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Kanyal A, Deshmukh B, Davies H, Mamatharani DV, Farheen D, Treeck M, Karmodiya K. PfHDAC1 is an essential regulator of P. falciparum asexual proliferation and host cell invasion genes with a dynamic genomic occupancy responsive to artemisinin stress. mBio 2024; 15:e0237723. [PMID: 38709067 PMCID: PMC11237754 DOI: 10.1128/mbio.02377-23] [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: 09/01/2023] [Accepted: 03/26/2024] [Indexed: 05/07/2024] Open
Abstract
Plasmodium falciparum, the deadly protozoan parasite responsible for malaria, has a tightly regulated gene expression profile closely linked to its intraerythrocytic development cycle. Epigenetic modifiers of the histone acetylation code have been identified as key regulators of the parasite's transcriptome but require further investigation. In this study, we map the genomic distribution of Plasmodium falciparum histone deacetylase 1 (PfHDAC1) across the erythrocytic asexual development cycle and find it has a dynamic occupancy over a wide array of developmentally relevant genes. Overexpression of PfHDAC1 results in a progressive increment in parasite load over consecutive rounds of the asexual infection cycle and is associated with enhanced gene expression of multiple families of host cell invasion factors (merozoite surface proteins, rhoptry proteins, etc.) and with increased merozoite invasion efficiency. With the use of class-specific inhibitors, we demonstrate that PfHDAC1 activity in parasites is crucial for timely intraerythrocytic development. Interestingly, overexpression of PfHDAC1 results in decreased sensitivity to frontline-drug dihydroartemisinin in parasites. Furthermore, we identify that artemisinin exposure can interfere with PfHDAC1 abundance and chromatin occupancy, resulting in enrichment over genes implicated in response/resistance to artemisinin. Finally, we identify that dihydroartemisinin exposure can interrupt the in vitro catalytic deacetylase activity and post-translational phosphorylation of PfHDAC1, aspects that are crucial for its genomic function. Collectively, our results demonstrate PfHDAC1 to be a regulator of critical functions in asexual parasite development and host invasion, which is responsive to artemisinin exposure stress and deterministic of resistance to it. IMPORTANCE Malaria is a major public health problem, with the parasite Plasmodium falciparum causing most of the malaria-associated mortality. It is spread by the bite of infected mosquitoes and results in symptoms such as cyclic fever, chills, and headache. However, if left untreated, it can quickly progress to a more severe and life-threatening form. The World Health Organization currently recommends the use of artemisinin combination therapy, and it has worked as a gold standard for many years. Unfortunately, certain countries in southeast Asia and Africa, burdened with a high prevalence of malaria, have reported cases of drug-resistant infections. One of the major problems in controlling malaria is the emergence of artemisinin resistance. Population genomic studies have identified mutations in the Kelch13 gene as a molecular marker for artemisinin resistance. However, several reports thereafter indicated that Kelch13 is not the main mediator but rather hinted at transcriptional deregulation as a major determinant of drug resistance. Earlier, we identified PfGCN5 as a global regulator of stress-responsive genes, which are known to play a central role in artemisinin resistance generation. In this study, we have identified PfHDAC1, a histone deacetylase as a cell cycle regulator, playing an important role in artemisinin resistance generation. Taken together, our study identified key transcriptional regulators that play an important role in artemisinin resistance generation.
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Affiliation(s)
- Abhishek Kanyal
- Department of Biology, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, India
| | - Bhagyashree Deshmukh
- Department of Biology, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, India
| | - Heledd Davies
- Signalling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, London, United Kingdom
| | - D. V. Mamatharani
- Department of Biology, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, India
| | - Dilsha Farheen
- Department of Biology, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, India
| | - Moritz Treeck
- Signalling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, London, United Kingdom
| | - Krishanpal Karmodiya
- Department of Biology, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, India
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De Salazar PM, Kamau A, Cavelan A, Akech S, Mpimbaza A, Snow RW, Penny MA. Severe outcomes of malaria in children under time-varying exposure. Nat Commun 2024; 15:4069. [PMID: 38744878 PMCID: PMC11094066 DOI: 10.1038/s41467-024-48191-7] [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: 08/31/2023] [Accepted: 04/22/2024] [Indexed: 05/16/2024] Open
Abstract
In malaria epidemiology, interpolation frameworks based on available observations are critical for policy decisions and interpreting disease burden. Updating our understanding of the empirical evidence across different populations, settings, and timeframes is crucial to improving inference for supporting public health. Here, via individual-based modeling, we evaluate a large, multicountry, contemporary Plasmodium falciparum severe malaria dataset to better understand the relationship between prevalence and incidence of malaria pediatric hospitalizations - a proxy of malaria severe outcomes- in East-Africa. We find that life-long exposure dynamics, and subsequent protection patterns in children, substantially determine the likelihood of malaria hospitalizations relative to ongoing prevalence at the population level. Unsteady transmission patterns over a lifetime in children -increasing or decreasing- lead to an exponential relationship of hospitalization rates versus prevalence rather than the asymptotic pattern observed under steady transmission. Addressing this increase in the complexity of malaria epidemiology is crucial to update burden assessments via inference models that guide current and future policy decisions.
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Affiliation(s)
- Pablo M De Salazar
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Alice Kamau
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Aurelien Cavelan
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Allschwil, Switzerland
- University of Basel, Basel, Switzerland
| | - Samuel Akech
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya
| | - Arthur Mpimbaza
- Child Health and Development Centre, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Robert W Snow
- Kenya Medical Research Institute (KEMRI)-Wellcome Trust Research Programme, Nairobi, Kenya
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Melissa A Penny
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Allschwil, Switzerland.
- University of Basel, Basel, Switzerland.
- Telethon Kids Institute, Nedlands, WA, Australia.
- Centre for Child Health Research, University of Western Australia, Crawley, WA, Australia.
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Ozodiegwu ID, Ambrose M, Galatas B, Runge M, Nandi A, Okuneye K, Dhanoa NP, Maikore I, Uhomoibhi P, Bever C, Noor A, Gerardin J. Application of mathematical modelling to inform national malaria intervention planning in Nigeria. Malar J 2023; 22:137. [PMID: 37101146 PMCID: PMC10130303 DOI: 10.1186/s12936-023-04563-w] [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: 12/01/2022] [Accepted: 04/15/2023] [Indexed: 04/28/2023] Open
Abstract
BACKGROUND For their 2021-2025 National Malaria Strategic Plan (NMSP), Nigeria's National Malaria Elimination Programme (NMEP), in partnership with the World Health Organization (WHO), developed a targeted approach to intervention deployment at the local government area (LGA) level as part of the High Burden to High Impact response. Mathematical models of malaria transmission were used to predict the impact of proposed intervention strategies on malaria burden. METHODS An agent-based model of Plasmodium falciparum transmission was used to simulate malaria morbidity and mortality in Nigeria's 774 LGAs under four possible intervention strategies from 2020 to 2030. The scenarios represented the previously implemented plan (business-as-usual), the NMSP at an 80% or higher coverage level and two prioritized plans according to the resources available to Nigeria. LGAs were clustered into 22 epidemiological archetypes using monthly rainfall, temperature suitability index, vector abundance, pre-2010 parasite prevalence, and pre-2010 vector control coverage. Routine incidence data were used to parameterize seasonality in each archetype. Each LGA's baseline malaria transmission intensity was calibrated to parasite prevalence in children under the age of five years measured in the 2010 Malaria Indicator Survey (MIS). Intervention coverage in the 2010-2019 period was obtained from the Demographic and Health Survey, MIS, the NMEP, and post-campaign surveys. RESULTS Pursuing a business-as-usual strategy was projected to result in a 5% and 9% increase in malaria incidence in 2025 and 2030 compared with 2020, while deaths were projected to remain unchanged by 2030. The greatest intervention impact was associated with the NMSP scenario with 80% or greater coverage of standard interventions coupled with intermittent preventive treatment in infants and extension of seasonal malaria chemoprevention (SMC) to 404 LGAs, compared to 80 LGAs in 2019. The budget-prioritized scenario with SMC expansion to 310 LGAs, high bed net coverage with new formulations, and increase in effective case management rate at the same pace as historical levels was adopted as an adequate alternative for the resources available. CONCLUSIONS Dynamical models can be applied for relative assessment of the impact of intervention scenarios but improved subnational data collection systems are required to allow increased confidence in predictions at sub-national level.
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Affiliation(s)
- Ifeoma D Ozodiegwu
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA.
| | | | - Beatriz Galatas
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | - Manuela Runge
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Aadrita Nandi
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Kamaldeen Okuneye
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
| | - Neena Parveen Dhanoa
- Weinberg College of Arts and Sciences, Northwestern University, Evanston, IL, USA
| | - Ibrahim Maikore
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | | | | | - Abdisalan Noor
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | - Jaline Gerardin
- Department of Preventive Medicine and Institute for Global Health, Northwestern University, Chicago, IL, USA
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4
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Otiende M, Bauni E, Nyaguara A, Amadi D, Nyundo C, Tsory E, Walumbe D, Kinuthia M, Kihuha N, Kahindi M, Nyutu G, Moisi J, Deribew A, Agweyu A, Marsh K, Tsofa B, Bejon P, Bottomley C, Williams TN, Scott JAG. Mortality in rural coastal Kenya measured using the Kilifi Health and Demographic Surveillance System: a 16-year descriptive analysis. Wellcome Open Res 2023; 6:327. [PMID: 37416502 PMCID: PMC10320326 DOI: 10.12688/wellcomeopenres.17307.2] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/06/2023] [Indexed: 10/30/2023] Open
Abstract
Background: The Kilifi Health and Demographic Surveillance System (KHDSS) was established in 2000 to define the incidence and prevalence of local diseases and evaluate the impact of community-based interventions. KHDSS morbidity data have been reported comprehensively but mortality has not been described. This analysis describes mortality in the KHDSS over 16 years. Methods: We calculated mortality rates from 2003-2018 in four intervals of equal duration and assessed differences in mortality across these intervals by age and sex. We calculated the period survival function and median survival using the Kaplan-Meier method and mean life expectancies using abridged life tables. We estimated trend and seasonality by decomposing a time series of monthly mortality rates. We used choropleth maps and random-effects Poisson regression to investigate geographical heterogeneity. Results: Mortality declined by 36% overall between 2003-2018 and by 59% in children aged <5 years. Most of the decline occurred between 2003 and 2006. Among adults, the greatest decline (49%) was observed in those aged 15-54 years. Life expectancy at birth increased by 12 years. Females outlived males by 6 years. Seasonality was only evident in the 1-4 year age group in the first four years. Geographical variation in mortality was ±10% of the median value and did not change over time. Conclusions: Between 2003 and 2018, mortality among children and young adults has improved substantially. The steep decline in 2003-2006 followed by a much slower reduction thereafter suggests improvements in health and wellbeing have plateaued in the last 12 years. However, there is substantial inequality in mortality experience by geographical location.
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Affiliation(s)
- Mark Otiende
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Evasius Bauni
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Amek Nyaguara
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - David Amadi
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Christopher Nyundo
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Emmanuel Tsory
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - David Walumbe
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Michael Kinuthia
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Norbert Kihuha
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Michael Kahindi
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Gideon Nyutu
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Jennifer Moisi
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Amare Deribew
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Ambrose Agweyu
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Kevin Marsh
- Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Benjamin Tsofa
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - Philip Bejon
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
- Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK
| | - Christian Bottomley
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Thomas N. Williams
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
| | - J. Anthony G. Scott
- Epidemiology and Demography, KEMRI-Wellcome Trust Research Programme, Kilifi, 80108, Kenya
- Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
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5
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Okell LC, Kwambai TK, Dhabangi A, Khairallah C, Nkosi-Gondwe T, Winskill P, Opoka R, Mousa A, Kühl MJ, Lucas TCD, Challenger JD, Idro R, Weiss DJ, Cairns M, Ter Kuile FO, Phiri K, Robberstad B, Mori AT. Projected health impact of post-discharge malaria chemoprevention among children with severe malarial anaemia in Africa. Nat Commun 2023; 14:402. [PMID: 36697413 PMCID: PMC9876927 DOI: 10.1038/s41467-023-35939-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 01/09/2023] [Indexed: 01/26/2023] Open
Abstract
Children recovering from severe malarial anaemia (SMA) remain at high risk of readmission and death after discharge from hospital. However, a recent trial found that post-discharge malaria chemoprevention (PDMC) with dihydroartemisinin-piperaquine reduces this risk. We developed a mathematical model describing the daily incidence of uncomplicated and severe malaria requiring readmission among 0-5-year old children after hospitalised SMA. We fitted the model to a multicentre clinical PDMC trial using Bayesian methods and modelled the potential impact of PDMC across malaria-endemic African countries. In the 20 highest-burden countries, we estimate that only 2-5 children need to be given PDMC to prevent one hospitalised malaria episode, and less than 100 to prevent one death. If all hospitalised SMA cases access PDMC in moderate-to-high transmission areas, 38,600 (range 16,900-88,400) malaria-associated readmissions could be prevented annually, depending on access to hospital care. We estimate that recurrent SMA post-discharge constitutes 19% of all SMA episodes in moderate-to-high transmission settings.
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Affiliation(s)
- Lucy C Okell
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College, London, W2 1PG, UK.
| | - Titus K Kwambai
- Centre for Global Health Research (CGHR), Kenya Medical Research Institute (KEMRI), Kisumu, Kenya
- Department of Clinical Sciences, Liverpool School of Tropical Medicine (LSTM), Liverpool, UK
| | - Aggrey Dhabangi
- College of Health Sciences, Makerere University, Kampala, Uganda
| | - Carole Khairallah
- Department of Clinical Sciences, Liverpool School of Tropical Medicine (LSTM), Liverpool, UK
| | - Thandile Nkosi-Gondwe
- Kamuzu University of Health Sciences, Blantyre, Malawi
- Training and Research Unit of Excellence, Blantyre, Malawi
| | - Peter Winskill
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College, London, W2 1PG, UK
| | - Robert Opoka
- College of Health Sciences, Makerere University, Kampala, Uganda
| | - Andria Mousa
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College, London, W2 1PG, UK
| | - Melf-Jakob Kühl
- Section for Ethics and Health Economics, Department of Global Public Health and Primary Care, University of Bergen, P.O. Box 7804, 5020, Bergen, Norway
| | - Tim C D Lucas
- Big Data Institute, University of Oxford, Oxford, UK
| | - Joseph D Challenger
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College, London, W2 1PG, UK
| | - Richard Idro
- College of Health Sciences, Makerere University, Kampala, Uganda
| | - Daniel J Weiss
- Malaria Atlas Project, Telethon Kids Institute, Perth Children's Hospital, 15 Hospital Avenue, Nedlands, Australia
- Curtin University, Bentley, Australia
| | - Matthew Cairns
- International Statistics and Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | - Feiko O Ter Kuile
- Centre for Global Health Research (CGHR), Kenya Medical Research Institute (KEMRI), Kisumu, Kenya
- Department of Clinical Sciences, Liverpool School of Tropical Medicine (LSTM), Liverpool, UK
| | - Kamija Phiri
- Kamuzu University of Health Sciences, Blantyre, Malawi
- Training and Research Unit of Excellence, Blantyre, Malawi
| | - Bjarne Robberstad
- Section for Ethics and Health Economics, Department of Global Public Health and Primary Care, University of Bergen, P.O. Box 7804, 5020, Bergen, Norway
| | - Amani Thomas Mori
- Section for Ethics and Health Economics, Department of Global Public Health and Primary Care, University of Bergen, P.O. Box 7804, 5020, Bergen, Norway.
- Chr. Michelsen Institute, P.O. Box 6033, N-5892, Bergen, Norway.
- Muhimbili University of Health and Allied Sciences, P.O.Box 65001, Dar es Salaam, Tanzania.
