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Furtado R, Paul M, Zhang J, Sung J, Karell P, Kim RS, Caillat-Zucman S, Liang L, Felgner P, Bauleni A, Gama S, Buchwald A, Taylor T, Seydel K, Laufer M, Delahaye F, Daily JP, Lauvau G. Cytolytic circumsporozoite-specific memory CD4 + T cell clones are expanded during Plasmodium falciparum infection. Nat Commun 2023; 14:7726. [PMID: 38001069 PMCID: PMC10673885 DOI: 10.1038/s41467-023-43376-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 11/08/2023] [Indexed: 11/26/2023] Open
Abstract
Clinical immunity against Plasmodium falciparum infection develops in residents of malaria endemic regions, manifesting in reduced clinical symptoms during infection and in protection against severe disease but the mechanisms are not fully understood. Here, we compare the cellular and humoral immune response of clinically immune (0-1 episode over 18 months) and susceptible (at least 3 episodes) during a mild episode of Pf malaria infection in a malaria endemic region of Malawi, by analysing peripheral blood samples using high dimensional mass cytometry (CyTOF), spectral flow cytometry and single-cell transcriptomic analyses. In the clinically immune, we find increased proportions of circulating follicular helper T cells and classical monocytes, while the humoral immune response shows characteristic age-related differences in the protected. Presence of memory CD4+ T cell clones with a strong cytolytic ZEB2+ T helper 1 effector signature, sharing identical T cell receptor clonotypes and recognizing the Pf-derived circumsporozoite protein (CSP) antigen are found in the blood of the Pf-infected participants gaining protection. Moreover, in clinically protected participants, ZEB2+ memory CD4+ T cells express lower level of inhibitory and chemotactic receptors. We thus propose that clonally expanded ZEB2+ CSP-specific cytolytic memory CD4+ Th1 cells may contribute to clinical immunity against the sporozoite and liver-stage Pf malaria.
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Affiliation(s)
- Raquel Furtado
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, 10461, USA
- RF: BioNTech US, 40 Erie Street, Cambridge, MA, 02139, USA
| | - Mahinder Paul
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, 10461, USA
| | - Jinghang Zhang
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, 10461, USA
| | - Joowhan Sung
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, 10461, USA
- Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Paul Karell
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, 10461, USA
| | - Ryung S Kim
- Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, 10461, USA
| | - Sophie Caillat-Zucman
- Université de Paris, AP-HP, Hôpital Saint-Louis, Laboratoire d'Immunologie et Histocompatiblité, INSERM UMR976, 75010, Paris, France
| | - Li Liang
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, 92697, USA
| | - Philip Felgner
- Department of Physiology and Biophysics, School of Medicine, University of California, Irvine, CA, 92697, USA
| | - Andy Bauleni
- Malaria Alert Centre, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Syze Gama
- Blantyre Malaria Project, Kamuzu University of Health Sciences, Blantyre, Malawi
| | - Andrea Buchwald
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Terrie Taylor
- Blantyre Malaria Project, Kamuzu University of Health Sciences, Blantyre, Malawi
- Department of Osteopathic Medical Specialties, Michigan State University, East Lansing, MI, 48824, USA
| | - Karl Seydel
- Blantyre Malaria Project, Kamuzu University of Health Sciences, Blantyre, Malawi
- Department of Osteopathic Medical Specialties, Michigan State University, East Lansing, MI, 48824, USA
| | - Miriam Laufer
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Fabien Delahaye
- Department of Genetics, Albert Einstein College of Medicine, Bronx, New York, 10461, USA
- FD: Precision Oncology, Sanofi, Vitry sur Seine, France
| | - Johanna P Daily
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, 10461, USA.
- Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, 10461, USA.
| | - Grégoire Lauvau
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York, 10461, USA.
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Kormos A, Dimopoulos G, Bier E, Lanzaro GC, Marshall JM, James AA. Conceptual risk assessment of mosquito population modification gene-drive systems to control malaria transmission: preliminary hazards list workshops. Front Bioeng Biotechnol 2023; 11:1261123. [PMID: 37965050 PMCID: PMC10641379 DOI: 10.3389/fbioe.2023.1261123] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 10/09/2023] [Indexed: 11/16/2023] Open
Abstract
The field-testing and eventual adoption of genetically-engineered mosquitoes (GEMs) to control vector-borne pathogen transmission will require them meeting safety criteria specified by regulatory authorities in regions where the technology is being considered for use and other locales that might be impacted. Preliminary risk considerations by researchers and developers may be useful for planning the baseline data collection and field research used to address the anticipated safety concerns. Part of this process is to identify potential hazards (defined as the inherent ability of an entity to cause harm) and their harms, and then chart the pathways to harm and evaluate their probability as part of a risk assessment. The University of California Malaria Initiative (UCMI) participated in a series of workshops held to identify potential hazards specific to mosquito population modification strains carrying gene-drive systems coupled to anti-parasite effector genes and their use in a hypothetical island field trial. The hazards identified were placed within the broader context of previous efforts discussed in the scientific literature. Five risk areas were considered i) pathogens, infections and diseases, and the impacts of GEMs on human and animal health, ii) invasiveness and persistence of GEMs, and interactions of GEMs with target organisms, iii) interactions of GEMs with non-target organisms including horizontal gene transfer, iv) impacts of techniques used for the management of GEMs and v) evolutionary and stability considerations. A preliminary hazards list (PHL) was developed and is made available here. This PHL is useful for internal project risk evaluation and is available to regulators at prospective field sites. UCMI project scientists affirm that the subsequent processes associated with the comprehensive risk assessment for the application of this technology should be driven by the stakeholders at the proposed field site and areas that could be affected by this intervention strategy.
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Affiliation(s)
- Ana Kormos
- Vector Genetics Laboratory, University of California, Davis, Davis, CA, United States
| | - George Dimopoulos
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Malaria Research Institute, Johns Hopkins University, Baltimore, MD, United States
| | - Ethan Bier
- Department of Cell and Developmental Biology, University of California, San Diego, San Diego, CA, United States
| | - Gregory C. Lanzaro
- Vector Genetics Laboratory, University of California, Davis, Davis, CA, United States
| | - John M. Marshall
- Divisions of Epidemiology and Biostatistics, School of Public Health, University of California, Berkeley, Berkeley, CA, United States
| | - Anthony A. James
- Departments of Microbiology and Molecular Genetics and Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
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3
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Genetic Diversity of Merozoite Surface Protein-1 and -2 Genes in Plasmodium falciparum Isolates among Asymptomatic Population in Boset and Badewacho Districts, Southern Ethiopia. J Parasitol Res 2022; 2022:7728975. [PMID: 36569519 PMCID: PMC9771644 DOI: 10.1155/2022/7728975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Revised: 07/13/2022] [Accepted: 11/26/2022] [Indexed: 12/15/2022] Open
Abstract
Background The genetic variation of Plasmodium falciparum has been studied to assess local malaria transmission genetic profile using evidence-based intervention measures. However, there are no known previous reports of P. falciparum polymorphism in Badewacho and Boset districts, Southern Ethiopia. The purpose of this study was to determine the genetic diversity of the merozoite surface protein-1 and -2 (msp-1 and msp-2) allelic families in P. falciparum isolates from an asymptomatic populations. Methods This study was conducted from finger-prick blood samples spotted on 3 mm Whatman filter paper collected during a community-based cross-sectional study. Nested polymerase chain reaction amplification was used to type the allelic variants of msp-1 and msp-2. Results From 669 asymptomatic study participants, a total of 50 samples positive for P. falciparum were included for molecular analysis. Of 50 positive samples, 43 P. falciparum isolates were successfully amplified for the msp-1 and msp-2 allelic families. A total of twelve different allele sizes (75-250 bp) were identified within the three allelic families of msp-1, whereas ten different allele sizes (250-500 bp) were detected within the two allelic families of msp-2. MAD20 had a higher allelic proportion, 65% among allelic families of msp-1, whereas the 3D7 allelic family 90.7% was higher in msp-2. A slightly higher frequency of polyclonal infection 53.5% was found in msp-2 allelic family, whereas a low proportion polyclonal infection 46.5% was found in msp-1 allelic family. The overall mean multiplicity of infection (MOI) for msp-1 and msp-2 was identical (MOI = 1.56). Correspondingly, the expected heterozygosity (He) value for msp-1 (He = 0.23) and msp-2 (He = 0.22) was almost similar. Conclusions The findings of this study revealed low genetic diversity of the msp-1 and msp-2 allelic families in P. falciparum isolates. However, continued monitoring status of the local genetic diversity profile in the P. falciparum population is required to support current malaria control and elimination strategies.
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Van Bortel W, Mariën J, Jacobs BKM, Sinzinkayo D, Sinarinzi P, Lampaert E, D’hondt R, Mafuko JM, De Weggheleire A, Vogt F, Alexander N, Wint W, Maes P, Vanlerberghe V, Leclair C. Long-lasting insecticidal nets provide protection against malaria for only a single year in Burundi, an African highland setting with marked malaria seasonality. BMJ Glob Health 2022; 7:bmjgh-2022-009674. [PMID: 36455989 PMCID: PMC9772646 DOI: 10.1136/bmjgh-2022-009674] [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: 05/20/2022] [Accepted: 10/08/2022] [Indexed: 12/05/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) are one of the key interventions in the global fight against malaria. Since 2014, mass distribution campaigns of LLINs aim for universal access by all citizens of Burundi. In this context, we assess the impact of LLINs mass distribution campaigns on malaria incidence, focusing on the endemic highland health districts. We also explored the possible correlation between observed trends in malaria incidence with any variations in climate conditions. METHODS Malaria cases for 2011-2019 were obtained from the National Health Information System. We developed a generalised additive model based on a time series of routinely collected data with malaria incidence as the response variable and timing of LLIN distribution as an explanatory variable to investigate the duration and magnitude of the LLIN effect on malaria incidence. We added a seasonal and continuous-time component as further explanatory variables, and health district as a random effect to account for random natural variation in malaria cases between districts. RESULTS Malaria transmission in Burundian highlands was clearly seasonal and increased non-linearly over the study period. Further, a fast and steep decline of malaria incidence was noted during the first year after mass LLIN distribution (p<0.0001). In years 2 and 3 after distribution, malaria cases started to rise again to levels higher than before the control intervention. CONCLUSION This study highlights that LLINs did reduce the incidence in the first year after a mass distribution campaign, but in the context of Burundi, LLINs lost their impact after only 1 year.
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Affiliation(s)
- Wim Van Bortel
- Outbreak Research Team, Institute of Tropical Medicine, Antwerpen, Belgium,Unit Entomology, Institute of Tropical Medicine, Antwerpen, Belgium
| | - Joachim Mariën
- Outbreak Research Team, Institute of Tropical Medicine, Antwerpen, Belgium,Evolutionary Ecology Group, University of Antwerp, Antwerpen, Belgium
| | - Bart K M Jacobs
- Department of Clinical Sciences, Institute of Tropical Medicine, Antwerpen, Belgium
| | - Denis Sinzinkayo
- National Malaria Control Programme, Bujumbura, Burundi,Doctoral School, University of Burundi, Bujumbura, Burundi
| | | | - Emmanuel Lampaert
- Department of Operations – Central African Regional Support Team, Médecins Sans Frontières, Kinshasa, Congo (the Democratic Republic of the)
| | - Rob D’hondt
- Medical Department, Environmental Health Unit, Médecins Sans Frontières, Brussels, Belgium
| | - Jean-Marie Mafuko
- Department of Operations, Médecins Sans Frontières, Bujumbura, Burundi
| | - Anja De Weggheleire
- Outbreak Research Team, Institute of Tropical Medicine, Antwerpen, Belgium,Unit of Mycobacterial Diseases and Neglected Tropical Diseases, Institute of Tropical Medicine, Antwerpen, Belgium
| | - Florian Vogt
- Outbreak Research Team, Institute of Tropical Medicine, Antwerpen, Belgium,The Kirby Institute, University of New South Wales, Sydney, New South Wales, Australia,National Centre for Epidemiology and Population Health, College of Health and Medicine, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Neil Alexander
- Environmental Research Group Oxford Ltd, c/o Department of Biology, University of Oxford, Oxford, UK
| | - William Wint
- Environmental Research Group Oxford Ltd, c/o Department of Biology, University of Oxford, Oxford, UK
| | - Peter Maes
- Chief of WASH (Water, Sanitation and Hygiene), UNICEF, Kinshasa, Congo (the Democratic Republic of the)
| | - Veerle Vanlerberghe
- Tropical Infectious Diseases Group, Institute of Tropical Medicine, Antwerpen, Belgium
| | - Corey Leclair
- Medical Department, Environmental Health Unit, Médecins Sans Frontières, Brussels, Belgium
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5
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Chakrabarti R, Chery-Karschney L, White J, Mascarenhas A, Skillman KM, Kanjee U, Babar PH, Patrapuvich R, Mohapatra PK, Patankar S, Smith JD, Anvikar A, Valecha N, Rahi M, Duraisingh MT, Rathod PK. Diverse Malaria Presentations across National Institutes of Health South Asia International Center for Excellence in Malaria Research Sites in India. Am J Trop Med Hyg 2022; 107:107-117. [PMID: 36228910 PMCID: PMC9662227 DOI: 10.4269/ajtmh.21-1344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 05/14/2022] [Indexed: 11/07/2022] Open
Abstract
The Malaria Evolution in South Asia (MESA) International Center for Excellence in Malaria Research (ICEMR) was established by the US National Institutes of Health (US NIH) as one of 10 malaria research centers in endemic countries. In 10 years of hospital-based and field-based work in India, the MESA-ICEMR has documented the changing epidemiology and transmission of malaria in four different parts of India. Malaria Evolution in South Asia-ICEMR activities, in collaboration with Indian partners, are carried out in the broad thematic areas of malaria case surveillance, vector biology and transmission, antimalarial resistance, pathogenesis, and host response. The program integrates insights from surveillance and field studies with novel basic science studies. This is a two-pronged approach determining the biology behind the disease patterns seen in the field, and generating new relevant biological questions about malaria to be tested in the field. Malaria Evolution in South Asia-ICEMR activities inform local and international stakeholders on the current status of malaria transmission in select parts of South Asia including updates on regional vectors of transmission of local parasites. The community surveys and new laboratory tools help monitor ongoing efforts to control and eliminate malaria in key regions of South Asia including the state of evolving antimalarial resistance in different parts of India, new host biomarkers of recent infection, and molecular markers of pathogenesis from uncomplicated and severe malaria.
