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Malizia V, de Vlas SJ, Roes KCB, Giardina F. Revisiting the impact of Schistosoma mansoni regulating mechanisms on transmission dynamics using SchiSTOP, a novel modelling framework. PLoS Negl Trop Dis 2024; 18:e0012464. [PMID: 39303001 DOI: 10.1371/journal.pntd.0012464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Accepted: 08/15/2024] [Indexed: 09/22/2024] Open
Abstract
BACKGROUND The transmission cycle of Schistosoma is remarkably complex, including sexual reproduction in human hosts and asexual reproduction in the intermediate host (freshwater snails). Patterns of rapid recrudescence after treatment and stable low transmission are often observed, hampering the achievement of control targets. Current mathematical models commonly assume regulation of transmission to occur at worm level through density-dependent egg production. However, conclusive evidence on this regulating mechanism is weak, especially for S. mansoni. In this study, we explore the interplay of different regulating mechanisms and their ability to explain observed patterns in S. mansoni epidemiology. METHODOLOGY/PRINCIPAL FINDINGS We developed SchiSTOP: a hybrid stochastic agent-based and deterministic modelling framework for S. mansoni transmission in an age-structured human population. We implemented different models with regulating mechanisms at: i) worm-level (density-dependent egg production), ii) human-level (anti-reinfection immunity), and iii) snail-level (density-dependent snail dynamics). Additionally, we considered two functional choices for the age-specific relative exposure to infection. We assessed the ability of each model to reproduce observed epidemiological patterns pre- and post-control, and compared successful models in their predictions of the impact of school-based and community-wide treatment. Simulations confirmed that assuming at least one regulating mechanism is required to reproduce a stable endemic equilibrium. Snail-level regulation was necessary to explain stable low transmission, while models combining snail- and human-level regulation with an age-exposure function informed with water contact data were successful in reproducing a rapid rebound after treatment. However, the predicted probability of reaching the control targets varied largely across models. CONCLUSIONS/SIGNIFICANCE The choice of regulating mechanisms in schistosomiasis modelling largely determines the expected impact of control interventions. Overall, this work suggests that reaching the control targets solely through mass drug administration may be more challenging than currently thought. We highlight the importance of regulating mechanisms to be included in transmission models used for policy.
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Affiliation(s)
- Veronica Malizia
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
- Radboud University Medical Center, Department IQ Health, Biostatistics Research Group, Nijmegen, The Netherlands
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Kit C B Roes
- Radboud University Medical Center, Department IQ Health, Biostatistics Research Group, Nijmegen, The Netherlands
| | - Federica Giardina
- Radboud University Medical Center, Department IQ Health, Biostatistics Research Group, Nijmegen, The Netherlands
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Zacharia A, Makene T, Haule S, Lukumay G, Omary H, Shabani M, Ngasala B. Urogenital schistosomiasis among adult male population in an endemic area of southern Tanzania: a descriptive cross-sectional study. BMJ Open 2024; 14:e079690. [PMID: 38889945 PMCID: PMC11191765 DOI: 10.1136/bmjopen-2023-079690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 04/26/2024] [Indexed: 06/20/2024] Open
Abstract
BACKGROUND Urogenital schistosomiasis (UGS) caused by Schistosoma haematobium is endemic in Southern Tanzania. The disease has significant implications for both socioeconomic and public health. Because infections with S. haematobium usually peak in childhood, the majority of studies have concentrated on school-aged children leaving other groups such as males which might be continuous reservoir of infection transmission. However, despite its chronic consequences in the male population, the disease has received insufficient attention, especially in sub-Saharan Africa. This study was conducted to describe the previous and current schistosomiasis status among adult males living in high-endemic areas of southern Tanzania DESIGN, SETTING AND PARTICIPANTS: A descriptive cross-sectional study was employed to gather data on the prevalence of UGS among adult men residing at schistosomiasis endemic in the Mtama District Council. Quantitative methods of data collection which included questionnaire and laboratory procedures were used. RESULTS Out of 245 participants, macrohaematuria and microhaematuria were found in 12 (4.9%, 95% CI 2.4% to 7.8%) and 66 (26.9%, 95% CI 21.6% to 32.7%) participants, respectively. S. haematobium ova were recovered from the urine samples of 54 (22.0%, 95% CI 16.7% to 27.3%) participants. The median intensity of infection was 20 eggs per 10 mL of urine ranging from 1 to 201 eggs per 10 mL of urine (IQR) 60.5). Out of 245 participants 33 (13.5% 95% CI 9.0% to 17.6%) had light intensity of infection and 21 (38.9%, 95% CI; 25.0% to 52.5%) had heavy intensity of infection. Overall, the prevalence of heavy intensity of infection was 8.6% (95% CI 4.9% to 12.6%). The prevalence and intensity of UGS varied significantly by age, marital status and village of residence. CONCLUSION This study sheds light on the prevalence of UGS among adult males in endemic areas of southern Tanzania. The results highlight the urgent need for comprehensive intervention strategies to address the burden of the disease.