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Masserey T, Lee T, Golumbeanu M, Shattock AJ, Kelly SL, Hastings IM, Penny MA. The influence of biological, epidemiological, and treatment factors on the establishment and spread of drug-resistant Plasmodium falciparum. eLife 2022; 11:e77634. [PMID: 35796430 PMCID: PMC9262398 DOI: 10.7554/elife.77634] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2022] [Accepted: 06/22/2022] [Indexed: 11/13/2022] Open
Abstract
The effectiveness of artemisinin-based combination therapies (ACTs) to treat Plasmodium falciparum malaria is threatened by resistance. The complex interplay between sources of selective pressure-treatment properties, biological factors, transmission intensity, and access to treatment-obscures understanding how, when, and why resistance establishes and spreads across different locations. We developed a disease modelling approach with emulator-based global sensitivity analysis to systematically quantify which of these factors drive establishment and spread of drug resistance. Drug resistance was more likely to evolve in low transmission settings due to the lower levels of (i) immunity and (ii) within-host competition between genotypes. Spread of parasites resistant to artemisinin partner drugs depended on the period of low drug concentration (known as the selection window). Spread of partial artemisinin resistance was slowed with prolonged parasite exposure to artemisinin derivatives and accelerated when the parasite was also resistant to the partner drug. Thus, to slow the spread of partial artemisinin resistance, molecular surveillance should be supported to detect resistance to partner drugs and to change ACTs accordingly. Furthermore, implementing more sustainable artemisinin-based therapies will require extending parasite exposure to artemisinin derivatives, and mitigating the selection windows of partner drugs, which could be achieved by including an additional long-acting drug.
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Affiliation(s)
- Thiery Masserey
- Swiss Tropical and Public Health InstituteAllschwilSwitzerland
- University of BaselBaselSwitzerland
| | - Tamsin Lee
- Swiss Tropical and Public Health InstituteAllschwilSwitzerland
- University of BaselBaselSwitzerland
| | - Monica Golumbeanu
- Swiss Tropical and Public Health InstituteAllschwilSwitzerland
- University of BaselBaselSwitzerland
| | - Andrew J Shattock
- Swiss Tropical and Public Health InstituteAllschwilSwitzerland
- University of BaselBaselSwitzerland
| | - Sherrie L Kelly
- Swiss Tropical and Public Health InstituteAllschwilSwitzerland
- University of BaselBaselSwitzerland
| | - Ian M Hastings
- Liverpool School of Tropical MedicineLiverpoolUnited Kingdom
| | - Melissa A Penny
- Swiss Tropical and Public Health InstituteAllschwilSwitzerland
- University of BaselBaselSwitzerland
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Nadeem AY, Shehzad A, Islam SU, Al-Suhaimi EA, Lee YS. Mosquirix™ RTS, S/AS01 Vaccine Development, Immunogenicity, and Efficacy. Vaccines (Basel) 2022; 10:vaccines10050713. [PMID: 35632469 PMCID: PMC9143879 DOI: 10.3390/vaccines10050713] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 04/11/2022] [Accepted: 04/17/2022] [Indexed: 12/10/2022] Open
Abstract
Malaria is a parasitic infection caused by bites from Plasmodium falciparum (P. falciparum)-infected mosquitoes with a present scale of symptoms ranging from moderate fever to neurological disorders. P. falciparum is the most lethal of the five strains of malaria, and is a major case of morbidity and mortality in endemic regions. Recent advancements in malaria diagnostic tools and prevention strategies have improved conjugation antimalarial therapies using fumigation and long-lasting insecticidal sprays, thus lowering malarial infections. Declines in the total number of infected individuals have been correlated with antimalarial drugs. Despite this, malaria remains a major health threat, affecting more than 30 million men, women, and children around the globe, and 20 percent of all children around the globe have malaria parasites in their blood. To overcome this life-threatening condition, novel therapeutic strategies, including immunization, are urgently needed to tackle this infection around the world. In line with this, the development of the RTS, S vaccine was a significant step forward in the fight against malaria. RTS, S is a vaccine for P. falciparum in which R specifies central repeat units, T the T-cell epitopes, and S indicates surface antigen. The RTS, S/AS01 malarial vaccine was synthesized and screened in several clinical trials between 2009 and 2014, involving thousands of young children in seven African countries, showing that children who received the vaccine did not suffer from severe malaria. Mosquirix™ was approved by the World Health Organization in 2021, indicating it to be safe and advocating its integration into routine immunization programs and existing malaria control measures. This paper examines the various stages of the vaccine’s development, including the evaluation of its immunogenicity and efficacy on the basis of a total of 2.3 million administered doses through a routine immunization program. The protection and effectiveness provided by the vaccine are strong, and evidence shows that it can be effectively delivered through the routine child immunization platform. The economic cost of the vaccine remains to be considered.
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Affiliation(s)
- Aroosa Younis Nadeem
- Department of Biomedical Sciences, School of Mechanical and Manufacturing Engineering (SMME), National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan; (A.Y.N.); (A.S.)
| | - Adeeb Shehzad
- Department of Biomedical Sciences, School of Mechanical and Manufacturing Engineering (SMME), National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan; (A.Y.N.); (A.S.)
| | - Salman Ul Islam
- Department of Pharmacy, CECOS University, Peshawar 25000, Pakistan;
| | - Ebtesam A. Al-Suhaimi
- Biology Department, College of Science and Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia;
| | - Young Sup Lee
- BK21 FOUR KNU Creative BioResearch Group, School of Life Sciences, College of Natural Sciences, Kyungpook National University, Daegu 41566, Korea
- Correspondence: ; Tel.: +82-53-950-6353; Fax: +82-53-943-2762
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8
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Otiende M, Bauni E, Nyaguara A, Amadi D, Nyundo C, Tsory E, Walumbe D, Kinuthia M, Kihuha N, Kahindi M, Nyutu G, Moisi J, Deribew A, Agweyu A, Marsh K, Tsofa B, Bejon P, Bottomley C, Williams TN, Scott JAG. Mortality in rural coastal Kenya measured using the Kilifi Health and Demographic Surveillance System: a 16-year descriptive analysis. Wellcome Open Res 2021. [DOI: 10.12688/wellcomeopenres.17307.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Background: The Kilifi Health and Demographic Surveillance System (KHDSS) was established in 2000 to define the incidence and prevalence of local diseases and evaluate the impact of community-based interventions. KHDSS morbidity data have been reported comprehensively but mortality has not been described. This analysis describes mortality in the KHDSS over 16 years. Methods: We calculated mortality rates from 2003–2018 in four intervals of equal duration and assessed differences in mortality across these intervals by age and sex. We calculated the period survival function and median survival using the Kaplan–Meier method and mean life expectancies using abridged life tables. We estimated trend and seasonality by decomposing a time series of monthly mortality rates. We used choropleth maps and random-effects Poisson regression to investigate geographical heterogeneity. Results: Mortality declined by 36% overall between 2003–2018 and by 59% in children aged <5 years. Most of the decline occurred between 2003 and 2006. Among adults, the greatest decline (49%) was observed in those aged 15–54 years. Life expectancy at birth increased by 12 years. Females outlived males by 6 years. Seasonality was only evident in the 1–4 year age group in the first four years. Geographical variation in mortality was ±10% of the median value and did not change over time. Conclusions: Between 2003 and 2018, mortality among children and young adults has improved substantially. The steep decline in 2003–2006 followed by a much slower reduction thereafter suggests improvements in health and wellbeing have plateaued in the last 12 years. However, there is substantial inequality in mortality experience by geographical location.
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9
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Ralaidovy AH, Lauer JA, Pretorius C, Briët OJT, Patouillard E. Priority Setting in HIV, Tuberculosis, and Malaria - New Cost-Effectiveness Results From WHO-CHOICE. Int J Health Policy Manag 2021; 10:678-696. [PMID: 33590743 PMCID: PMC9278379 DOI: 10.34172/ijhpm.2020.251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Accepted: 12/07/2020] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND This paper forms part of an update of the World Health Organization Choosing Interventions that are Cost-Effective (WHO-CHOICE) programmes. It provides an assessment of global health system performance during the first decade of the 21st century (2000-2010) with respect to allocative efficiency in HIV, tuberculosis (TB) and malaria control, thereby shining a spotlight on programme development and scale up in these Millennium Development Goal (MDG) priority areas; and examining the cost-effectiveness of selected best-practice interventions and intervention packages commonly in use during that period. METHODS Generalized cost-effectiveness analysis (GCEA) was used to determine the cost-effectiveness of the selected interventions. Impact modelling was performed using the OpenMalaria platform for malaria and using the Goals and TIME (TB Impact Model and Estimates) models in Spectrum for HIV and TB. All health system costs, regardless of payer, were included and reported in international dollars. Health outcomes are estimated and reported as the gain in healthy life years (HLYs) due to the specific intervention or combination. Analysis was restricted to eastern sub-Saharan Africa and Southeast Asia. RESULTS At the reference year of 2010, commonly used interventions for HIV, TB and malaria were cost-effective, with cost-effectiveness ratios less than I$ 100/HLY saved for virtually all interventions included. HIV, TB and malaria prevention and treatment interventions are highly cost-effective and can be implemented through a phased approach to full coverage to achieve maximum health benefits and contribute to the progressive elimination of these diseases. CONCLUSION During the first decade of the 21st century (2000-2010), the global community has done well overall for HIV, TB, and malaria programmes as regards both economic efficiency and programmatic selection criteria. The role of international assistance, financial and technical, arguably was critical to these successes. As the global community now tackles the challenge of universal health coverage, this analysis can reinforce commitment to Sustainable Development Goal targets but also the importance of continued focus on these critical programme areas.
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Affiliation(s)
- Ambinintsoa H. Ralaidovy
- World Health Organization (WHO), Geneva, Switzerland
- CERDI-CNRS-IRD-UCA, Clermont-Ferrand, France
| | - Jeremy Addison Lauer
- World Health Organization (WHO), Geneva, Switzerland
- University of Strathclyde, Glasgow, UK
| | | | - Olivier JT Briët
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
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10
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Ndeketa L, Mategula D, Terlouw DJ, Bar-Zeev N, Sauboin CJ, Biernaux S. Cost-effectiveness and public health impact of RTS,S/AS01 E malaria vaccine in Malawi, using a Markov static model. Wellcome Open Res 2021; 5:260. [PMID: 34632084 PMCID: PMC8491149 DOI: 10.12688/wellcomeopenres.16224.2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/02/2021] [Indexed: 12/02/2022] Open
Abstract
Background: The RTS,S/AS01
E malaria vaccine is being assessed in Malawi, Ghana and Kenya as part of a large-scale pilot implementation programme. Even if impactful, its incorporation into immunisation programmes will depend on demonstrating cost-effectiveness. We analysed the cost-effectiveness and public health impact of the RTS,S/AS01
E malaria vaccine use in Malawi. Methods: We calculated the Incremental Cost Effectiveness Ratio (ICER) per disability-adjusted life year (DALY) averted by vaccination and compared it to Malawi’s mean per capita Gross Domestic Product. We used a previously validated Markov model, which simulated malaria progression in a 2017 Malawian birth cohort for 15 years. We used a 46% vaccine efficacy, 75% vaccine coverage, USD5 estimated cost per vaccine dose, published local treatment costs for clinical malaria and Malawi specific malaria indicators for interventions such as bed net and antimalarial use. We took a healthcare provider, household and societal perspective. Costs were discounted at 3% per year, no discounting was applied to DALYs. For public health impact, we calculated the DALYs, and malaria events averted. Results: The ICER/DALY averted was USD115 and USD109 for the health system perspective and societal perspective respectively, lower than GDP per capita of USD398.6 for Malawi. Sensitivity analyses exploring the impact of variation in vaccine costs, vaccine coverage rate and coverage of four doses showed vaccine implementation would be cost-effective across a wide range of different outcomes. RTS,S/AS01 was predicted to avert a median of 93,940 (range 20,490–126,540) clinical cases and 394 (127–708) deaths for the three-dose schedule, or 116,480 (31,450–160,410) clinical cases and 484 (189–859) deaths for the four-dose schedule, per 100 000 fully vaccinated children. Conclusions: We predict the introduction of the RTS,S/AS01 vaccine in the Malawian expanded programme of immunisation (EPI) likely to be highly cost effective.
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Affiliation(s)
- Latif Ndeketa
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Donnie Mategula
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Dianne J Terlouw
- Malawi-Liverpool-Wellcome Trust Clinical Research Programme, College of Medicine, College of Medicine, University of Malawi, Blantyre, Malawi.,Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Naor Bar-Zeev
- International Vaccine Access Center, Department of International Health, 3. Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | | | - Sophie Biernaux
- Coalition for Epidemic Preparedness Innovations, London, NW1 2BE, UK
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11
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Ndeketa L, Mategula D, Terlouw DJ, Bar-Zeev N, Sauboin CJ, Biernaux S. Cost-effectiveness and public health impact of RTS,S/AS01E malaria vaccine in Malawi, using a Markov static model. Wellcome Open Res 2020; 5:260. [DOI: 10.12688/wellcomeopenres.16224.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2020] [Indexed: 11/20/2022] Open
Abstract
Background: The RTS,S/AS01E malaria vaccine is being assessed in Malawi, Ghana and Kenya as part of a large-scale pilot implementation programme. Even if impactful, its incorporation into immunisation programmes will depend on demonstrating cost-effectiveness. We analysed the cost-effectiveness and public health impact of the RTS,S/AS01E malaria vaccine use in Malawi. Methods: We calculated the Incremental Cost Effectiveness Ratio (ICER) per disability-adjusted life year (DALY) averted by vaccination and compared it to Malawi’s mean per capita Gross Domestic Product. We used a previously validated Markov model, which simulated malaria progression in a 2017 Malawian birth cohort for 15 years. We used a 46% vaccine efficacy, 75% vaccine coverage, USD5 estimated cost per vaccine dose, published local treatment costs for clinical malaria and Malawi specific malaria indicators for interventions such as bed net and antimalarial use. We took a healthcare provider, household and societal perspective. Costs were discounted at 3% per year, no discounting was applied to DALYs. For public health impact, we calculated the DALYs, and malaria events averted. Results: The ICER/DALY averted was USD115 and USD109 for the health system perspective and societal perspective respectively, lower than GDP per capita of USD398.6 for Malawi. Sensitivity analyses exploring the impact of variation in vaccine costs, vaccine coverage rate and coverage of four doses showed vaccine implementation would be cost-effective across a wide range of different outcomes. RTS,S/AS01 was predicted to avert a median of 93,940 (range 20,490–126,540) clinical cases and 394 (127–708) deaths for the three-dose schedule, or 116,480 (31,450–160,410) clinical cases and 484 (189–859) deaths for the four-dose schedule, per 100 000 fully vaccinated children. Conclusions: We predict the introduction of the RTS,S/AS01 vaccine in the Malawian expanded programme of immunisation (EPI) likely to be highly cost effective.
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12
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Ugwu CLJ, Zewotir T. Evaluating the Effects of Climate and Environmental Factors on Under-5 Children Malaria Spatial Distribution Using Generalized Additive Models (GAMs). J Epidemiol Glob Health 2020; 10:304-314. [PMID: 33009733 PMCID: PMC7758859 DOI: 10.2991/jegh.k.200814.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 06/20/2020] [Indexed: 11/09/2022] Open
Abstract
Although malaria burden has declined globally following scale up of intervention, the disease has remained a leading cause of hospitalization and deaths among children aged under-5 years in Nigeria. Malaria is known to be related to climate and environmental conditions. Previous research has usually studied the effects of these factors, neglecting possible correlation between them, high correlation among variables is a source of multicollinearity that induces overfitting in regression modelling. In this paper, a factor analysis was first introduced to circumvent the issue of multicollinearity and a Generalized Additive Model (GAM) was subsequently explored to identify the important risk factors that might influence the prevalence of childhood malaria in Nigeria. The GAM incorporated the complexity of the survey data, while simultaneously modelling the nonlinear and spatial random effects to allow a more precise identification of the major malaria risk factors that influence the geographical distribution of the disease. From our findings, the three latent factor components (constituted by humidity, precipitation, potential evapotranspiration, and wet days/maximum and minimum temperature/proximity to permanent waters, respectively) were significantly associated with malaria prevalence. Our analysis also detected statistically significant and nonlinear effect of altitude: the risk of malaria increased with lower values but declined sharply with higher values. A significant spatial variability in under-5 malaria prevalence across the survey clusters was also observed; malaria burden was higher in the northern part of Nigeria. Investigating the impact of important risk factors and geographical location on childhood malaria is of high relevance for the sustainable development goals (SDGs) 2015–2030 Agenda on malaria eradication, and we believe that the information obtained from this study and the generated risk maps can be useful to effectively target intervention efforts to high-risk areas based on climate and environmental context.
