors to the artemisinin-resistance phenotype in Pursat, western Cambodia. METHODS Between June 19 and Nov 28, 2009, and June 26 and Dec 6, 2010, we enrolled patients aged 10 years or older with uncomplicated falciparum malaria, a density of asexual parasites of at least 10,000 per μL of whole blood, no symptoms or signs of severe malaria, no other cause of febrile illness, and no chronic illness. We gave participants 4 mg/kg artesunate at 0, 24, and 48 h, 15 mg/kg mefloquine at 72 h, and 10 mg/kg mefloquine at 96 h. We assessed parasite density on thick blood films every 6 h until undetectable. The parasite clearance half-life was calculated from the parasite clearance curve. We genotyped parasites with 18 microsatellite markers and patients for haemoglobin E, α-thalassaemia, and a mutation of G6PD, which encodes glucose-6-phosphate dehydrogenase. To account for the possible effects of acquired immunity on half-life, we used three surrogates for increased likelihood of exposure to P falciparum: age, sex, and place of residence. This study is registered with ClinicalTrials.gov, number NCT00341003. FINDINGS We assessed 3504 individuals from all six districts of Pursat province seeking treatment for malaria symptoms. We enrolled 168 patients with falciparum malaria who met inclusion criteria. The geometric mean half-life was 5·85 h (95% CI 5·54-6·18) in Pursat, similar to that reported in Pailin (p=0·109). We identified two genetically different parasite clone groups: parasite group 1 (PG1) and parasite group 2 (PG2). Non-significant increases in parasite clearance half-life were seen in patients with haemoglobin E (0·55 h; p=0·078), those of male sex (0·96 h; p=0·064), and in 2010 (0·68 h; p=0·068); PG1 was associated with a significant increase (0·79 h; p=0·033). The mean parasite heritability of half-life was 0·40 (SD 0·17). INTERPRETATION Heritable artemisinin resistance is established in a second Cambodian province. To accurately identify parasites that are intrinsically susceptible or resistant to artemisinins, future studies should explore the effect of erythrocyte polymorphisms and specific immune responses on half-life variation. FUNDING Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health.
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Affiliation(s)
- Chanaki Amaratunga
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20852, USA
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655
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Hien TT, Thuy-Nhien NT, Phu NH, Boni MF, Thanh NV, Nha-Ca NT, Thai LH, Thai CQ, Toi PV, Thuan PD, Long LT, Dong LT, Merson L, Dolecek C, Stepniewska K, Ringwald P, White NJ, Farrar J, Wolbers M. In vivo susceptibility of Plasmodium falciparum to artesunate in Binh Phuoc Province, Vietnam. Malar J 2012; 11:355. [PMID: 23101492 PMCID: PMC3504531 DOI: 10.1186/1475-2875-11-355] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 10/20/2012] [Indexed: 11/25/2022] Open
Abstract
Background By 2009, there were worrying signs from western Cambodia that parasitological responses to artesunate-containing treatment regimens for uncomplicated Plasmodium falciparum malaria were slower than elsewhere which suggested the emergence of artemisinin resistance. Vietnam shares a long land border with Cambodia with a large number of migrants crossing it on a daily basis. Therefore, there is an urgent need to investigate whether there is any evidence of a change in the parasitological response to the artemisinin derivatives in Vietnam. Methods From August 2010 to May 2011, a randomized controlled clinical trial in uncomplicated falciparum malaria was conducted to compare two doses of artesunate (AS) (2mg/kg/day versus 4 mg/kg/day for three days) followed by dihydroartemisinin-piperaquine (DHA-PPQ) and a control arm of DHA-PPQ. The goal was characterization of the current efficacy of artesunate in southern Vietnam. The primary endpoint of this study was the parasite clearance half-life; secondary endpoints included the parasite reduction ratios at 24 and 48 hours and the parasite clearance time. Results 166 patients were recruited into the study. The median parasite clearance half-lives were 3.54 (AS 2mg/kg), 2.72 (AS 4mg/kg), and 2.98 hours (DHA-PPQ) (p=0.19). The median parasite-reduction ratio at 24 hours was 48 in the AS 2mg/kg group compared with 212 and 113 in the other two groups, respectively (p=0.02). The proportions of patients with a parasite clearance time of >72 hours for AS 2mg/kg, AS 4mg/kg and DHA-PPQ were 27%, 27%, and 22%, respectively. Early treatment failure occurred in two (4%) and late clinical failure occurred in one (2%) of the 55 patients in the AS 2mg/kg group, as compared with none in the other two study arms. The PCR-corrected adequate clinical and parasitological response (APCR) rates in the three groups were 94%, 100%, and 100% (p=0.04). Conclusions This study demonstrated faster P. falciparum parasite clearance in southern Vietnam than in western Cambodia but slower clearance in comparison with historical data from Vietnam. Further studies to determine whether this represents the emergence of artemisinin resistance in this area are needed. Currently, the therapeutic response to DHA-PPQ remains satisfactory in southern Vietnam. Trial registration NTC01165372
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Affiliation(s)
- Tran Tinh Hien
- Wellcome Trust Major Overseas Programme (MOP), Oxford University Clinical Research Unit (OUCRU), Ho Chi Minh City, Vietnam.
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656
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Butler CD. Infectious disease emergence and global change: thinking systemically in a shrinking world. Infect Dis Poverty 2012; 1:5. [PMID: 23849217 PMCID: PMC3710192 DOI: 10.1186/2049-9957-1-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Accepted: 09/23/2012] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Concern intensifying that emerging infectious diseases and global environmental changes that could generate major future human pandemics. METHOD A focused literature review was undertaken, partly informed by a forthcoming report on environment, agriculture and infectious diseases of poverty, facilitated by the Special Programme for Tropical Diseases. RESULTS More than ten categories of infectious disease emergence exist, but none formally analyse past, current or future burden of disease. Other evidence suggests that the dominant public health concern focuses on two informal groupings. Most important is the perceived threat of newly recognised infections, especially viruses that arise or are newly discovered in developing countries that originate in species exotic to developed countries, such as non-human primates, bats and rodents. These pathogens may be transmitted by insects or bats, or via direct human contact with bushmeat. The second group is new strains of influenza arising from intensively farmed chickens or pigs, or emerging from Asian "wet markets" where several bird species have close contact. Both forms appear justified because of two great pandemics: HIV/AIDS (which appears to have originated from bushmeat hunting in Africa before emerging globally) and Spanish influenza, which killed up to 2.5% of the human population around the end of World War I. Insufficiently appreciated is the contribution of the milieu which appeared to facilitate the high disease burden in these pandemics. Additionally, excess anxiety over emerging infectious diseases diverts attention from issues of greater public health importance, especially: (i) existing (including neglected) infectious diseases and (ii) the changing milieu that is eroding the determinants of immunity and public health, caused by adverse global environmental changes, including climate change and other components of stressed life and civilisation-supporting systems. CONCLUSIONS The focus on novel pathogens and minor forms of anti-microbial resistance in emerging disease literature is unjustified by their burden of disease, actual and potential, and diverts attention from far more important health problems and determinants. There is insufficient understanding of systemic factors that promote pandemics. Adverse global change could generate circumstances conducive to future pandemics with a high burden of disease, arising via anti-microbial and insecticidal resistance, under-nutrition, conflict, and public health breakdown.