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Affiliation(s)
- Rimi Chakrabarti
- Department of Chemistry, University of Washington, Seattle, Washington
- Department of Medicine, Goa Medical College and Hospital, Bambolim, Goa, India
| | | | - John White
- Department of Chemistry, University of Washington, Seattle, Washington
| | - Anjali Mascarenhas
- Department of Chemistry, University of Washington, Seattle, Washington
- Department of Medicine, Goa Medical College and Hospital, Bambolim, Goa, India
| | - Kristen M. Skillman
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
| | - Usheer Kanjee
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
| | - Prasad H. Babar
- Department of Chemistry, University of Washington, Seattle, Washington
- Department of Medicine, Goa Medical College and Hospital, Bambolim, Goa, India
| | - Rapatbhorn Patrapuvich
- Drug Research Unit for Malaria (DRUM), Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | | - Swati Patankar
- Department of Biosciences and Bioengineering, IIT Bombay, Powai, Mumbai, India
| | | | - Anup Anvikar
- National Institute of Biologicals, Noida, UP, India
| | - Neena Valecha
- National Institute of Malaria Research, New Delhi, India
| | - Manju Rahi
- Division of Epidemiology and Communicable Disease, Indian Council of Medical Research, New Delhi, India
| | - Manoj T. Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, Massachusetts
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6
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Loeffel M, Ross A. The relative impact of interventions on sympatric Plasmodium vivax and Plasmodium falciparum malaria: A systematic review. PLoS Negl Trop Dis 2022; 16:e0010541. [PMID: 35767578 PMCID: PMC9242512 DOI: 10.1371/journal.pntd.0010541] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Accepted: 05/27/2022] [Indexed: 11/18/2022] Open
Abstract
Background
In areas with both Plasmodium vivax and Plasmodium falciparum malaria, interventions can reduce the burden of both species but the impact may vary due to their different biology. Knowing the expected relative impact on the two species over time for vector- and drug-based interventions, and the factors affecting this, could help plan and evaluate intervention strategies.
Methods
For three interventions (treated bed nets (ITN), mass drug administration (MDA) and indoor residual spraying (IRS)), we identified studies providing information on the proportion of clinical illness and patent infections attributed to P. vivax over time using a literature search. The change in the proportion of malaria attributed to P. vivax up to two years since implementation was estimated using logistic regression accounting for clustering with random effects. Potential factors (intervention type, coverage, relapse pattern, transmission intensity, seasonality, initial proportion of P. vivax and round of intervention) were assessed.
Results
In total there were 55 studies found that led to 72 series of time-points for clinical case data and 69 series for patent infection data. The main reason of study exclusion was insufficient information on interventions. There was considerable variation in the proportion of malaria attributed to P. vivax over time by study and location for all of the interventions. Overall, there was an increase apart from MDA in the short-term. The potential factors could not be ruled in or out. Although not consistently significant, coverage, transmission intensity and relapse pattern are possible factors that explain some of the variation found.
Conclusion
While there are reports of an increase in the proportion of malaria due to P. vivax following interventions in the long-term, there was substantial variation for the shorter time-scales considered in this study (up to 24 months for IRS and ITN, and up to six months for MDA). The large variability points to the need for the monitoring of both species after an intervention. Studies should report intervention timing and characteristics to allow inclusion in systematic reviews.
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Affiliation(s)
- Melanie Loeffel
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Amanda Ross
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
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Orish VN, Boakye-Yiadom E, Ansah EK, Alhassan RK, Duedu K, Awuku YA, Owusu-Agyei S, Gyapong JO. Is malaria immunity a possible protection against severe symptoms and outcomes of COVID-19? Ghana Med J 2022; 55:56-63. [PMID: 35233116 PMCID: PMC8853697 DOI: 10.4314/gmj.v55i2s.9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Malaria-endemic areas of the world are noted for high morbidity and mortality from malaria. Also noted in these areas is the majority of persons in the population having acquired malaria immunity. Though this acquired malaria immunity does not prevent infection, it resists the multiplication of Plasmodium parasites, restricting disease to merely uncomplicated cases or asymptomatic infections. Does this acquired malaria immunity in endemic areas protect against other diseases, especially outbreak diseases like COVID-19? Does malaria activation of innate immunity resulting in trained or tolerance immunity contribute to protection against COVID-19? In an attempt to answer these questions, this review highlights the components of malaria and viral immunity and explores possible links with immunity against COVID-19. With malaria-endemic areas of the world having a fair share of cases of COVID-19, it is important to direct research in this area to evaluate and harness any benefits of acquired malaria immunity to help mitigate the effects of COVID-19 and any possible future outbreaks. Funding None declared.
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Affiliation(s)
- Verner N Orish
- Department of Microbiology and Immunology, School of Medicine, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - Emily Boakye-Yiadom
- Department of Microbiology and Immunology, School of Medicine, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - Evelyn K Ansah
- Centre for Malaria Research, Institute for Health Research, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - Robert K Alhassan
- Institute of Health Research, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - Kwabena Duedu
- Department of Biomedical Sciences, School of Basic and Biomedical Sciences, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - Yaw A Awuku
- Department of Internal Medicine, School of Medicine, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - Seth Owusu-Agyei
- Institute of Health Research, University of Health and Allied Sciences, Ho, Volta Region, Ghana
| | - John O Gyapong
- Institute of Health Research, University of Health and Allied Sciences, Ho, Volta Region, Ghana
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8
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Lacy K, Schaefer KA, Scheitrum DP, Klein EY. The economic value of genetically engineered mosquitoes as a Malaria control strategy depends on local transmission rates. Biotechnol J 2021; 17:e2100373. [PMID: 34873849 DOI: 10.1002/biot.202100373] [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: 07/16/2021] [Revised: 12/02/2021] [Accepted: 12/03/2021] [Indexed: 11/05/2022]
Abstract
This paper assesses the economic value of genetically engineered (GE) Anopheles gambiae mosquitoes as a malaria control strategy. We use an epidemiological-economic model of malaria transmission to evaluate this technology for a range of village-level transmission settings. In each setting, we evaluate public health outcomes following introduction of GE mosquitoes relative to a "status quo" baseline scenario. We also assess results both in contrast to-and in combination with-a Mass Drug Administration (MDA) strategy. We find that-in low transmission settings-the present value (PV) public health benefits of GE mosquito release are substantial, both relative to status quo dynamics and MDA. In contrast, in high transmission settings, the release of GE mosquitoes may increase steady-state infection rates. Our results indicate that there are substantial policy complementarities when GE mosquito release is combined with local MDA-the combined control strategy can lead to local eradication.
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Affiliation(s)
- Katherine Lacy
- Department of Economics, University of Nevada, Reno, USA
| | - K Aleks Schaefer
- Department of Agricultural Economics, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Daniel P Scheitrum
- Department of Agricultural and Resource Economics, University of Arizona, Tucson, USA
| | - Eili Y Klein
- Department of Emergency Medicine, Johns Hopkins University, Baltimore, USA.,Center for Disease Dynamics, Economics and Policy, Washington, DC, USA
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9
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Galactionova K, Smith TA, Penny MA. Insights from modelling malaria vaccines for policy decisions: the focus on RTS,S. Malar J 2021; 20:439. [PMID: 34794430 PMCID: PMC8600337 DOI: 10.1186/s12936-021-03973-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 11/04/2021] [Indexed: 11/17/2022] Open
Abstract
Mathematical models are increasingly used to inform decisions throughout product development pathways from pre-clinical studies to country implementation of novel health interventions. This review illustrates the utility of simulation approaches by reviewing the literature on malaria vaccine modelling, with a focus on its link to the development of policy guidance for the first licensed product, RTS,S/AS01. The main contributions of modelling studies have been in inferring the mechanism of action and efficacy profile of RTS,S; to predicting the public health impact; and economic modelling mainly comprising cost-effectiveness analysis. The value of both product-specific and generic modelling of vaccines is highlighted.
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Affiliation(s)
- Katya Galactionova
- Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland.,University of Basel, 4001, Basel, Switzerland.,European Center of Pharmaceutical Medicine, Brombacherstrasse 5, 4057, Basel, Switzerland
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, 4001, Basel, Switzerland.
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland.,University of Basel, 4001, Basel, Switzerland
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10
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Connolly JB, Mumford JD, Fuchs S, Turner G, Beech C, North AR, Burt A. Systematic identification of plausible pathways to potential harm via problem formulation for investigational releases of a population suppression gene drive to control the human malaria vector Anopheles gambiae in West Africa. Malar J 2021; 20:170. [PMID: 33781254 PMCID: PMC8006393 DOI: 10.1186/s12936-021-03674-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Revised: 02/24/2021] [Accepted: 02/25/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Population suppression gene drive has been proposed as a strategy for malaria vector control. A CRISPR-Cas9-based transgene homing at the doublesex locus (dsxFCRISPRh) has recently been shown to increase rapidly in frequency in, and suppress, caged laboratory populations of the malaria mosquito vector Anopheles gambiae. Here, problem formulation, an initial step in environmental risk assessment (ERA), was performed for simulated field releases of the dsxFCRISPRh transgene in West Africa. METHODS Building on consultative workshops in Africa that previously identified relevant environmental and health protection goals for ERA of gene drive in malaria vector control, 8 potentially harmful effects from these simulated releases were identified. These were stratified into 46 plausible pathways describing the causal chain of events that would be required for potential harms to occur. Risk hypotheses to interrogate critical steps in each pathway, and an analysis plan involving experiments, modelling and literature review to test each of those risk hypotheses, were developed. RESULTS Most potential harms involved increased human (n = 13) or animal (n = 13) disease transmission, emphasizing the importance to subsequent stages of ERA of data on vectorial capacity comparing transgenics to non-transgenics. Although some of the pathways (n = 14) were based on known anatomical alterations in dsxFCRISPRh homozygotes, many could also be applicable to field releases of a range of other transgenic strains of mosquito (n = 18). In addition to population suppression of target organisms being an accepted outcome for existing vector control programmes, these investigations also revealed that the efficacy of population suppression caused by the dsxFCRISPRh transgene should itself directly affect most pathways (n = 35). CONCLUSIONS Modelling will play an essential role in subsequent stages of ERA by clarifying the dynamics of this relationship between population suppression and reduction in exposure to specific potential harms. This analysis represents a comprehensive identification of plausible pathways to potential harm using problem formulation for a specific gene drive transgene and organism, and a transparent communication tool that could inform future regulatory studies, guide subsequent stages of ERA, and stimulate further, broader engagement on the use of population suppression gene drive to control malaria vectors in West Africa.
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Affiliation(s)
- John B Connolly
- Department of Life Sciences, Imperial College London, London, UK.
| | - John D Mumford
- Centre for Environmental Policy, Imperial College London, London, UK
| | - Silke Fuchs
- Department of Life Sciences, Imperial College London, London, UK
| | - Geoff Turner
- Department of Life Sciences, Imperial College London, London, UK
| | | | - Ace R North
- Department of Zoology, University of Oxford, Oxford, UK
| | - Austin Burt
- Department of Life Sciences, Imperial College London, London, UK
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11
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Kitojo C, Chacky F, Kigadye ES, Mugasa JP, Lusasi A, Mohamed A, Walker P, Reaves EJ, Gutman JR, Ishengoma DS. Evaluation of a single screen and treat strategy to detect asymptomatic malaria among pregnant women from selected health facilities in Lindi region, Tanzania. Malar J 2020; 19:438. [PMID: 33256758 PMCID: PMC7708125 DOI: 10.1186/s12936-020-03513-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Accepted: 11/19/2020] [Indexed: 02/07/2023] Open
Abstract
Background In areas of high transmission, malaria in pregnancy (MiP) primarily causes asymptomatic infections; these infections nonetheless increase the risk of adverse maternal and fetal outcomes. In 2014, Tanzania initiated a single screening and treatment (SST) strategy for all pregnant women at their first antenatal care (ANC) visit using malaria rapid diagnostic tests (RDT) for surveillance purposes. However, there is paucity of data on the effectiveness of SST in the prevention of MiP. The objective of this study was to estimate the number of asymptomatic infections among pregnant women detected by SST, which would have been missed in the absence of the policy. Methods Data from pregnant women attending their first ANC visits between October 2017 and June 2018, including gestational age, history of fever, and RDT results, were abstracted from ANC registers in eight health centres in two randomly selected districts, Kilwa and Lindi, in Lindi Region. The proportion of symptomatic (with history of fever in the past 48 h) and asymptomatic pregnant women with positive RDTs were calculated and stratified by trimester (first, second and third). The study areas were categorized as low transmission with prevalence < 10% or moderate/high with ≥ 10%. Results Over the study period, 1,845 women attended their first ANC visits; 22.1% were in the first trimester (< 12 weeks gestation age). Overall 15.0% of the women had positive RDTs, and there was a trend towards higher malaria prevalence in the first (15.9%) and second (15.2%) trimesters, compared to the third (7.1%), although the differences were not statistically significant (p = 0.07). In total, 6.9% of women reported fever within the past 48 h and, of these, 96.1% were RDT positive. For every 100 pregnant women in the moderate/high and low transmission areas, SST identified 60 and 26 pregnant women, respectively, with asymptomatic infections that would have otherwise been missed. Among the 15.9% of women detected in the first trimester, 50.7% were asymptomatic. Conclusion In areas of moderate/high transmission, many infected women were asymptomatic, and would have been missed in the absence of SST. The benefits on maternal and fetal birth outcomes of identifying these infections depend heavily on the protection afforded by treatment, which is likely to be greatest for women presenting in the first trimester when intermittent preventive treatment (IPTp) with sulfadoxine-pyrimethamine (SP) is contraindicated, and in areas with high SP resistance, such as most parts of Tanzania. An evaluation of the impact and cost-effectiveness of SST across different transmission strata is warranted.
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Affiliation(s)
- Chonge Kitojo
- US President's Malaria Initiative, United States Agency for International Development, Dar es Salaam, United Republic of Tanzania. .,The Open University of Tanzania, Dar es Salaam, United Republic of Tanzania.
| | - Frank Chacky
- National Malaria Control Programme, Dodoma, United Republic of Tanzania
| | - Emmanuel S Kigadye
- The Open University of Tanzania, Dar es Salaam, United Republic of Tanzania
| | - Joseph P Mugasa
- USAID Boresha Afya Southern Zone, FHI 360, Dar es Salaam, United Republic of Tanzania
| | - Abdallah Lusasi
- National Malaria Control Programme, Dodoma, United Republic of Tanzania
| | - Ally Mohamed
- National Malaria Control Programme, Dodoma, United Republic of Tanzania
| | - Patrick Walker
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Erik J Reaves
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention and US President's Malaria Initiative, Dar es Salaam, United Republic of Tanzania.,Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, USA
| | - Julie R Gutman
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, USA
| | - Deus S Ishengoma
- National Institute for Medical Research, Dar Es Salaam, United Republic of Tanzania.,Faculty of Pharmaceutical Sciences, Monash University, Melbourne, Australia.,Harvard T.H. Chan School of Public Health, Boston, MA, USA
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12
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Arinaitwe E, Mpimbaza A, Nankabirwa JI, Kamya V, Asiimwe A, Kuule JK, Kamya MR, Drakeley C, Dorsey G, Rosenthal PJ, Staedke SG. Malaria Diagnosed in an Urban Setting Strongly Associated with Recent Overnight Travel: A Case-Control Study from Kampala, Uganda. Am J Trop Med Hyg 2020; 103:1517-1524. [PMID: 32840203 DOI: 10.4269/ajtmh.20-0189] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Malaria is frequently diagnosed in urban Kampala, despite low transmission intensity. To evaluate the association between recent travel out of Kampala and malaria, we conducted a matched case-control study. Cases were febrile outpatients with a positive malaria test; controls were febrile outpatients with a negative test. For every two cases, five controls were selected, matching on age. Data were collected on recent overnight travel out of Kampala (past 60 days), destination and duration of travel, and behavioral factors, including sleeping under an insecticide-treated net (ITN) during travel. From July to August 2019, 162 cases and 405 controls were enrolled. The locations of residence of cases and controls were similar. More controls were female (62.7% versus 46.3%, P < 0.001). Overall, 158 (27.9%) participants reported recent overnight travel. Travelers were far more likely to be diagnosed with malaria than those who did not travel (80.4% versus 8.6%, OR 58.9, 95% CI: 23.1-150.1, P < 0.001). Among travelers, traveling to a district not receiving indoor residual spraying of insecticide (OR 35.0, 95% CI: 4.80-254.9, P < 0.001), no ITN use (OR 30.1, 95% CI: 6.37-142.7, P < 0.001), engaging in outdoor activities (OR 22.0, 95% CI: 3.42-141.8, P = 0.001), and age < 16 years (OR 8.36, 95% CI: 2.22-56.2, P = 0.03) were associated with increased odds of malaria. Kampala residents who traveled overnight out of the city were at substantially higher risk of malaria than those who did not travel. For these travelers, personal protection measures, including sleeping under an ITN when traveling, should be advocated.