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Affiliation(s)
- Chigozie Louisa Jane Ugwu
- School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Private Bag X54001 Durban 4000, 3630 Westville, Durban, South Africa
| | - Temesgen Zewotir
- School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Private Bag X54001 Durban 4000, 3630 Westville, Durban, South Africa
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13
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Comparative Analysis of the Serological Reactivity of Individuals with Clinical History of Malaria using Two Different ELISA Tests. Diagnostics (Basel) 2019; 9:diagnostics9040168. [PMID: 31671536 PMCID: PMC6963549 DOI: 10.3390/diagnostics9040168] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 10/27/2019] [Accepted: 10/28/2019] [Indexed: 01/29/2023] Open
Abstract
Early diagnosis of malaria reduces disease, prevents deaths, and contributes to decreased malaria transmission. The use of specific and sensitive antigens in the execution of serological diagnostics may have an impact on the transmission of the disease. However, many individuals cannot be easily diagnosed by serological tests due to low levels of antibodies in the serum. Using two different Enzyme-Linked Immunosorbent Assay (ELISA) tests (a commercial and an in-house ELISA), a total of 365 serum samples from individuals with a clinical history of malaria were analyzed. From the serum samples analyzed, 192 (53%) samples from the commercial ELISA and 219 (60%) samples from the in-house ELISA presented positive serological reactivity to malaria. The concordance of the samples tested (n = 365) between both ELISAs was of 67% (n = 242), and with the negative control was 100% (n = 17). We demonstrated that the in-house ELISA showed high antigenic reactivity to Plasmodium falciparum antigens when compared with the commercial ELISA. The degree of concordance of both ELISAs suggested the possibility of existence of other P. falciparum antigens present in the crude extract of P. falciparum that are important in the serological response during malaria infection.
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14
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Camponovo F, Ockenhouse CF, Lee C, Penny MA. Mass campaigns combining antimalarial drugs and anti-infective vaccines as seasonal interventions for malaria control, elimination and prevention of resurgence: a modelling study. BMC Infect Dis 2019; 19:920. [PMID: 31664924 PMCID: PMC6820916 DOI: 10.1186/s12879-019-4467-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 09/12/2019] [Indexed: 11/25/2022] Open
Abstract
Background The only licensed malaria vaccine, RTS,S/AS01, has been developed for morbidity-control in young children. The potential impact on transmission of deploying such anti-infective vaccines to wider age ranges, possibly with co-administration of antimalarial treatment, is unknown. Combinations of existing malaria interventions is becoming increasingly important as evidence mounts that progress on reducing malaria incidence is stalling and threatened by resistance. Methods Malaria transmission and intervention dynamics were simulated using OpenMalaria, an individual-based simulation model of malaria transmission, by considering a seasonal transmission setting and by varying epidemiological and setting parameters such as transmission intensity, case management, intervention types and intervention coverages. Chemopreventive drugs and anti-infective vaccine efficacy profiles were based on previous studies in which model parameters were fitted to clinical trial data. These intervention properties were used to evaluate the potential of seasonal mass applications of preventative anti-infective malaria vaccines, alone or in combination with chemoprevention, to reduce malaria transmission, prevent resurgence, and/or reach transmission interruption. Results Deploying a vaccine to all ages on its own is a less effective intervention strategy compared to chemoprevention alone. However, vaccines combined with drugs are likely to achieve dramatic prevalence reductions and in few settings, transmission interruption. The combined mass intervention will result in lower prevalence following the intervention compared to chemoprevention alone and will increase chances of interruption of transmission resulting from a synergistic effect between both interventions. The combination of vaccine and drug increases the time before transmission resurges after mass interventions cease compared to mass treatment alone. Deploying vaccines and drugs together requires fewer rounds of mass intervention and fewer years of intervention to achieve the same public health impact as chemoprevention alone. Conclusions Through simulations we identified a previously unidentified value of deploying vaccines with drugs, namely the greatest benefit will be in preventing and delaying transmission resurgence for longer periods than with other human targeted interventions. This is suggesting a potential role for deploying vaccines alongside drugs in transmission foci as part of surveillance-response strategies.
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Affiliation(s)
- Flavia Camponovo
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | | | - Cynthia Lee
- PATH's Malaria Vaccine Initiative, Washington, DC, USA
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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15
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Elliott RC, Smith DL, Echodu DC. Synergy and timing: a concurrent mass medical campaign predicted to augment indoor residual spraying for malaria. Malar J 2019; 18:160. [PMID: 31060554 PMCID: PMC6501353 DOI: 10.1186/s12936-019-2788-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 04/23/2019] [Indexed: 11/12/2022] Open
Abstract
Background Control programmes for high burden countries are tasked with charting effective multi-year strategies for malaria control within significant resource constraints. Synergies between different control tools, in which more than additive benefit accrues from interventions used together, are of interest because they may be used to obtain savings or to maximize health impact per expenditure. One commonly used intervention in sub-Saharan Africa is indoor residual spraying (IRS), typically deployed through a mass campaign. While possible synergies between IRS and long-lasting insecticide-treated nets (LLINs) have been investigated in multiple transmission settings, coordinated synergy between IRS and other mass medical distribution campaigns have not attracted much attention. Recently, a strong timing-dependent synergy between an IRS campaign and a mass drug administration (MDA) was theoretically quantified. These synergistic benefits likely differ across settings depending on transmission intensity and its overall seasonal pattern. Methods High coverage interventions are modelled in different transmission environments using two methods: a Ross–Macdonald model variant and openmalaria simulations. The impact of each intervention strategy was measured through its ability to prevent host infections over time, and the effects were compared to the baseline case of deploying interventions in isolation. Results By modelling IRS and MDA together and varying their deployment times, a strong synergy was found when the administered interventions overlapped. The added benefit of co-timed interventions was robust to differences in the models. In the Ross–Macdonald model, the impact compared was roughly double the sequential interventions in most transmission settings. Openmalaria simulations of this medical control augmentation of an IRS campaign show an even stronger response with the same timing relationship. Conclusions The strong synergies found for these control tools between the complementary interventions demonstrate a general feature of effective concurrent campaign-style vector and medical interventions. A mass treatment campaign is normally short-lived, especially in higher transmission settings. When co-timed, the rapid clearing of the host parasite reservoir via chemotherapy is protected from resurgence by the longer duration of the vector control. An effective synchronous treatment campaign has the potential to greatly augment the impact of indoor residual spraying. Mass screening and treatment (MSAT) with highly sensitive rapid diagnostic tests may demonstrate a comparable trend while mass LLIN campaigns may similarly coordinate with MDA/MSAT.
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Affiliation(s)
- Richard C Elliott
- Micron School of Materials Science and Engineering, Boise State University, Engineering Building, Suite 338, Boise, ID, 83725, USA. .,Pilgrim Africa, 115 N 85th St #202, Seattle, WA, 98103, USA.
| | - David L Smith
- Institute for Health Metrics and Evaluation, University of Washington, 2301 Fifth Ave., Suite 600, Seattle, WA, 98121, USA
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16
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Smith NR, Trauer JM, Gambhir M, Richards JS, Maude RJ, Keith JM, Flegg JA. Agent-based models of malaria transmission: a systematic review. Malar J 2018; 17:299. [PMID: 30119664 PMCID: PMC6098619 DOI: 10.1186/s12936-018-2442-y] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 08/04/2018] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND Much of the extensive research regarding transmission of malaria is underpinned by mathematical modelling. Compartmental models, which focus on interactions and transitions between population strata, have been a mainstay of such modelling for more than a century. However, modellers are increasingly adopting agent-based approaches, which model hosts, vectors and/or their interactions on an individual level. One reason for the increasing popularity of such models is their potential to provide enhanced realism by allowing system-level behaviours to emerge as a consequence of accumulated individual-level interactions, as occurs in real populations. METHODS A systematic review of 90 articles published between 1998 and May 2018 was performed, characterizing agent-based models (ABMs) relevant to malaria transmission. The review provides an overview of approaches used to date, determines the advantages of these approaches, and proposes ideas for progressing the field. RESULTS The rationale for ABM use over other modelling approaches centres around three points: the need to accurately represent increased stochasticity in low-transmission settings; the benefits of high-resolution spatial simulations; and heterogeneities in drug and vaccine efficacies due to individual patient characteristics. The success of these approaches provides avenues for further exploration of agent-based techniques for modelling malaria transmission. Potential extensions include varying elimination strategies across spatial landscapes, extending the size of spatial models, incorporating human movement dynamics, and developing increasingly comprehensive parameter estimation and optimization techniques. CONCLUSION Collectively, the literature covers an extensive array of topics, including the full spectrum of transmission and intervention regimes. Bringing these elements together under a common framework may enhance knowledge of, and guide policies towards, malaria elimination. However, because of the diversity of available models, endorsing a standardized approach to ABM implementation may not be possible. Instead it is recommended that model frameworks be contextually appropriate and sufficiently described. One key recommendation is to develop enhanced parameter estimation and optimization techniques. Extensions of current techniques will provide the robust results required to enhance current elimination efforts.
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Affiliation(s)
- Neal R Smith
- School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.
| | - James M Trauer
- School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia
| | - Manoj Gambhir
- School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia
- IBM Research Australia, Melbourne, Australia
| | - Jack S Richards
- Life Sciences, Burnet Institute, Melbourne, Australia
- Department of Medicine, University of Melbourne, Parkville, Australia
- Department of Infectious Diseases, Monash University, Melbourne, Australia
| | - Richard J Maude
- Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
- Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK
- Harvard TH Chan School of Public Health, Harvard University, Boston, USA
| | - Jonathan M Keith
- School of Mathematical Sciences, Monash University, Clayton, Australia
| | - Jennifer A Flegg
- School of Mathematics and Statistics, University of Melbourne, Parkville, Australia
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17
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Elliott RC, Smith DL, Echodu D. Medical and entomological malarial interventions, a comparison and synergy of two control measures using a Ross/Macdonald model variant and openmalaria simulation. Math Biosci 2018; 300:187-200. [PMID: 29655551 PMCID: PMC6013649 DOI: 10.1016/j.mbs.2018.04.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 12/04/2017] [Accepted: 04/10/2018] [Indexed: 01/23/2023]
Abstract
An adaptation of the classical Ross–Macdonald model for vector disease transmission to incorporate time-dependent medical and entomological control measures. Modeling both mass drug administration and indoor residual spraying campaigns, the synchronous deployment of both yields a synergy where the impact of a joint intervention exceeds that of isolated campaigns. Openmalaria simulations, separately run, indicate comparable intervention impacts to the Ross/Macdonald model variant. The vector reservoir of parasitemia is found to be labile, and this dictates the impacts of the medical and entomological interventions. A scaling-law level of analysis is performed that estimates the rebound of infections in a community after interventions expire, and not only do higher transmission environments bounce back to prevalent infections faster, communities with stronger interventions are shown to have a slower relapse to parasitemia.
Using an established Ross/Macdonald model variant for mosquito-born parasite transmission, we extend the formalism to simply incorporate time-dependent control measures. In particular, two interventions are considered, mass drug administration (MDA) and indoor residual spraying (IRS), whose individual intensities during their respective campaigns are set to the same intervention-reduced reproductive number R0. The impacts of these interventions, measured as each campaign’s ability over time to reduce infections in a community, are found based on the transmission setting, coverage, and their associated durations. These impacts are compared for both interventions and their joint deployment. Synchronous campaigns of IRS deployed with MDA have a cooperative, synergistic effect whose impact exceeds that when the campaigns are deployed in isolation. Simulations with openmalaria, with its more complex model of transmission, are separately performed and show a similar impact enhancement with these interventions. A new, associated analysis yields simple scaling relationships that estimate the dynamical resurgence time, post-intervention, to infection proliferation in a community.
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Affiliation(s)
- R C Elliott
- Micron School of Materials Science and Engineering, Boise State University, Engineering Building Suite 338, Boise, ID 83725, USA; Pilgrim Africa, 115 N 85th St #202, Seattle, WA 98103, USA.
| | - D L Smith
- Institute of Health Metrics and Evaluation, University of Washington, 2301 Fifth Ave., Suite 600, Seattle, WA 98121, USA.
| | - D Echodu
- Pilgrim Africa, 115 N 85th St #202, Seattle, WA 98103, USA.
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18
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Amek NO, Van Eijk A, Lindblade KA, Hamel M, Bayoh N, Gimnig J, Laserson KF, Slutsker L, Smith T, Vounatsou P. Infant and child mortality in relation to malaria transmission in KEMRI/CDC HDSS, Western Kenya: validation of verbal autopsy. Malar J 2018; 17:37. [PMID: 29347942 PMCID: PMC5774157 DOI: 10.1186/s12936-018-2184-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Accepted: 01/10/2018] [Indexed: 12/02/2022] Open
Abstract
Background Malaria transmission reduction is a goal of many malaria control programmes. Little is known of how much mortality can be reduced by specific reductions in transmission. Verbal autopsy (VA) is widely used for estimating malaria specific mortality rates, but does not reliably distinguish malaria from other febrile illnesses. Overall malaria attributable mortality includes both direct and indirect deaths. It is unclear what proportion of the deaths averted by reducing malaria transmission are classified as malaria in VA. Methods Both all-cause, and cause-specific mortality reported by VA for children under 5 years of age, were assembled from the KEMRI/CDC health and demographic surveillance system in Siaya county, rural Western Kenya for the years 2002–2004. These were linked to household-specific estimates of the Plasmodium falciparum entomological inoculation rate (EIR) based on high resolution spatio-temporal geostatistical modelling of entomological data. All-cause and malaria specific mortality (by VA), were analysed in relation to EIR, insecticide-treated net use (ITN), socioeconomic status (SES) and parameters describing space–time correlation. Time at risk for each child was analysed using Bayesian geostatistical Cox proportional hazard models, with time-dependent covariates. The outputs were used to estimate the diagnostic performance of VA in measuring mortality that can be attributed to malaria exposure. Results The overall under-five mortality rate was 80 per 1000 person-years during the study period. Eighty-one percent of the total deaths were assigned causes of death by VA, with malaria assigned as the main cause of death except in the neonatal period. Although no trend was observed in malaria-specific mortality assessed by VA, ITN use was associated with reduced all-cause mortality in infants (hazard ratio 0.15, 95% CI 0.02, 0.63) and the EIR was strongly associated with both all-cause and malaria-specific mortality. 48.2% of the deaths could be attributed to malaria by analysing the exposure–response relationship, though only 20.5% of VAs assigned malaria as the cause and the sensitivity of VAs was estimated to be only 26%. Although VAs assigned some deaths to malaria even in areas where there was estimated to be no exposure, the specificity of the VAs was estimated to be 85%. Conclusion Interventions that reduce P. falciparum transmission intensity will not only significantly reduce malaria-diagnosed mortality, but also mortality assigned to other causes in under-5 year old children in endemic areas. In this setting, the VA tool based on clinician review substantially underestimates the number of deaths that could be averted by reducing malaria exposure in childhood, but has a reasonably high specificity. This suggests that malaria transmission-reducing interventions such as ITNs can potentially reduce overall child mortality by as much as twice the total direct malaria burden estimated from VAs. Electronic supplementary material The online version of this article (10.1186/s12936-018-2184-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Nyaguara O Amek
- Kenya Medical Research Institute, Centre for Global Health Research, P.O. Box 1578, Kisumu, Kenya. .,Swiss Tropical and Public Health Institute, Socinstr. 57, P.O. Box, 4002, Basel, Switzerland. .,University of Basel, Petersplatz 1, P.O. Box, 4003, Basel, Switzerland.