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Affiliation(s)
- Colin D Butler
- National Centre for Epidemiology and Population Health College of Medicine Biology and Environment, Australian National University, Canberra, Australia.
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657
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Affiliation(s)
- Brian Greenwood
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London NW3 5AB, UK.
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658
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Hwang J, Jaroensuk J, Leimanis ML, Russell B, McGready R, Day N, Snounou G, Nosten F, Imwong M. Long-term storage limits PCR-based analyses of malaria parasites in archival dried blood spots. Malar J 2012; 11:339. [PMID: 23043522 PMCID: PMC3507721 DOI: 10.1186/1475-2875-11-339] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 10/03/2012] [Indexed: 11/15/2022] Open
Abstract
Background Blood samples collected in epidemiological and clinical investigations and then stored, often at room temperature, as blood spots dried on a filter paper have become one of the most popular source of material for further molecular analyses of malaria parasites. The dried blood spots are often archived so that they can be used for further retrospective investigations of parasite prevalence, or as new genetic markers come to the fore. However, the suitability of the template obtained from dried blood spots that have been stored for long periods for DNA amplification is not known. Methods DNA from 267 archived blood spots collected over a period of 12 years from persons with microscopically confirmed Plasmodium falciparum infection was purified by one of two methods, Chelex and Qiagen columns. These templates were subjected to highly sensitive nested PCR amplification targeting three parasite loci that differ in length and/or copy number. Results When a 1.6 kb fragment of the parasites’ small subunit ribosomal RNA was targeted (primary amplification), the efficiency of P. falciparum detection decreased in samples archived for more than six years, reaching very low levels for those stored for more than 10 years. Positive amplification was generally obtained more often with Qiagen-extracted templates. P. falciparum could be detected in 32 of the 40 negative Qiagen-extracted templates when a microsatellite of about 180 bp was targeted. The remaining eight samples gave a positive amplification when a small region of 238 bp of the higher copy number (20 to 200) mitochondrial genome was targeted. Conclusions The average length of DNA fragments that can be recovered from dried blood spots decreases with storage time. Recovery of the DNA is somewhat improved, especially in older samples, by the use of a commercial DNA purification column, but targets larger than 1.5 kb are unlikely to be present 10 years after the initial blood collection, when the average length of the DNA fragments present is likely to be around a few hundred bp. In conclusion, the utility of archived dried blood spots for molecular analyses decreases with storage time.
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Affiliation(s)
- Joyce Hwang
- Shoklo Malaria Research Unit, Mae Sot, Tak Province, Thailand
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659
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Castelli F, Tomasoni LR, Matteelli A. Advances in the treatment of malaria. Mediterr J Hematol Infect Dis 2012; 4:e2012064. [PMID: 23170193 PMCID: PMC3499999 DOI: 10.4084/mjhid.2012.064] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2012] [Accepted: 09/24/2012] [Indexed: 12/25/2022] Open
Abstract
Malaria still claims a heavy toll of deaths and disabilities even at the beginning of the third millennium. The inappropriate sequential use of drug monotherapy in the past has facilitated the spread of drug-resistant P. falciparum, and to a lesser extend P. vivax, strains in most of the malaria endemic areas, rendering most anti-malarial ineffective. In the last decade, a new combination strategy based on artemisinin derivatives (ACT) has become the standard of treatment for most P. falciparum malaria infections. This strategy could prevent the selection of resistant strains by rapidly decreasing the parasitic burden (by the artemisinin derivative, mostly artesunate) and exposing the residual parasite to effective concentrations of the partner drug. The widespread use of this strategy is somehow constrained by cost and by the inappropriate use of artemisinin, with possible impact on resistance, as already sporadically observed in South East Asia. Parenteral artesunate has now become the standard of care for severe malaria, even if quinine still retains its value in case artesunate is not immediately available. The appropriateness of pre-referral use of suppository artesunate is under close monitoring, while waiting for an effective anti-malarial vaccine to be made available.
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Affiliation(s)
- Francesco Castelli
- Chair of Infectious Diseases, University of Brescia, Italy
- University Division of Infectious and Tropical Diseases, University of Brescia and Spedali Civili General Hospital, Brescia (Italy)
| | - Lina Rachele Tomasoni
- University Division of Infectious and Tropical Diseases, University of Brescia and Spedali Civili General Hospital, Brescia (Italy)
| | - Alberto Matteelli
- University Division of Infectious and Tropical Diseases, University of Brescia and Spedali Civili General Hospital, Brescia (Italy)
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660
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Hoyer S, Nguon S, Kim S, Habib N, Khim N, Sum S, Christophel EM, Bjorge S, Thomson A, Kheng S, Chea N, Yok S, Top S, Ros S, Sophal U, Thompson MM, Mellor S, Ariey F, Witkowski B, Yeang C, Yeung S, Duong S, Newman RD, Menard D. Focused Screening and Treatment (FSAT): a PCR-based strategy to detect malaria parasite carriers and contain drug resistant P. falciparum, Pailin, Cambodia. PLoS One 2012; 7:e45797. [PMID: 23049687 PMCID: PMC3462177 DOI: 10.1371/journal.pone.0045797] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Accepted: 08/24/2012] [Indexed: 11/19/2022] Open
Abstract
Recent studies have shown that Plasmodium falciparum malaria parasites in Pailin province, along the border between Thailand and Cambodia, have become resistant to artemisinin derivatives. To better define the epidemiology of P. falciparum populations and to assess the risk of the possible spread of these parasites outside Pailin, a new epidemiological tool named “Focused Screening and Treatment” (FSAT), based on active molecular detection of asymptomatic parasite carriers was introduced in 2010. Cross-sectional malariometric surveys using PCR were carried out in 20 out of 109 villages in Pailin province. Individuals detected as P. falciparum carriers were treated with atovaquone-proguanil combination plus a single dose of primaquine if the patient was non-G6PD deficient. Interviews were conducted to elicit history of cross-border travel that might contribute to the spread of artemisinin-resistant parasites. After directly observed treatment, patients were followed up and re-examined on day 7 and day 28. Among 6931 individuals screened, prevalence of P. falciparum carriers was less than 1%, of whom 96% were asymptomatic. Only 1.6% of the individuals had a travel history or plans to go outside Cambodia, with none of those tested being positive for P. falciparum. Retrospective analysis, using 2010 routine surveillance data, showed significant differences in the prevalence of asymptomatic carriers discovered by FSAT between villages classified as “high risk” and “low risk” based on malaria incidence data. All positive individuals treated and followed-up until day 28 were cured. No mutant-type allele related to atovaquone resistance was found. FSAT is a potentially useful tool to detect, treat and track clusters of asymptomatic carriers of P. falciparum along with providing valuable epidemiological information regarding cross-border movements of potential malaria parasite carriers and parasite gene flow.