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Affiliation(s)
- Abdallah Zacharia
- Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Dar es Salaam, Tanzania, United Republic of
| | - Twilumba Makene
- Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Dar es Salaam, Tanzania, United Republic of
| | - Stanley Haule
- Pathology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Dar es Salaam, Tanzania, United Republic of
| | - Gift Lukumay
- Community Health Nursing, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania, United Republic of
| | - Huda Omary
- Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania, United Republic of
| | - Monica Shabani
- Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Dar es Salaam, Tanzania, United Republic of
| | - Billy Ngasala
- Parasitology and Medical Entomology, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Dar es Salaam, Tanzania, United Republic of
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Gurarie D, Mondal A, Ndeffo-Mbah ML. Improved Assessment of Schistosoma Community Infection Through Data Resampling Method. Open Forum Infect Dis 2024; 11:ofad659. [PMID: 38328495 PMCID: PMC10847808 DOI: 10.1093/ofid/ofad659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 12/18/2023] [Indexed: 02/09/2024] Open
Abstract
Background The conventional diagnostic for Schistosoma mansoni infection is stool microscopy with the Kato-Katz (KK) technique to detect eggs. Its outcomes are highly variable on a day-to-day basis and may lead to biased estimates of community infection used to inform public health programs. Our goal is to develop a resampling method that leverages data from a large-scale randomized trial to accurately predict community infection. Methods We developed a resampling method that provides unbiased community estimates of prevalence, intensity and other statistics for S mansoni infection when a community survey is conducted using KK stool microscopy with a single sample per host. It leverages a large-scale data set, collected in the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) project, and allows linking single-stool specimen community screening to its putative multiday "true statistics." Results SCORE data analysis reveals the limited sensitivity of KK stool microscopy and systematic bias of single-day community testing versus multiday testing; for prevalence estimate, it can fall up to 50% below the true value. The proposed SCORE cluster method reduces systematic bias and brings the estimated prevalence values within 5%-10% of the true value. This holds for a broad swath of transmission settings, including SCORE communities, and other data sets. Conclusions Our SCORE cluster method can markedly improve the S mansoni prevalence estimate in settings using stool microscopy.
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Affiliation(s)
- David Gurarie
- Department of Mathematics, Applied Mathematics, and Statistics, Case Western Reserve University, Cleveland, Ohio, USA
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA
| | - Anirban Mondal
- Department of Mathematics, Applied Mathematics, and Statistics, Case Western Reserve University, Cleveland, Ohio, USA
| | - Martial L Ndeffo-Mbah
- Department of Veterinary and Integrative Biosciences, School of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas, USA
- Department of Epidemiology and Biostatistics, School of Public Health, Texas A&M University, College Station, Texas, USA
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Petukhova VZ, Aboagye SY, Ardini M, Lullo RP, Fata F, Byrne ME, Gabriele F, Martin LM, Harding LNM, Gone V, Dangi B, Lantvit DD, Nikolic D, Ippoliti R, Effantin G, Ling WL, Johnson JJ, Thatcher GRJ, Angelucci F, Williams DL, Petukhov PA. Non-covalent inhibitors of thioredoxin glutathione reductase with schistosomicidal activity in vivo. Nat Commun 2023; 14:3737. [PMID: 37349300 PMCID: PMC10287695 DOI: 10.1038/s41467-023-39444-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Accepted: 06/12/2023] [Indexed: 06/24/2023] Open
Abstract
Only praziquantel is available for treating schistosomiasis, a disease affecting more than 200 million people. Praziquantel-resistant worms have been selected for in the lab and low cure rates from mass drug administration programs suggest that resistance is evolving in the field. Thioredoxin glutathione reductase (TGR) is essential for schistosome survival and a validated drug target. TGR inhibitors identified to date are irreversible and/or covalent inhibitors with unacceptable off-target effects. In this work, we identify noncovalent TGR inhibitors with efficacy against schistosome infections in mice, meeting the criteria for lead progression indicated by WHO. Comparisons with previous in vivo studies with praziquantel suggests that these inhibitors outperform the drug of choice for schistosomiasis against juvenile worms.