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Affiliation(s)
- Emmanuel Arinaitwe
- Infectious Diseases Research Collaboration, Kampala, Uganda.,London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Arthur Mpimbaza
- Child Health and Development Centre, Makerere University College of Health Sciences, Kampala, Uganda.,Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Joaniter I Nankabirwa
- Department of Medicine, Makerere University, Kampala, Uganda.,Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Victor Kamya
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Alan Asiimwe
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Julius K Kuule
- Uganda Malaria Research Centre, Ministry of Health, Kampala, Uganda
| | - Moses R Kamya
- Department of Medicine, Makerere University, Kampala, Uganda.,Infectious Diseases Research Collaboration, Kampala, Uganda
| | - Chris Drakeley
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Grant Dorsey
- Department of Medicine, University of California, San Francisco, California
| | - Philip J Rosenthal
- Department of Medicine, University of California, San Francisco, California
| | - Sarah G Staedke
- London School of Hygiene and Tropical Medicine, London, United Kingdom
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13
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Ugya AY, Hasan DB, Ari HA, Ajibade FO, Imam TS, Abba A, Hua X. Natural freshwater microalgae biofilm as a tool for the clean-up of water resulting from mining activities. ALL LIFE 2020. [DOI: 10.1080/26895293.2020.1844307] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Adamu Yunusa Ugya
- Key Lab of Groundwater Resources and Environment of Ministry of Education, Key Lab of Water Resources and Aquatic Environment of Jilin Province, College of New Energy and Environment, Jilin University, Changchun, People’s Republic of China
- Department of Environmental Management, Kaduna State University, Kaduna, Nigeria
| | | | - Hadiza Abdullahi Ari
- Key Lab of Groundwater Resources and Environment of Ministry of Education, Key Lab of Water Resources and Aquatic Environment of Jilin Province, College of New Energy and Environment, Jilin University, Changchun, People’s Republic of China
- Faculty of Sciences, National Open University of Nigeria, Lagos, Nigeria
| | - Fidelis Odedishemi Ajibade
- Department of Civil and Environmental Engineering, Federal University of Technology Akure, Akure, Nigeria
- Key Lab of Environmental Biotechnology, Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | | | - Abidina Abba
- Department of Biological Sciences, Federal University Lokoja, Anyigba, Nigeria
| | - Xiuyi Hua
- Key Lab of Groundwater Resources and Environment of Ministry of Education, Key Lab of Water Resources and Aquatic Environment of Jilin Province, College of New Energy and Environment, Jilin University, Changchun, People’s Republic of China
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14
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Microscopic and Submicroscopic Asymptomatic Plasmodium falciparum Infections in Ghanaian Children and Protection against Febrile Malaria. Infect Immun 2020; 88:IAI.00125-20. [PMID: 32719157 PMCID: PMC7504941 DOI: 10.1128/iai.00125-20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 07/20/2020] [Indexed: 11/20/2022] Open
Abstract
Naturally acquired immunity to Plasmodium falciparum malaria is thought to be nonsterile and sustained by persistence of low-level parasitemia. This study assessed the association between baseline microscopic and submicroscopic asymptomatic P. falciparum infections and antimalarial antibody levels and whether these parasitemia modify protective associations between antibody levels and malaria in Ghanaian children. Healthy children (N = 973, aged 0.5 to 12 years) were recruited into a 50-week longitudinal malaria cohort study from January 2016 to January 2017. Baseline asymptomatic parasitemia were determined by microscopy (microscopic parasitemia) and PCR (submicroscopic parasitemia), and antibody levels against crude schizont antigens were measured by enzyme-limited immunosorbent assay (ELISA). Antibody levels, parasite diversity, and risk of malaria in the ensuing transmission season were compared among children who had baseline asymptomatic microscopic or submicroscopic or no P. falciparum infections. Of the 99 asymptomatic baseline infections, 46 (46.5%) were microscopic and 53 (53.5%), submicroscopic. Cox regression analysis adjusting for age group, sex and community found a strong association between both baseline microscopic (hazard ratio [HR] = 0.36, 95% confidence interval [95% CI] = 0.21 to 0.63; P < 0.001) and submicroscopic (HR = 0.22, 95% CI = 0.11 to 0.44; P < 0.001) asymptomatic parasitemia and a reduced risk of febrile malaria compared to those who were uninfected at baseline. Baseline asymptomatic submicroscopic parasitemia had a significant effect on associations between antischizont antibodies and protection against febrile malaria (P < 0.001; likelihood ratio test). The study found both baseline P. falciparum asymptomatic microscopic and more strongly submicroscopic infections to be associated with protection against febrile malaria in the ensuing transmission season. This could have important implications for malaria seroepidemiological studies and vaccine trials.
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15
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Mpimbaza A, Walemwa R, Kapisi J, Sserwanga A, Namuganga JF, Kisambira Y, Tagoola A, Nanteza JF, Rutazaana D, Staedke SG, Dorsey G, Opigo J, Kamau A, Snow RW. The age-specific incidence of hospitalized paediatric malaria in Uganda. BMC Infect Dis 2020; 20:503. [PMID: 32660434 PMCID: PMC7359223 DOI: 10.1186/s12879-020-05215-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 07/01/2020] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Understanding the relationship between malaria infection risk and disease outcomes represents a fundamental component of morbidity and mortality burden estimations. Contemporary data on severe malaria risks among populations of different parasite exposures are scarce. Using surveillance data, we compared rates of paediatric malaria hospitalisation in areas of varying parasite exposure levels. METHODS Surveillance data at five public hospitals; Jinja, Mubende, Kabale, Tororo, and Apac were assembled among admissions aged 1 month to 14 years between 2017 and 2018. The address of each admission was used to define a local catchment population where national census data was used to define person-year-exposure to risk. Within each catchment, historical infection prevalence was assembled from previously published data and current infection prevalence defined using 33 population-based school surveys among 3400 children. Poisson regression was used to compute the overall and site-specific incidences with 95% confidence intervals. RESULTS Both current and historical Plasmodium falciparum prevalence varied across the five sites. Current prevalence ranged from < 1% in Kabale to 54% in Apac. Overall, the malaria admission incidence rate (IR) was 7.3 per 1000 person years among children aged 1 month to 14 years of age (95% CI: 7.0, 7.7). The lowest rate was described at Kabale (IR = 0.3; 95 CI: 0.1, 0.6) and highest at Apac (IR = 20.3; 95 CI: 18.9, 21.8). There was a correlation between IR across the five sites and the current parasite prevalence in school children, though findings were not statistically significant. Across all sites, except Kabale, malaria admissions were concentrated among young children, 74% were under 5 years. The median age of malaria admissions at Kabale hospital was 40 months (IQR 20, 72), and at Apac hospital was 36 months (IQR 18, 69). Overall, severe anaemia (7.6%) was the most common presentation and unconsciousness (1.8%) the least common. CONCLUSION Malaria hospitalisation rates remain high in Uganda particularly among young children. The incidence of hospitalized malaria in different locations in Uganda appears to be influenced by past parasite exposure, immune acquisition, and current risks of infection. Interruption of transmission through vector control could influence age-specific severe malaria risk.
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Affiliation(s)
- Arthur Mpimbaza
- Child Health and Development Centre, College of Health Sciences, Makerere University, Kampala, Uganda.
- Infectious Diseases Research Collaboration, Kampala, Uganda.
| | - Richard Walemwa
- Department of Prevention, Care and Treatment, Infectious Diseases Institute, Kampala, Uganda
| | - James Kapisi
- Infectious Diseases Research Collaboration, Kampala, Uganda
| | | | | | | | - Abner Tagoola
- Jinja Regional Referral, Hospital, Republic of Uganda Ministry of Health, Jinja, Uganda
| | - Jane Frances Nanteza
- Mubende Regional Referral, Hospital, Republic of Uganda Ministry of Health, Mubende, Uganda
| | - Damain Rutazaana
- National Malaria Control Program, Ministry of Health Uganda, Kampala, Uganda
| | | | - Grant Dorsey
- Department of Medicine, San Francisco General Hospital, University of California San Francisco, San Francisco, USA
| | - Jimmy Opigo
- National Malaria Control Program, Ministry of Health Uganda, Kampala, Uganda
| | - Alice Kamau
- Population Health Unit, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya
| | - Robert W Snow
- Population Health Unit, Kenya Medical Research Institute/Wellcome Trust Research Programme, Nairobi, Kenya
- Nuffield Department of Medicine, Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, UK
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16
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Mhamilawa LE, Ngasala B, Morris U, Kitabi EN, Barnes R, Soe AP, Mmbando BP, Björkman A, Mårtensson A. Parasite clearance, cure rate, post-treatment prophylaxis and safety of standard 3-day versus an extended 6-day treatment of artemether-lumefantrine and a single low-dose primaquine for uncomplicated Plasmodium falciparum malaria in Bagamoyo district, Tanzania: a randomized controlled trial. Malar J 2020; 19:216. [PMID: 32576258 PMCID: PMC7310382 DOI: 10.1186/s12936-020-03287-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 06/12/2020] [Indexed: 11/19/2022] Open
Abstract
Background Artemisinin-based combination therapy (ACT) resistant Plasmodium falciparum represents an increasing threat to Africa. Extended ACT regimens from standard 3 to 6 days may represent a means to prevent its development and potential spread in Africa. Methods Standard 3-day treatment with artemether–lumefantrine (control) was compared to extended 6-day treatment and single low-dose primaquine (intervention); in a randomized controlled, parallel group, superiority clinical trial of patients aged 1–65 years with microscopy confirmed uncomplicated P. falciparum malaria, enrolled in Bagamoyo district, Tanzania. The study evaluated parasite clearance, including proportion of PCR detectable P. falciparum on days 5 and 7 (primary endpoint), cure rate, post-treatment prophylaxis, safety and tolerability. Clinical, and laboratory assessments, including ECG were conducted during 42 days of follow-up. Blood samples were collected for parasite detection (by microscopy and PCR), molecular genotyping and pharmacokinetic analyses. Kaplan–Meier survival analyses were done for both parasite clearance and recurrence. Results A total of 280 patients were enrolled, 141 and 139 in the control and intervention arm, respectively, of whom 121 completed 42 days follow-up in each arm. There was no difference in proportion of PCR positivity across the arms at day 5 (80/130 (61.5%) vs 89/134 (66.4%), p = 0.44), or day 7 (71/129 (55.0%) vs 70/134 (52.2%), p = 0.71). Day 42 microscopy determined cure rates (PCR adjusted) were 97.4% (100/103) and 98.3% (110/112), p = 0.65, in the control and intervention arm, respectively. Microscopy determined crude recurrent parasitaemia during follow-up was 21/121 (17.4%) in the control and 14/121 (11.6%) in the intervention arm, p = 0.20, and it took 34 days and 42 days in the respective arms for 90% of the patients to remain without recurrent parasitaemia. Lumefantrine exposure was significantly higher in intervention arm from D3 to D42, but cardiac, biochemical and haematological safety was high and similar in both arms. Conclusion Extended 6-day artemether–lumefantrine treatment and a single low-dose of primaquine was not superior to standard 3-day treatment for ACT sensitive P. falciparum infections but, importantly, equally efficacious and safe. Thus, extended artemether–lumefantrine treatment may be considered as a future treatment regimen for ACT resistant P. falciparum, to prolong the therapeutic lifespan of ACT in Africa. Trial registration ClinicalTrials.gov, NCT03241901. Registered July 27, 2017 https://clinicaltrials.gov/show/NCT03241901
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Affiliation(s)
- Lwidiko E Mhamilawa
- Department of Women's and Children's Health, International Maternal and Child Health (IMCH), Uppsala University, Uppsala, Sweden. .,Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania.
| | - Billy Ngasala
- Department of Women's and Children's Health, International Maternal and Child Health (IMCH), Uppsala University, Uppsala, Sweden.,Department of Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania
| | - Ulrika Morris
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Eliford Ngaimisi Kitabi
- Office of Clinical Pharmacology, Division of Pharmacometrics, Food and Drugs Administration, Silver Spring, MD, USA
| | - Rory Barnes
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Aung Paing Soe
- Department of Women's and Children's Health, International Maternal and Child Health (IMCH), Uppsala University, Uppsala, Sweden.,Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Bruno P Mmbando
- Tanga Centre, National Institute for Medical Research, Tanga, Tanzania
| | - Anders Björkman
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden
| | - Andreas Mårtensson
- Department of Women's and Children's Health, International Maternal and Child Health (IMCH), Uppsala University, Uppsala, Sweden
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17
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Sanchez L, Vidal M, Jairoce C, Aguilar R, Ubillos I, Cuamba I, Nhabomba AJ, Williams NA, Díez-Padrisa N, Cavanagh D, Angov E, Coppel RL, Gaur D, Beeson JG, Dutta S, Aide P, Campo JJ, Moncunill G, Dobaño C. Antibody responses to the RTS,S/AS01 E vaccine and Plasmodium falciparum antigens after a booster dose within the phase 3 trial in Mozambique. NPJ Vaccines 2020; 5:46. [PMID: 32550014 PMCID: PMC7272643 DOI: 10.1038/s41541-020-0192-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 05/07/2020] [Indexed: 01/08/2023] Open
Abstract
The RTS,S/AS01E vaccine has shown consistent but partial vaccine efficacy in a pediatric phase 3 clinical trial using a 3-dose immunization schedule. A fourth-dose 18 months after the primary vaccination was shown to restore the waning efficacy. However, only total IgG against the immunodominant malaria vaccine epitope has been analyzed following the booster. To better characterize the magnitude, nature, and longevity of the immune response to the booster, we measured levels of total IgM, IgG, and IgG1-4 subclasses against three constructs of the circumsporozoite protein (CSP) and the hepatitis B surface antigen (HBsAg, also present in RTS,S) by quantitative suspension array technology in 50 subjects in the phase 3 trial in Manhiça, Mozambique. To explore the impact of vaccination on naturally acquired immune responses, we measured antibodies to P. falciparum antigens not included in RTS,S. We found increased IgG, IgG1, IgG3 and IgG4, but not IgG2 nor IgM, levels against vaccine antigens 1 month after the fourth dose. Overall, antibody responses to the booster dose were lower than the initial peak response to primary immunization and children had higher IgG and IgG1 levels than infants. Higher anti-Rh5 IgG and IgG1-4 levels were detected after the booster dose, suggesting that RTS,S partial protection could increase some blood stage antibody responses. Our work shows that the response to the RTS,S/AS01E booster dose is different from the primary vaccine immune response and highlights the dynamic changes in subclass antibody patterns upon the vaccine booster and with acquisition of adaptive immunity to malaria.