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Affiliation(s)
- Stefan Hoyer
- World Health Organization, Global Malaria Programme, Geneva, Switzerland
- * E-mail: (SH); (DM)
| | - Sokomar Nguon
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | | | - Nimol Khim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Sarorn Sum
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Eva-Maria Christophel
- World Health Organization, Regional Office for the Western Pacific, Manilla, Philippines
| | | | | | - Sim Kheng
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Nguon Chea
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Sovann Yok
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Samphornarann Top
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Seyha Ros
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Uth Sophal
- Malaria Consortium, Phnom Penh, Cambodia
| | | | | | - Frédéric Ariey
- Unité d'Immunologie Moléculaire des Parasites, Institut Pasteur, Paris, France
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Chhiang Yeang
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Shunmay Yeung
- Malaria Centre, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Socheat Duong
- National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Robert D. Newman
- World Health Organization, Global Malaria Programme, Geneva, Switzerland
| | - Didier Menard
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia
- * E-mail: (SH); (DM)
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661
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Brown T, Smith LS, Oo EKS, Shawng K, Lee TJ, Sullivan D, Beyrer C, Richards AK. Molecular surveillance for drug-resistant Plasmodium falciparum in clinical and subclinical populations from three border regions of Burma/Myanmar: cross-sectional data and a systematic review of resistance studies. Malar J 2012; 11:333. [PMID: 22992214 PMCID: PMC3518194 DOI: 10.1186/1475-2875-11-333] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 08/15/2012] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND Confirmation of artemisinin-delayed parasite clearance in Plasmodium falciparum along the Thai-Myanmar border has inspired a global response to contain and monitor drug resistance to avert the disastrous consequences of a potential spread to Africa. However, resistance data from Myanmar are sparse, particularly from high-risk areas where limited health services and decades of displacement create conditions for resistance to spread. Subclinical infections may represent an important reservoir for resistance genes that confer a fitness disadvantage relative to wild-type alleles. This study estimates the prevalence of resistance genotypes in three previously unstudied remote populations in Myanmar and tests the a priori hypothesis that resistance gene prevalence would be higher among isolates collected from subclinical infections than isolates collected from febrile clinical patients. A systematic review of resistance studies is provided for context. METHODS Community health workers in Karen and Kachin States and an area spanning the Indo-Myanmar border collected dried blood spots from 988 febrile clinical patients and 4,591 villagers with subclinical infection participating in routine prevalence surveys. Samples positive for P. falciparum 18 s ribosomal RNA by real-time PCR were genotyped for P. falciparum multidrug resistance protein (pfmdr1) copy number and the pfcrt K76T polymorphism using multiplex real-time PCR. RESULTS Pfmdr1 copy number increase and the pfcrt K76 polymorphism were determined for 173 and 269 isolates, respectively. Mean pfmdr1 copy number was 1.2 (range: 0.7 to 3.7). Pfmdr1 copy number increase was present in 17.5%, 9.6% and 11.1% of isolates from Karen and Kachin States and the Indo-Myanmar border, respectively. Pfmdr1 amplification was more prevalent in subclinical isolates (20.3%) than clinical isolates (6.4%, odds ratio 3.7, 95% confidence interval 1.1 - 12.5). Pfcrt K76T prevalence ranged from 90-100%. CONCLUSIONS Community health workers can contribute to molecular surveillance of drug resistance in remote areas of Myanmar. Marginal and displaced populations under-represented among previous resistance investigations can and should be included in resistance surveillance efforts, particularly once genetic markers of artemisinin-delayed parasite clearance are identified. Subclinical infections may contribute to the epidemiology of drug resistance, but determination of gene amplification from desiccated filter samples requires further validation when DNA concentration is low.
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Affiliation(s)
- Tyler Brown
- Johns Hopkins University School of Medicine, Broadway Research Building, 733 N. Broadway, Suite 147, Baltimore, MD, 21205, USA
- Global Health Access Program, 2550 Ninth Street, Ste 111, Berkeley, CA, 94710, USA
| | - Linda S Smith
- Global Health Access Program, 2550 Ninth Street, Ste 111, Berkeley, CA, 94710, USA
| | - Eh Kalu Shwe Oo
- Karen Department of Health and Welfare, PO Box 189, Mae Sot, Tak, 63110, Thailand
| | - Kum Shawng
- Office of the Director of the Health Department, Kachin Baptist Convention 135/Shan Su (South), Myitkyina, Kachin State, Myanmar
| | - Thomas J Lee
- Global Health Access Program, 2550 Ninth Street, Ste 111, Berkeley, CA, 94710, USA
- School of Medicine, University of California at Los Angeles, 924 Westwood Blvd, Suite 300, Los Angeles, CA, 90024, USA
| | - David Sullivan
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health 615 North Wolfe St, Room E5628, Baltimore, MD, 21205, USA
| | - Chris Beyrer
- Department of Epidemiology Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe St., Suite E7152, Baltimore, MD, 21205, USA
| | - Adam K Richards
- Global Health Access Program, 2550 Ninth Street, Ste 111, Berkeley, CA, 94710, USA
- Department of General Internal Medicine and Health Services Research, University of California at Los Angeles, 911 Broxton Ave, Los Angeles, CA, 90025, USA
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662
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Adhin MR, Labadie-Bracho M, Vreden SG. Status of potential PfATP6 molecular markers for artemisinin resistance in Suriname. Malar J 2012; 11:322. [PMID: 22966810 PMCID: PMC3468384 DOI: 10.1186/1475-2875-11-322] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 09/06/2012] [Indexed: 11/10/2022] Open
Abstract
Background Polymorphisms within the PfATP6 gene have been indicated as potential molecular markers for artemisinin efficacy. Since 2004, the use of artemisinin combination therapy (ACT) was introduced as first-line treatment of the uncomplicated malaria cases in Suriname. The aim of this research was to determine changes in Suriname in the status of the polymorphic markers in the PfATP6 gene before and after the adoption of the ACT-regimen, particularly of the S769N mutation, which was reported to be associated with in vitro Artemether resistance in the neighboring country French Guiana. Methods The PfATP6 gene from Plasmodium falciparum parasites in Suriname was investigated in 28 samples using PCR amplification and restriction enzyme analysis, to assess and determine the prevalence of potentially interesting single nucleotide polymorphisms. The polymorphisms [L263E; A623E; S769N], which may be associated with the artemisinin resistant phenotype were characterized in parasites from three endemic regions before and after the adoption of the ACT-regimen. In addition, the status of these molecular markers was compared in paired P. falciparum isolates from patients with recurring malaria after controlled ACT. Results All the investigated samples exhibit the wild-type genotype at all three positions; L263, A623, S769. Conclusion All investigated isolates before and after the adoption of the ACT-regimen and independent of endemic region harbored the wild-type genotype for the three investigated polymorphisms. The study revealed that decreased artemisinin susceptibility could occur independent from PfATP6 mutations, challenging the assumption that artemisinin resistance is associated with these mutations in the PfATP6 gene.