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Grants
- R33 AI127635 NIAID NIH HHS
- Division of Intramural Research, National Institute of Allergy and Infectious Diseases (Division of Intramural Research of the NIAID)
- Oncomelania hupensis subsp. hupensis, Chinese strain, infected with S. japonicum, Chinese strain, and Biomphalaria glabrata, strain NMRI, infected with S. mansoni, strain NMRI, were provided by the NIAID Schistosomiasis Resource Center for distribution through BEI Resources, NIAID, NIH. We are grateful to Dr. Guy Schoehn (Univ. Grenoble Alpes, CEA, CNRS, Institut de Biologie Structurale, Grenoble, France), Prof. Beatrice Vallone (Sapienza University of Rome, Italy) and Dr. Linda C. Montemiglio (IBPM, National Research Council, Italy) for helpful discussions of the cryo-EM studies. We acknowledge the Elettra-Sincrotrone Trieste (Italy) for support in X-ray data collections and the European Synchrotron Radiation Facility for provision of microscope time on CM01. The study was funded in part by US NIH/NIAID R33AI127635 to F.A., P.A.P., G.R.T. and D.L.W. This work benefited from access to Research Resources Centre and UICentre at University of Illinois at Chicago and used the platforms of the Grenoble Instruct-ERIC center (ISBG; UAR 3518 CNRS-CEA-UGA-EMBL) within the Grenoble Partnership for Structural Biology (PSB), supported by FRISBI (ANR-10-INBS-0005-02) and GRAL, financed within the University Grenoble Alpes graduate school (Ecoles Universitaires de Recherche) CBH-EUR-GS (ANR-17-EURE-0003). The IBS Electron Microscope facility is supported by the Auvergne Rhône-Alpes Region, the Fonds Feder, the Fondation pour la Recherche Médicale and GIS-IBiSA. The IBS acknowledges integration into the Interdisciplinary Research Institute of Grenoble (IRIG, CEA). M.A. has been supported by MIUR - Ministero dell'Istruzione Ministero dell'Università e della Ricerca (Ministry of Education, University and Research) under the national project FSE/FESR - PON Ricerca e Innovazione 2014-2020 (N° AIM1887574, CUP: E18H19000350007). We acknowledge OpenEye/Cadence for providing us with an academic license for the software used in these studies.
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Affiliation(s)
- Valentina Z Petukhova
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
| | - Sammy Y Aboagye
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL, USA
| | - Matteo Ardini
- Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy
| | - Rachel P Lullo
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL, USA
| | - Francesca Fata
- Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy
| | - Margaret E Byrne
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL, USA
| | - Federica Gabriele
- Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy
| | - Lucy M Martin
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL, USA
| | - Luke N M Harding
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
| | - Vamshikrishna Gone
- UICentre, Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
| | - Bikash Dangi
- Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
| | - Daniel D Lantvit
- UICentre, Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
| | - Dejan Nikolic
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
| | - Rodolfo Ippoliti
- Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy
| | - Grégory Effantin
- University of Grenoble Alpes, CEA, CNRS, IBS, F-38000, Grenoble, France
| | - Wai Li Ling
- University of Grenoble Alpes, CEA, CNRS, IBS, F-38000, Grenoble, France
| | - Jeremy J Johnson
- Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
| | - Gregory R J Thatcher
- Department of Pharmacology & Toxicology, R. Ken Coit College of Pharmacy, University of Arizona, Tucson, AZ, USA
| | - Francesco Angelucci
- Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
| | - David L Williams
- Department of Microbial Pathogens and Immunity, Rush University Medical Center, Chicago, IL, USA.
| | - Pavel A Petukhov
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA.
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Association between polymorphisms of IL4, IL13, IL10, STAT6 and IFNG genes, cytokines and immunoglobulin E levels with high burden of Schistosoma mansoni in children from schistosomiasis endemic areas of Cameroon. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2023; 111:105416. [PMID: 36889485 PMCID: PMC10167540 DOI: 10.1016/j.meegid.2023.105416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 02/02/2023] [Accepted: 02/08/2023] [Indexed: 03/08/2023]
Abstract
Eliminating schistosomiasis as a public health problem by 2030 requires a better understanding of the disease transmission, especially the asymmetric distribution of worm burden in individuals living and sharing the same environment. It is in this light that this study was designed to identify human genetic determinants associated with high burden of S. mansoni and also with the plasma concentrations of IgE and four cytokines in children from two schistosomiasis endemic areas of Cameroon. In school-aged children of schistosomiasis endemic areas of Makenene and Nom-Kandi of Cameroon, S. mansoni infections and their infection intensities were evaluated in urine and stool samples using respectively the Point-of-care Circulating Cathodic Antigen test (POC-CCA) and the Kato Katz (KK) test. Thereafter, blood samples were collected in children harbouring high burden of schistosome infections as well as in their parents and siblings. DNA extracts and plasma were obtained from blood. Polymorphisms at 14 loci of five genes were assessed using PCR-restriction fragment length polymorphism and amplification-refractory mutation system. The ELISA test enabled to determine the plasma concentrations of IgE, IL-13, IL-10, IL-4 and IFN-γ. The prevalence of S. mansoni infections was significantly higher (P < 0.0001 for POC-CCA; P = 0.001 for KK) in Makenene (48.6% for POC-CCA and 7.9% for KK) compared to Nom-Kandi (31% for POC-CCA and 4.3% for KK). The infection intensities were also higher (P < 0.0001 for POC-CCA; P = 0.001 for KK) in children from Makenene than those from Nom-Kandi. The allele C of SNP rs3024974 of STAT6 was associated with an increased risk of bearing high burden of S. mansoni both in the additive (p = 0.009) and recessive model (p = 0.01) while the allele C of SNP rs1800871 of IL10 was protective (p = 0.0009) against high burden of S. mansoni. The alleles A of SNP rs2069739 of IL13 and G of SNP rs2243283 of IL4 were associated with an increased risk of having low plasma concentrations of IL-13 (P = 0.04) and IL-10 (P = 0.04), respectively. This study showed that host genetic polymorphisms may influence the outcome (high or low worm burden) of S. mansoni infections and also the plasma concentrations of some cytokines.