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Affiliation(s)
- Lina Sanchez
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain.,UnivLyon, Université Claude Bernard Lyon 1, 69100 Villeurbanne, France
| | - Marta Vidal
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain
| | - Chenjerai Jairoce
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain.,Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Ruth Aguilar
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain
| | - Itziar Ubillos
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain
| | - Inocencia Cuamba
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | | | - Nana Aba Williams
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain
| | - Núria Díez-Padrisa
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain
| | - David Cavanagh
- Institute of Immunology & Infection Research and Centre for Immunity, Infection & Evolution, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, King's Buildings, Edinburgh, UK
| | - Evelina Angov
- U.S. Military Malaria Vaccine Program, Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD USA
| | - Ross L Coppel
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Melbourne, VIC Australia
| | - Deepak Gaur
- Malaria Group, International Centre for Genetic Engineering and Biotechnology (ICGEB), New Delhi, India.,Laboratory of Malaria and Vaccine Research, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | | | - Sheetij Dutta
- U.S. Military Malaria Vaccine Program, Walter Reed Army Institute of Research (WRAIR), Silver Spring, MD USA
| | - Pedro Aide
- Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Joseph J Campo
- UnivLyon, Université Claude Bernard Lyon 1, 69100 Villeurbanne, France.,Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Gemma Moncunill
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain.,Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Carlota Dobaño
- ISGlobal, Hospital Clínic-Universitat de Barcelona, Barcelona, Catalonia Spain.,Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
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18
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Ketema T, Bassat Q. Estimating the hidden magnitude of the malaria community burden. THE LANCET. INFECTIOUS DISEASES 2020; 20:881-883. [PMID: 32277909 DOI: 10.1016/s1473-3099(20)30142-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 02/18/2020] [Indexed: 11/26/2022]
Affiliation(s)
- Tsige Ketema
- Jimma University, Department of Biology, College of Natural Sciences, Jimma, Ethiopia
| | - Quique Bassat
- Barcelona Institute for Global Health (ISGlobal), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain; Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique; ICREA, Pg. Lluís Companys 23, Barcelona, Spain; Pediatric Infectious Diseases Unit, Pediatrics Department, Hospital Sant Joan de Déu (University of Barcelona), Barcelona, Spain; Consorcio de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Madrid, Spain.
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19
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Kotraiah V, Phares TW, Browne CD, Pannucci J, Mansour M, Noe AR, Tucker KD, Christen JM, Reed C, MacKay A, Weir GM, Rajagopalan R, Stanford MM, Chung CS, Ayala A, Huang J, Tsuji M, Gutierrez GM. Novel Peptide-Based PD1 Immunomodulators Demonstrate Efficacy in Infectious Disease Vaccines and Therapeutics. Front Immunol 2020; 11:264. [PMID: 32210956 PMCID: PMC7068811 DOI: 10.3389/fimmu.2020.00264] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Accepted: 01/31/2020] [Indexed: 12/31/2022] Open
Abstract
Many pathogens use the same immune evasion mechanisms as cancer cells. Patients with chronic infections have elevated levels of checkpoint receptors (e.g., programed cell death 1, PD1) on T cells. Monoclonal antibody (mAb)-based inhibitors to checkpoint receptors have also been shown to enhance T-cell responses in models of chronic infection. Therefore, inhibitors have the potential to act as a vaccine “adjuvant” by facilitating the expansion of vaccine antigen-specific T-cell repertoires. Here, we report the discovery and characterization of a peptide-based class of PD1 checkpoint inhibitors, which have a potent adaptive immunity adjuvant capability for vaccines against infectious diseases. Briefly, after identifying peptides that bind to the recombinant human PD1, we screened for in vitro efficacy in reporter assays and human peripheral blood mononuclear cells (PBMC) readouts. We first found the baseline in vivo performance of the peptides in a standard mouse oncology model that demonstrated equivalent efficacy compared to mAbs against the PD1 checkpoint. Subsequently, two strategies were used to demonstrate the utility of our peptides in infectious disease indications: (1) as a therapeutic in a bacteria-induced lethal sepsis model in which our peptides were found to increase survival with enhanced bacterial clearance and increased macrophage function; and (2) as an adjuvant in combination with a prophylactic malaria vaccine in which our peptides increased T-cell immunogenicity and the protective efficacy of the vaccine. Therefore, our peptides are promising as both a therapeutic agent and a vaccine adjuvant for infectious disease with a potentially safer and more cost-effective target product profile compared to mAbs. These findings are essential for deploying a new immunomodulatory regimen in infectious disease primary and clinical care settings.
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Affiliation(s)
- Vinayaka Kotraiah
- Explorations in Global Health (ExGloH), Leidos Inc., Frederick, MD, United States
| | - Timothy W Phares
- Explorations in Global Health (ExGloH), Leidos Inc., Frederick, MD, United States
| | | | - James Pannucci
- Explorations in Global Health (ExGloH), Leidos Inc., Frederick, MD, United States
| | - Marc Mansour
- MM Scientific Consultants, Inc., Halifax, NS, Canada
| | - Amy R Noe
- Leidos Life Sciences, Leidos Inc., Frederick, MD, United States
| | | | | | - Charles Reed
- Inovio Pharmaceuticals, Plymouth Meeting, PA, United States
| | | | | | | | | | | | - Alfred Ayala
- Lifespan-Rhode Island Hospital, Providence, RI, United States
| | - Jing Huang
- The Aaron Diamond AIDS Research Center, New York, NY, United States
| | - Moriya Tsuji
- The Aaron Diamond AIDS Research Center, New York, NY, United States
| | - Gabriel M Gutierrez
- Explorations in Global Health (ExGloH), Leidos Inc., Frederick, MD, United States
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20
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Odhiambo G, Bergmann-Leitner E, Maraka M, Wanjala CNL, Duncan E, Waitumbi J, Andagalu B, Jura WGZO, Dutta S, Angov E, Ogutu BR, Kamau E, Ochiel D. Correlation Between Malaria-Specific Antibody Profiles and Responses to Artemisinin Combination Therapy for Treatment of Uncomplicated Malaria in Western Kenya. J Infect Dis 2020; 219:1969-1979. [PMID: 30649381 DOI: 10.1093/infdis/jiz027] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/11/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND The impact of preexisting immunity on the efficacy of artemisinin combination therapy must be examined to monitor resistance, and for implementation of new treatment strategies. METHODS Serum samples obtained from a clinical trial in Western Kenya randomized to receive artemether-lumefantrine (AL) or artesunate-mefloquine (ASMQ) were screened for total immunoglobulin G against preerythrocytic and erythrocytic antigens. The association and correlation between different variables, and impact of preexisting immunity on parasite slope half-life (t½) was determined. RESULTS There was no significant difference in t½, but the number of individuals with lag phase was significantly higher in the AL than in the ASMQ arm (29 vs 13, respectively; P < .01). Circumsporozoite protein-specific antibodies correlate positively with t½ (AL, P = .03; ASMQ, P = .09), but negatively with clearance rate in both study arms (AL, P = .16; ASMQ, P = .02). The t½ correlated negatively with age in ASMQ group. When stratified based on t½, the antibody titers against circumsporozoite protein and merozoite surface protein 1 were significantly higher in participants who cleared parasites rapidly in the AL group (P = .01 and P = .02, respectively). CONCLUSION Data presented here define immunoprofiles associated with distinct responses to 2 different antimalarial drugs, revealing impact of preexisting immunity on the efficacy of artemisinin combination therapy regimens in a malaria-holoendemic area. CLINICAL TRIALS REGISTRATION NCT01976780.
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Affiliation(s)
- Geoffrey Odhiambo
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu.,Maseno University School of Physical and Biological Sciences Zoology Department, Maseno, Kenya
| | - Elke Bergmann-Leitner
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Moureen Maraka
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu
| | - Christine N L Wanjala
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu.,Maseno University School of Physical and Biological Sciences Zoology Department, Maseno, Kenya
| | - Elizabeth Duncan
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - John Waitumbi
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu
| | - Ben Andagalu
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu
| | - Walter G Z O Jura
- Maseno University School of Physical and Biological Sciences Zoology Department, Maseno, Kenya
| | - Sheetij Dutta
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Evelina Angov
- Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Bernhards R Ogutu
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu.,Kenya Medical Research Institute, Nairobi
| | - Edwin Kamau
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu.,Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, Maryland
| | - Daniel Ochiel
- Department of Emerging and Infectious Diseases, United States Army Medical Research Directorate-Africa, Kenya Medical Research Institute/Walter Reed Project , Kisumu.,Maseno University School of Physical and Biological Sciences Zoology Department, Maseno, Kenya
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21
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Greenhalgh S, Chandwani V. Advocating an attack against severe malaria: a cost-effectiveness analysis. BMC Public Health 2020; 20:17. [PMID: 31910842 PMCID: PMC6947859 DOI: 10.1186/s12889-019-8141-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 12/30/2019] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND A recent study found that the gut microbiota, Lactobacillus and Bifidobacterium, have the ability to modulate the severity of malaria. The modulation of the severity of malaria is not however, the typical focal point of most widespread interventions. Thus, an essential element of information required before serious consideration of any intervention that targets reducing severe malaria incidence is a prediction of the health benefits and costs required to be cost-effective. METHODS Here, we developed a mathematical model of malaria transmission to evaluate an intervention that targets reducing severe malaria incidence. We consider intervention scenarios of a 2-, 7-, and 14-fold reduction in severe malaria incidence, based on the potential reduction in severe malaria incidence caused by gut microbiota, under entomological inoculation rates occurring in 41 countries in sub-Saharan Africa. For each intervention scenario, disability-adjusted life years averted and incremental cost-effectiveness ratios were estimated using country specific data, including the reported proportions of severe malaria incidence in healthcare settings. RESULTS Our results show that an intervention that targets reducing severe malaria incidence with annual costs between $23.65 to $30.26 USD per person and causes a 14-fold reduction in severe malaria incidence would be cost-effective in 15-19 countries and very cost-effective in 9-14 countries respectively. Furthermore, if model predictions are based on the distribution of gut microbiota through a freeze-dried yogurt that cost $0.20 per serving, a 2- to 14-fold reduction in severe malaria incidence would be cost-effective in 29 countries and very cost-effective in 25 countries. CONCLUSION Our findings indicate interventions that target severe malaria can be cost-effective, in conjunction with standard interventions, for reducing the health burden and costs attributed to malaria. While our results illustrate a stronger cost-effectiveness for greater reductions, they consistently show that even a limited reduction in severe malaria provides substantial health benefits, and could be economically viable. Therefore, we suggest that interventions that target severe malaria are worthy of consideration, and merit further empirical and clinical investigation.
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Affiliation(s)
- Scott Greenhalgh
- Department of Mathematics, Siena College, 515 Loudon Road, Loudonville, NY, 12211, USA.
| | - Veda Chandwani
- Department of Biology, Siena College, 515 Loudon Road, Loudonville, NY, 12211, USA
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22
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Patel H, Althubaiti N, Parmar R, Yadav N, Joshi U, Tyagi RK, Krzych U, Dalai SK. Parasite load stemming from immunization route determines the duration of liver-stage immunity. Parasite Immunol 2019; 41:e12622. [PMID: 30854655 PMCID: PMC6584043 DOI: 10.1111/pim.12622] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 12/28/2018] [Accepted: 02/22/2019] [Indexed: 02/05/2023]
Abstract
Immunization with radiation-attenuated Plasmodium sporozoites (RAS) induces sterile and long-lasting protective immunity. Although intravenous (IV) route of RAS immunization is reported to induce superior immunity compared to intradermal (ID) injection, its role in the maintenance of sterile immunity is yet to be understood. We investigated whether the route of homologous sporozoite challenge of Plasmodium berghei (Pb) RAS-immunized mice would influence the longevity of protection. C57BL/6 mice immunized with Pb-RAS by IV were 100% protected upon primary IV/ID sporozoite challenge. In contrast, ID immunization resulted in 80% protection, regardless of primary challenge route. Interestingly, the route of primary challenge was found to bring difference in the maintenance of sterile protection. While IV Pb RAS-immunized mice remained protected at all challenges regardless of the route of primary challenge, ID Pb-RAS-immunized mice receiving ID primary challenge became parasitaemic upon secondary IV challenge. Significantly, primary IV challenge of Pb RAS ID-immunized mice resulted in 80% and 50% survival at secondary and tertiary challenges, respectively. According to phenotypically diverse liver CD8+ T cells, the percentages and the numbers of both CD8+ T effector memory and resident memory cells were significantly higher in IV than in ID Pb RAS-immunized mice. IFN-γ-producing CD8+ T cells specific to Pb TRAP130 and MIP-4-Kb-17 were also found significantly higher in IV mice than in ID mice. The enhanced T-cell generation and the longevity of protection appear to be dependent on the parasite load during challenge when infection is tolerated under suboptimal CD8+ T-cell response.