| | - Annemieke Van Eijk
- Kenya Medical Research Institute, Centre for Global Health Research, P.O. Box 1578, Kisumu, Kenya
| | - Kim A Lindblade
- Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA, 30301, USA
| | - Mary Hamel
- Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA, 30301, USA
| | - Nabie Bayoh
- Kenya Medical Research Institute, Centre for Global Health Research, P.O. Box 1578, Kisumu, Kenya
| | - John Gimnig
- Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA, 30301, USA
| | - Kayla F Laserson
- Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA, 30301, USA
| | - Laurence Slutsker
- Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA, 30301, USA
| | - Thomas Smith
- Swiss Tropical and Public Health Institute, Socinstr. 57, P.O. Box, 4002, Basel, Switzerland.,University of Basel, Petersplatz 1, P.O. Box, 4003, Basel, Switzerland
| | - Penelope Vounatsou
- Swiss Tropical and Public Health Institute, Socinstr. 57, P.O. Box, 4002, Basel, Switzerland.,University of Basel, Petersplatz 1, P.O. Box, 4003, Basel, Switzerland
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19
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Korenromp E, Hamilton M, Sanders R, Mahiané G, Briët OJT, Smith T, Winfrey W, Walker N, Stover J. Impact of malaria interventions on child mortality in endemic African settings: comparison and alignment between LiST and Spectrum-Malaria model. BMC Public Health 2017; 17:781. [PMID: 29143637 PMCID: PMC5688465 DOI: 10.1186/s12889-017-4739-0] [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] [Indexed: 12/02/2022] Open
Abstract
Background In malaria-endemic countries, malaria prevention and treatment are critical for child health. In the context of intervention scale-up and rapid changes in endemicity, projections of intervention impact and optimized program scale-up strategies need to take into account the consequent dynamics of transmission and immunity. Methods The new Spectrum-Malaria program planning tool was used to project health impacts of Insecticide-Treated mosquito Nets (ITNs) and effective management of uncomplicated malaria cases (CMU), among other interventions, on malaria infection prevalence, case incidence and mortality in children 0–4 years, 5–14 years of age and adults. Spectrum-Malaria uses statistical models fitted to simulations of the dynamic effects of increasing intervention coverage on these burdens as a function of baseline malaria endemicity, seasonality in transmission and malaria intervention coverage levels (estimated for years 2000 to 2015 by the World Health Organization and Malaria Atlas Project). Spectrum-Malaria projections of proportional reductions in under-five malaria mortality were compared with those of the Lives Saved Tool (LiST) for the Democratic Republic of the Congo and Zambia, for given (standardized) scenarios of ITN and/or CMU scale-up over 2016–2030. Results Proportional mortality reductions over the first two years following scale-up of ITNs from near-zero baselines to moderately higher coverages align well between LiST and Spectrum-Malaria —as expected since both models were fitted to cluster-randomized ITN trials in moderate-to-high-endemic settings with 2-year durations. For further scale-up from moderately high ITN coverage to near-universal coverage (as currently relevant for strategic planning for many countries), Spectrum-Malaria predicts smaller additional ITN impacts than LiST, reflecting progressive saturation. For CMU, especially in the longer term (over 2022–2030) and for lower-endemic settings (like Zambia), Spectrum-Malaria projects larger proportional impacts, reflecting onward dynamic effects not fully captured by LiST. Conclusions Spectrum-Malaria complements LiST by extending the scope of malaria interventions, program packages and health outcomes that can be evaluated for policy making and strategic planning within and beyond the perspective of child survival. Electronic supplementary material The online version of this article (10.1186/s12889-017-4739-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Matthew Hamilton
- Avenir Health, 655 Winding Brook Drive, Glastonbury, CT-06033, USA
| | - Rachel Sanders
- Avenir Health, 655 Winding Brook Drive, Glastonbury, CT-06033, USA
| | - Guy Mahiané
- Avenir Health, 655 Winding Brook Drive, Glastonbury, CT-06033, USA
| | - Olivier J T Briët
- Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland.,Epidemiology and Public Health, University of Basel, Basel, Switzerland
| | - Thomas Smith
- Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051, Basel, Switzerland.,Epidemiology and Public Health, University of Basel, Basel, Switzerland
| | - William Winfrey
- Avenir Health, 655 Winding Brook Drive, Glastonbury, CT-06033, USA
| | - Neff Walker
- Department of International Health, Institute for International Programs, Johns Hopkins University Bloomberg School of Public Health, 615 N. Wolfe St., Baltimore, MD, 21205, USA
| | - John Stover
- Avenir Health, 655 Winding Brook Drive, Glastonbury, CT-06033, USA
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Dalrymple U, Cameron E, Bhatt S, Weiss DJ, Gupta S, Gething PW. Quantifying the contribution of Plasmodium falciparum malaria to febrile illness amongst African children. eLife 2017; 6:29198. [PMID: 29034876 PMCID: PMC5665646 DOI: 10.7554/elife.29198] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 10/12/2017] [Indexed: 12/31/2022] Open
Abstract
Suspected malaria cases in Africa increasingly receive a rapid diagnostic test (RDT) before antimalarials are prescribed. While this ensures efficient use of resources to clear parasites, the underlying cause of the individual's fever remains unknown due to potential coinfection with a non-malarial febrile illness. Widespread use of RDTs does not necessarily prevent over-estimation of clinical malaria cases or sub-optimal case management of febrile patients. We present a new approach that allows inference of the spatiotemporal prevalence of both Plasmodium falciparum malaria-attributable and non-malarial fever in sub-Saharan African children from 2006 to 2014. We estimate that 35.7% of all self-reported fevers were accompanied by a malaria infection in 2014, but that only 28.0% of those (10.0% of all fevers) were causally attributable to malaria. Most fevers among malaria-positive children are therefore caused by non-malaria illnesses. This refined understanding can help improve interpretation of the burden of febrile illness and shape policy on fever case management.
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Affiliation(s)
- Ursula Dalrymple
- Department of Zoology, University of Oxford, Oxford, United Kingdom.,Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Ewan Cameron
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Samir Bhatt
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom.,Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Daniel J Weiss
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Sunetra Gupta
- Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - Peter W Gething
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
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21
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Hamilton M, Mahiane G, Werst E, Sanders R, Briët O, Smith T, Cibulskis R, Cameron E, Bhatt S, Weiss DJ, Gething PW, Pretorius C, Korenromp EL. Spectrum-Malaria: a user-friendly projection tool for health impact assessment and strategic planning by malaria control programmes in sub-Saharan Africa. Malar J 2017; 16:68. [PMID: 28183343 PMCID: PMC5301449 DOI: 10.1186/s12936-017-1705-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 01/19/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Scale-up of malaria prevention and treatment needs to continue but national strategies and budget allocations are not always evidence-based. This article presents a new modelling tool projecting malaria infection, cases and deaths to support impact evaluation, target setting and strategic planning. METHODS Nested in the Spectrum suite of programme planning tools, the model includes historic estimates of case incidence and deaths in groups aged up to 4, 5-14, and 15+ years, and prevalence of Plasmodium falciparum infection (PfPR) among children 2-9 years, for 43 sub-Saharan African countries and their 602 provinces, from the WHO and malaria atlas project. Impacts over 2016-2030 are projected for insecticide-treated nets (ITNs), indoor residual spraying (IRS), seasonal malaria chemoprevention (SMC), and effective management of uncomplicated cases (CMU) and severe cases (CMS), using statistical functions fitted to proportional burden reductions simulated in the P. falciparum dynamic transmission model OpenMalaria. RESULTS In projections for Nigeria, ITNs, IRS, CMU, and CMS scale-up reduced health burdens in all age groups, with largest proportional and especially absolute reductions in children up to 4 years old. Impacts increased from 8 to 10 years following scale-up, reflecting dynamic effects. For scale-up of each intervention to 80% effective coverage, CMU had the largest impacts across all health outcomes, followed by ITNs and IRS; CMS and SMC conferred additional small but rapid mortality impacts. DISCUSSION Spectrum-Malaria's user-friendly interface and intuitive display of baseline data and scenario projections holds promise to facilitate capacity building and policy dialogue in malaria programme prioritization. The module's linking to the OneHealth Tool for costing will support use of the software for strategic budget allocation. In settings with moderately low coverage levels, such as Nigeria, improving case management and achieving universal coverage with ITNs could achieve considerable burden reductions. Projections remain to be refined and validated with local expert input data and actual policy scenarios.
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Affiliation(s)
- Matthew Hamilton
- Avenir Health, Geneva, 1 route de Morillons/150 Route de Ferney (WCC, office 164), PO box 2100, 1211 Geneva 2, Switzerland
- Avenir Health, Glastonbury, USA
| | - Guy Mahiane
- Avenir Health, Geneva, 1 route de Morillons/150 Route de Ferney (WCC, office 164), PO box 2100, 1211 Geneva 2, Switzerland
- Avenir Health, Glastonbury, USA
| | - Elric Werst
- Avenir Health, Geneva, 1 route de Morillons/150 Route de Ferney (WCC, office 164), PO box 2100, 1211 Geneva 2, Switzerland
- Avenir Health, Glastonbury, USA
| | - Rachel Sanders
- Avenir Health, Geneva, 1 route de Morillons/150 Route de Ferney (WCC, office 164), PO box 2100, 1211 Geneva 2, Switzerland
- Avenir Health, Glastonbury, USA
| | - Olivier Briët
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Thomas Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Richard Cibulskis
- World Health Organization Global Malaria Programme, Geneva, Switzerland
| | - Ewan Cameron
- Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
| | - Samir Bhatt
- Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
- Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Daniel J. Weiss
- Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
| | - Peter W. Gething
- Oxford Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, UK
| | - Carel Pretorius
- Avenir Health, Geneva, 1 route de Morillons/150 Route de Ferney (WCC, office 164), PO box 2100, 1211 Geneva 2, Switzerland
- Avenir Health, Glastonbury, USA
| | - Eline L. Korenromp
- Avenir Health, Geneva, 1 route de Morillons/150 Route de Ferney (WCC, office 164), PO box 2100, 1211 Geneva 2, Switzerland
- Avenir Health, Glastonbury, USA
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22
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Camponovo F, Bever CA, Galactionova K, Smith T, Penny MA. Incidence and admission rates for severe malaria and their impact on mortality in Africa. Malar J 2017; 16:1. [PMID: 28049519 PMCID: PMC5209951 DOI: 10.1186/s12936-016-1650-6] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 12/15/2016] [Indexed: 12/04/2022] Open
Abstract
Background Appropriate treatment of life-threatening Plasmodium falciparum malaria requires in-patient care. Although the proportion of severe cases accessing in-patient care in endemic settings strongly affects overall case fatality rates and thus disease burden, this proportion is generally unknown. At present, estimates of malaria mortality are driven by prevalence or overall clinical incidence data, ignoring differences in case fatality resulting from variations in access. Consequently, the overall impact of preventive interventions on disease burden have not been validly compared with those of improvements in access to case management or its quality. Methods Using a simulation-based approach, severe malaria admission rates and the subsequent severe malaria disease and mortality rates for 41 malaria endemic countries of sub-Saharan Africa were estimated. Country differences in transmission and health care settings were captured by use of high spatial resolution data on demographics and falciparum malaria prevalence, as well as national level estimates of effective coverage of treatment for uncomplicated malaria. Reported and modelled estimates of cases, admissions and malaria deaths from the World Malaria Report, along with predicted burden from simulations, were combined to provide revised estimates of access to in-patient care and case fatality rates. Results There is substantial variation between countries’ in-patient admission rates and estimated levels of case fatality rates. It was found that for many African countries, most patients admitted for in-patient treatment would not meet strict criteria for severe disease and that for some countries only a small proportion of the total severe cases are admitted. Estimates are highly sensitive to the assumed community case fatality rates. Re-estimation of national level malaria mortality rates suggests that there is substantial burden attributable to inefficient in-patient access and treatment of severe disease. Conclusions The model-based methods proposed here offer a standardized approach to estimate the numbers of severe malaria cases and deaths based on national level reporting, allowing for coverage of both curative and preventive interventions. This makes possible direct comparisons of the potential benefits of scaling-up either category of interventions. The profound uncertainties around these estimates highlight the need for better data. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1650-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Flavia Camponovo
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Caitlin A Bever
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland.,Institute for Disease Modeling, Bellevue, WA, 98005, USA
| | - Katya Galactionova
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Thomas Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Melissa A Penny
- Swiss Tropical and Public Health Institute, Basel, Switzerland. .,University of Basel, Basel, Switzerland.
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Galactionova K, Tediosi F, Camponovo F, Smith TA, Gething PW, Penny MA. Country specific predictions of the cost-effectiveness of malaria vaccine RTS,S/AS01 in endemic Africa. Vaccine 2016; 35:53-60. [PMID: 27890400 DOI: 10.1016/j.vaccine.2016.11.042] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Revised: 11/03/2016] [Accepted: 11/14/2016] [Indexed: 10/20/2022]
Abstract
BACKGROUND RTS,S/AS01 is a safe and moderately efficacious vaccine considered for implementation in endemic Africa. Model predictions of impact and cost-effectiveness of this new intervention could aid in country adoption decisions. METHODS The impact of RTS,S was assessed in 43 countries using an ensemble of models of Plasmodium falciparum epidemiology. Informed by the 32months follow-up data from the phase 3 trial, vaccine effectiveness was evaluated at country levels of malaria parasite prevalence, coverage of control interventions and immunization. Benefits and costs of the program incremental to routine malaria control were evaluated for a four dose schedule: first dose administered at six months, second and third - before 9months, and fourth dose at 27months of age. Sensitivity analyses around vaccine properties, transmission, and economic inputs were conducted. RESULTS If implemented in all 43 countries the vaccine has the potential to avert 123 (117;129) million malaria episodes over the first 10years. Burden averted averages 18,413 (range of country median estimates 156-40,054) DALYs per 100,000 fully vaccinated children with much variation across settings primarily driven by differences in transmission intensity. At a price of $5 per dose program costs average $39.8 per fully vaccinated child with a median cost-effectiveness ratio of $188 (range $78-$22,448) per DALY averted; the ratio is lower by one third - $136 (range $116-$220) - in settings where parasite prevalence in children aged 2-10years is at or above 10%. CONCLUSION RTS,S/AS01has the potential to substantially reduce malaria burden in children across Africa. Conditional on assumptions on price, coverage, and vaccine properties, adding RTS,S to routine malaria control interventions would be highly cost-effective. Implementation decisions will need to further consider feasibility of scaling up existing control programs, and operational constraints in reaching children at risk with the schedule.
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Affiliation(s)
- Katya Galactionova
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
| | - Fabrizio Tediosi
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - Flavia Camponovo
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - Thomas A Smith
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | | | - Melissa A Penny
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
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van den Bogaart E, Mens PF, Adams ER, Grobusch MP, Schallig HDFH. Phagocytosis of hemozoin by RAW 264.7 cells, but not THP-1 cells, promotes infection by Leishmania donovani with a nitric oxide-independent mechanism. Parasitol Int 2016; 66:196-206. [PMID: 27623326 DOI: 10.1016/j.parint.2016.09.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 08/19/2016] [Accepted: 09/08/2016] [Indexed: 01/28/2023]
Abstract
During its intra-erythrocytic development, the malaria parasite Plasmodium falciparum synthesizes insoluble hemozoin (HZ) crystals that are released into the circulation upon rupture of parasitized red blood cells, and rapidly phagocytized by host mononuclear cells. Here, HZ persists undigested, causing functional impairment and possibly leading to increased host susceptibility to secondary infections. In patients with malaria and visceral leishmaniasis (VL) co-infections, HZ-loaded macrophages are likely to co-harbor Leishmania donovani parasites, but whether this might influence the course of the Leishmania infection is unknown. In this study, L. donovani amastigote growth was monitored in mouse RAW 264.7 macrophages and PMA-differentiated THP-1 cells previously exposed to increasing amounts of HZ or its synthetic analogue β-hematin (BH). Latex beads were used as a phagocytic control. Data demonstrate that phagocytosis of HZ and BH by RAW 264.7 cells promoted infection therein by L. donovani parasites in a dose-dependent fashion. Similar results were not observed when using THP-1 cells, despite a clear persistence of undigested heme up to 48h after phagocytosis. Conditioning with lipopolysaccharide (LPS)/interferon (IFN)-γ prior to Leishmania infection triggered the release in RAW 264.7 cells of nitric oxide (NO), a highly leishmanicidal metabolite. However, neither HZ nor BH pre-ingestion were able to inhibit NO production following stimulation with LPS/IFN-γ, suggesting that the HZ- and BH-promoting effect on L. donovani infection occurred with an NO-independent mechanism. In conclusion, these preliminary findings highlight a possible detrimental effect of HZ on the course of VL, warranting further investigation into the clinical relevance of the current models.