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Dial NJ, Croft SL, Chapman LAC, Terris-Prestholt F, Medley GF. Challenges of using modelling evidence in the visceral leishmaniasis elimination programme in India. PLOS GLOBAL PUBLIC HEALTH 2022; 2:e0001049. [PMID: 36962829 PMCID: PMC10021829 DOI: 10.1371/journal.pgph.0001049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 10/25/2022] [Indexed: 06/18/2023]
Abstract
As India comes closer to the elimination of visceral leishmaniasis (VL) as a public health problem, surveillance efforts and elimination targets must be continuously revised and strengthened. Mathematical modelling is a compelling research discipline for informing policy and programme design in its capacity to project incidence across space and time, the likelihood of achieving benchmarks, and the impact of different interventions. To gauge the extent to which modelling informs policy in India, this qualitative analysis explores how and whether policy makers understand, value, and reference recently produced VL modelling research. Sixteen semi-structured interviews were carried out with both users- and producers- of VL modelling research, guided by a knowledge utilisation framework grounded in knowledge translation theory. Participants reported that barriers to knowledge utilisation include 1) scepticism that models accurately reflect transmission dynamics, 2) failure of modellers to apply their analyses to specific programme operations, and 3) lack of accountability in the process of translating knowledge to policy. Political trust and support are needed to translate knowledge into programme activities, and employment of a communication intermediary may be a necessary approach to improve this process.
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Affiliation(s)
- Natalie J. Dial
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Simon L. Croft
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Lloyd A. C. Chapman
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Fern Terris-Prestholt
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Graham F. Medley
- Department of Global Health and Development, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Lo NC, Bezerra FSM, Colley DG, Fleming FM, Homeida M, Kabatereine N, Kabole FM, King CH, Mafe MA, Midzi N, Mutapi F, Mwanga JR, Ramzy RMR, Satrija F, Stothard JR, Traoré MS, Webster JP, Utzinger J, Zhou XN, Danso-Appiah A, Eusebi P, Loker ES, Obonyo CO, Quansah R, Liang S, Vaillant M, Murad MH, Hagan P, Garba A. Review of 2022 WHO guidelines on the control and elimination of schistosomiasis. THE LANCET. INFECTIOUS DISEASES 2022; 22:e327-e335. [PMID: 35594896 DOI: 10.1016/s1473-3099(22)00221-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 03/13/2022] [Accepted: 03/21/2022] [Indexed: 01/13/2023]
Abstract
Schistosomiasis is a helminthiasis infecting approximately 250 million people worldwide. In 2001, the World Health Assembly (WHA) 54.19 resolution defined a new global strategy for control of schistosomiasis through preventive chemotherapy programmes. This resolution culminated in the 2006 WHO guidelines that recommended empirical treatment by mass drug administration with praziquantel, predominately to school-aged children in endemic settings at regular intervals. Since then, school-based and community-based preventive chemotherapy programmes have been scaled-up, reducing schistosomiasis-associated morbidity. Over the past 15 years, new scientific evidence-combined with a more ambitious goal of eliminating schistosomiasis and an increase in the global donated supply of praziquantel-has highlighted the need to update public health guidance worldwide. In February, 2022, WHO published new guidelines with six recommendations to update the global public health strategy against schistosomiasis, including expansion of preventive chemotherapy eligibility from the predominant group of school-aged children to all age groups (2 years and older), lowering the prevalence threshold for annual preventive chemotherapy, and increasing the frequency of treatment. This Review, written by the 2018-2022 Schistosomiasis Guidelines Development Group and its international partners, presents a summary of the new WHO guideline recommendations for schistosomiasis along with their historical context, supporting evidence, implications for public health implementation, and future research needs.