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Affiliation(s)
- Hardik Patel
- Institute of Science, Nirma University, Ahmedabad, Gujarat, India
| | - Nouf Althubaiti
- Department of Cellular Immunology, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Rajesh Parmar
- Institute of Science, Nirma University, Ahmedabad, Gujarat, India
| | - Naveen Yadav
- Institute of Science, Nirma University, Ahmedabad, Gujarat, India
| | - Urja Joshi
- Institute of Science, Nirma University, Ahmedabad, Gujarat, India
| | - Rajeev K Tyagi
- Institute of Science, Nirma University, Ahmedabad, Gujarat, India
| | - Urszula Krzych
- Department of Cellular Immunology, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, USA
| | - Sarat K Dalai
- Department of Cellular Immunology, Malaria Vaccine Branch, Walter Reed Army Institute of Research, Silver Spring, MD, USA
- Correspondence: Sarat Kumar Dalai, Institute of Science, Nirma University, Sarkhej-Gandhinagar Highway, Ahmedabad 382 481, Gujarat, India,
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23
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Dalrymple U, Cameron E, Arambepola R, Battle KE, Chestnutt EG, Keddie SH, Twohig KA, Pfeffer DA, Gibson HS, Weiss DJ, Bhatt S, Gething PW. The contribution of non-malarial febrile illness co-infections to Plasmodium falciparum case counts in health facilities in sub-Saharan Africa. Malar J 2019; 18:195. [PMID: 31186004 PMCID: PMC6560910 DOI: 10.1186/s12936-019-2830-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 06/04/2019] [Indexed: 01/20/2023] Open
Abstract
Background The disease burden of Plasmodium falciparum malaria illness is generally estimated using one of two distinct approaches: either by transforming P. falciparum infection prevalence estimates into incidence estimates using conversion formulae; or through adjustment of counts of recorded P. falciparum-positive fever cases from clinics. Whilst both ostensibly seek to evaluate P. falciparum disease burden, there is an implicit and problematic difference in the metric being estimated. The first enumerates only symptomatic malaria cases, while the second enumerates all febrile episodes coincident with a P. falciparum infection, regardless of the fever’s underlying cause. Methods Here, a novel approach was used to triangulate community-based data sources capturing P. falciparum infection, fever, and care-seeking to estimate the fraction of P. falciparum-positive fevers amongst children under 5 years of age presenting at health facilities that are attributable to P. falciparum infection versus other non-malarial causes. A Bayesian hierarchical model was used to assign probabilities of malaria-attributable fever (MAF) and non-malarial febrile illness (NMFI) to children under five from a dataset of 41 surveys from 21 countries in sub-Saharan Africa conducted between 2006 and 2016. Using subsequent treatment-seeking outcomes, the proportion of MAF and NMFI amongst P. falciparum-positive febrile children presenting at public clinics was estimated. Results Across all surveyed malaria-positive febrile children who sought care at public clinics across 41 country-years in sub-Saharan Africa, P. falciparum infection was estimated to be the underlying cause of only 37.7% (31.1–45.4, 95% CrI) of P. falciparum-positive fevers, with significant geographical and temporal heterogeneity between surveys. Conclusions These findings highlight the complex nature of the P. falciparum burden amongst children under 5 years of age and indicate that for many children presenting at health clinics, a positive P. falciparum diagnosis and a fever does not necessarily mean P. falciparum is the underlying cause of the child’s symptoms, and thus other causes of illness should always be investigated, in addition to prescribing an effective anti-malarial medication. In addition to providing new large-scale estimates of malaria-attributable fever prevalence, the results presented here improve comparability between different methods for calculating P. falciparum disease burden, with significant implications for national and global estimation of malaria burden. Electronic supplementary material The online version of this article (10.1186/s12936-019-2830-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ursula Dalrymple
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK.,Department of Zoology, University of Oxford, Zoology Research and Administration Building, 11a Mansfield Road, Oxford, OX1 3SZ, UK
| | - Ewan Cameron
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Rohan Arambepola
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Katherine E Battle
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Elisabeth G Chestnutt
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Suzanne H Keddie
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Katherine A Twohig
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Daniel A Pfeffer
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK.,Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Australia
| | - Harry S Gibson
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Daniel J Weiss
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK
| | - Samir Bhatt
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK.,School of Public Health, Faculty of Medicine, Imperial College London, St Mary's Hospital, Norfolk Place, London, W2 1PG, UK
| | - Peter W Gething
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, OX3 7LF, UK.
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24
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Venkatesh A, Jain A, Davies H, Periera L, Maki JN, Gomes E, Felgner PL, Srivastava S, Patankar S, Rathod PK. Hospital-derived antibody profiles of malaria patients in Southwest India. Malar J 2019; 18:138. [PMID: 30995911 PMCID: PMC6472095 DOI: 10.1186/s12936-019-2771-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 04/08/2019] [Indexed: 11/10/2022] Open
Abstract
Background Naturally acquired immunity to malaria across the globe varies in intensity and protective powers. Many of the studies on immunity are from hyperendemic regions of Africa. In Asia, particularly in India, there are unique opportunities for exploring and understanding malaria immunity relative to host age, co-occurrence of Plasmodium falciparum and Plasmodium vivax infections, varying travel history, and varying disease severity. Variation in immunity in hospital settings is particularly understudied. Methods A US NIH ICEMR (South Asia) team examined the level of immunity in an Indian malaria patient population visiting or admitted to Goa Medical College and Hospital in Goa, India. Sera from 200 patients of different ages, in different seasons, infected with P. falciparum or P. vivax or both species, and with different clinical severity were applied to an established protein array system with over 1000 P. falciparum and P. vivax antigens. Differential binding of patient IgG to different antigens was measured. Results Even though Goa itself has much more P. vivax than P. falciparum, IgG reactivity towards P. falciparum antigens was very strong and comparable to that seen in regions of the world with high P. falciparum endemicity. Of 248 seropositive P. falciparum antigens, the strongest were VAR, MSP10, HSP70, PTP5, AP2, AMA1, and SYN6. In P. vivax patients, ETRAMPs, MSPs, and ApiAP2, sexual stage antigen s16, RON3 were the strongest IgG binders. Both P. falciparum and P. vivax patients also revealed strong binding to new antigens with unknown functions. Seropositives showed antigens unique to the young (HSP40, ACS6, GCVH) or to non-severe malaria (MSP3.8 and PHIST). Conclusion Seroreactivity at a major hospital in Southwest India reveals antibody responses to P. falciparum and P. vivax in a low malaria transmission region with much migration. In addition to markers of transmission, the data points to specific leads for possible protective immunity against severe disease. Several, but not all, key antigens overlap with work from different settings around the globe and from other parts of India. Together, these studies confidently help define antigens with the greatest potential chance of universal application for surveillance and possibly for disease protection, in many different parts of India and the world. Electronic supplementary material The online version of this article (10.1186/s12936-019-2771-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Apoorva Venkatesh
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Aarti Jain
- Vaccine R&D Center, University of California, Irvine, CA, 92697, USA
| | - Huw Davies
- Vaccine R&D Center, University of California, Irvine, CA, 92697, USA
| | - Ligia Periera
- Department of Chemistry and Department of Global Health, University of Washington, Seattle, WA, 98195, USA
| | - Jennifer N Maki
- Department of Chemistry and Department of Global Health, University of Washington, Seattle, WA, 98195, USA
| | - Edwin Gomes
- Department of Medicine, Goa Medical College and Hospital, Bambolim, Goa, 403202, India
| | - Philip L Felgner
- Vaccine R&D Center, University of California, Irvine, CA, 92697, USA
| | - Sanjeeva Srivastava
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Swati Patankar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai, India
| | - Pradipsinh K Rathod
- Department of Chemistry and Department of Global Health, University of Washington, Seattle, WA, 98195, USA.
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25
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Hogan AB, Winskill P, Verity R, Griffin JT, Ghani AC. Modelling population-level impact to inform target product profiles for childhood malaria vaccines. BMC Med 2018; 16:109. [PMID: 30001708 PMCID: PMC6044028 DOI: 10.1186/s12916-018-1095-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 06/05/2018] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND The RTS,S/AS01 vaccine for Plasmodium falciparum malaria demonstrated moderate efficacy in 5-17-month-old children in phase 3 trials, and from 2018, the vaccine will be evaluated through a large-scale pilot implementation program. Work is ongoing to optimise this vaccine, with higher efficacy for a different schedule demonstrated in a phase 2a challenge study. The objective of our study was to investigate the population-level impact of a modified RTS,S/AS01 schedule and dose amount in order to inform the target product profile for a second-generation malaria vaccine. METHODS We used a mathematical modelling approach as the basis for our study. We simulated the changing anti-circumsporozoite antibody titre following vaccination and related the titre to vaccine efficacy. We then implemented this efficacy profile within an individual-based model of malaria transmission. We compared initial efficacy, duration and dose timing, and evaluated the potential public health impact of a modified vaccine in children aged 5-17 months, measuring clinical cases averted in children younger than 5 years. RESULTS In the first decade of delivery, initial efficacy was associated with a higher reduction in childhood clinical cases compared to vaccine duration. This effect was more pronounced in high transmission settings and was due to the efficacy benefit occurring in younger ages where disease burden is highest. However, the low initial efficacy and long duration schedule averted more cases across all age cohorts if a longer time horizon was considered. We observed an age-shifting effect due to the changing immunological profile in higher transmission settings, in scenarios where initial efficacy was higher, and the fourth dose administered earlier. CONCLUSIONS Our findings indicate that, for an imperfect childhood malaria vaccine with suboptimal efficacy, it may be advantageous to prioritise initial efficacy over duration. We predict that a modified vaccine could outperform the current RTS,S/AS01, although fourth dose timing will affect the age group that derives the greatest benefit. Further, the outcome measure and timeframe over which a vaccine is assessed are important when prioritising vaccine elements. This study provides insight into the most important characteristics of a malaria vaccine for at-risk groups and shows how distinct vaccine properties translate to public health outcomes. These findings may be used to prioritise target product profile elements for second-generation childhood malaria vaccines.
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Affiliation(s)
- Alexandra B. Hogan
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, School of Public Health, St Mary’s Campus, Norfolk Place, London, W2 1PG UK
| | - Peter Winskill
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, School of Public Health, St Mary’s Campus, Norfolk Place, London, W2 1PG UK
| | - Robert Verity
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, School of Public Health, St Mary’s Campus, Norfolk Place, London, W2 1PG UK
| | - Jamie T. Griffin
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, School of Public Health, St Mary’s Campus, Norfolk Place, London, W2 1PG UK
- School of Mathematical Sciences, Queen Mary University London, Mile End Road, London, E1 4NS UK
| | - Azra C. Ghani
- Department of Infectious Disease Epidemiology, MRC Centre for Global Infectious Disease Analysis, Imperial College London, School of Public Health, St Mary’s Campus, Norfolk Place, London, W2 1PG UK
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26
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Eikenberry SE, Gumel AB. Mathematical modeling of climate change and malaria transmission dynamics: a historical review. J Math Biol 2018; 77:857-933. [PMID: 29691632 DOI: 10.1007/s00285-018-1229-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 03/16/2018] [Indexed: 12/24/2022]
Abstract
Malaria, one of the greatest historical killers of mankind, continues to claim around half a million lives annually, with almost all deaths occurring in children under the age of five living in tropical Africa. The range of this disease is limited by climate to the warmer regions of the globe, and so anthropogenic global warming (and climate change more broadly) now threatens to alter the geographic area for potential malaria transmission, as both the Plasmodium malaria parasite and Anopheles mosquito vector have highly temperature-dependent lifecycles, while the aquatic immature Anopheles habitats are also strongly dependent upon rainfall and local hydrodynamics. A wide variety of process-based (or mechanistic) mathematical models have thus been proposed for the complex, highly nonlinear weather-driven Anopheles lifecycle and malaria transmission dynamics, but have reached somewhat disparate conclusions as to optimum temperatures for transmission, and the possible effect of increasing temperatures upon (potential) malaria distribution, with some projecting a large increase in the area at risk for malaria, but others predicting primarily a shift in the disease's geographic range. More generally, both global and local environmental changes drove the initial emergence of P. falciparum as a major human pathogen in tropical Africa some 10,000 years ago, and the disease has a long and deep history through the present. It is the goal of this paper to review major aspects of malaria biology, methods for formalizing these into mathematical forms, uncertainties and controversies in proper modeling methodology, and to provide a timeline of some major modeling efforts from the classical works of Sir Ronald Ross and George Macdonald through recent climate-focused modeling studies. Finally, we attempt to place such mathematical work within a broader historical context for the "million-murdering Death" of malaria.
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Affiliation(s)
- Steffen E Eikenberry
- Global Security Initiative, Arizona State University, Tempe, AZ, USA. .,School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ, USA.
| | - Abba B Gumel
- School of Mathematical and Statistical Sciences, Arizona State University, Tempe, AZ, USA
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van Eer ED, Bretas G, Hiwat H. Decreased endemic malaria in Suriname: moving towards elimination. Malar J 2018; 17:56. [PMID: 29378594 PMCID: PMC5789749 DOI: 10.1186/s12936-018-2204-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 01/20/2018] [Indexed: 11/30/2022] Open
Abstract
Background Suriname has moved from being the country with the highest annual parasite index in the Americas to one on the threshold of elimination. The progress toward elimination in the stable populations of Suriname between 2000 and 2015 is reviewed. Methods Data was obtained from the Medical Mission and the Ministry of Health Malaria Programme case-reporting systems, and analysed with a focus on disease burden and differentiation of the disease geographically, by malaria species, age, gender, ethnicity, incidence and gametocytaemia. Results Between 2000 and 2015 there were 57,811 locally acquired cases of malaria in the stable populations of Suriname. A significant reduction in indigenous malaria cases was observed from 2006 to 2015. The number of imported malaria cases saw a relative increase compared to the number of autochthonous cases. In 2015 over 95% of the cases reported in stable communities are imported, mainly from neighbouring French Guiana, a department of France. The overall decline in malaria case incidence followed the mass-distribution of free long-lasting insecticide-impregnated mosquito nets and increased awareness building efforts, improved access to malaria services as a result of the introduction of Rapid Diagnostic Tests and the implementation of active case detection in high risk areas. In addition, improved management of Plasmodium falciparum infections was achieved with the introduction of artemisinin combination therapy. Conclusions The existence of a network of policlinics in the interior ran by Medical Mission, for the indigenous population, allowed the rapid implementation of the strategy in stable communities. The success of malaria control in Suriname indicates that the availability at local level, of prompt and adequate prevention, diagnosis and treatment is a key requirement for the elimination of malaria.
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Affiliation(s)
| | - Gustavo Bretas
- Independent Consultant, João Lira 84, 804, Leblon, Brazil
| | - Hélène Hiwat
- Ministry of Health Malaria Programme, Anamoestraat 44bov, Paramaribo, Suriname
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28
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Stephens JK, Kyei-Baafour E, Dickson EK, Ofori JK, Ofori MF, Wilson ML, Quakyi IA, Akanmori BD. Effect of IPTp on Plasmodium falciparum antibody levels among pregnant women and their babies in a sub-urban coastal area in Ghana. Malar J 2017; 16:224. [PMID: 28549426 PMCID: PMC5446726 DOI: 10.1186/s12936-017-1857-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Accepted: 05/12/2017] [Indexed: 12/31/2022] Open
Abstract
Background Women exposed to Plasmodium infection develop antibodies and become semi-immune. This immunity is suppressed during pregnancy making both the pregnant woman and the foetus vulnerable to the adverse effects of malaria, particularly by Plasmodium falciparum. Intermittent preventive treatment of malaria in pregnancy (IPTp) with Sulfadoxine–pyrimethamine (SP) tablets is one of the current interventions to mitigate the effects of malaria on both the pregnant woman and the unborn child. The extent to which IPTp may interfere with the acquisition of protective immunity against pregnancy-associated malaria (PAM) is undefined in Ghana. Methods Three-hundred-and-twenty pregnant women were randomly enrolled at the antenatal clinic (ANC) in Madina, Accra. Venous blood samples were obtained at first ANC registration and at 4-week intervals (post-IPTp administration). Placental and cord blood samples were obtained at delivery and the infants were followed monthly for 6 months after birth. Anti-IgG and IgM antibodies against a crude antigen preparation and the glutamate-rich protein (GLURP) of P. falciparum were quantified by the enzyme-linked immunosorbent assay (ELISA). Results There was a general decline in the trend of mean concentrations of all the antibodies from enrolment to delivery. The levels of antibodies in cord blood and placenta were well correlated. Children did not show clinical signs of malaria at 6 months after birth. Conclusions IgG against both crude antigen and GLURP were present in placenta and cord blood and it is therefore concluded that there is a trend of declining antibody from enrolment to delivery and IPTp-SP may have reduced malaria exposure, however, this does not impact on the transfer of antibodies to the foetus in utero. The levels of maternal and cord blood antibodies at delivery showed no adverse implications on malaria among the children at 6 months. However, the quantum and quality of the antibody transferred needs further investigation to ensure that the infants are protected from severe episodes of malaria.