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Affiliation(s)
- Malti R Adhin
- Faculty of Medical Sciences, Department of Biochemistry, Anton de Kom Universiteit van Suriname, Kernkampweg 5, Paramaribo, Suriname.
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663
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Ng CL, Fidock DA. No evidence of decreased artemisinin efficacy in a high-transmission malaria setting in Mali. Am J Trop Med Hyg 2012; 87:16-17. [PMID: 22764285 PMCID: PMC3391042 DOI: 10.4269/ajtmh.2012.12-0344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
| | - David A. Fidock
- *Address correspondence to David A. Fidock, Department of Microbiology and Immunology, Columbia University Medical Center, 701 West 168th Street, Hammer HSC Room 1502, New York, NY 10032. E-mail:
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664
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Anthony MP, Burrows JN, Duparc S, JMoehrle J, Wells TNC. The global pipeline of new medicines for the control and elimination of malaria. Malar J 2012; 11:316. [PMID: 22958514 PMCID: PMC3472257 DOI: 10.1186/1475-2875-11-316] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Accepted: 07/21/2012] [Indexed: 12/03/2022] Open
Abstract
Over the past decade, there has been a transformation in the portfolio of medicines to combat malaria. New fixed-dose artemisinin combination therapy is available, with four different types having received approval from Stringent Regulatory Authorities or the World Health Organization (WHO). However, there is still scope for improvement. The Malaria Eradication Research agenda identified several gaps in the current portfolio. Simpler regimens, such as a single-dose cure are needed, compared with the current three-day treatment. In addition, new medicines that prevent transmission and also relapse are needed, but with better safety profiles than current medicines. There is also a big opportunity for new medicines to prevent reinfection and to provide chemoprotection. This study reviews the global portfolio of new medicines in development against malaria, as of the summer of 2012. Cell-based phenotypic screening, and 'fast followers' of clinically validated classes, mean that there are now many new classes of molecules starting in clinical development, especially for the blood stages of malaria. There remain significant gaps for medicines blocking transmission, preventing relapse, and long-duration molecules for chemoprotection. The nascent pipeline of new medicines is significantly stronger than five years ago. However, there are still risks ahead in clinical development and sustainable funding of clinical studies is vital if this early promise is going to be delivered.
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Affiliation(s)
- Melinda P Anthony
- Medicines for Malaria Venture (MMV), 20 rte de Pré-Bois 1215, Geneva, Switzerland
| | - Jeremy N Burrows
- Medicines for Malaria Venture (MMV), 20 rte de Pré-Bois 1215, Geneva, Switzerland
| | - Stephan Duparc
- Medicines for Malaria Venture (MMV), 20 rte de Pré-Bois 1215, Geneva, Switzerland
| | - Joerg JMoehrle
- Medicines for Malaria Venture (MMV), 20 rte de Pré-Bois 1215, Geneva, Switzerland
| | - Timothy NC Wells
- Medicines for Malaria Venture (MMV), 20 rte de Pré-Bois 1215, Geneva, Switzerland
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665
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Mapping the aetiology of non-malarial febrile illness in Southeast Asia through a systematic review--terra incognita impairing treatment policies. PLoS One 2012; 7:e44269. [PMID: 22970193 PMCID: PMC3435412 DOI: 10.1371/journal.pone.0044269] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Accepted: 07/31/2012] [Indexed: 11/19/2022] Open
Abstract
Background An increasing use of point of care diagnostic tests that exclude malaria, coupled with a declining malaria burden in many endemic countries, is highlighting the lack of ability of many health systems to manage other causes of febrile disease. A lack of knowledge of distribution of these pathogens, and a lack of screening and point-of-care diagnostics to identify them, prevents effective management of these generally treatable contributors to disease burden. While prospective data collection is vital, an untapped body of knowledge already exists in the published health literature. Methods Focusing on the Mekong region of Southeast Asia, published data from 1986 to 2011 was screened to for frequency of isolation of pathogens implicated in aetiology of non-malarial febrile illness. Eligibility criteria included English-language peer-reviewed studies recording major pathogens for which specific management is likely to be warranted. Of 1,252 identified papers, 146 met inclusion criteria and were analyzed and data mapped. Results Data tended to be clustered around specific areas where research institutions operate, and where resources to conduct studies are greater. The most frequently reported pathogen was dengue virus (n = 70), followed by Orientia tsutsugamushi and Rickettsia species (scrub typhus/murine typhus/spotted fever group n = 58), Leptospira spp. (n = 35), Salmonella enterica serovar Typhi and Paratyphi (enteric fever n = 24), Burkholderia pseudomallei (melioidosis n = 14), and Japanese encephalitis virus (n = 18). Wide tracts with very little published data on aetiology of fever are apparent. Discussion and Conclusions This mapping demonstrates a very heterogeneous distribution of information on the causes of fever in the Mekong countries. Further directed data collection to address gaps in the evidence-base, and expansion to a global database of pathogen distribution, is readily achievable, and would help define wider priorities for research and development to improve syndromic management of fever, prioritize diagnostic development, and guide empirical therapy.
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666
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Vijaykadga S, Alker AP, Satimai W, MacArthur JR, Meshnick SR, Wongsrichanalai C. Delayed Plasmodium falciparum clearance following artesunate-mefloquine combination therapy in Thailand, 1997-2007. Malar J 2012; 11:296. [PMID: 22929382 PMCID: PMC3478203 DOI: 10.1186/1475-2875-11-296] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 08/20/2012] [Indexed: 11/17/2022] Open
Abstract
Background There is concern that artesunate resistance is developing in Southeast Asia. The purpose of this study is to investigate the prevalence of parasitaemia in the few days following treatment with artesunate-mefloquine (AM), which is an indirect measure of decreased artesunate susceptibility. Methods This is a retrospective analysis of 31 therapeutic efficacy studies involving 1,327 patients treated with AM conducted by the Thai National Malaria Control Programme from 1997–2007. Results The prevalence of patients with parasitaemia on day 2 was higher in the east compared to the west (east: 20%, west: 9%, OR 2.47, 95% CI: 1.77, 3.45). In addition, the prevalence of day-2 parasitaemia increased over time (OR for each year = 1.10, 95% CI: 1.03, 1.19). After controlling for initial parasitaemia and age, year and region remained important determinants of day-2 parasitaemia (OR for region = 3.98, 95%CI 2.63, 6.00; OR for year = 1.28, 95%CI: 1.17, 1.39). The presence of parasitaemia on day 2 and day 3 were specific, but not sensitive predictors of treatment failure. Discussion Delayed resolution of parasitaemia after AM treatment increased in eastern Thailand between 1997 and 2007, which may be an early manifestation of decreased artesunate susceptibility. However, clinical and parasitological treatment failure after 28 days (which is related to both mefloquine and artesunate decreased susceptibility) is not changing over time. The presence of parasitaemia on day 2 is a poor indicator of AM 28-day treatment failure.