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Affiliation(s)
- Nathan C Lo
- Division of HIV, Infectious Diseases, and Global Medicine, University of California, San Francisco, CA, USA.
| | | | - Daniel G Colley
- Department of Microbiology, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, USA
| | | | - Mamoun Homeida
- Academy of Medical Sciences and Technology, Khartoum, Sudan
| | - Narcis Kabatereine
- Accelerating Resilient, Innovative, and Sustainable Elimination of NTDs, Vector Control Division, Kampala, Uganda
| | | | - Charles H King
- Center for Global Health and Diseases, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | | | - Nicholas Midzi
- National Institute of Health Research, Ministry of Health and Child Care, Harare, Zimbabwe
| | - Francisca Mutapi
- Institute of Immunology and Infection Research, Tackling Infections to Benefit Africa Partnership, University of Edinburgh, Edinburgh, UK
| | - Joseph R Mwanga
- Department of Epidemiology, Biostatistics and Behavioral Sciences, School of Public Health, Catholic University of Health and Allied Sciences, Mwanza, Tanzania
| | - Reda M R Ramzy
- National Nutrition Institute, General Organization for Teaching Hospitals and Institutes, Cairo, Egypt
| | - Fadjar Satrija
- School of Veterinary Medicine and Biomedicine, IPB University, Bogor, Indonesia
| | - J Russell Stothard
- Department of Tropical Disease Biology, Liverpool School of Tropical Medicine, Liverpool, UK
| | | | - Joanne P Webster
- Department of Pathobiology and Population Science, Royal Veterinary College, University of London, London, UK
| | - Jürg Utzinger
- Swiss Tropical and Public Health Institute, Allschwil, Switzerland; University of Basel, Basel, Switzerland
| | - Xiao-Nong Zhou
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, China; School of Global Health, Chinese Center for Tropical Diseases Research, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | | | - Paolo Eusebi
- Department of Medicine and Surgery, University of Perugia, Perugia, Italy
| | - Eric S Loker
- Department of Biology, University of New Mexico, Albuquerque, NM, USA
| | - Charles O Obonyo
- Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | | | - Song Liang
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, FL, USA; Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA
| | - Michel Vaillant
- Competence Centre for Methodology and Statistics, Luxembourg Institute of Health, Strassen, Luxembourg
| | - M Hassan Murad
- Evidence-based Practice Center, Mayo Clinic, Rochester, NY, USA
| | - Paul Hagan
- Faculty of Health Sciences, University of Hull, Hull, UK
| | - Amadou Garba
- Department of Control of Neglected Tropical Diseases, WHO, Geneva, Switzerland
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Fine-scale mapping of Schistosoma mansoni infections and infection intensities in sub-districts of Makenene in the Centre region of Cameroon. PLoS Negl Trop Dis 2022; 16:e0010852. [PMID: 36227962 PMCID: PMC9595529 DOI: 10.1371/journal.pntd.0010852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 10/25/2022] [Accepted: 09/28/2022] [Indexed: 11/06/2022] Open
Abstract
Background Schistosomiasis control relies mainly on mass drug administration of Praziquantel (PZQ) to school aged children (SAC). Although precision mapping has recently guided decision making, the sub-districts and the epidemiological differences existing between bio-ecological settings in which infected children come from were not taken into consideration. This study was designed to fill this gap by using POC-CCA and KK to comparatively determine the prevalence and infection intensities of Schistosoma mansoni (S. mansoni) and to perform fine-scale mapping of S. mansoni infections and its infection intensities with the overarching goal of identifying sub-districts presenting high transmission risk where control operations must be boosted to achieve schistosomiasis elimination. Methodology During a cross- sectional study conducted in Makenene, 1773 stool and 2253 urine samples were collected from SAC of ten primary schools. S. mansoni infections were identified using the point of care circulating cathodic antigen (POC-CCA) and Kato-Katz (KK) test respectively on urine and stool samples. Geographical coordinates of houses of infected SAC were recorded using a global position system device. Schistosome infections and infection intensities were map using QGIS software. Results The prevalence of S. mansoni inferred from POC-CCA and KK were 51.3% and 7.3% respectively. Most infected SAC and those bearing heavy infections intensities were clustered in sub-districts of Baloua, Mock-sud and Carrière. Houses with heavily-infected SAC were close to risky biotopes. Conclusion This study confirms the low sensitivity of KK test compared to POC-CCA to accurately identify children with schistosome infection and bearing different schistosome burden. Fine-scale mapping of schistosome infections and infection intensities enabled to identify high transmission sub-districts where control measures must be boosted to reach schistosomiasis elimination. Although some disparities in terms of prevalence and infection intensities have been acknowledged within and between schistosomiasis endemic areas, the current control measures did not take into consideration the disparities within endemic areas. To improve the control of schistosomiasis, a fine-scale mapping of schistosome infections and their intensities were undertaken using KK in comparison to POC-CCA to identify sub-districts with potential high transmission risk and where control operations must be boosted to achieve elimination. After the identification of schistosome infections by the point of care circulating cathodic antigen (POC-CCA) and Kato-Katz (KK) test, the geographical coordinates of each infected child’s house were recorded using a global position system device (GPS). QGIS software was used to create a map showing schistosome infections and their infection intensities. Our results showed that the majority of infected children and those bearing heavy infection intensities were clustering mostly in Baloua, Carrière and Mock-Sud sub-districts of Makenene while children with light and moderate infection intensity were widely distributed and far away from risky biotopes. The fine-scale mapping of schistosome infections and their infection intensities enable to identify hotspot transmission sites where control strategy must be boosted to achieve the elimination of intestinal schistosomiasis in Makenene.