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Affiliation(s)
- Erika van den Bogaart
- Parasitology Unit, Department of Biomedical Research, Royal Tropical Institute (KIT), Meibergdreef 39, 1105 AZ Amsterdam, The Netherlands.
| | - Pètra F Mens
- Parasitology Unit, Department of Medical Microbiology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Emily R Adams
- Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Pl, Liverpool, Merseyside L3 5QA, United Kingdom
| | - Martin P Grobusch
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
| | - Henk D F H Schallig
- Parasitology Unit, Department of Medical Microbiology, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
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25
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Korenromp E, Mahiané G, Hamilton M, Pretorius C, Cibulskis R, Lauer J, Smith TA, Briët OJT. Malaria intervention scale-up in Africa: effectiveness predictions for health programme planning tools, based on dynamic transmission modelling. Malar J 2016; 15:417. [PMID: 27538889 PMCID: PMC4991118 DOI: 10.1186/s12936-016-1461-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Accepted: 07/29/2016] [Indexed: 12/22/2022] Open
Abstract
Background Scale-up of malaria prevention and treatment needs to continue to further important gains made in the past decade, but national strategies and budget allocations are not always evidence-based. Statistical models were developed summarizing dynamically simulated relations between increases in coverage and intervention impact, to inform a malaria module in the Spectrum health programme planning tool. Methods The dynamic Plasmodiumfalciparum transmission model OpenMalaria was used to simulate health effects of scale-up of insecticide-treated net (ITN) usage, indoor residual spraying (IRS), management of uncomplicated malaria cases (CM) and seasonal malaria chemoprophylaxis (SMC) over a 10-year horizon, over a range of settings with stable endemic malaria. Generalized linear regression models (GLMs) were used to summarize determinants of impact across a range of sub-Sahara African settings. Results Selected (best) GLMs explained 94–97 % of variation in simulated post-intervention parasite infection prevalence, 86–97 % of variation in case incidence (three age groups, three 3-year horizons), and 74–95 % of variation in malaria mortality. For any given effective population coverage, CM and ITNs were predicted to avert most prevalent infections, cases and deaths, with lower impacts for IRS, and impacts of SMC limited to young children reached. Proportional impacts were larger at lower endemicity, and (except for SMC) largest in low-endemic settings with little seasonality. Incremental health impacts for a given coverage increase started to diminish noticeably at above ~40 % coverage, while in high-endemic settings, CM and ITNs acted in synergy by lowering endemicity. Vector control and CM, by reducing endemicity and acquired immunity, entail a partial rebound in malaria mortality among people above 5 years of age from around 5–7 years following scale-up. SMC does not reduce endemicity, but slightly shifts malaria to older ages by reducing immunity in child cohorts reached. Conclusion Health improvements following malaria intervention scale-up vary with endemicity, seasonality, age and time. Statistical models can emulate epidemiological dynamics and inform strategic planning and target setting for malaria control. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1461-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | - Richard Cibulskis
- World Health Organization Global Malaria Programme, Geneva, Switzerland
| | - Jeremy Lauer
- World Health Organization Health Systems Governance and Financing dept., Geneva, Switzerland
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
| | - Olivier J T Briët
- Swiss Tropical and Public Health Institute, Basel, Switzerland.,University of Basel, Basel, Switzerland
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26
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Sauboin CJ, Van Bellinghen LA, Van De Velde N, Van Vlaenderen I. Potential public health impact of RTS,S malaria candidate vaccine in sub-Saharan Africa: a modelling study. Malar J 2015; 14:524. [PMID: 26702637 PMCID: PMC4690265 DOI: 10.1186/s12936-015-1046-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 12/09/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Adding malaria vaccination to existing interventions could help to reduce the health burden due to malaria. This study modelled the potential public health impact of the RTS,S candidate malaria vaccine in 42 malaria-endemic countries in sub-Saharan Africa. METHODS An individual-based Markov cohort model was constructed with three categories of malaria transmission intensity and six successive malaria immunity levels. The cycle time was 5 days. Vaccination was assumed to reduce the risk of infection, with no other effects. Vaccine efficacy was assumed to wane exponentially over time. Malaria incidence and vaccine efficacy data were taken from a Phase III trial of the RTS,S vaccine with 18 months of follow-up (NCT00866619). The model was calibrated to reproduce the malaria incidence in the control arm of the trial in each transmission category and published age distribution data. Individual-level heterogeneity in malaria exposure and vaccine protection was accounted for. Parameter uncertainty and variability were captured by using stochastic model transitions. The model followed a cohort from birth to 10 years of age without malaria vaccination, or with RTS,S malaria vaccination administered at age 6, 10 and 14 weeks or at age 6, 7-and-a-half and 9 months. Median and 95% confidence intervals were calculated for the number of clinical malaria cases, severe cases, malaria hospitalizations and malaria deaths expected to be averted by each vaccination strategy. Univariate sensitivity analysis was conducted by varying the values of key input parameters. RESULTS Vaccination assuming the coverage of diphtheria-tetanus-pertussis (DTP3) at age 6, 10 and 14 weeks is estimated to avert over five million clinical malaria cases, 119,000 severe malaria cases, 98,600 malaria hospitalizations and 31,000 malaria deaths in the 42 countries over the 10-year period. Vaccination at age 6, 7-and-a-half and 9 months with 75% of DTP3 coverage is estimated to avert almost 12.5 million clinical malaria cases, 250,000 severe malaria cases, 208,000 malaria hospitalizations and 65,400 malaria deaths in the 42 countries. Univariate sensitivity analysis indicated that for both vaccination strategies, the parameters with the largest impact on the malaria mortality estimates were waning of vaccine efficacy and malaria case-fatality rate. CONCLUSIONS Addition of RTS,S malaria vaccination to existing malaria interventions is estimated to reduce substantially the incidence of clinical malaria, severe malaria, malaria hospitalizations and malaria deaths across 42 countries in sub-Saharan Africa.
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Penny MA, Pemberton-Ross P, Smith TA. The time-course of protection of the RTS,S vaccine against malaria infections and clinical disease. Malar J 2015; 14:437. [PMID: 26537608 PMCID: PMC4634589 DOI: 10.1186/s12936-015-0969-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 10/27/2015] [Indexed: 01/08/2023] Open
Abstract
Background Recent publications have reported follow-up of the RTS,S/AS01 malaria vaccine candidate Phase III trials at 11 African sites for 32 months (or longer). This includes site- and time-specific estimates of incidence and efficacy against clinical disease with four different vaccination schedules. These data allow estimation of the time-course of protection against infection associated with two different ages of vaccination, both with and without a booster dose. Methods Using an ensemble of individual-based stochastic models, each trial cohort in the Phase III trial was simulated assuming many different hypothetical profiles for the vaccine efficacy against infection in time, for both the primary course and boosting dose and including the potential for either exponential or non-exponential decay. The underlying profile of protection was determined by Bayesian fitting of these model predictions to the site- and time-specific incidence of clinical malaria over 32 months (or longer) of follow-up. Using the same stochastic models, projections of clinical efficacy in each of the sites were modelled and compared to available observed trial data. Results The initial protection of RTS,S immediately following three doses is estimated as providing an efficacy against infection of 65 % (when immunizing infants aged 6–12 weeks old) and 91 % (immunizing children aged 5–17 months old at first vaccination). This protection decays relatively rapidly, with an approximately exponential decay for the 6–12 weeks old cohort (with a half-life of 7.2 months); for the 5–17 months old cohort a biphasic decay with a similar half-life is predicted, with an initial rapid decay followed by a slower decay. The boosting dose was estimated to return protection to an efficacy against infection of 50–55 % for both cohorts. Estimates of clinical efficacy by trial site are consistent with those reported in the trial for all cohorts. Conclusions The site- and time-specific clinical observations from the RTS,S/AS01 trial data allowed a reasonably precise estimation of the underlying vaccine protection against infection which is consistent with common underlying efficacy and decay rates across the trial sites. This calibration suggests that the decay in efficacy against clinical disease is more rapid than that against infection because of age-shifts in the incidence of disease. The dynamical models predict that clinical effectiveness will continue to decay and that likely effects beyond the time-scale of the trial will be small. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0969-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Melissa A Penny
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, Petersplatz 1, Basel, Switzerland.
| | - Peter Pemberton-Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, Petersplatz 1, Basel, Switzerland.
| | - Thomas A Smith
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, 4051, Basel, Switzerland. .,University of Basel, Petersplatz 1, Basel, Switzerland.
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Distribution of malaria exposure in endemic countries in Africa considering country levels of effective treatment. Malar J 2015; 14:384. [PMID: 26437798 PMCID: PMC4595196 DOI: 10.1186/s12936-015-0864-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 08/23/2015] [Indexed: 11/10/2022] Open
Abstract
Background Malaria prevalence, clinical incidence, treatment, and transmission rates are dynamically interrelated. Prevalence is often considered a measure of malaria transmission, but treatment of clinical malaria reduces prevalence, and consequently also infectiousness to the mosquito vector and onward transmission. The impact of the frequency of treatment on prevalence in a population is generally not considered. This can lead to potential underestimation of malaria exposure in settings with good health systems. Furthermore, these dynamical relationships between prevalence, treatment, and transmission have not generally been taken into account in estimates of burden. Methods Using prevalence as an input, estimates of disease incidence and transmission [as the distribution of the entomological inoculation rate (EIR)] for Plasmodium falciparum have now been made for 43 countries in Africa using both empirical relationships (that do not allow for treatment) and OpenMalaria dynamic micro-simulation models (that explicitly include the effects of treatment). For each estimate, prevalence inputs were taken from geo-statistical models fitted for the year 2010 by the Malaria Atlas Project to all available observed prevalence data. National level estimates of the effectiveness of case management in treating clinical attacks were used as inputs to the estimation of both EIR and disease incidence by the dynamic models. Results and conclusions When coverage of effective treatment is taken into account, higher country level estimates of average EIR and thus higher disease burden, are obtained for a given prevalence level, especially where access to treatment is high, and prevalence relatively low. These methods provide a unified framework for comparison of both the immediate and longer-term impacts of case management and of preventive interventions. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0864-3) contains supplementary material, which is available to authorized users.
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Defining the relationship between infection prevalence and clinical incidence of Plasmodium falciparum malaria. Nat Commun 2015; 6:8170. [PMID: 26348689 PMCID: PMC4569718 DOI: 10.1038/ncomms9170] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 07/24/2015] [Indexed: 01/08/2023] Open
Abstract
In many countries health system data remain too weak to accurately enumerate Plasmodium falciparum malaria cases. In response, cartographic approaches have been developed that link maps of infection prevalence with mathematical relationships to predict the incidence rate of clinical malaria. Microsimulation (or ‘agent-based') models represent a powerful new paradigm for defining such relationships; however, differences in model structure and calibration data mean that no consensus yet exists on the optimal form for use in disease-burden estimation. Here we develop a Bayesian statistical procedure combining functional regression-based model emulation with Markov Chain Monte Carlo sampling to calibrate three selected microsimulation models against a purpose-built data set of age-structured prevalence and incidence counts. This allows the generation of ensemble forecasts of the prevalence–incidence relationship stratified by age, transmission seasonality, treatment level and exposure history, from which we predict accelerating returns on investments in large-scale intervention campaigns as transmission and prevalence are progressively reduced. Mathematical models are used to predict malaria burden to inform disease control efforts. Here, Cameron et al. use Bayesian statistics to calibrate previous models against a data set of age-structured prevalence and incidence, generating stratified forecasts of the prevalence–incidence relationship.
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Penny MA, Galactionova K, Tarantino M, Tanner M, Smith TA. The public health impact of malaria vaccine RTS,S in malaria endemic Africa: country-specific predictions using 18 month follow-up Phase III data and simulation models. BMC Med 2015; 13:170. [PMID: 26219380 PMCID: PMC4518512 DOI: 10.1186/s12916-015-0408-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 06/25/2015] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The RTS,S/AS01 malaria vaccine candidate recently completed Phase III trials in 11 African sites. Recommendations for its deployment will partly depend on predictions of public health impact in endemic countries. Previous predictions of these used only limited information on underlying vaccine properties and have not considered country-specific contextual data. METHODS Each Phase III trial cohort was simulated explicitly using an ensemble of individual-based stochastic models, and many hypothetical vaccine profiles. The true profile was estimated by Bayesian fitting of these models to the site- and time-specific incidence of clinical malaria in both trial arms over 18 months of follow-up. Health impacts of implementation via two vaccine schedules in 43 endemic sub-Saharan African countries, using country-specific prevalence, access to care, immunisation coverage and demography data, were predicted via weighted averaging over many simulations. RESULTS The efficacy against infection of three doses of vaccine was initially approximately 65 % (when immunising 6-12 week old infants) and 80 % (children 5-17 months old), with a 1 year half-life (exponential decay). Either schedule will avert substantial disease, but predicted impact strongly depends on the decay rate of vaccine effects and average transmission intensity. CONCLUSIONS For the first time Phase III site- and time-specific data were available to estimate both the underlying profile of RTS,S/AS01 and likely country-specific health impacts. Initial efficacy will probably be high, but decay rapidly. Adding RTS,S to existing control programs, assuming continuation of current levels of malaria exposure and of health system performance, will potentially avert 100-580 malaria deaths and 45,000 to 80,000 clinical episodes per 100,000 fully vaccinated children over an initial 10-year phase.
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Affiliation(s)
- Melissa A Penny
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Katya Galactionova
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Michael Tarantino
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Marcel Tanner
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
- University of Basel, Basel, Switzerland.
| | - Thomas A Smith
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
- University of Basel, Basel, Switzerland.
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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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Woolhouse MEJ, Thumbi SM, Jennings A, Chase-Topping M, Callaby R, Kiara H, Oosthuizen MC, Mbole-Kariuki MN, Conradie I, Handel IG, Poole EJ, Njiiri E, Collins NE, Murray G, Tapio M, Auguet OT, Weir W, Morrison WI, Kruuk LEB, Bronsvoort BMDC, Hanotte O, Coetzer K, Toye PG. Co-infections determine patterns of mortality in a population exposed to parasite infection. SCIENCE ADVANCES 2015; 1:e1400026. [PMID: 26601143 PMCID: PMC4643819 DOI: 10.1126/sciadv.1400026] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 02/11/2015] [Indexed: 05/11/2023]
Abstract
Many individual hosts are infected with multiple parasite species, and this may increase or decrease the pathogenicity of the infections. This phenomenon is termed heterologous reactivity and is potentially an important determinant of both patterns of morbidity and mortality and of the impact of disease control measures at the population level. Using infections with Theileria parva (a tick-borne protozoan, related to Plasmodium) in indigenous African cattle [where it causes East Coast fever (ECF)] as a model system, we obtain the first quantitative estimate of the effects of heterologous reactivity for any parasitic disease. In individual calves, concurrent co-infection with less pathogenic species of Theileria resulted in an 89% reduction in mortality associated with T. parva infection. Across our study population, this corresponds to a net reduction in mortality due to ECF of greater than 40%. Using a mathematical model, we demonstrate that this degree of heterologous protection provides a unifying explanation for apparently disparate epidemiological patterns: variable disease-induced mortality rates, age-mortality profiles, weak correlations between the incidence of infection and disease (known as endemic stability), and poor efficacy of interventions that reduce exposure to multiple parasite species. These findings can be generalized to many other infectious diseases, including human malaria, and illustrate how co-infections can play a key role in determining population-level patterns of morbidity and mortality due to parasite infections.