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Affiliation(s)
- Saowanit Vijaykadga
- Bureau of Vector Borne Diseases, Department of Diseases Control, Ministry of Public Health, Nonthaburi, Thailand
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667
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Chou M, Kim S, Khim N, Chy S, Sum S, Dourng D, Canier L, Nguon C, Ménard D. Performance of "VIKIA Malaria Ag Pf/Pan" (IMACCESS®), a new malaria rapid diagnostic test for detection of symptomatic malaria infections. Malar J 2012; 11:295. [PMID: 22920654 PMCID: PMC3478208 DOI: 10.1186/1475-2875-11-295] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Accepted: 08/15/2012] [Indexed: 11/17/2022] Open
Abstract
Background Recently, IMACCESS® developed a new malaria test (VIKIA Malaria Ag Pf/Pan™), based on the detection of falciparum malaria (HRP-2) and non-falciparum malaria (aldolase). Methods The performance of this new malaria rapid diagnostic test (RDT) was assessed using 1,000 febrile patients seeking malaria treatment in four health centres in Cambodia from August to December 2011. The results of the VIKIA Malaria Ag Pf/Pan were compared with those obtained by microscopy, the CareStart Malaria™ RDT (AccessBio®) which is currently used in Cambodia, and real-time PCR (as “gold standard”). Results The best performances of the VIKIA Malaria Ag Pf/Pan™ test for detection of both Plasmodium falciparum and non-P. falciparum were with 20–30 min reading times (sensitivity of 93.4% for P. falciparum and 82.8% for non-P. falciparum and specificity of 98.6% for P. falciparum and 98.9% for non-P. falciparum) and were similar to those for the CareStart Malaria™ test. Conclusions This new RDT performs similarly well as other commercially available tests (especially the CareStart Malaria™ test, used as comparator), and conforms to the World Health Organization’s recommendations for RDT performance. It is a good alternative tool for the diagnosis of malaria in endemic areas.
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Affiliation(s)
- Monidarin Chou
- Faculty of Pharmacy, Université des Sciences de la Santé, Phnom Penh, Cambodia
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668
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Ding XC, Ubben D, Wells TNC. A framework for assessing the risk of resistance for anti-malarials in development. Malar J 2012; 11:292. [PMID: 22913649 PMCID: PMC3478971 DOI: 10.1186/1475-2875-11-292] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2012] [Accepted: 08/01/2012] [Indexed: 11/10/2022] Open
Abstract
Resistance is a constant challenge for anti-infective drug development. Since they kill sensitive organisms, anti-infective agents are bound to exert an evolutionary pressure toward the emergence and spread of resistance mechanisms, if such resistance can arise by stochastic mutation events. New classes of medicines under development must be designed or selected to stay ahead in this vicious circle of resistance control. This involves both circumventing existing resistance mechanisms and selecting molecules which are resilient against the development and spread of resistance. Cell-based screening methods have led to a renaissance of new classes of anti-malarial medicines, offering us the potential to select and modify molecules based on their resistance potential. To that end, a standardized in vitro methodology to assess quantitatively these characteristics in Plasmodium falciparum during the early phases of the drug development process has been developed and is presented here. It allows the identification of anti-malarial compounds with overt resistance risks and the prioritization of the most robust ones. The integration of this strategy in later stages of development, registration, and deployment is also discussed.
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Affiliation(s)
- Xavier C Ding
- Medicines for Malaria Venture, 20 rte de Pré Bois, Geneva CH 1215, Switzerland.
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669
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Anti-plasmodial activity of Dicoma tomentosa (Asteraceae) and identification of urospermal A-15-O-acetate as the main active compound. Malar J 2012; 11:289. [PMID: 22909422 PMCID: PMC3483198 DOI: 10.1186/1475-2875-11-289] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 08/15/2012] [Indexed: 11/18/2022] Open
Abstract
Background Natural products could play an important role in the challenge to discover new anti-malarial drugs. In a previous study, Dicoma tomentosa (Asteraceae) was selected for its promising anti-plasmodial activity after a preliminary screening of several plants traditionally used in Burkina Faso to treat malaria. The aim of the present study was to further investigate the anti-plasmodial properties of this plant and to isolate the active anti-plasmodial compounds. Methods Eight crude extracts obtained from D. tomentosa whole plant were tested in vitro against two Plasmodium falciparum strains (3D7 and W2) using the p-LDH assay (colorimetric method). The Peters’ four-days suppressive test model (Plasmodium berghei-infected mice) was used to evaluate the in vivo anti-plasmodial activity. An in vitro bioguided fractionation was undertaken on a dichloromethane extract, using preparative HPLC and TLC techniques. The identity of the pure compound was assessed using UV, MS and NMR spectroscopic analysis. In vitro cytotoxicity against WI38 human fibroblasts (WST-1 assay) and haemolytic activity were also evaluated for extracts and pure compounds in order to check selectivity. Results The best in vitro anti-plasmodial results were obtained with the dichloromethane, diethylether, ethylacetate and methanol extracts, which exhibited a high activity (IC50 ≤ 5 μg/ml). Hot water and hydroethanolic extracts also showed a good activity (IC50 ≤ 15 μg/ml), which confirmed the traditional use and the promising anti-malarial potential of the plant. The activity was also confirmed in vivo for all tested extracts. However, most of the active extracts also exhibited cytotoxic activity, but no extract was found to display any haemolytic activity. The bioguided fractionation process allowed to isolate and identify a sesquiterpene lactone (urospermal A-15-O-acetate) as the major anti-plasmodial compound of the plant (IC50 < 1 μg/ml against both 3D7 and W2 strains). This was also found to be the main cytotoxic compound (SI = 3.3). While this melampolide has already been described in the plant, this paper is the first report on the biological properties of this compound. Conclusions The present study highlighted the very promising anti-plasmodial activity of D. tomentosa and enabled to identify its main active compound, urospermal A-15-O-acetate. The high anti-plasmodial activity of this compound merits further study about its anti-plasmodial mechanism of action. The active extracts of D. tomentosa, as well as urospermal A 15-O-acetate, displayed only a moderate selectivity, and further studies are needed to assess the safety of the use of the plant by the local population.