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Ogongo P, Nyakundi RK, Chege GK, Ochola L. The Road to Elimination: Current State of Schistosomiasis Research and Progress Towards the End Game. Front Immunol 2022; 13:846108. [PMID: 35592327 PMCID: PMC9112563 DOI: 10.3389/fimmu.2022.846108] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2021] [Accepted: 03/21/2022] [Indexed: 12/14/2022] Open
Abstract
The new WHO Roadmap for Neglected Tropical Diseases targets the global elimination of schistosomiasis as a public health problem. To date, control strategies have focused on effective diagnostics, mass drug administration, complementary and integrative public health interventions. Non-mammalian intermediate hosts and other vertebrates promote transmission of schistosomiasis and have been utilized as experimental model systems. Experimental animal models that recapitulate schistosomiasis immunology, disease progression, and pathology observed in humans are important in testing and validation of control interventions. We discuss the pivotal value of these models in contributing to elimination of schistosomiasis. Treatment of schistosomiasis relies heavily on mass drug administration of praziquantel whose efficacy is comprised due to re-infections and experimental systems have revealed the inability to kill juvenile schistosomes. In terms of diagnosis, nonhuman primate models have demonstrated the low sensitivity of the gold standard Kato Katz smear technique. Antibody assays are valuable tools for evaluating efficacy of candidate vaccines, and sera from graded infection experiments are useful for evaluating diagnostic sensitivity of different targets. Lastly, the presence of Schistosomes can compromise the efficacy of vaccines to other infectious diseases and its elimination will benefit control programs of the other diseases. As the focus moves towards schistosomiasis elimination, it will be critical to integrate treatment, diagnostics, novel research tools such as sequencing, improved understanding of disease pathogenesis and utilization of experimental models to assist with evaluating performance of new approaches.
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Affiliation(s)
- Paul Ogongo
- Division of Experimental Medicine, Department of Medicine, University of California, San Francisco, San Francisco, CA, United States
- Department of Tropical and Infectious Diseases, Institute of Primate Research, Nairobi, Kenya
| | - Ruth K. Nyakundi
- Department of Tropical and Infectious Diseases, Institute of Primate Research, Nairobi, Kenya
| | - Gerald K. Chege
- Primate Unit & Delft Animal Centre, South African Medical Research Council, Cape Town, South Africa
- Department of Pathology, University of Cape Town, Cape Town, South Africa
| | - Lucy Ochola
- Department of Tropical and Infectious Diseases, Institute of Primate Research, Nairobi, Kenya
- Department of Environmental Health, School of Behavioural and Lifestyle Sciences, Faculty of Health Sciences, Nelson Mandela University, Gqeberha, South Africa
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10
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Phillips AE, Tohon Z, Dhanani NA, Sofo B, Gnandou I, Sidikou B, Noma AG, Madougou B, Alto O, Sebangou H, Halilou KM, Andia R, Garba A, Fenwick A, Hamidou AA. Evaluating the impact of biannual school-based and community-wide treatment on urogenital schistosomiasis in Niger. Parasit Vectors 2020; 13:557. [PMID: 33203477 PMCID: PMC7672903 DOI: 10.1186/s13071-020-04411-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 10/21/2020] [Indexed: 11/10/2022] Open
Abstract
Background The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) coordinated a five-year study implemented in several countries, including Niger, to provide an evidence-base for programmatic decisions regarding cost-effective approaches to preventive chemotherapy for schistosomiasis control. Methods This was a cluster-randomised trial investigating six possible combinations of annual or biannual community-wide treatment (CWT), school-based treatment (SBT), and holidays from mass treatment over four years. The most intense arm involved two years of annual CWT followed by 2 years of biannual CWT, while the least intensive arm involved one year of annual SBT followed by a year without treatment and two more years of annual SBT. The primary outcome of interest was prevalence and intensity of Schistosoma haematobium among 100 children aged 9–12 years sampled each year. In addition, 100 children aged 5–8 years in their first year of school and 50 adults (aged 20–55 years) were tested in the first and final fifth year of the study. Results In total, data were collected from 167,500 individuals across 225 villages in nine districts within the Niger River valley, Western Niger. Overall, the prevalence of S. haematobium decreased from baseline to Year 5 across all study arms. The relative reduction of prevalence was greater in biannual compared with annual treatment across all arms; however, the only significant difference was seen in areas with a high starting prevalence. Although adults were not targeted for treatment in SBT arms, a statistically significant decrease in prevalence among adults was seen in moderate prevalence areas receiving biannual (10.7% to 4.8%) SBT (P < 0.001). Adults tested in the annual SBT group also showed a decrease in prevalence between Year 1 and Year 5 (12.2% to 11.0%), but this difference was not significant. Conclusions These findings are an important consideration for schistosomiasis control programmes that are considering elimination and support the idea that scaling up the frequency of treatment rounds, particularly in areas of low prevalence, will not eliminate schistosomiasis. Interestingly, the finding that prevalence decreased among adults in SBT arms suggests that transmission in the community can be reduced, even where only school children are being treated, which could have logistical and cost-saving implications for the national control programmes.