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Affiliation(s)
- Mark E. J. Woolhouse
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
- Corresponding author. E-mail:
| | - Samuel M. Thumbi
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
- Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA 99164–7090, USA
| | - Amy Jennings
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
- The Roslin Institute, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
| | - Margo Chase-Topping
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
| | - Rebecca Callaby
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
- The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
| | - Henry Kiara
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
| | - Marinda C. Oosthuizen
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
| | - Mary N. Mbole-Kariuki
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
- School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Ilana Conradie
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
| | - Ian G. Handel
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
- The Roslin Institute, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
| | - E. Jane Poole
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
| | - Evalyne Njiiri
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
| | - Nicola E. Collins
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
| | - Gemma Murray
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
| | - Miika Tapio
- Natural Resources Institute Finland (Luke), Green technology, FI-31600 Jokioinen, Finland
| | - Olga Tosas Auguet
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
| | - Willie Weir
- Henry Wellcome Building, Institute of Biodiversity, Animal Health and Comparative Medicine, Garscube Campus, College of Medical, Veterinary and Life Sciences, University of Glasgow, Bearsden Road, Glasgow G61 1QH, UK
| | - W. Ivan Morrison
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
- The Roslin Institute, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
| | - Loeske E. B. Kruuk
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
- Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory 0200, Australia
| | - B. Mark de C. Bronsvoort
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
- The Roslin Institute, University of Edinburgh, The Roslin Building, Easter Bush, Midlothian EH25 9RG, UK
| | - Olivier Hanotte
- School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Koos Coetzer
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa
| | - Philip G. Toye
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
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Streatfield PK, Khan WA, Bhuiya A, Hanifi SMA, Alam N, Diboulo E, Sié A, Yé M, Compaoré Y, Soura AB, Bonfoh B, Jaeger F, Ngoran EK, Utzinger J, Melaku YA, Mulugeta A, Weldearegawi B, Gomez P, Jasseh M, Hodgson A, Oduro A, Welaga P, Williams J, Awini E, Binka FN, Gyapong M, Kant S, Misra P, Srivastava R, Chaudhary B, Juvekar S, Wahab A, Wilopo S, Bauni E, Mochamah G, Ndila C, Williams TN, Desai M, Hamel MJ, Lindblade KA, Odhiambo FO, Slutsker L, Ezeh A, Kyobutungi C, Wamukoya M, Delaunay V, Diallo A, Douillot L, Sokhna C, Gómez-Olivé FX, Kabudula CW, Mee P, Herbst K, Mossong J, Chuc NTK, Arthur SS, Sankoh OA, Tanner M, Byass P. Malaria mortality in Africa and Asia: evidence from INDEPTH health and demographic surveillance system sites. Glob Health Action 2014; 7:25369. [PMID: 25377329 PMCID: PMC4220130 DOI: 10.3402/gha.v7.25369] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Revised: 09/06/2014] [Accepted: 09/06/2014] [Indexed: 11/14/2022] Open
Abstract
Background Malaria continues to be a major cause of infectious disease mortality in tropical regions. However, deaths from malaria are most often not individually documented, and as a result overall understanding of malaria epidemiology is inadequate. INDEPTH Network members maintain population surveillance in Health and Demographic Surveillance System sites across Africa and Asia, in which individual deaths are followed up with verbal autopsies. Objective To present patterns of malaria mortality determined by verbal autopsy from INDEPTH sites across Africa and Asia, comparing these findings with other relevant information on malaria in the same regions. Design From a database covering 111,910 deaths over 12,204,043 person-years in 22 sites, in which verbal autopsy data were handled according to the WHO 2012 standard and processed using the InterVA-4 model, over 6,000 deaths were attributed to malaria. The overall period covered was 1992–2012, but two-thirds of the observations related to 2006–2012. These deaths were analysed by site, time period, age group and sex to investigate epidemiological differences in malaria mortality. Results Rates of malaria mortality varied by 1:10,000 across the sites, with generally low rates in Asia (one site recording no malaria deaths over 0.5 million person-years) and some of the highest rates in West Africa (Nouna, Burkina Faso: 2.47 per 1,000 person-years). Childhood malaria mortality rates were strongly correlated with Malaria Atlas Project estimates of Plasmodium falciparum parasite rates for the same locations. Adult malaria mortality rates, while lower than corresponding childhood rates, were strongly correlated with childhood rates at the site level. Conclusions The wide variations observed in malaria mortality, which were nevertheless consistent with various other estimates, suggest that population-based registration of deaths using verbal autopsy is a useful approach to understanding the details of malaria epidemiology.
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Affiliation(s)
- P Kim Streatfield
- Matlab HDSS, Bangladesh; International Centre for Diarrhoeal Disease Research, Bangladesh; INDEPTH Network, Accra, Ghana
| | - Wasif A Khan
- International Centre for Diarrhoeal Disease Research, Bangladesh; INDEPTH Network, Accra, Ghana; Bandarban HDSS, Bangladesh
| | - Abbas Bhuiya
- INDEPTH Network, Accra, Ghana; Chakaria HDSS, Bangladesh; Centre for Equity and Health Systems, International Centre for Diarrhoeal Disease Research, Bangladesh
| | - Syed M A Hanifi
- INDEPTH Network, Accra, Ghana; Chakaria HDSS, Bangladesh; Centre for Equity and Health Systems, International Centre for Diarrhoeal Disease Research, Bangladesh
| | - Nurul Alam
- INDEPTH Network, Accra, Ghana; AMK HDSS, Bangladesh; Centre for Population, Urbanisation and Climate Change, International Centre for Diarrhoeal Disease Research, Bangladesh
| | - Eric Diboulo
- INDEPTH Network, Accra, Ghana; Nouna HDSS, Burkina Faso; Nouna Health Research Centre, Nouna, Burkina Faso
| | - Ali Sié
- INDEPTH Network, Accra, Ghana; Nouna HDSS, Burkina Faso; Nouna Health Research Centre, Nouna, Burkina Faso
| | - Maurice Yé
- INDEPTH Network, Accra, Ghana; Nouna HDSS, Burkina Faso; Nouna Health Research Centre, Nouna, Burkina Faso
| | - Yacouba Compaoré
- INDEPTH Network, Accra, Ghana; Ouagadougou HDSS, Burkina Faso; Institut Supérieur des Sciences de la Population, Université de Ouagadougou, Burkina Faso
| | - Abdramane B Soura
- INDEPTH Network, Accra, Ghana; Ouagadougou HDSS, Burkina Faso; Institut Supérieur des Sciences de la Population, Université de Ouagadougou, Burkina Faso
| | - Bassirou Bonfoh
- INDEPTH Network, Accra, Ghana; Taabo HDSS, Côte d'Ivoire; , Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire
| | - Fabienne Jaeger
- INDEPTH Network, Accra, Ghana; Taabo HDSS, Côte d'Ivoire; Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Eliezer K Ngoran
- INDEPTH Network, Accra, Ghana; Taabo HDSS, Côte d'Ivoire; Université Félix Houphoët-Boigny, Abidjan, Côte d'Ivoire
| | - Juerg Utzinger
- INDEPTH Network, Accra, Ghana; Taabo HDSS, Côte d'Ivoire; Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Yohannes A Melaku
- INDEPTH Network, Accra, Ghana; Kilite-Awlaelo HDSS, Ethiopia; Department of Public Health, College of Health Sciences, Mekelle University, Mekelle, Ethiopia
| | - Afework Mulugeta
- INDEPTH Network, Accra, Ghana; Kilite-Awlaelo HDSS, Ethiopia; Department of Public Health, College of Health Sciences, Mekelle University, Mekelle, Ethiopia
| | - Berhe Weldearegawi
- INDEPTH Network, Accra, Ghana; Kilite-Awlaelo HDSS, Ethiopia; Department of Public Health, College of Health Sciences, Mekelle University, Mekelle, Ethiopia
| | - Pierre Gomez
- INDEPTH Network, Accra, Ghana; Farafenni HDSS, The Gambia; Medical Research Council, The Gambia Unit, Fajara, The Gambia
| | - Momodou Jasseh
- INDEPTH Network, Accra, Ghana; Farafenni HDSS, The Gambia; Medical Research Council, The Gambia Unit, Fajara, The Gambia
| | - Abraham Hodgson
- INDEPTH Network, Accra, Ghana; Navrongo HDSS, Ghana; Navrongo Health Research Centre, Navrongo, Ghana
| | - Abraham Oduro
- INDEPTH Network, Accra, Ghana; Navrongo HDSS, Ghana; Navrongo Health Research Centre, Navrongo, Ghana
| | - Paul Welaga
- INDEPTH Network, Accra, Ghana; Navrongo HDSS, Ghana; Navrongo Health Research Centre, Navrongo, Ghana
| | - John Williams
- INDEPTH Network, Accra, Ghana; Navrongo HDSS, Ghana; Navrongo Health Research Centre, Navrongo, Ghana
| | - Elizabeth Awini
- INDEPTH Network, Accra, Ghana; Dodowa HDSS, Ghana; Dodowa Health Research Centre, Dodowa, Ghana; School of Public Health, University of Ghana, Legon, Ghana
| | - Fred N Binka
- INDEPTH Network, Accra, Ghana; Dodowa HDSS, Ghana; School of Public Health, University of Ghana, Legon, Ghana
| | - Margaret Gyapong
- INDEPTH Network, Accra, Ghana; Dodowa HDSS, Ghana; School of Public Health, University of Ghana, Legon, Ghana
| | - Shashi Kant
- INDEPTH Network, Accra, Ghana; Ballabgarh HDSS, India; All India Institute of Medical Sciences, New Delhi, India
| | - Puneet Misra
- INDEPTH Network, Accra, Ghana; Ballabgarh HDSS, India; All India Institute of Medical Sciences, New Delhi, India
| | - Rahul Srivastava
- INDEPTH Network, Accra, Ghana; Ballabgarh HDSS, India; All India Institute of Medical Sciences, New Delhi, India
| | - Bharat Chaudhary
- INDEPTH Network, Accra, Ghana; Vadu HDSS, India; Vadu Rural Health Program, KEM Hospital Research Centre, Pune, India
| | - Sanjay Juvekar
- INDEPTH Network, Accra, Ghana; Vadu HDSS, India; Vadu Rural Health Program, KEM Hospital Research Centre, Pune, India
| | - Abdul Wahab
- INDEPTH Network, Accra, Ghana; Purworejo HDSS, Indonesia; Department of Public Health, Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - Siswanto Wilopo
- INDEPTH Network, Accra, Ghana; Purworejo HDSS, Indonesia; Department of Public Health, Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - Evasius Bauni
- INDEPTH Network, Accra, Ghana; Kilifi HDSS, Kenya; KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - George Mochamah
- INDEPTH Network, Accra, Ghana; Kilifi HDSS, Kenya; KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Carolyne Ndila
- INDEPTH Network, Accra, Ghana; Kilifi HDSS, Kenya; KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Thomas N Williams
- INDEPTH Network, Accra, Ghana; Kilifi HDSS, Kenya; KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya; Department of Medicine, Imperial College, St. Mary's Hospital, London
| | | | - Mary J Hamel
- INDEPTH Network, Accra, Ghana; Kisumu HDSS, Kenya; KEMRI/CDC Research and Public Health Collaboration and KEMRI Center for Global Health Research, Kisumu, Kenya
| | - Kim A Lindblade
- INDEPTH Network, Accra, Ghana; Kisumu HDSS, Kenya; KEMRI/CDC Research and Public Health Collaboration and KEMRI Center for Global Health Research, Kisumu, Kenya
| | - Frank O Odhiambo
- INDEPTH Network, Accra, Ghana; Kisumu HDSS, Kenya; KEMRI/CDC Research and Public Health Collaboration and KEMRI Center for Global Health Research, Kisumu, Kenya
| | - Laurence Slutsker
- INDEPTH Network, Accra, Ghana; Kisumu HDSS, Kenya; KEMRI/CDC Research and Public Health Collaboration and KEMRI Center for Global Health Research, Kisumu, Kenya
| | - Alex Ezeh
- INDEPTH Network, Accra, Ghana; Nairobi HDSS, Kenya; African Population and Health Research Center, Nairobi, Kenya
| | - Catherine Kyobutungi
- INDEPTH Network, Accra, Ghana; Nairobi HDSS, Kenya; African Population and Health Research Center, Nairobi, Kenya
| | - Marylene Wamukoya
- INDEPTH Network, Accra, Ghana; Nairobi HDSS, Kenya; African Population and Health Research Center, Nairobi, Kenya
| | - Valérie Delaunay
- INDEPTH Network, Accra, Ghana; Niakhar HDSS, Senegal; Institut de Recherche pour le Developpement (IRD), Dakar, Sénégal
| | - Aldiouma Diallo
- INDEPTH Network, Accra, Ghana; Niakhar HDSS, Senegal; Institut de Recherche pour le Developpement (IRD), Dakar, Sénégal
| | - Laetitia Douillot
- INDEPTH Network, Accra, Ghana; Niakhar HDSS, Senegal; Institut de Recherche pour le Developpement (IRD), Dakar, Sénégal
| | - Cheikh Sokhna
- INDEPTH Network, Accra, Ghana; Niakhar HDSS, Senegal; Institut de Recherche pour le Developpement (IRD), Dakar, Sénégal
| | - F Xavier Gómez-Olivé
- INDEPTH Network, Accra, Ghana; Agincourt HDSS, South Africa; MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Chodziwadziwa W Kabudula
- INDEPTH Network, Accra, Ghana; Agincourt HDSS, South Africa; MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Paul Mee
- INDEPTH Network, Accra, Ghana; Agincourt HDSS, South Africa; MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Kobus Herbst
- INDEPTH Network, Accra, Ghana; Africa Centre HDSS, South Africa; Africa Centre for Health and Population Studies, University of KwaZulu-Natal, Somkhele, KwaZulu-Natal, South Africa
| | - Joël Mossong
- INDEPTH Network, Accra, Ghana; Africa Centre HDSS, South Africa; Africa Centre for Health and Population Studies, University of KwaZulu-Natal, Somkhele, KwaZulu-Natal, South Africa; National Health Laboratory, Surveillance & Epidemiology of Infectious Diseases, Dudelange, Luxembourg
| | - Nguyen T K Chuc
- INDEPTH Network, Accra, Ghana; FilaBavi HDSS, Vietnam; Health System Research, Hanoi Medical University, Hanoi, Vietnam
| | | | - Osman A Sankoh
- INDEPTH Network, Accra, Ghana; School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa; Hanoi Medical University, Hanoi, Vietnam;
| | - Marcel Tanner
- WHO Collaborating Centre for Verbal Autopsy, Umeå Centre for Global Health Research, Umeå University, Umeå, Sweden
| | - Peter Byass
- MRC/Wits Rural Public Health and Health Transitions Research Unit (Agincourt), School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa
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Rumisha SF, Smith TA, Masanja H, Abdulla S, Vounatsou P. Relationship between child survival and malaria transmission: an analysis of the malaria transmission intensity and mortality burden across Africa (MTIMBA) project data in Rufiji demographic surveillance system, Tanzania. Malar J 2014; 13:124. [PMID: 24679119 PMCID: PMC4021084 DOI: 10.1186/1475-2875-13-124] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 02/19/2014] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND The precise nature of the relationship between malaria mortality and levels of transmission is unclear. Due to methodological limitations, earlier efforts to assess the linkage have lead to inconclusive results. The malaria transmission intensity and mortality burden across Africa (MTIMBA) project initiated by the INDEPTH Network collected longitudinally entomological data within a number of sites in sub-Saharan Africa to study this relationship. This work linked the MTIMBA entomology database with the routinely collected vital events within the Rufiji Demographic Surveillance System to analyse the transmission-mortality relation in the region. METHODS Bayesian Bernoulli spatio-temporal Cox proportional hazards models with village clustering, adjusted for age and insecticide-treated nets (ITNs), were fitted to assess the relation between mortality and malaria transmission measured by entomology inoculation rate (EIR). EIR was predicted at household locations using transmission models and it was incorporated in the model as a covariate with measure of uncertainty. Effects of covariates estimated by the model are reported as hazard ratios (HR) with 95% Bayesian confidence interval (BCI) and spatial and temporal parameters are presented. RESULTS Separate analysis was carried out for neonates, infants and children 1-4 years of age. No significant relation between all-cause mortality and intensity of malaria transmission was indicated at any age in childhood. However, a strong age effect was shown. Comparing effects of ITN and EIR on mortality at different age categories, a decrease in protective efficacy of ITN was observed (i.e. neonates: HR = 0.65; 95% BCI:0.39-1.05; infants: HR = 0.72; 95% BCI:0.48-1.07; children 1-4 years: HR = 0.88; 95% BCI:0.62-1.23) and reduction on the effect of malaria transmission exposure was detected (i.e. neonates: HR = 1.15; 95% BCI:0.95-1.36; infants: HR = 1.13; 95% BCI:0.98-1.25; children 1-4 years: HR = 1.04; 95% BCI:0.89-1.18). A very strong spatial correlation was also observed. CONCLUSION These results imply that assessing the malaria transmission-mortality relation involves more than the knowledge on the performance of interventions and control measures. This relation depends on the levels of malaria endemicity and transmission intensity, which varies significantly between different settings. Thus, sub-regions analyses are necessary to validate and assess reproducibility of findings.