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670
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Parker D, Lerdprom R, Srisatjarak W, Yan G, Sattabongkot J, Wood J, Sirichaisinthop J, Cui L. Longitudinal in vitro surveillance of Plasmodium falciparum sensitivity to common anti-malarials in Thailand between 1994 and 2010. Malar J 2012; 11:290. [PMID: 22908880 PMCID: PMC3472280 DOI: 10.1186/1475-2875-11-290] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 07/22/2012] [Indexed: 11/23/2022] Open
Abstract
Background Drug and multidrug-resistant Plasmodium falciparum malaria has existed in Thailand for several decades. Furthermore, Thailand serves as a sentinel for drug-resistant malaria within the Greater Mekong sub-region. However, the drug resistance situation is highly dynamic, changing quickly over time. Here parasite in vitro drug sensitivity is reported for artemisinin derivatives, mefloquine, chloroquine and quinine, across Thailand. Methods Blood was drawn from patients infected with P. falciparum in seven sentinel provinces along Thai international borders with Cambodia, Myanmar, Laos, and Malaysia. In vitro parasite sensitivity was tested using the World Health Organization’s microtest (mark III) (between 1994 and 2002) and the histidine-rich protein-2 (HRP2)-based enzyme-linked immunosorbent assay (in 2010). Following World Health Organization protocol, at least 30 isolates were collected for each province and year represented in this study. Where possible, t-tests were used to test for significant differences. Results There appears to be little variation across study sites with regard to parasite sensitivity to chloroquine. Quinine resistance appears to have been rising prior to 1997, but has subsequently decreased. Mefloquine sensitivity appears high across the provinces, especially along the north-western border with Myanmar and the eastern border with Cambodia. Finally, the data suggest that parasite sensitivity to artemisinin and its derivatives is significantly higher in provinces along the north-western border with Myanmar. Conclusions Parasite sensitivity to anti-malarials in Thailand is highly variable over time and largely mirrors official drug use policy. The findings with regard to reduced sensitivity to artemisinin derivatives are supported by recent reports of reduced parasite clearance associated with artemisinin. This trend is alarming since artemisinin is considered the last defence against malaria. Continued surveillance in Thailand, along with increased collaboration and surveillance across the entire Greater Mekong sub-region, is clearly warranted.
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Affiliation(s)
- Daniel Parker
- Department of Anthropology, The Pennsylvania State University, 409 Carpenter Building, University Park, PA 16802, USA
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671
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Huang F, Tang L, Yang H, Zhou S, Sun X, Liu H. Therapeutic efficacy of artesunate in the treatment of uncomplicated Plasmodium falciparum malaria and anti-malarial, drug-resistance marker polymorphisms in populations near the China-Myanmar border. Malar J 2012; 11:278. [PMID: 22898135 PMCID: PMC3492106 DOI: 10.1186/1475-2875-11-278] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 07/17/2012] [Indexed: 11/13/2022] Open
Abstract
Background The aim of this study was to evaluate the clinical outcome after seven-day artesunate monotherapy for uncomplicated Plasmodium falciparum malaria in Yingjiang County along the China-Myanmar border and investigate genetic polymorphisms in the P. falciparum chloroquine-resistance transporter (pfcrt), multidrug resistance 1 (pfmdr1), dihydrofolate reductase (pfdhfr), dihydropteroate synthase (pfdhps) and ATPase (pfatp6) genes. Methods Patients ≥ one year of age with fever (axillary temperature ≥37.5°C) or history of fever and P. falciparum mono-infection were included. Patients received anti-malarial treatment with artesunate (total dose of 16 mg/kg over seven days) by directly observed therapy. After a 28-day follow-up, treatment efficacy and effectiveness were assessed based on clinical and parasitological outcomes. Treatment failure was defined as recrudescence of the original parasite and distinguished with new infection confirmed by PCR. Analysis of gene mutation and amplification were performed by nested polymerase chain reaction. Results Sixty-five patients were enrolled; 10 withdrew from the study, and six were lost to follow-up. All but two patients demonstrated adequate clinical and parasitological response; 12 had detectable parasitaemia on day 3. These two patients were confirmed to be new infection by PCR. The efficacy of artesunate was 95.9%. The pfcrt mutation in codon 76 was found in all isolates (100%), and mutations in codons 71 and 72 were found in 4.8% of parasite isolates. No mutation of pfmdr1 (codons 86 or 1246) was found. Among all samples, 5.1% were wild type for pfdhfr, whereas the other samples had mutations in four codons (51, 59, 108 and 164), and mutations in pfdhps (codons 436, 437, 540 and 581) were found in all isolates. No samples had mutations in pfatp6 codons 623 or 769, but two new mutations (N683K and R756K) were found in 4.6% and 9.2% of parasite isolates, respectively. Conclusion Plasmodium falciparum infection was associated with slow parasite clearance and suspected artemisinin resistance at the China-Myanmar border area. The prevalence of pfcrt 76 T and markers for SP resistance are still high. It should be strengthened further on parasite clearance time or clearance half life to confirm the resistance status, and molecular epidemiology should provide complementary information to assess the appropriateness of current policies based on artemisinin derivatives.
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Affiliation(s)
- Fang Huang
- National Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis, Key Laboratory of Parasite and Vector Biology, Ministry of Health, Shanghai 200025, PR China
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672
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Pigott DM, Atun R, Moyes CL, Hay SI, Gething PW. Funding for malaria control 2006-2010: a comprehensive global assessment. Malar J 2012; 11:246. [PMID: 22839432 PMCID: PMC3444429 DOI: 10.1186/1475-2875-11-246] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 07/13/2012] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND The last decade has seen a dramatic increase in international and domestic funding for malaria control, coupled with important declines in malaria incidence and mortality in some regions of the world. As the ongoing climate of financial uncertainty places strains on investment in global health, there is an increasing need to audit the origin, recipients and geographical distribution of funding for malaria control relative to populations at risk of the disease. METHODS A comprehensive review of malaria control funding from international donors, bilateral sources and national governments was undertaken to reconstruct total funding by country for each year 2006 to 2010. Regions at risk from Plasmodium falciparum and/or Plasmodium vivax transmission were identified using global risk maps for 2010 and funding was assessed relative to populations at risk. Those nations with unequal funding relative to a regional average were identified and potential explanations highlighted, such as differences in national policies, government inaction or donor neglect. RESULTS US$8.9 billion was disbursed for malaria control and elimination programmes over the study period. Africa had the largest levels of funding per capita-at-risk, with most nations supported primarily by international aid. Countries of the Americas, in contrast, were supported typically through national government funding. Disbursements and government funding in Asia were far lower with a large variation in funding patterns. Nations with relatively high and low levels of funding are discussed. CONCLUSIONS Global funding for malaria control is substantially less than required. Inequity in funding is pronounced in some regions particularly when considering the distinct goals of malaria control and malaria elimination. Efforts to sustain and increase international investment in malaria control should be informed by evidence-based assessment of funding equity.