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Affiliation(s)
- Anna E Phillips
- London Centre for Neglected Tropical Disease Research (LCNTDR), Department of Infectious Disease Epidemiology, Imperial College London, London, UK.
| | - Zilahatou Tohon
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Neerav A Dhanani
- Schistosomiasis control Initiative (SCI), Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Boubacar Sofo
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | | | - Boubacar Sidikou
- Hôpital National de Niamey rond-point Hôpital, BP 238, Niamey, Niger
| | - Adamou Garba Noma
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Bassirou Madougou
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Oumarou Alto
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Hannatou Sebangou
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Kader M Halilou
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Roumanatou Andia
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Amadou Garba
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
| | - Alan Fenwick
- Schistosomiasis control Initiative (SCI), Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Amina A Hamidou
- Aménagement et Lutte (RISEAL NIGER), Réseau International Schistosomiases Environnement, Avenue de l'indépendance, BP. 13724, Niamey, Niger
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11
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Campbell CH, Binder S, King CH, Knopp S, Rollinson D, Person B, Webster B, Allan F, Utzinger J, Ame SM, Ali SM, Kabole F, N'Goran EK, Tediosi F, Salari P, Ouattara M, Diakité NR, Hattendorf J, S Andros T, Kittur N, Colley DG. SCORE Operational Research on Moving toward Interruption of Schistosomiasis Transmission. Am J Trop Med Hyg 2020; 103:58-65. [PMID: 32400354 PMCID: PMC7351301 DOI: 10.4269/ajtmh.19-0825] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
As part of its diverse portfolio, the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) included two cluster-randomized trials evaluating interventions that could potentially lead to interruption of schistosomiasis transmission (elimination) in areas of Africa with low prevalence and intensity of infection. These studies, conducted in Zanzibar and Côte d’Ivoire, demonstrated that multiyear mass drug administration (MDA) with praziquantel failed to interrupt the transmission of urogenital schistosomiasis, even when provided biannually and/or supplemented by small-scale implementation of additional interventions. Other SCORE activities related to elimination included a feasibility and acceptability assessment of test–treat–track–test–treat (T5) strategies and mathematical modeling. Future evaluations of interventions to eliminate schistosomiasis should recognize the difficulties inherent in conducting randomized controlled trials on elimination and in measuring small changes where baseline prevalence is low. Highly sensitive and specific diagnostic tests for use in very low–prevalence areas for schistosomiasis are not routinely available, which complicates accurate measurement of infection rates and assessment of changes resulting from interventions in these settings. Although not encountered in these two studies, as prevalence and intensity decrease, political and community commitment to population-wide MDA may decrease. Because of this potential problem, SCORE developed and funded the T5 strategy implemented in Egypt, Kenya, and Tanzania. It is likely that focal MDA campaigns, along with more targeted approaches, including a T5 strategy and snail control, will need to be supplemented with the provision of clean water and sanitation and behavior change communications to achieve interruption of schistosome transmission.