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Affiliation(s)
- Susan F Rumisha
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 Basel, Switzerland
- University of Basel, Petersplatz 1, 4051 Basel, Switzerland
- National Institute for Medical Research, PO Box 9653, Dar es Salaam, Tanzania
| | - Thomas A Smith
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 Basel, Switzerland
- University of Basel, Petersplatz 1, 4051 Basel, Switzerland
| | | | - Salim Abdulla
- Ifakara Health Institute, PO Box 78373, Dar es Salaam, Tanzania
| | - Penelope Vounatsou
- Swiss Tropical and Public Health Institute, Socinstrasse 57, 4051 Basel, Switzerland
- University of Basel, Petersplatz 1, 4051 Basel, Switzerland
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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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Stuckey EM, Smith TA, Chitnis N. Estimating malaria transmission through mathematical models. Trends Parasitol 2013; 29:477-82. [PMID: 24001452 DOI: 10.1016/j.pt.2013.08.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 08/02/2013] [Accepted: 08/05/2013] [Indexed: 10/26/2022]
Abstract
Evaluating the effectiveness of malaria control interventions on the basis of their impact on transmission is increasingly important as countries move from malaria control to pre-elimination programs. Mathematical modeling can examine relationships between malaria indicators, allowing translation of easily measured data into measures of transmission, and addressing key concerns with traditional methods for quantifying transmission. Simulations show these indicators are statistically correlated, allowing direct comparisons of malaria transmission using data collected using different methods across a range of transmission intensities and seasonal patterns. Results from such models can provide public health officials with accurate estimates of transmission, by seasonal pattern, that are necessary for assessing and tailoring malaria control and elimination programs to specific settings.
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Affiliation(s)
- Erin M Stuckey
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, Postfach, 4002 Basel, Switzerland; University of Basel, Petersplatz 1, 4003 Basel, Switzerland.
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Nunes JK, Cárdenas V, Loucq C, Maire N, Smith T, Shaffer C, Måseide K, Brooks A. Modeling the public health impact of malaria vaccines for developers and policymakers. BMC Infect Dis 2013; 13:295. [PMID: 23815273 PMCID: PMC3711926 DOI: 10.1186/1471-2334-13-295] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Accepted: 06/17/2013] [Indexed: 11/15/2022] Open
Abstract
Background Efforts to develop malaria vaccines show promise. Mathematical model-based estimates of the potential demand, public health impact, and cost and financing requirements can be used to inform investment and adoption decisions by vaccine developers and policymakers on the use of malaria vaccines as complements to existing interventions. However, the complexity of such models may make their outputs inaccessible to non-modeling specialists. This paper describes a Malaria Vaccine Model (MVM) developed to address the specific needs of developers and policymakers, who need to access sophisticated modeling results and to test various scenarios in a user-friendly interface. The model’s functionality is demonstrated through a hypothetical vaccine. Methods The MVM has three modules: supply and demand forecast; public health impact; and implementation cost and financing requirements. These modules include pre-entered reference data and also allow for user-defined inputs. The model includes an integrated sensitivity analysis function. Model functionality was demonstrated by estimating the public health impact of a hypothetical pre-erythrocytic malaria vaccine with 85% efficacy against uncomplicated disease and a vaccine efficacy decay rate of four years, based on internationally-established targets. Demand for this hypothetical vaccine was estimated based on historical vaccine implementation rates for routine infant immunization in 40 African countries over a 10-year period. Assumed purchase price was $5 per dose and injection equipment and delivery costs were $0.40 per dose. Results The model projects the number of doses needed, uncomplicated and severe cases averted, deaths and disability-adjusted life years (DALYs) averted, and cost to avert each. In the demonstration scenario, based on a projected demand of 532 million doses, the MVM estimated that 150 million uncomplicated cases of malaria and 1.1 million deaths would be averted over 10 years. This is equivalent to 943 uncomplicated cases and 7 deaths averted per 1,000 vaccinees. In discounted 2011 US dollars, this represents $11 per uncomplicated case averted and $1,482 per death averted. If vaccine efficacy were reduced to 75%, the estimated uncomplicated cases and deaths averted over 10 years would decrease by 14% and 19%, respectively. Conclusions The MVM can provide valuable information to assist decision-making by vaccine developers and policymakers, information which will be refined and strengthened as field studies progress allowing further validation of modeling assumptions.
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Crowell V, Briët OJT, Hardy D, Chitnis N, Maire N, Di Pasquale A, Smith TA. Modelling the cost-effectiveness of mass screening and treatment for reducing Plasmodium falciparum malaria burden. Malar J 2013; 12:4. [PMID: 23286228 PMCID: PMC3544609 DOI: 10.1186/1475-2875-12-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Accepted: 12/19/2012] [Indexed: 12/31/2022] Open
Abstract
Background Past experience and modelling suggest that, in most cases, mass treatment strategies are not likely to succeed in interrupting Plasmodium falciparum malaria transmission. However, this does not preclude their use to reduce disease burden. Mass screening and treatment (MSAT) is preferred to mass drug administration (MDA), as the latter involves massive over-use of drugs. This paper reports simulations of the incremental cost-effectiveness of well-conducted MSAT campaigns as a strategy for P. falciparum malaria disease-burden reduction in settings with varying receptivity (ability of the combined vector population in a setting to transmit disease) and access to case management. Methods MSAT incremental cost-effectiveness ratios (ICERs) were estimated in different sub-Saharan African settings using simulation models of the dynamics of malaria and a literature-based MSAT cost estimate. Imported infections were simulated at a rate of two per 1,000 population per annum. These estimates were compared to the ICERs of scaling up case management or insecticide-treated net (ITN) coverage in each baseline health system, in the absence of MSAT. Results MSAT averted most episodes, and resulted in the lowest ICERs, in settings with a moderate level of disease burden. At a low pre-intervention entomological inoculation rate (EIR) of two infectious bites per adult per annum (IBPAPA) MSAT was never more cost-effective than scaling up ITNs or case management coverage. However, at pre-intervention entomological inoculation rates (EIRs) of 20 and 50 IBPAPA and ITN coverage levels of 40 or 60%, respectively, the ICER of MSAT was similar to that of scaling up ITN coverage further. Conclusions In all the transmission settings considered, achieving a minimal level of ITN coverage is a “best buy”. At low transmission, MSAT probably is not worth considering. Instead, MSAT may be suitable at medium to high levels of transmission and at moderate ITN coverage. If undertaken as a burden-reducing intervention, MSAT should be continued indefinitely and should complement, not replace, case management and vector control interventions.
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Affiliation(s)
- Valerie Crowell
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel, Switzerland.
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Gurarie D, Karl S, Zimmerman PA, King CH, St. Pierre TG, Davis TME. Mathematical modeling of malaria infection with innate and adaptive immunity in individuals and agent-based communities. PLoS One 2012; 7:e34040. [PMID: 22470511 PMCID: PMC3314696 DOI: 10.1371/journal.pone.0034040] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 02/21/2012] [Indexed: 11/26/2022] Open
Abstract
Background Agent-based modeling of Plasmodium falciparum infection offers an attractive alternative to the conventional Ross-Macdonald methodology, as it allows simulation of heterogeneous communities subjected to realistic transmission (inoculation patterns). Methodology/Principal Findings We developed a new, agent based model that accounts for the essential in-host processes: parasite replication and its regulation by innate and adaptive immunity. The model also incorporates a simplified version of antigenic variation by Plasmodium falciparum. We calibrated the model using data from malaria-therapy (MT) studies, and developed a novel calibration procedure that accounts for a deterministic and a pseudo-random component in the observed parasite density patterns. Using the parasite density patterns of 122 MT patients, we generated a large number of calibrated parameters. The resulting data set served as a basis for constructing and simulating heterogeneous agent-based (AB) communities of MT-like hosts. We conducted several numerical experiments subjecting AB communities to realistic inoculation patterns reported from previous field studies, and compared the model output to the observed malaria prevalence in the field. There was overall consistency, supporting the potential of this agent-based methodology to represent transmission in realistic communities. Conclusions/Significance Our approach represents a novel, convenient and versatile method to model Plasmodium falciparum infection.
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Affiliation(s)
- David Gurarie
- Department of Mathematics, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Stephan Karl
- School of Physics, The University of Western Australia, Crawley, Western Australia, Australia
- School of Medicine and Pharmacology, The University of Western Australia, Fremantle Hospital, Fremantle, Western Australia, Australia
- * E-mail:
| | - Peter A. Zimmerman
- The Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Charles H. King
- The Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Timothy G. St. Pierre
- School of Physics, The University of Western Australia, Crawley, Western Australia, Australia
| | - Timothy M. E. Davis
- School of Medicine and Pharmacology, The University of Western Australia, Fremantle Hospital, Fremantle, Western Australia, Australia
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Brooks A, Briët OJT, Hardy D, Steketee R, Smith TA. Simulated impact of RTS,S/AS01 vaccination programs in the context of changing malaria transmission. PLoS One 2012; 7:e32587. [PMID: 22412892 PMCID: PMC3295753 DOI: 10.1371/journal.pone.0032587] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 02/01/2012] [Indexed: 12/29/2022] Open
Abstract
Introduction The RTS,S/AS01 pre-erythrocytic malaria vaccine is in phase III clinical trials. It is critical to anticipate where and how it should be implemented if trials are successful. Such planning may be complicated by changing levels of malaria transmission. Methods/results Computer simulations were used to examine RTS,S/AS01 impact, using a vaccine profile based on phase II trial results, and assuming that protection decays only slowly. Settings were simulated in which baseline transmission (in the absence of vaccine) was fixed or varied between 2 and 20 infectious mosquito bites per person per annum (ibpa) over ten years. Four delivery strategies were studied: routine infant immunization (EPI), EPI plus infant catch-up, EPI plus school-based campaigns, and EPI plus mass campaigns. Impacts in changing transmission settings were similar to those in fixed settings. Assuming a persistent effect of vaccination, at 2 ibpa, the vaccine averted approximately 5–7 deaths per 1000 doses of vaccine when delivered via mass campaigns, but the benefit was less at higher transmission levels. EPI, catch-up and school-based strategies averted 2–3 deaths per 1000 doses in settings with 2 ibpa. In settings where transmission was decreasing or increasing, EPI, catch-up and school-based strategies averted approximately 3–4 deaths per 1000 doses. Discussion Where transmission is changing, it appears to be sufficient to consider simulations of pre-erythrocytic vaccine impact at a range of initial transmission levels. At 2 ibpa, mass campaigns averted the most deaths and reduced transmission, but this requires further study. If delivered via EPI, RTS,S/AS01 could avert approximately 6–11 deaths per 1000 vaccinees in all examined settings, similar to estimates for pneumococcal conjugate vaccine in African infants. These results support RTS,S/AS01 implementation via EPI, for example alongside vector control interventions, providing that the phase III trials provide support for our assumptions about efficacy.
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Affiliation(s)
- Alan Brooks
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
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Importance of factors determining the effective lifetime of a mass, long-lasting, insecticidal net distribution: a sensitivity analysis. Malar J 2012; 11:20. [PMID: 22244509 PMCID: PMC3273435 DOI: 10.1186/1475-2875-11-20] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 01/13/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Long-lasting insecticidal nets (LLINs) reduce malaria transmission by protecting individuals from infectious bites, and by reducing mosquito survival. In recent years, millions of LLINs have been distributed across sub-Saharan Africa (SSA). Over time, LLINs decay physically and chemically and are destroyed, making repeated interventions necessary to prevent a resurgence of malaria. Because its effects on transmission are important (more so than the effects of individual protection), estimates of the lifetime of mass distribution rounds should be based on the effective length of epidemiological protection. METHODS Simulation models, parameterised using available field data, were used to analyse how the distribution's effective lifetime depends on the transmission setting and on LLIN characteristics. Factors considered were the pre-intervention transmission level, initial coverage, net attrition, and both physical and chemical decay. An ensemble of 14 stochastic individual-based model variants for malaria in humans was used, combined with a deterministic model for malaria in mosquitoes. RESULTS The effective lifetime was most sensitive to the pre-intervention transmission level, with a lifetime of almost 10 years at an entomological inoculation rate of two infectious bites per adult per annum (ibpapa), but of little more than 2 years at 256 ibpapa. The LLIN attrition rate and the insecticide decay rate were the next most important parameters. The lifetime was surprisingly insensitive to physical decay parameters, but this could change as physical integrity gains importance with the emergence and spread of pyrethroid resistance. CONCLUSIONS The strong dependency of the effective lifetime on the pre-intervention transmission level indicated that the required distribution frequency may vary more with the local entomological situation than with LLIN quality or the characteristics of the distribution system. This highlights the need for malaria monitoring both before and during intervention programmes, particularly since there are likely to be strong variations between years and over short distances. The majority of SSA's population falls into exposure categories where the lifetime is relatively long, but because exposure estimates are highly uncertain, it is necessary to consider subsequent interventions before the end of the expected effective lifetime based on an imprecise transmission measure.
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A periodically-forced mathematical model for the seasonal dynamics of malaria in mosquitoes. Bull Math Biol 2012; 74:1098-124. [PMID: 22218880 PMCID: PMC3339865 DOI: 10.1007/s11538-011-9710-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Accepted: 11/24/2011] [Indexed: 11/01/2022]
Abstract
We describe and analyze a periodically-forced difference equation model for malaria in mosquitoes that captures the effects of seasonality and allows the mosquitoes to feed on a heterogeneous population of hosts. We numerically show the existence of a unique globally asymptotically stable periodic orbit and calculate periodic orbits of field-measurable quantities that measure malaria transmission. We integrate this model with an individual-based stochastic simulation model for malaria in humans to compare the effects of insecticide-treated nets (ITNs) and indoor residual spraying (IRS) in reducing malaria transmission, prevalence, and incidence. We show that ITNs are more effective than IRS in reducing transmission and prevalence though IRS would achieve its maximal effects within 2 years while ITNs would need two mass distribution campaigns over several years to do so. Furthermore, the combination of both interventions is more effective than either intervention alone. However, although these interventions reduce transmission and prevalence, they can lead to increased clinical malaria; and all three malaria indicators return to preintervention levels within 3 years after the interventions are withdrawn.
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Smith T, Ross A, Maire N, Chitnis N, Studer A, Hardy D, Brooks A, Penny M, Tanner M. Ensemble modeling of the likely public health impact of a pre-erythrocytic malaria vaccine. PLoS Med 2012; 9:e1001157. [PMID: 22272189 PMCID: PMC3260300 DOI: 10.1371/journal.pmed.1001157] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 11/30/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The RTS,S malaria vaccine may soon be licensed. Models of impact of such vaccines have mainly considered deployment via the World Health Organization's Expanded Programme on Immunization (EPI) in areas of stable endemic transmission of Plasmodium falciparum, and have been calibrated for such settings. Their applicability to low transmission settings is unclear. Evaluations of the efficiency of different deployment strategies in diverse settings should consider uncertainties in model structure. METHODS AND FINDINGS An ensemble of 14 individual-based stochastic simulation models of P. falciparum dynamics, with differing assumptions about immune decay, transmission heterogeneity, and treatment access, was constructed. After fitting to an extensive library of field data, each model was used to predict the likely health benefits of RTS,S deployment, via EPI (with or without catch-up vaccinations), supplementary vaccination of school-age children, or mass vaccination every 5 y. Settings with seasonally varying transmission, with overall pre-intervention entomological inoculation rates (EIRs) of two, 11, and 20 infectious bites per person per annum, were considered. Predicted benefits of EPI vaccination programs over the simulated 14-y time horizon were dependent on duration of protection. Nevertheless, EPI strategies (with an initial catch-up phase) averted the most deaths per dose at the higher EIRs, although model uncertainty increased with EIR. At two infectious bites per person per annum, mass vaccination strategies substantially reduced transmission, leading to much greater health effects per dose, even at modest coverage. CONCLUSIONS In higher transmission settings, EPI strategies will be most efficient, but vaccination additional to the EPI in targeted low transmission settings, even at modest coverage, might be more efficient than national-level vaccination of infants. The feasibility and economics of mass vaccination, and the circumstances under which vaccination will avert epidemics, remain unclear. The approach of using an ensemble of models provides more secure conclusions than a single-model approach, and suggests greater confidence in predictions of health effects for lower transmission settings than for higher ones.