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Affiliation(s)
- Judith K Stephens
- Biological, Environmental and Occupational and Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. Box LG 13, Legon, Accra, Ghana.
| | - Eric Kyei-Baafour
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana
| | - Emmanuel K Dickson
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana
| | - Jones K Ofori
- Biological, Environmental and Occupational and Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. Box LG 13, Legon, Accra, Ghana
| | - Michael F Ofori
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana
| | - Mark L Wilson
- Department of Epidemiology, School of Public Health, The University of Michigan, 109 Observatory Street, Ann Arbor, MI, 48109-2029, USA
| | - Isabella A Quakyi
- Biological, Environmental and Occupational and Health Sciences Department, School of Public Health, College of Health Sciences, University of Ghana, P. O. Box LG 13, Legon, Accra, Ghana
| | - Bartholomew D Akanmori
- Immunology Department Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, P. O. Box LG 581, Legon, Accra, Ghana.,Vaccine Research and Development, Immunization and Vaccines Development Cluster, Office of the Regional Director, WHO Regional Office for Africa, P. O. Box 06, Djoue, Brazzaville, Congo
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Cai L, Li X, Tuncer N, Martcheva M, Lashari AA. Optimal control of a malaria model with asymptomatic class and superinfection. Math Biosci 2017; 288:94-108. [PMID: 28284964 DOI: 10.1016/j.mbs.2017.03.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Revised: 02/22/2017] [Accepted: 03/01/2017] [Indexed: 10/20/2022]
Abstract
In this paper, we introduce a malaria model with an asymptomatic class in human population and exposed classes in both human and vector populations. The model assumes that asymptomatic individuals can get re-infected and move to the symptomatic class. In the case of an incomplete treatment, symptomatic individuals move to the asymptomatic class. If successfully treated, the symptomatic individuals recover and move to the susceptible class. The basic reproduction number, R0, is computed using the next generation approach. The system has a disease-free equilibrium (DFE) which is locally asymptomatically stable when R0<1, and may have up to four endemic equilibria. The model exhibits backward bifurcation generated by two mechanisms; standard incidence and superinfection. If the model does not allow for superinfection or deaths due to the disease, then DFE is globally stable which suggests that backward bifurcation is no longer possible. Simulations suggest that total prevalence of malaria is the highest if all individuals show symptoms upon infection, but then undergoes an incomplete treatment and the lowest when all the individuals first move to the symptomatic class then treated successfully. Total prevalence is average if more individuals upon infection move to the asymptomatic class. We study optimal control strategies applied to bed-net use and treatment as main tools for reducing the total number of symptomatic and asymptomatic individuals. Simulations suggest that the optimal control strategies are very dynamic. Although they always lead to decrease in the symptomatic infectious individuals, they may lead to increase in the number of asymptomatic infectious individuals. This last scenario occurs if a large portion of newly infected individuals move to the symptomatic class but many of them do not complete treatment or if they all complete treatment but the superinfection rate of asymptomatic individuals is average.
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Affiliation(s)
- Liming Cai
- College of Mathematics and Statistic Science, Xinyang Normal University, Xinyang, 46400, CHINA.
| | - Xuezhi Li
- College of Mathematics and information Science, Xinyang Normal University, Xinyang, 46400, CHINA
| | - Necibe Tuncer
- Department of Mathematical Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA.
| | - Maia Martcheva
- Department of Mathematics, University of Florida, 358 Little Hall, PO Box 118105, Gainesville, FL 32611-8105, United States.
| | - Abid Ali Lashari
- Department of Mathematics, Stockholms University, SE-106 91 Stockholm, Sweden
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Slater HC, Okell LC, Ghani AC. Mathematical Modelling to Guide Drug Development for Malaria Elimination. Trends Parasitol 2017; 33:175-184. [PMID: 27727128 PMCID: PMC5347022 DOI: 10.1016/j.pt.2016.09.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Revised: 09/05/2016] [Accepted: 09/12/2016] [Indexed: 11/16/2022]
Abstract
Mathematical models of the dynamics of a drug within the host are now frequently used to guide drug development. These generally focus on assessing the efficacy and duration of response to guide patient therapy. Increasingly, antimalarial drugs are used at the population level, to clear infections, provide chemoprevention, and to reduce onward transmission of infection. However, there is less clarity on the extent to which different drug properties are important for these different uses. In addition, the emergence of drug resistance poses new threats to longer-term use and highlights the need for rational drug development. Here, we argue that integrating within-host pharmacokinetic and pharmacodynamic (PK/PD) models with mathematical models for the population-level transmission of malaria is key to guiding optimal drug design to aid malaria elimination.
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Affiliation(s)
- Hannah C Slater
- MRC Centre for Outbreak Analysis & Modelling, Department of Infectious Disease Epidemiology, Imperial College London, UK
| | - Lucy C Okell
- MRC Centre for Outbreak Analysis & Modelling, Department of Infectious Disease Epidemiology, Imperial College London, UK
| | - Azra C Ghani
- MRC Centre for Outbreak Analysis & Modelling, Department of Infectious Disease Epidemiology, Imperial College London, UK.
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31
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Ayieko C, Ogola BS, Ochola L, Ngwena GAM, Ayodo G, Hodges JS, Noland GS, John CC. Interferon- γ responses to Plasmodium falciparum vaccine candidate antigens decrease in the absence of malaria transmission. PeerJ 2017; 5:e2855. [PMID: 28097063 PMCID: PMC5228499 DOI: 10.7717/peerj.2855] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 12/02/2016] [Indexed: 01/29/2023] Open
Abstract
Background Malaria elimination campaigns are planned or active in many countries. The effects of malaria elimination on immune responses such as antigen-specific IFN- γ responses are not well characterized. Methods IFN- γ responses to the P. falciparum antigens circumsporozoite protein, liver stage antigen-1, thrombospondin-related adhesive protein, apical membrane antigen-1, MB2, and merozoite surface protein-1 were tested by ELISA in 243 individuals in highland Kenya in April 2008, October 2008, and April 2009, after a one-year period of interrupted malaria transmission from April 2007 to March 2008. Results While one individual (0.4%) tested positive for P. falciparum by PCR inOctober 2008 and another two (0.9%) tested positive in April 2009, no clinical malaria cases were detected during weekly visits. Levels of IFN-γ to all antigens decreased significantly from April 2008 to April 2009 (all P < 0.001). Discussion Naturally acquired IFN- γ responses to P. falciparum antigensare short-lived in the absence of repeated P. falciparum infection. Even short periods of malaria interruption may significantly decrease IFN-γ responses to P. falciparum antigens.
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Affiliation(s)
- Cyrus Ayieko
- Department of Zoology, Maseno University, Maseno, Kenya
| | - Bilha S Ogola
- Department of Biological Sciences, Masai Mara University, Narok, Kenya
| | - Lyticia Ochola
- Department Biological Sciences, Kabianga University, Kericho, Kenya
| | | | - George Ayodo
- School of Health Sciences, Jaramogi Oginga Odinga University of Science and Technology, Bondo, Kenya
| | - James S Hodges
- School of Public Health, University of Minnesota, Minneapolis, MN, United States
| | - Gregory S Noland
- Medical School, University of Minnesota, Minneapolis, MN, United States
| | - Chandy C John
- Medical School, Indiana University, Indianapolis, IN, United States
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Frank C, Krumkamp R, Sarpong N, Sothmann P, Fobil JN, Foli G, Jaeger A, Ehlkes L, Owusu-Dabo E, Adu-Sarkodie Y, Marks F, Schumann RR, May J, Kreuels B. Spatial heterogeneity of malaria in Ghana: a cross-sectional study on the association between urbanicity and the acquisition of immunity. Malar J 2016; 15:84. [PMID: 26867774 PMCID: PMC4751679 DOI: 10.1186/s12936-016-1138-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 01/29/2016] [Indexed: 11/30/2022] Open
Abstract
Background Malaria incidence has declined considerably over the last decade. This is partly due to a scale-up of control measures but is also attributed to increasing urbanization. This study aimed to analyse the association between malaria and urbanization and the effect of urbanicity on the acquisition of semi-immunity. Methods In 2012, children with fever presenting to St Michael’s Hospital Pramso/Ghana were recruited. The malaria-positive-fraction (MPF) of fever cases was calculated on community-level to approximate the malaria risk. The mean age of malaria cases was calculated for each community to estimate the acquisition of semi-immunity. The level of urbanicity for the communities was calculated and associations between MPF, urbanicity and immunity were modelled using linear regression. Results Twenty-six villages were included into the study with a mean MPF of 35 %. A linear decrease of 5 % (95 % CI: 4–6 %) in MPF with every ten-point increase in urbanicity was identified. The mean age of malaria patients increased by 2.9 months (95 % CI: 1.0–4.8) with every ten-point increase in urbanicity. Discussion The results confirm an association between an increase in urbanicity and declining malaria risk and demonstrate that the acquisition of semi-immunity is heterogeneous on a micro-epidemiological scale and is associated with urbanicity. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1138-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Clemens Frank
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,Institute of Microbiology and Hygiene, Charité-University Medicine, Berlin, Germany.
| | - Ralf Krumkamp
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,German Centre for Infection Research (DZIF), Partner Site Hamburg-Borstel-Lübeck, Hamburg, Germany.
| | - Nimako Sarpong
- Kumasi Centre for Collaborative Research in Tropical Medicine, College of Health Sciences, KNUST, Kumasi, Ghana.
| | - Peter Sothmann
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,Division of Tropical Medicine, 1st Department of Medicine, University Medical Centre Hamburg Eppendorf, Hamburg, Germany.
| | - Julius N Fobil
- School of Public Health, University of Ghana, Accra, Ghana.
| | - Geoffrey Foli
- Kumasi Centre for Collaborative Research in Tropical Medicine, College of Health Sciences, KNUST, Kumasi, Ghana.
| | - Anna Jaeger
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
| | - Lutz Ehlkes
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
| | - Ellis Owusu-Dabo
- Kumasi Centre for Collaborative Research in Tropical Medicine, College of Health Sciences, KNUST, Kumasi, Ghana.
| | - Yaw Adu-Sarkodie
- School of Medical Sciences, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
| | | | - Ralf R Schumann
- Institute of Microbiology and Hygiene, Charité-University Medicine, Berlin, Germany.
| | - Jürgen May
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,German Centre for Infection Research (DZIF), Partner Site Hamburg-Borstel-Lübeck, Hamburg, Germany.
| | - Benno Kreuels
- Research Group Infectious Disease Epidemiology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany. .,German Centre for Infection Research (DZIF), Partner Site Hamburg-Borstel-Lübeck, Hamburg, Germany. .,Division of Tropical Medicine, 1st Department of Medicine, University Medical Centre Hamburg Eppendorf, Hamburg, Germany.
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Galatas B, Bassat Q, Mayor A. Malaria Parasites in the Asymptomatic: Looking for the Hay in the Haystack. Trends Parasitol 2015; 32:296-308. [PMID: 26708404 DOI: 10.1016/j.pt.2015.11.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 11/21/2015] [Accepted: 11/24/2015] [Indexed: 12/11/2022]
Abstract
With malaria elimination back on the international agenda, programs face the challenge of targeting all Plasmodium infections, not only symptomatic cases. As asymptomatic individuals are unlikely to seek treatment, they are missed by passive surveillance while remaining infectious to mosquitoes, thus acting as silent reservoirs of transmission. To estimate the risk of asymptomatic infections in various phases of malaria elimination, we need a deeper understanding of the underlying mechanisms favoring carriage over disease, which may involve both pathogen and host factors. Here we review our current knowledge on the determinants leading to Plasmodium falciparum symptomless infections. Understanding the host-pathogen interactions that are most likely to affect transitions between malaria disease states could guide the development of tools to tackle asymptomatic carriers in elimination settings.
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Affiliation(s)
- Beatriz Galatas
- ISGlobal, Barcelona Centre for International Health Research (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain; Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Quique Bassat
- ISGlobal, Barcelona Centre for International Health Research (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain; Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique
| | - Alfredo Mayor
- ISGlobal, Barcelona Centre for International Health Research (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain; Centro de Investigação em Saúde de Manhiça (CISM), Maputo, Mozambique.
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Helb DA, Tetteh KKA, Felgner PL, Skinner J, Hubbard A, Arinaitwe E, Mayanja-Kizza H, Ssewanyana I, Kamya MR, Beeson JG, Tappero J, Smith DL, Crompton PD, Rosenthal PJ, Dorsey G, Drakeley CJ, Greenhouse B. Novel serologic biomarkers provide accurate estimates of recent Plasmodium falciparum exposure for individuals and communities. Proc Natl Acad Sci U S A 2015; 112:E4438-47. [PMID: 26216993 PMCID: PMC4538641 DOI: 10.1073/pnas.1501705112] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Tools to reliably measure Plasmodium falciparum (Pf) exposure in individuals and communities are needed to guide and evaluate malaria control interventions. Serologic assays can potentially produce precise exposure estimates at low cost; however, current approaches based on responses to a few characterized antigens are not designed to estimate exposure in individuals. Pf-specific antibody responses differ by antigen, suggesting that selection of antigens with defined kinetic profiles will improve estimates of Pf exposure. To identify novel serologic biomarkers of malaria exposure, we evaluated responses to 856 Pf antigens by protein microarray in 186 Ugandan children, for whom detailed Pf exposure data were available. Using data-adaptive statistical methods, we identified combinations of antibody responses that maximized information on an individual's recent exposure. Responses to three novel Pf antigens accurately classified whether an individual had been infected within the last 30, 90, or 365 d (cross-validated area under the curve = 0.86-0.93), whereas responses to six antigens accurately estimated an individual's malaria incidence in the prior year. Cross-validated incidence predictions for individuals in different communities provided accurate stratification of exposure between populations and suggest that precise estimates of community exposure can be obtained from sampling a small subset of that community. In addition, serologic incidence predictions from cross-sectional samples characterized heterogeneity within a community similarly to 1 y of continuous passive surveillance. Development of simple ELISA-based assays derived from the successful selection strategy outlined here offers the potential to generate rich epidemiologic surveillance data that will be widely accessible to malaria control programs.