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Affiliation(s)
- David M Pigott
- Department of Zoology, Spatial Ecology and Epidemiology Group, University of Oxford, South Parks Road, Oxford, UK
| | - Rifat Atun
- Health Management Group, Imperial College Business School, Imperial College London, London, UK
| | - Catherine L Moyes
- Department of Zoology, Spatial Ecology and Epidemiology Group, University of Oxford, South Parks Road, Oxford, UK
| | - Simon I Hay
- Department of Zoology, Spatial Ecology and Epidemiology Group, University of Oxford, South Parks Road, Oxford, UK
| | - Peter W Gething
- Department of Zoology, Spatial Ecology and Epidemiology Group, University of Oxford, South Parks Road, Oxford, UK
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673
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Gemma S, Camodeca C, Sanna Coccone S, Joshi BP, Bernetti M, Moretti V, Brogi S, Bonache de Marcos MC, Savini L, Taramelli D, Basilico N, Parapini S, Rottmann M, Brun R, Lamponi S, Caccia S, Guiso G, Summers RL, E. Martin R, Saponara S, Gorelli B, Novellino E, Campiani G, Butini S. Optimization of 4-Aminoquinoline/Clotrimazole-Based Hybrid Antimalarials: Further Structure–Activity Relationships, in Vivo Studies, and Preliminary Toxicity Profiling. J Med Chem 2012; 55:6948-67. [DOI: 10.1021/jm300802s] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sandra Gemma
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Caterina Camodeca
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Salvatore Sanna Coccone
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Bhupendra P. Joshi
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Matteo Bernetti
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Vittoria Moretti
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Simone Brogi
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | | | - Luisa Savini
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Donatella Taramelli
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
- Dipartimento
di Scienze Farmacologiche
e Biomolecolari, Università degli Studi di Milano, Via Balzaretti 9, 20133 Milano, Italy
| | - Nicoletta Basilico
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
- Dipartimento di Scienze Biomediche,
Chirurgiche e Odontoiatriche, Università degli Studi di Milano, Via Pascal 36, 20133 Milano, Italy
| | - Silvia Parapini
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
- Dipartimento
di Scienze Farmacologiche
e Biomolecolari, Università degli Studi di Milano, Via Balzaretti 9, 20133 Milano, Italy
| | - Matthias Rottmann
- Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4002 Basel,
Switzerland and University of Basel, CH-4003 Basel, Switzerland
| | - Reto Brun
- Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4002 Basel,
Switzerland and University of Basel, CH-4003 Basel, Switzerland
| | - Stefania Lamponi
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Silvio Caccia
- Istituto di Ricerche Farmacologiche “Mario Negri”, Via la Masa
19, 20156 Milano, Italy
| | - Giovanna Guiso
- Istituto di Ricerche Farmacologiche “Mario Negri”, Via la Masa
19, 20156 Milano, Italy
| | - Robert L. Summers
- Research School of Biology, The Australian National University, Canberra ACT 0200,
Australia
| | - Rowena E. Martin
- Research School of Biology, The Australian National University, Canberra ACT 0200,
Australia
| | - Simona Saponara
- Dipartimento di
Neuroscienze, University of Siena, via
A. Moro, 53100, Siena, Italy
| | - Beatrice Gorelli
- Dipartimento di
Neuroscienze, University of Siena, via
A. Moro, 53100, Siena, Italy
| | - Ettore Novellino
- Dipartimento di Chimica Farmaceutica
e Tossicologica, Università di Napoli Federico II, Via D. Montesano 49, 80131 Napoli, Italy
| | - Giuseppe Campiani
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
| | - Stefania Butini
- CIRM Centro Interuniversitario
di Ricerche sulla Malaria, Università di Torino, Torino, Italy
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674
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Brücher K, Illarionov B, Held J, Tschan S, Kunfermann A, Pein MK, Bacher A, Gräwert T, Maes L, Mordmüller B, Fischer M, Kurz T. α-Substituted β-oxa isosteres of fosmidomycin: synthesis and biological evaluation. J Med Chem 2012; 55:6566-75. [PMID: 22731758 DOI: 10.1021/jm300652f] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Specific inhibition of enzymes of the non-mevalonate pathway is a promising strategy for the development of novel antiplasmodial drugs. α-Aryl-substituted β-oxa isosteres of fosmidomycin with a reverse orientation of the hydroxamic acid group were synthesized and evaluated for their inhibitory activity against recombinant 1-deoxy-d-xylulose 5-phosphate reductoisomerase (IspC) of Plasmodium falciparum and for their in vitro antiplasmodial activity against chloroquine-sensitive and resistant strains of P. falciparum . The most active derivative inhibits IspC protein of P. falciparum (PfIspC) with an IC(50) value of 12 nM and shows potent in vitro antiplasmodial activity. In addition, lipophilic ester prodrugs demonstrated improved P. falciparum growth inhibition in vitro.
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Affiliation(s)
- Karin Brücher
- Institut für Pharmazeutische und Medizinische Chemie, Heinrich Heine Universität, Universitätsstr. 1, 40225 Düsseldorf, Germany
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675
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Lowes D, Pradhan A, Iyer LV, Parman T, Gow J, Zhu F, Furimsky A, Lemoff A, Guiguemde WA, Sigal M, Clark JA, Wilson E, Tang L, Connelly MC, Derisi JL, Kyle DE, Mirsalis J, Guy RK. Lead optimization of antimalarial propafenone analogues. J Med Chem 2012; 55:6087-93. [PMID: 22708838 DOI: 10.1021/jm300286a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previously reported studies identified analogues of propafenone that had potent antimalarial activity, reduced cardiac ion channel activity, and properties that suggested the potential for clinical development for malaria. Careful examination of the bioavailability, pharmacokinetics, toxicology, and efficacy of this series of compounds using rodent models revealed orally bioavailable compounds that are nontoxic and suppress parasitemia in vivo. Although these compounds possess potential for further preclinical development, they also carry some significant challenges.