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Affiliation(s)
- Thomas Smith
- Swiss Tropical and Public Health Institute, Basel, Switzerland.
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Gething PW, Patil AP, Smith DL, Guerra CA, Elyazar IRF, Johnston GL, Tatem AJ, Hay SI. A new world malaria map: Plasmodium falciparum endemicity in 2010. Malar J 2011; 10:378. [PMID: 22185615 PMCID: PMC3274487 DOI: 10.1186/1475-2875-10-378] [Citation(s) in RCA: 468] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 12/20/2011] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Transmission intensity affects almost all aspects of malaria epidemiology and the impact of malaria on human populations. Maps of transmission intensity are necessary to identify populations at different levels of risk and to evaluate objectively options for disease control. To remain relevant operationally, such maps must be updated frequently. Following the first global effort to map Plasmodium falciparum malaria endemicity in 2007, this paper describes the generation of a new world map for the year 2010. This analysis is extended to provide the first global estimates of two other metrics of transmission intensity for P. falciparum that underpin contemporary questions in malaria control: the entomological inoculation rate (PfEIR) and the basic reproductive number (PfR). METHODS Annual parasite incidence data for 13,449 administrative units in 43 endemic countries were sourced to define the spatial limits of P. falciparum transmission in 2010 and 22,212 P. falciparum parasite rate (PfPR) surveys were used in a model-based geostatistical (MBG) prediction to create a continuous contemporary surface of malaria endemicity within these limits. A suite of transmission models were developed that link PfPR to PfEIR and PfR and these were fitted to field data. These models were combined with the PfPR map to create new global predictions of PfEIR and PfR. All output maps included measured uncertainty. RESULTS An estimated 1.13 and 1.44 billion people worldwide were at risk of unstable and stable P. falciparum malaria, respectively. The majority of the endemic world was predicted with a median PfEIR of less than one and a median PfRc of less than two. Values of either metric exceeding 10 were almost exclusive to Africa. The uncertainty described in both PfEIR and PfR was substantial in regions of intense transmission. CONCLUSIONS The year 2010 has a particular significance as an evaluation milestone for malaria global health policy. The maps presented here contribute to a rational basis for control and elimination decisions and can serve as a baseline assessment as the global health community looks ahead to the next series of milestones targeted at 2015.
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Affiliation(s)
- Peter W Gething
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK
| | - Anand P Patil
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK
| | - David L Smith
- Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA
- Department of Biology and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Carlos A Guerra
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK
| | - Iqbal RF Elyazar
- Eijkman-Oxford Clinical Research Unit, Jalan Diponegoro No. 69, Jakarta 10430, Indonesia
| | - Geoffrey L Johnston
- School of International and Public Affairs, Columbia University, 420 West 118th St, New York, USA
- Department of Microbiology and Immunology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | - Andrew J Tatem
- Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA
- Department of Geography and Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
| | - Simon I Hay
- Spatial Ecology and Epidemiology Group, Tinbergen Building, Department of Zoology, University of Oxford, South Parks Road, Oxford, UK
- Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA
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Maire N, Shillcutt SD, Walker DG, Tediosi F, Smith TA. Cost-effectiveness of the introduction of a pre-erythrocytic malaria vaccine into the expanded program on immunization in sub-Saharan Africa: analysis of uncertainties using a stochastic individual-based simulation model of Plasmodium falciparum malaria. VALUE IN HEALTH : THE JOURNAL OF THE INTERNATIONAL SOCIETY FOR PHARMACOECONOMICS AND OUTCOMES RESEARCH 2011; 14:1028-1038. [PMID: 22152171 DOI: 10.1016/j.jval.2011.06.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 06/10/2011] [Accepted: 06/13/2011] [Indexed: 05/31/2023]
Abstract
OBJECTIVE To evaluate the cost-effectiveness of introducing the RTS,S malaria vaccine into the Expanded Programme on Immunization (EPI) in Sub-Saharan Africa (SSA), the contributions of different sources of uncertainty, and the associated expected value of perfect information (EVPI). METHODS Vaccination was simulated in populations of 100,000 people at 10 different entomological inoculation rates (EIRs), using an existing stochastic model and a 10-year time horizon. Incremental cost-effectiveness ratios (ICERs) and EVPI were computed from weighted averages of outputs using two different assignments of the EIR distribution in 2007. Uncertainty was evaluated by resampling of epidemiological, vaccination, and health systems model parameters. RESULTS Health benefits were predicted consistently only at low transmission, and program costs always substantially exceeded case management savings. Optimal cost-effectiveness was at EIR of about 10 infectious bites per annum (ibpa). Main contributors to ICER uncertainty were uncertainty in transmission intensity, price per vaccine dose, decay rate of the vaccine effect, degree of homogeneity in host response, and some epidemiological model parameters. Other health system costs were unimportant. With a ceiling ratio of 207 international dollars per disability-adjusted life-year averted, 52.4% of parameterizations predicted cost-effectiveness in the primary analysis. CONCLUSIONS Cost-effectiveness of RTS,S will be maximal in low endemicity settings (EIR 2-20 ibpa). Widespread deployment of other transmission-reducing interventions will thus improve cost-effectiveness, suggesting a selective introduction strategy. EVPI is substantial. Accrual of up-to-date information on local endemicity to guide deployment decisions would be highly efficient.
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Affiliation(s)
- Nicolas Maire
- Swiss Tropical and Public Health Institute, Basel, Switzerland
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Crowell V, Hardy D, Briët O, Chitnis N, Maire N, Smith T. Can we depend on case management to prevent re-establishment of P. falciparum malaria, after local interruption of transmission? Epidemics 2011; 4:1-8. [PMID: 22325009 DOI: 10.1016/j.epidem.2011.10.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 09/01/2011] [Accepted: 10/31/2011] [Indexed: 10/15/2022] Open
Abstract
Recent declines in malaria burden in many parts of the world have prompted consideration of how interruption of Plasmodium falciparum transmission could be maintained, if achieved, and notably whether large-scale vector control could be replaced with surveillance. This information is essential for elimination feasibility assessments and planning. The risk of re-establishment of transmission depends mainly on vectorial capacity (receptivity), likely to rebound once vector control is removed, the rate of importation of infections (vulnerability), the capacity to detect and treat infections and the level of immunity in infected individuals. Timely detection and removal of new infections is likely to be critical to prevent re-establishment of transmission. We assess, through mathematical modeling and simulation, which levels of case detection and treatment (case management) are required to prevent re-establishment of transmission of P. falciparum after local interruption of transmission has been achieved, in settings with varying receptivity and vulnerability. We find that, even at rather low levels of receptivity, case management alone cannot reliably prevent re-establishment of P. falciparum malaria transmission in the face of medium to high importation rates. Thus, if vector control is to be discontinued, preventing the importations by controlling transmission in source areas will generally be necessary for preventing reintroduction in such settings, and cannot be substituted by very high levels of case management coverage.
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Affiliation(s)
- Valerie Crowell
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
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Scott JAG, Berkley JA, Mwangi I, Ochola L, Uyoga S, Macharia A, Ndila C, Lowe BS, Mwarumba S, Bauni E, Marsh K, Williams TN. Relation between falciparum malaria and bacteraemia in Kenyan children: a population-based, case-control study and a longitudinal study. Lancet 2011; 378:1316-23. [PMID: 21903251 PMCID: PMC3192903 DOI: 10.1016/s0140-6736(11)60888-x] [Citation(s) in RCA: 231] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Many investigators have suggested that malaria infection predisposes individuals to bacteraemia. We tested this hypothesis with mendelian randomisation studies of children with the malaria-protective phenotype of sickle-cell trait (HbAS). METHODS This study was done in a defined area around Kilifi District Hospital, Kilifi, Kenya. We did a matched case-control study to identify risk factors for invasive bacterial disease, in which cases were children aged 3 months to 13 years who were admitted to hospital with bacteraemia between Sept 16, 1999, and July 31, 2002. We aimed to match two controls, by age, sex, location, and time of recruitment, for every case. We then did a longitudinal case-control study to assess the relation between HbAS and invasive bacterial disease as malaria incidence decreased. Cases were children aged 0-13 years who were admitted to hospital with bacteraemia between Jan 1, 1999, and Dec 31, 2007. Controls were born in the study area between Jan 1, 2006, and June 23, 2009. Finally, we modelled the annual incidence of bacteraemia against the community prevalence of malaria during 9 years with Poisson regression. RESULTS In the matched case-control study, we recruited 292 cases-we recruited two controls for 236, and one for the remaining 56. Sickle-cell disease, HIV, leucocyte haemozoin pigment, and undernutrition were positively associated with bacteraemia and HbAS was strongly negatively associated with bacteraemia (odds ratio 0·36; 95% CI 0·20-0·65). In the longitudinal case-control study, we assessed data from 1454 cases and 10,749 controls. During the study period, the incidence of admission to hospital with malaria per 1000 child-years decreased from 28·5 to 3·45, with a reduction in protection afforded by HbAS against bacteraemia occurring in parallel (p=0·0008). The incidence of hospital admissions for bacteraemia per 1000 child-years also decreased from 2·59 to 1·45. The bacteraemia incidence rate ratio associated with malaria parasitaemia was 6·69 (95% CI 1·31-34·3) and, at a community parasite prevalence of 29% in 1999, 62% (8·2-91) of bacteraemia cases were attributable to malaria. INTERPRETATION Malaria infection strongly predisposes individuals to bacteraemia and can account for more than half of all cases of bacteraemia in malaria-endemic areas. Interventions to control malaria will have a major additional benefit by reducing the burden of invasive bacterial disease. FUNDING Wellcome Trust.
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Affiliation(s)
- J Anthony G Scott
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
- INDEPTH Network, Accra, Ghana
- Correspondence to: Dr Anthony Scott, KEMRI-Wellcome Trust Programme, Centre for Geographic Medicine Research-Coast, P O Box 230, Kilifi, Kenya
| | - James A Berkley
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
| | - Isaiah Mwangi
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Lucy Ochola
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Sophie Uyoga
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Alexander Macharia
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Carolyne Ndila
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Brett S Lowe
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Salim Mwarumba
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Evasius Bauni
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Kevin Marsh
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
| | - Thomas N Williams
- Kenya Medical Research Institute-Wellcome Trust Research Programme, Kilifi, Kenya
- Nuffield Department of Medicine, University of Oxford, Oxford, UK
- INDEPTH Network, Accra, Ghana
- Department of Paediatrics, University of Oxford, Oxford, UK
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Ross A, Maire N, Sicuri E, Smith T, Conteh L. Determinants of the cost-effectiveness of intermittent preventive treatment for malaria in infants and children. PLoS One 2011; 6:e18391. [PMID: 21490967 PMCID: PMC3072385 DOI: 10.1371/journal.pone.0018391] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 02/28/2011] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Trials of intermittent preventive treatment in infants (IPTi) and children (IPTc) have shown promising results in reducing malaria episodes but with varying efficacy and cost-effectiveness. The effects of different intervention and setting characteristics are not well known. We simulate the effects of the different target age groups and delivery channels, seasonal or year-round delivery, transmission intensity, seasonality, proportions of malaria fevers treated and drug characteristics. METHODS We use a dynamic, individual-based simulation model of Plasmodium falciparum malaria epidemiology, antimalarial drug action and case management to simulate DALYs averted and the cost per DALY averted by IPTi and IPTc. IPT cost components were estimated from economic studies alongside trials. RESULTS IPTi and IPTc were predicted to be cost-effective in most of the scenarios modelled. The cost-effectiveness is driven by the impact on DALYs, particularly for IPTc, and the low costs, particularly for IPTi which uses the existing delivery strategy, EPI. Cost-effectiveness was predicted to decrease with low transmission, badly timed seasonal delivery in a seasonal setting, short-acting and more expensive drugs, high frequencies of drug resistance and high levels of treatment of malaria fevers. Seasonal delivery was more cost-effective in seasonal settings, and year-round in constant transmission settings. The difference was more pronounced for IPTc than IPTi due to the different proportions of fixed costs and also different assumed drug spacing during the transmission season. The number of DALYs averted was predicted to decrease as a target five-year age-band for IPTc was shifted from children under 5 years into older ages, except at low transmission intensities. CONCLUSIONS Modelling can extend the information available by predicting impact and cost-effectiveness for scenarios, for outcomes and for multiple strategies where, for practical reasons, trials cannot be carried out. Both IPTi and IPTc are generally cost-effective but could be rendered cost-ineffective by characteristics of the setting, drug or implementation.
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Affiliation(s)
- Amanda Ross
- Swiss Tropical and Public Health Institute, Basel, Switzerland.
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Duthé G, Faye SHD, Guyavarch E, Arduin P, Kanté AM, Diallo A, Laurent R, Marra A, Pison G. [Change of protocol in the verbal autopsy method and measure of malaria mortality in rural areas in Senegal]. ACTA ACUST UNITED AC 2010; 103:327-32. [PMID: 20821179 DOI: 10.1007/s13149-010-0078-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 06/01/2010] [Indexed: 10/19/2022]
Abstract
In rural Senegal, three populations have been followed up since several decades and the malaria mortality trend has been observed since the mid-1980s. However, limits are associated with the verbal autopsy method used to determine causes of death, especially deaths due to malaria. A change in protocol occurred in recent years in two of these three sites with the involvement of two physicians (instead of only one) in the diagnosis. The objective is here to measure its potential impact on diagnosis of malaria deaths. Five hundred and fifteen diagnoses reported on child deaths occurred from 2000 to 2005 have been analysed. We have identified, on the basis of a multinomial logistic regression model, factors affecting the determination of malaria deaths among the characteristics of the child, the death, the illness and its symptoms, and we also took into account method factors. Factors related to the method do not play on the malaria diagnosis. This result insures the continuity of the series on malaria mortality statistics since 2000 in the two sites despite changes in the method. However, the new protocol leads to vanish possibility of having deaths among ill-defined or unknown causes. In the African context of absence of health statistics, data obtained through the verbal autopsy method in demographic surveillance system can provide accurate information in the epidemiological field, even regarding malaria.
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Affiliation(s)
- G Duthé
- Institut National d'Etudes Démographiques (INED, Paris), 133 Boulevard Davout, F-75980, Paris Cedex 20, France.
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Ross A, Smith T. Interpreting malaria age-prevalence and incidence curves: a simulation study of the effects of different types of heterogeneity. Malar J 2010; 9:132. [PMID: 20478060 PMCID: PMC2888834 DOI: 10.1186/1475-2875-9-132] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Accepted: 05/17/2010] [Indexed: 11/18/2022] Open
Abstract
Background Individuals in a malaria endemic community differ from one another. Many of these differences, such as heterogeneities in transmission or treatment-seeking behaviour, affect malaria epidemiology. The different kinds of heterogeneity are likely to be correlated. Little is known about their impact on the shape of age-prevalence and incidence curves. In this study, the effects of heterogeneity in transmission, treatment-seeking and risk of co-morbidity were simulated. Methods Simple patterns of heterogeneity were incorporated into a comprehensive individual-based model of Plasmodium falciparum malaria epidemiology. The different types of heterogeneity were systematically simulated individually, and in independent and co-varying pairs. The effects on age-curves for parasite prevalence, uncomplicated and severe episodes, direct and indirect mortality and first-line treatments and hospital admissions were examined. Results Different heterogeneities affected different outcomes with large effects reserved for outcomes which are directly affected by the action of the heterogeneity rather than via feedback on acquired immunity or fever thresholds. Transmission heterogeneity affected the age-curves for all outcomes. The peak parasite prevalence was reduced and all age-incidence curves crossed those of the reference scenario with a lower incidence in younger children and higher in older age-groups. Heterogeneity in the probability of seeking treatment reduced the peak incidence of first-line treatment and hospital admissions. Heterogeneity in co-morbidity risk showed little overall effect, but high and low values cancelled out for outcomes directly affected by its action. Independently varying pairs of heterogeneities produced additive effects. More variable results were produced for co-varying heterogeneities, with striking differences compared to independent pairs for some outcomes which were affected by both heterogeneities individually. Conclusions Different kinds of heterogeneity both have different effects and affect different outcomes. Patterns of co-variation are also important. Alongside the absolute levels of different factors affecting age-curves, patterns of heterogeneity should be considered when parameterizing or validating models, interpreting data and inferring from one outcome to another.
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Affiliation(s)
- Amanda Ross
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland.
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