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Affiliation(s)
- Danica A Helb
- Department of Medicine, University of California, San Francisco, CA 94110; Division of Infectious Diseases, School of Public Health, University of California, Berkeley, CA 94720; Global Health Group, University of California, San Francisco, CA 94158
| | - Kevin K A Tetteh
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
| | - Philip L Felgner
- Division of Infectious Diseases, Department of Medicine, University of California, Irvine, CA 92697
| | - Jeff Skinner
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20852
| | - Alan Hubbard
- Division of Biostatistics, School of Public Health, University of California, Berkeley, CA 94720
| | | | - Harriet Mayanja-Kizza
- Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | | | - Moses R Kamya
- Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda
| | - James G Beeson
- Center for Biomedical Research, Burnet Institute for Medical Research and Public Health, Melbourne, VIC, Canada 3004
| | - Jordan Tappero
- Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333
| | - David L Smith
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom; Sanaria Institute for Global Health and Tropical Medicine, Rockville, MD 20850
| | - Peter D Crompton
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20852
| | - Philip J Rosenthal
- Department of Medicine, University of California, San Francisco, CA 94110
| | - Grant Dorsey
- Department of Medicine, University of California, San Francisco, CA 94110
| | - Christopher J Drakeley
- Department Immunology and Infection, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
| | - Bryan Greenhouse
- Department of Medicine, University of California, San Francisco, CA 94110;
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Pemberton-Ross P, Smith TA, Hodel EM, Kay K, Penny MA. Age-shifting in malaria incidence as a result of induced immunological deficit: a simulation study. Malar J 2015; 14:287. [PMID: 26206255 PMCID: PMC4513612 DOI: 10.1186/s12936-015-0805-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 07/10/2015] [Indexed: 11/10/2022] Open
Abstract
Effective population-level interventions against Plasmodium falciparum malaria lead to age-shifts, delayed morbidity or rebounds in morbidity and mortality whenever they are deployed in ways that do not permanently interrupt transmission. When long-term intervention programmes target specific age-groups of human hosts, the age-specific morbidity rates ultimately adjust to new steady-states, but it is very difficult to study these rates and the temporal dynamics leading up to them empirically because the changes occur over very long time periods. This study investigates the age and magnitude of age- and time- shifting of incidence induced by either pre-erythrocytic vaccination (PEV) programmes or seasonal malaria chemo-prevention (SMC), using an ensemble of individual-based stochastic simulation models of P. falciparum dynamics. The models made various assumptions about immunity decay, transmission heterogeneity and were parameterized with data on both age-specific infection and disease incidence at different levels of exposure, on the durations of different stages of the parasite life-cycle and on human demography. Effects of transmission intensity, and of levels of access to malaria treatment were considered. While both PEV and SMC programmes are predicted to have overall strongly positive health effects, a shift of morbidity into older children is predicted to be induced by either programme if transmission levels remain static and not reduced by other interventions. Predicted shifting of burden continue into the second decade of the programme. Even if long-term surveillance is maintained it will be difficult to avoid mis-attribution of such long-term changes in age-specific morbidity patterns to other factors. Conversely, short-lived transient changes in incidence measured soon after introduction of a new intervention may give over-positive views of future impacts. Complementary intervention strategies could be designed to specifically protect those age-groups at risk from burden shift.
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Affiliation(s)
- Peter Pemberton-Ross
- Swiss Tropical and Public Health Institute, 4002, Basel, Switzerland.
- Universität Basel, 4003, Basel, Switzerland.
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, 4002, Basel, Switzerland.
- Universität Basel, 4003, Basel, Switzerland.
| | - Eva Maria Hodel
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
| | - Katherine Kay
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, 4002, Basel, Switzerland.
- Universität Basel, 4003, Basel, Switzerland.
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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.
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Salvador F, Cossio Y, Riera M, Sánchez-Montalvá A, Bocanegra C, Mendioroz J, Eugenio AN, Sulleiro E, Meredith W, López T, Moreno M, Molina I. Changes in malaria epidemiology in a rural area of Cubal, Angola. Malar J 2015; 14:21. [PMID: 25604647 PMCID: PMC4308942 DOI: 10.1186/s12936-014-0540-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 12/29/2014] [Indexed: 11/20/2022] Open
Abstract
Background Scarce information about malaria epidemiology in Angola has been published. The objective of this study is to describe the epidemiology of malaria at the Hospital Nossa Senhora da Paz (Cubal, Angola) and the fatality rate due to malaria (total and in children under five years) in the last five years. Methods A retrospective, observational study was performed at the Hospital Nossa Senhora da Paz, a 400-bed rural hospital located in Benguela Province of Angola. The study population included all patients who attended the hospital from January 2009 to December 2013. Outcome variables were calculated as follows: the percentage of malaria cases (number of positive thick blood films, divided by the total thick blood films performed); the percentage of in-patients for malaria (number of in-patients diagnosed with malaria, divided by the total number of in-patients); and, the fatality rate (number of deaths due to malaria divided by the number of positive thick blood films). Results Overall, 23,106 thick blood films were performed, of which 3,279 (14.2%) were positive for Plasmodium falciparum infection. During this five-year period, a reduction of 40% (95% CI 37-43%, p < 0.001) in the malaria-positive slides was detected. Distribution of positive-malaria slides showed a seasonal distribution with a peak from December to March (rainy season). An average annual reduction of 52% (95% CI 50-54%, p < 0.001) in the admissions due to malaria was observed. The overall fatality rate due to malaria was 8.3%, and no significant differences in the annual fatality rate were found (p = 0.553). Conclusions A reduction in the number of malaria cases and the number of admissions due to malaria has been observed at the Hospital Nossa Senhora da Paz, during the last five years, and incidence along the study period showed a seasonal distribution. All this information could be useful when deciding which malaria control strategies have to be implemented in this area.
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Affiliation(s)
- Fernando Salvador
- Department of Infectious Diseases, Vall d'Hebron University Hospital, Universitat Autònoma de Barcelona, Barcelona, Spain.
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Färnert A, Wyss K, Dashti S, Naucler P. Duration of residency in a non-endemic area and risk of severe malaria in African immigrants. Clin Microbiol Infect 2014; 21:494-501. [PMID: 25656623 DOI: 10.1016/j.cmi.2014.12.011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 12/06/2014] [Accepted: 12/14/2014] [Indexed: 11/26/2022]
Abstract
In malaria-endemic areas, adults very rarely succumb to severe malaria, suggesting that immunity to severe disease is life-long under conditions of repeated exposure. To what extent this protection persists in the absence of exposure remains to be established. The aim of this study was to assess whether duration of residency in a malaria-free country affects the risk for severe malaria in immigrants originating from sub-Saharan Africa. We conducted a retrospective chart review of 948 cases of malaria diagnosed in Stockholm, Sweden in 1995-2013. Among 501 adult patients with Plasmodium falciparum (315 of endemic origin and 186 of non-endemic origin, mainly Sweden), 41 (8.2%) had severe malaria according to WHO criteria (including 5% with parasitaemia), 22 (4.4%) had factors prognostic of poor outcome, and 35 (7.0%) were admitted to intensive care. Overall, patient origin did not affect the odds of severe malaria, according to any of these definitions. However, when the immigrants were stratified with regard to their duration of residency in Sweden, the risk of factors prognostic for poor outcome was associated with duration of prior residency in a malaria-free country among patients of endemic origin (p 0.02), and immigrants who had lived for ≥ 15 years in Sweden had a similar risk as non-immune travellers. The results of this explorative study suggest that, although immunity to severe malaria is maintained for several years in African adults, this protection might be lost with time without repeated re-exposure. A larger study, preferably including multiple centres, will be needed to confirm our findings.
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Affiliation(s)
- A Färnert
- Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden; Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
| | - K Wyss
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Department of Emergency Medicine, Karolinska University Hospital, Stockholm, Sweden
| | - S Dashti
- Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - P Naucler
- Department of Infectious Diseases, Karolinska University Hospital, Stockholm, Sweden; Infectious Diseases Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
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Segula D, Frosch AP, SanJoaquin M, Taulo D, Skarbinski J, Mathanga DP, Allain TJ, Molyneux M, Laufer MK, Heyderman RS. Prevalence and spectrum of illness among hospitalized adults with malaria in Blantyre, Malawi. Malar J 2014; 13:391. [PMID: 25277278 PMCID: PMC4190438 DOI: 10.1186/1475-2875-13-391] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Accepted: 09/27/2014] [Indexed: 11/30/2022] Open
Abstract
Background As control interventions are rolled out, the burden of malaria may shift from young children to older children and adults as acquisition of immunity is slowed and persistence of immunity is short-lived. Data for malaria disease in adults are difficult to obtain because of co-morbid conditions and because parasitaemia may be asymptomatic. Regular surveys of adult admissions to a hospital in Malawi were conducted to characterize the clinical spectrum of malaria and to establish a baseline to monitor changes that occur in future. Methods In 2011–2012, at Queen Elizabeth Hospital, Blantyre, four separated one-week surveys in the peak malaria transmission period (wet season) and three one-week surveys in the low transmission period (dry season) were conducted using rapid diagnostic tests (RDT) with confirmation of parasitaemia by microscopy. All adults (aged ≥15) being admitted to the adult medical wards regardless of the suspected diagnosis, were enrolled. Participants with a positive malaria test underwent a standardized physical examination and laboratory tests. Malaria syndromes were characterized by reviewing charts and laboratory results on discharge. Results 765 adult admissions were screened. 63 (8.2%) were RDT-positive with 61 (8.0%) positive by microscopy. Over the course of the seven study weeks, two patients were judged to have incidental parasitaemia, 31 (4.1%) had uncomplicated malaria and 28 (3.7%) had severe malaria. Both uncomplicated and severe malaria cases were more common in the rainy season than the dry season. Prostration (22/28 cases) and hyperparasitaemia (>250,000 parasites/μl) (9/28) were the most common features of severe malaria. Jaundice (4/28), severe anaemia (2/28), hyperlactataemia (2/28), shock (1/28) and haemoglobinuria (1/28) were less commonly seen, and no patient had severe metabolic derangement or organ failure. There were no deaths attributable to malaria. Conclusion In this study of adults admitted to hospital in southern Malawi, an area with year-round transmission of Plasmodium falciparum, classical metabolic and organ complications of malaria were not encountered. Prostration and hyperparasitaemia were more common indicators of severity in patients admitted with malaria, none of whom died. These data will provide a baseline for monitoring trends in the frequency and clinical patterns of severe malaria in adults.
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Affiliation(s)
- Dalitso Segula
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, University of Malawi College of Medicine, P,O, Box 30096 Blantyre, Malawi.
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Shayo A, Mandara CI, Shahada F, Buza J, Lemnge MM, Ishengoma DS. Therapeutic efficacy and safety of artemether-lumefantrine for the treatment of uncomplicated falciparum malaria in North-Eastern Tanzania. Malar J 2014; 13:376. [PMID: 25240962 PMCID: PMC4177150 DOI: 10.1186/1475-2875-13-376] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 09/18/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The World Health Organization recommends that regular efficacy monitoring should be undertaken by all malaria endemic countries that have deployed artemisinin combination therapy (ACT). Although ACT is still efficacious for treatment of uncomplicated malaria, artemisinin resistance has been reported in South East Asia suggesting that surveillance needs to be intensified by all malaria endemic countries. This study assessed the efficacy and safety of artemether-lumefantrine (AL) for the treatment of uncomplicated falciparum malaria in Muheza district of north-eastern Tanzania, an area where the transmission has significantly declined in recent years. METHODS Eighty eight children (aged 6 months to 10 years) with uncomplicated falciparum malaria were recruited into the study. The patients were treated with standard doses of AL and followed up for 28 days. The primary end point was parasitological cure on day 28 while the secondary end points included: improvement in haemoglobin levels and occurrence, and severity of adverse events. RESULTS A total of 163 febrile patients were screened, out of which 88 patients (56 under-fives and 32 aged ≥ 5 years) were enrolled and 79 (89.8%) completed the 28 days of follow-up. There were no cases of early treatment failure whilst 40 (78.4%) under-fives and 21(75.0%) older children had adequate clinical and parasitological response (ACPR) before PCR correction. Late clinical failure was seen in 5.6% (n=51) and 3.6% (n=28) of the under-fives and older children respectively; while 15.7% and 21.6% had late parasitological failure in the two groups respectively. After PCR correction, ACPR was 100% in both groups. Reported adverse events included cough (49.7%), fever (20.2%), abdominal pain (10.1%), diarrhoea (1.3%), headache (1.3%) and skin rashes (1.3%). CONCLUSION This study showed that AL was safe, well-tolerated and efficacious for treatment of uncomplicated falciparum malaria. Since Muheza has historically been a hotspot of drug resistance (e.g. pyrimethamine, chloroquine, and SP), surveillance needs to be continued to detect future changes in parasite sensitivity to ACT.
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Affiliation(s)
| | | | | | | | | | - Deus S Ishengoma
- National Institute for Medical Research, Tanga Medical Research Centre, P,O, BOX 5004, Tanga, Tanzania.
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Garira W, Mathebula D, Netshikweta R. A mathematical modelling framework for linked within-host and between-host dynamics for infections with free-living pathogens in the environment. Math Biosci 2014; 256:58-78. [PMID: 25149595 DOI: 10.1016/j.mbs.2014.08.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 07/31/2014] [Accepted: 08/03/2014] [Indexed: 11/16/2022]
Abstract
In this study we develop a mathematical modelling framework for linking the within-host and between-host dynamics of infections with free-living pathogens in the environment. The resulting linked models are sometimes called immuno-epidemiological models. However, there is still no generalised framework for linking the within-host and between-host dynamics of infectious diseases. Furthermore, for infections with free-living pathogens in the environment, there is an additional stumbling block in that there is a gap in knowledge on how environmental factors (through water, air, soil, food, fomites, etc.) alter many aspects of such infections including susceptibility to infective dose, persistence of infection, pathogen shedding and severity of the disease. In this work, we link the two subsystems (within-host and between-host models) by identifying the within-host and between-host variables and parameters associated with the environmental dynamics of the pathogen and then design a feedback of the variables and parameters across the within-host and between-host models using human schistosomiasis as a case study. We study the mathematical properties of the linked model and show that the model is epidemiologically well-posed. Using results from the analysis of the endemic equilibrium expression, the disease reproductive number R0, and numerical simulations of the full model, we adequately account for the reciprocal influence of the linked within-host and between-host models. In particular, we illustrate that for human schistosomiasis, the outcome of infection at the individual level determines if, when and how much the individual host will further transmit the infectious agent into the environment, eventually affecting the spread of the infection in the host population. We expect the conceptual modelling framework developed here to be applicable to many infectious disease with free-living pathogens in the environment beyond the specific disease system of human schistosomiasis considered here.
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Affiliation(s)
- Winston Garira
- Modelling Health and Environmental Linkages Research Group (MHELRG), C/o Department of Mathematics and Applied Mathematics, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa.
| | - Dephney Mathebula
- Modelling Health and Environmental Linkages Research Group (MHELRG), C/o Department of Mathematics and Applied Mathematics, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa
| | - Rendani Netshikweta
- Modelling Health and Environmental Linkages Research Group (MHELRG), C/o Department of Mathematics and Applied Mathematics, University of Venda, Private Bag X5050, Thohoyandou 0950, South Africa
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Modeling malaria infection and immunity against variant surface antigens in Príncipe Island, West Africa. PLoS One 2014; 9:e88110. [PMID: 24520349 PMCID: PMC3919732 DOI: 10.1371/journal.pone.0088110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 01/07/2014] [Indexed: 11/21/2022] Open
Abstract
After remarkable success of vector control campaigns worldwide, concerns about loss of immunity against Plasmodium falciparum due to lack of exposure to the parasite are relevant since an increase of severe cases in less immune individuals is expected. We present a mathematical model to investigate the impact of reducing exposure to the parasite on the immune repertoire against P. falciparum erythrocyte membrane protein 1 (PfEMP1) variants. The model was parameterized with data from Príncipe Island, West Africa, and applied to simulate two alternative transmission scenarios: one where control measures are continued to eventually drive the system to elimination; and another where the effort is interrupted after 6 years of its initiation and the system returns to the initial transmission potential. Population dynamics of parasite prevalence predict that in a few years infection levels return to the pre-control values, while the re-acquisition of the immune repertoire against PfEMP1 is slower, creating a window for increased severity. The model illustrates the consequences of loss of immune repertoire against PfEMP1 in a given setting and can be applied to other regions where similar data may be available.