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Affiliation(s)
- David Lowes
- Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
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676
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Espié E, Lima A, Atua B, Dhorda M, Flévaud L, Sompwe EM, Palma Urrutia PP, Guerin PJ. Efficacy of fixed-dose combination artesunate-amodiaquine versus artemether-lumefantrine for uncomplicated childhood Plasmodium falciparum malaria in Democratic Republic of Congo: a randomized non-inferiority trial. Malar J 2012; 11:174. [PMID: 22631564 PMCID: PMC3413505 DOI: 10.1186/1475-2875-11-174] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Accepted: 05/25/2012] [Indexed: 12/25/2022] Open
Abstract
Background In 2005, the Democratic Republic of Congo (DRC) adopted artesunate and amodiaquine (ASAQ) as first-line anti-malarial treatment. In order to compare the efficacy of the fixed-dose formulation ASAQ versus artemether-lumefantrine (AL), a randomized, non-inferiority open-label trial was conducted in Katanga. Methods Children aged six and 59 months with uncomplicated Plasmodium falciparum malaria were enrolled and randomly allocated into one of the two regimens. The risk of recurrent parasitaemia by day 42, both unadjusted and adjusted by PCR genotyping to distinguish recrudescence from new infection, was analysed. Results Between April 2008 and March 2009, 301 children were included: 156 with ASAQ and 145 with AL. No early treatment failures were reported. Among the 256 patients followed-up at day 42, 32 patients developed late clinical or parasitological failure (9.9% (13/131) in the ASAQ group and 15.2% (19/125) in the AL group). After PCR correction, cure rates were 98.3% (95%CI, 94.1-99.8) in the ASAQ group and 99.1% (95%CI, 94.9-99.9) in the AL group (difference −0.7%, one sided 95% CI −3.1). Kaplan-Meier PCR-adjusted cure rates were similar. Both treatment regimens were generally well tolerated. Conclusion Both ASAQ and AL are highly effective and currently adequate as the first-line treatment of uncomplicated falciparum malaria in this area of Katanga, DRC. However, in a very large country, such as DRC, and because of possible emergence of resistance from other endemic regions, surveillance of efficacy of artemisinin-based combination treatments, including other evaluations of the resistance of ASAQ, need to be done in other provinces. Trial registration The protocol was registered with the clinicaltrials.gov, open clinical trial registry under the identifier number NCT01567423.
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Affiliation(s)
- Emmanuelle Espié
- Division of Malaria and Parasitic Diseases, National Institute of Health, Korea Centers for Disease Control and Prevention, Cheongwon-gun 363-951, Republic of Korea.
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677
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Sibley CH, Price RN. Monitoring antimalarial drug resistance: Applying lessons learned from the past in a fast-moving present. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2012; 2:126-33. [PMID: 24533274 DOI: 10.1016/j.ijpddr.2012.03.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 03/25/2012] [Accepted: 03/28/2012] [Indexed: 11/19/2022]
Abstract
The need for robust surveillance of antimalarial drugs is more urgent than it has ever been. In the western region of Cambodia, artemisinin resistance has emerged in Plasmodium falciparum and threatens to undermine the efficacy of highly effective artemisinin combination therapies. Although some manfestations of artemisinin tolerance are unique to this class of drug, many of its properties mirror previous experience in understanding and tracking resistance to other antimalarials. In this review we outline the spectrum of approaches that were developed to understand the evolution and spread of antifolate resistance, highlighting the importance of integrating information from different methodologies towards a better understanding of the underlying biologic processes. We consider how to apply our experience in investigating and attempting to contain antifolate resistance to inform our prospective assessment of novel antimalarial resistance patterns and their subsequent spread.
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Affiliation(s)
- Carol Hopkins Sibley
- WorldWide Antimalarial Resistance Network, Box 355065, University of Washington, Seattle, WA 98195 5065, USA
| | - Ric N Price
- Global Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Northern Territory, Australia ; Center for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, United Kingdom
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678
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Cheeseman IH, Miller BA, Nair S, Nkhoma S, Tan A, Tan JC, Saai SA, Phyo AP, Moo CL, Lwin KM, McGready R, Ashley E, Imwong M, Stepniewska K, Yi P, Dondorp AM, Mayxay M, Newton PN, White NJ, Nosten F, Ferdig MT, Anderson TJ. A major genome region underlying artemisinin resistance in malaria. Science 2012; 336:79-82. [PMID: 22491853 PMCID: PMC3355473 DOI: 10.1126/science.1215966] [Citation(s) in RCA: 314] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Evolving resistance to artemisinin-based compounds threatens to derail attempts to control malaria. Resistance has been confirmed in western Cambodia and has recently emerged in western Thailand, but is absent from neighboring Laos. Artemisinin resistance results in reduced parasite clearance rates (CRs) after treatment. We used a two-phase strategy to identify genome region(s) underlying this ongoing selective event. Geographical differentiation and haplotype structure at 6969 polymorphic single-nucleotide polymorphisms (SNPs) in 91 parasites from Cambodia, Thailand, and Laos identified 33 genome regions under strong selection. We screened SNPs and microsatellites within these regions in 715 parasites from Thailand, identifying a selective sweep on chromosome 13 that shows strong association (P = 10(-6) to 10(-12)) with slow CRs, illustrating the efficacy of targeted association for identifying the genetic basis of adaptive traits.
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Affiliation(s)
| | - Becky A. Miller
- The Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
| | - Shalini Nair
- Texas Biomedical Research Institute, San Antonio, Texas 78245
| | | | - Asako Tan
- The Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
| | - John C. Tan
- The Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
| | - Salma Al Saai
- Texas Biomedical Research Institute, San Antonio, Texas 78245
| | - Aung Pyae Phyo
- Shoklo Malaria Research Unit (SMRU), Mae Sot, Tak, Thailand
| | - Carit Ler Moo
- Shoklo Malaria Research Unit (SMRU), Mae Sot, Tak, Thailand
| | | | - Rose McGready
- Shoklo Malaria Research Unit (SMRU), Mae Sot, Tak, Thailand
- Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine, Churchill Hospital, Oxford, UK
| | - Elizabeth Ashley
- Shoklo Malaria Research Unit (SMRU), Mae Sot, Tak, Thailand
- Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine, Churchill Hospital, Oxford, UK
| | - Mallika Imwong
- Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Kasia Stepniewska
- Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine, Churchill Hospital, Oxford, UK
- Worldwide Antimalarial Resistance Network, Oxford, UK
| | - Poravuth Yi
- The National Center for Parasitology, Entomology, and Malaria Control, Phnom Penh, Cambodia
| | - Arjen M. Dondorp
- Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine, Churchill Hospital, Oxford, UK
| | - Mayfong Mayxay
- Wellcome Trust-Mahosot Hospital-Oxford Tropical Medicine Research Collaboration, Mahosot Hospital, Vientiane, Lao People's Democratic Republic
| | - Paul N. Newton
- Centre for Tropical Medicine, Churchill Hospital, Oxford, UK
- Wellcome Trust-Mahosot Hospital-Oxford Tropical Medicine Research Collaboration, Mahosot Hospital, Vientiane, Lao People's Democratic Republic
| | - Nicholas J. White
- Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine, Churchill Hospital, Oxford, UK
| | - François Nosten
- Shoklo Malaria Research Unit (SMRU), Mae Sot, Tak, Thailand
- Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine, Churchill Hospital, Oxford, UK
| | - Michael T. Ferdig
- The Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556
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679
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Genome analysis homes in on malaria-drug resistance. Nature 2012. [DOI: 10.1038/nature.2012.10398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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