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Gosling RD, Cairns ME, Chico RM, Chandramohan D. Intermittent preventive treatment against malaria: an update. Expert Rev Anti Infect Ther 2014; 8:589-606. [DOI: 10.1586/eri.10.36] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Lindblade KA, Steinhardt L, Samuels A, Kachur SP, Slutsker L. The silent threat: asymptomatic parasitemia and malaria transmission. Expert Rev Anti Infect Ther 2014; 11:623-39. [PMID: 23750733 DOI: 10.1586/eri.13.45] [Citation(s) in RCA: 338] [Impact Index Per Article: 33.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Scale-up of malaria control interventions has resulted in a substantial decline in global malaria morbidity and mortality. Despite this achievement, there is evidence that current interventions alone will not lead to malaria elimination in most malaria-endemic areas and additional strategies need to be considered. Use of antimalarial drugs to target the reservoir of malaria infection is an option to reduce the transmission of malaria between humans and mosquito vectors. However, a large proportion of human malaria infections are asymptomatic, requiring treatment that is not triggered by care-seeking for clinical illness. This article reviews the evidence that asymptomatic malaria infection plays an important role in malaria transmission and that interventions to target this parasite reservoir may be needed to achieve malaria elimination in both low- and high-transmission areas.
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Affiliation(s)
- Kim A Lindblade
- Malaria Branch, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, 1600 Clifton Rd. NE, MS A-06, Atlanta, GA 30333, USA.
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Tusting LS, Bousema T, Smith DL, Drakeley C. Measuring changes in Plasmodium falciparum transmission: precision, accuracy and costs of metrics. ADVANCES IN PARASITOLOGY 2014; 84:151-208. [PMID: 24480314 PMCID: PMC4847140 DOI: 10.1016/b978-0-12-800099-1.00003-x] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
As malaria declines in parts of Africa and elsewhere, and as more countries move towards elimination, it is necessary to robustly evaluate the effect of interventions and control programmes on malaria transmission. To help guide the appropriate design of trials to evaluate transmission-reducing interventions, we review 11 metrics of malaria transmission, discussing their accuracy, precision, collection methods and costs and presenting an overall critique. We also review the nonlinear scaling relationships between five metrics of malaria transmission: the entomological inoculation rate, force of infection, sporozoite rate, parasite rate and the basic reproductive number, R0. Our chapter highlights that while the entomological inoculation rate is widely considered the gold standard metric of malaria transmission and may be necessary for measuring changes in transmission in highly endemic areas, it has limited precision and accuracy and more standardised methods for its collection are required. In areas of low transmission, parasite rate, seroconversion rates and molecular metrics including MOI and mFOI may be most appropriate. When assessing a specific intervention, the most relevant effects will be detected by examining the metrics most directly affected by that intervention. Future work should aim to better quantify the precision and accuracy of malaria metrics and to improve methods for their collection.
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Affiliation(s)
- Lucy S Tusting
- Department of Disease Control, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Teun Bousema
- Department of Infection and Immunity, London School of Hygiene and Tropical Medicine, London, United Kingdom; Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | - David L Smith
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA; Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA; Fogarty International Center, NIH, Bethesda, Maryland, USA.
| | - Chris Drakeley
- Department of Infection and Immunity, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Supargiyono S, Bretscher MT, Wijayanti MA, Sutanto I, Nugraheni D, Rozqie R, Kosasih AA, Sulistyawati S, Hawley WA, Lobo NF, Cook J, Drakeley CJ. Seasonal changes in the antibody responses against Plasmodium falciparum merozoite surface antigens in areas of differing malaria endemicity in Indonesia. Malar J 2013; 12:444. [PMID: 24321092 PMCID: PMC3866602 DOI: 10.1186/1475-2875-12-444] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Accepted: 12/04/2013] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND The transmission of malaria in Indonesia is highly heterogeneous spatially and seasonally. Anti-malaria antibody responses can help characterize this variation. In the present study antibody responses to Plasmodium falciparum MSP-1 and AMA-1 were measured to assess the transmission intensity in a hypo-endemic area of Purworejo and a meso-endemic area of Lampung during low and high transmission seasons. METHODS Filter-paper blood spot samples collected from Purworejo and Lampung by cross-sectional survey during high and low transmission season were stored at -20°C. Indirect ELISA assays were carried out using PfMSP1-19 and PfAMA1 antigens. A positivity threshold was determined by samples from local unexposed individuals, and the differences in seroprevalence, antibody level and correlation between antibody level and age in each site were statistically analysed. RESULTS Prevalence of antibodies to either PfMSP1-19 or PfAMA1 was higher in Lampung than in Purworejo in both the low (51.3 vs 25.0%) and high transmission season (53.9 vs 37.5%). The magnitude of antibody responses was associated with increasing age in both sites and was higher in Lampung. Age-adjusted seroconversion rates showed an approximately ten-fold difference between Lampung and Purowejo. Two different seroconversion rates were estimated for Lampung suggesting behaviour-related differences in exposure. In both settings antibody responses to PfMSP1-19 were significantly lower in the low season compared to the high season. CONCLUSION Seasonal changes may be detectable by changes in antibody responses. This is particularly apparent in lower transmission settings and with less immunogenic antigens (in this case PfMSP1-19). Examination of antibody levels rather than seroprevalence is likely to be a more sensitive indicator of changes in transmission. These data suggest that sero-epidemiological analysis may have a role in assessing short-term changes in exposure especially in low or seasonal transmission settings.
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Affiliation(s)
- Supargiyono Supargiyono
- Center for Tropical Medicine, Faculty of Medicine, Gadjah Mada University, Jln Teknika Utara, Barek, Yogyakarta 55281, Indonesia
| | - Michael T Bretscher
- MRC Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, St Mary’s Campus, Norfolk Place, London W2 1PG, UK
| | - Mahardika A Wijayanti
- Center for Tropical Medicine, Faculty of Medicine, Gadjah Mada University, Jln Teknika Utara, Barek, Yogyakarta 55281, Indonesia
| | - Inge Sutanto
- Department of Parasitology Faculty of Medicine, University of Indonesia, Jln Salemba Raya, Jakarta, Indonesia
| | - Dian Nugraheni
- Center for Tropical Medicine, Faculty of Medicine, Gadjah Mada University, Jln Teknika Utara, Barek, Yogyakarta 55281, Indonesia
| | - Royhan Rozqie
- Center for Tropical Medicine, Faculty of Medicine, Gadjah Mada University, Jln Teknika Utara, Barek, Yogyakarta 55281, Indonesia
| | - Ayleen A Kosasih
- Department of Parasitology Faculty of Medicine, University of Indonesia, Jln Salemba Raya, Jakarta, Indonesia
| | - Sulistyawati Sulistyawati
- Center for Tropical Medicine, Faculty of Medicine, Gadjah Mada University, Jln Teknika Utara, Barek, Yogyakarta 55281, Indonesia
- Department of Public Health Science, Faulty of Public Health, Ahmad Dahlan University, Jln Prof Dr Soepomo, Warungboto, Umbulharjo, Yogyakarta, Indonesia
| | | | - Neil F Lobo
- Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Jackie Cook
- Malaria Research Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
| | - Chris J Drakeley
- Department of Immunology & Infection, London School of Hygiene and Tropical Medicine, London W1CE 7HT, UK
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Aidoo M. Factoring quality laboratory diagnosis into the malaria control agenda for sub-Saharan Africa. Am J Trop Med Hyg 2013; 89:403-6. [PMID: 24006294 DOI: 10.4269/ajtmh.13-0108] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Recent progress in malaria control in sub-Saharan Africa has been achieved primarily through provision of insecticide-treated nets, indoor residual spraying, and antimalarial drugs. Although these interventions are important, proper case identification and accurate measurement of their impact depend on quality diagnostic testing. Current availability of diagnostic testing for malaria in sub-Saharan Africa is inadequate to support disease management, prevention programs, and surveillance needs. Challenges faced include a dearth of skilled workforce, inadequate health systems infrastructure, and lack of political will. A coordinated approach to providing pre-service clinical and laboratory training together with systems that support a scale-up of laboratory services could provide means not only for effective malaria case management but also, management of non-malaria febrile illnesses, disease surveillance, and accurate control program evaluation. A synthesis of the challenges faced in ensuring quality malaria testing and how to include this information in the malaria control and elimination agenda are presented.
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Affiliation(s)
- Michael Aidoo
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
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Briët OJ, Penny MA. Repeated mass distributions and continuous distribution of long-lasting insecticidal nets: modelling sustainability of health benefits from mosquito nets, depending on case management. Malar J 2013; 12:401. [PMID: 24200296 PMCID: PMC4228503 DOI: 10.1186/1475-2875-12-401] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 11/04/2013] [Indexed: 11/10/2022] Open
Abstract
Background Stagnating funds for malaria control have spurred interest in the question of how to sustain the gains of recent successes with long-lasting insecticidal nets (LLINs) and improved case management (CM). This simulation study examined the malaria transmission and disease dynamics in scenarios with sustained LLINs and CM interventions and tried to determine optimal LLIN distribution rates. The effects of abruptly halting LLIN distribution were also examined. Methods Dynamic simulations of malaria in humans and mosquitoes were run on the OpenMalaria platform, using stochastic individual-based simulation models. LLINs were distributed in a range of transmission settings, with varying CM coverage levels. Results In the short-term, LLINs were beneficial over the entire transmission spectrum, reducing both transmission and disease burden. In the long-term, repeated distributions sustainably reduced transmission in all settings. However, because of the resulting reduction in acquired immunity in the population, the malaria disease burden, after initially being reduced, gradually increased and eventually stabilized at a new level. This new level was higher than the pre-intervention level in previously high transmission settings, if there is a maximum disease burden in the relationship between transmission and disease burden at intermediate transmission levels. This result could lead one to conclude that sustained LLIN distribution might not be cost-effective in high transmission settings in the long term. However, improved CM rendered LLINs more cost-effective in higher transmission settings than in those without improved CM and the majority of the African population lives in areas where CM and LLINs are sustainably combined. The effects of changes in LLIN distribution rate on cost-effectiveness were relatively small compared to the effects of changes in transmission setting and CM. Abruptly halting LLIN distribution led to temporary morbidity peaks, which were particularly large in low to intermediate transmission settings. Conclusions This study reaffirms the importance of context specific intervention planning. Intervention planning must include combinations of malaria vector control and CM, and must consider both the pre-intervention transmission level and the intervention history to account for the loss of immunity and the potential for rebounds in disease burden.
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Affiliation(s)
- Olivier Jt Briët
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
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David AS, Kaser JM, Morey AC, Roth AM, Andow DA. Release of genetically engineered insects: a framework to identify potential ecological effects. Ecol Evol 2013; 3:4000-15. [PMID: 24198955 PMCID: PMC3810890 DOI: 10.1002/ece3.737] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 07/14/2013] [Accepted: 07/15/2013] [Indexed: 12/19/2022] Open
Abstract
Genetically engineered (GE) insects have the potential to radically change pest management worldwide. With recent approvals of GE insect releases, there is a need for a synthesized framework to evaluate their potential ecological and evolutionary effects. The effects may occur in two phases: a transitory phase when the focal population changes in density, and a steady state phase when it reaches a new, constant density. We review potential effects of a rapid change in insect density related to population outbreaks, biological control, invasive species, and other GE organisms to identify a comprehensive list of potential ecological and evolutionary effects of GE insect releases. We apply this framework to the Anopheles gambiae mosquito - a malaria vector being engineered to suppress the wild mosquito population - to identify effects that may occur during the transitory and steady state phases after release. Our methodology reveals many potential effects in each phase, perhaps most notably those dealing with immunity in the transitory phase, and with pathogen and vector evolution in the steady state phase. Importantly, this framework identifies knowledge gaps in mosquito ecology. Identifying effects in the transitory and steady state phases allows more rigorous identification of the potential ecological effects of GE insect release.
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Affiliation(s)
- Aaron S David
- Department of Ecology, Evolution, and Behavior, University of Minnesota St. Paul, Minnesota, 55108, USA
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Ishengoma DS, Mmbando BP, Segeja MD, Alifrangis M, Lemnge MM, Bygbjerg IC. Declining burden of malaria over two decades in a rural community of Muheza district, north-eastern Tanzania. Malar J 2013; 12:338. [PMID: 24053121 PMCID: PMC3850962 DOI: 10.1186/1475-2875-12-338] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 09/18/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The recently reported declining burden of malaria in some African countries has been attributed to scaling-up of different interventions although in some areas, these changes started before implementation of major interventions. This study assessed the long-term trends of malaria burden for 20 years (1992-2012) in Magoda and for 15 years in Mpapayu village of Muheza district, north-eastern Tanzania, in relation to different interventions as well as changing national malaria control policies. METHODS Repeated cross-sectional surveys recruited individuals aged 0 - 19 years from the two villages whereby blood smears were collected for detection of malaria parasites by microscopy. Prevalence of Plasmodium falciparum infections and other indices of malaria burden (prevalence of anaemia, splenomegaly and gametocytes) were compared across the years and between the study villages. Major interventions deployed including a mobile clinic, bed nets and other research activities, and changes in national malaria control policies were also marked. RESULTS In Magoda, the prevalence of P. falciparum infections initially decreased between 1992 and 1996 (from 83.5 to 62.0%), stabilized between 1996 and 1997, and further declined to 34.4% in 2004. A temporary increase between 2004 and 2008 was followed by a progressive decline to 7.2% in 2012, which is more than 10-fold decrease since 1992. In Mpapayu (from 1998), the highest prevalence was 81.5% in 1999 and it decreased to 25% in 2004. After a slight increase in 2008, a steady decline followed, reaching <5% from 2011 onwards. Bed net usage was high in both villages from 1999 to 2004 (≥88%) but it decreased between 2008 and 2012 (range, 28% - 68%). After adjusting for the effects of bed nets, age, fever and year of study, the risk of P. falciparum infections decreased significantly by ≥97% in both villages between 1999 and 2012 (p < 0.001). The prevalence of splenomegaly (>40% to <1%) and gametocytes (23% to <1%) also decreased in both villages. DISCUSSION AND CONCLUSIONS A remarkable decline in the burden of malaria occurred between 1992 and 2012 and the initial decline (1992 - 2004) was most likely due to deployment of interventions, such as bed nets, and better services through research activities. Apart from changes of drug policies, the steady decline observed from 2008 occurred when bed net coverage was low suggesting that other factors contributed to the most recent pattern. These results suggest that continued monitoring is required to determine causes of the changing malaria epidemiology and also to monitor the progress towards maintaining low malaria transmission and reaching related millennium development goals.
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Affiliation(s)
- Deus S Ishengoma
- National Institute for Medical Research, Tanga Medical Research Centre, P,O Box 5004, Tanga, Tanzania.
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