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Affiliation(s)
- Carl H Campbell
- Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
| | - Sue Binder
- Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
| | - Charles H King
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio.,Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
| | - Stefanie Knopp
- Department of Life Sciences, Wolfson Wellcome Biomedical Laboratories, Natural History Museum, London, United Kingdom.,University of Basel, Basel, Switzerland.,Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - David Rollinson
- London Centre for Neglected Tropical Disease Research, Imperial College Faculty of Medicine, London, United Kingdom.,Department of Life Sciences, Wolfson Wellcome Biomedical Laboratories, Natural History Museum, London, United Kingdom
| | - Bobbie Person
- Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
| | - Bonnie Webster
- London Centre for Neglected Tropical Disease Research, Imperial College Faculty of Medicine, London, United Kingdom.,Department of Life Sciences, Wolfson Wellcome Biomedical Laboratories, Natural History Museum, London, United Kingdom
| | - Fiona Allan
- London Centre for Neglected Tropical Disease Research, Imperial College Faculty of Medicine, London, United Kingdom.,Department of Life Sciences, Wolfson Wellcome Biomedical Laboratories, Natural History Museum, London, United Kingdom
| | - Jürg Utzinger
- University of Basel, Basel, Switzerland.,Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Shaali M Ame
- Public Health Laboratory - Ivo de Carneri, Pemba, United Republic of Tanzania
| | - Said M Ali
- Public Health Laboratory - Ivo de Carneri, Pemba, United Republic of Tanzania
| | - Fatma Kabole
- Neglected Tropical Diseases Unit, Ministry of Health Zanzibar, Unguja, United Republic of Tanzania
| | - Eliézer K N'Goran
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire.,Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire
| | - Fabrizio Tediosi
- University of Basel, Basel, Switzerland.,Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Paola Salari
- University of Basel, Basel, Switzerland.,Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Mamadou Ouattara
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire.,Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire
| | - Nana R Diakité
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire.,Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire
| | - Jan Hattendorf
- University of Basel, Basel, Switzerland.,Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Tamara S Andros
- Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
| | - Nupur Kittur
- Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
| | - Daniel G Colley
- Department of Microbiology, University of Georgia, Athens, Georgia.,Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
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12
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King CH, Yoon N, Wang X, Lo NC, Alsallaq R, Ndeffo-Mbah M, Li E, Gurarie D. Application of Schistosomiasis Consortium for Operational Research and Evaluation Study Findings to Refine Predictive Modeling of Schistosoma mansoni and Schistosoma haematobium Control in Sub-Saharan Africa. Am J Trop Med Hyg 2020; 103:97-104. [PMID: 32400357 PMCID: PMC7351296 DOI: 10.4269/ajtmh.19-0852] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
An essential mission of the Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) was to help inform global health practices related to the control and elimination of schistosomiasis. To provide more accurate, evidence-based projections of the most likely impact of different control interventions, whether implemented alone or in combination, SCORE supported mathematical modeling teams to provide simulations of community-level Schistosoma infection outcomes in the setting of real or hypothetical programs implementing multiyear mass drug administration (MDA) for parasite control. These models were calibrated using SCORE experience with Schistosoma mansoni and Schistosoma haematobium gaining and sustaining control studies, and with data from comparable programs that used community-based or school-based praziquantel MDA in other parts of sub-Saharan Africa. From 2010 to 2019, models were developed and refined, first to project the likely SCORE control outcomes, and later to more accurately reflect impact of MDA across different transmission settings, including the role of snail ecology and the impact of seasonal rainfall on snail abundance. Starting in 2014, SCORE modeling projections were also compared with the models of colleagues in the Neglected Tropical Diseases Modelling Consortium. To explore further possible improvement to program-based control, later simulations examined the cost-effectiveness of combining MDA with environmental snail control, and the utility of early impact assessment to more quickly identify persistent hot spots of transmission. This article provides a nontechnical summary of the 11 SCORE-related modeling projects and provides links to the original open-access articles describing model development and projections relevant to schistosomiasis control policy.
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Affiliation(s)
- Charles H King
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio.,Schistosomiasis Consortium for Operational Research and Evaluation, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia
| | - Nara Yoon
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, Ohio
| | - Xiaoxia Wang
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, Ohio
| | - Nathan C Lo
- Department of Medicine, University of California, San Francisco, San Francisco, California
| | - Ramzi Alsallaq
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio
| | | | - Emily Li
- School of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - David Gurarie
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, Ohio.,Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio
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13
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Malishev M, Civitello DJ. Modelling how resource competition among snail hosts affects the mollusciciding frequency and intensity needed to control human schistosomes. Funct Ecol 2020. [DOI: 10.1111/1365-2435.13602] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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14
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Li EY, Gurarie D, Lo NC, Zhu X, King CH. Improving public health control of schistosomiasis with a modified WHO strategy: a model-based comparison study. LANCET GLOBAL HEALTH 2020; 7:e1414-e1422. [PMID: 31537371 PMCID: PMC7024988 DOI: 10.1016/s2214-109x(19)30346-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 07/08/2019] [Accepted: 07/18/2019] [Indexed: 01/19/2023]
Abstract
Background Schistosomiasis is endemic in many low-income and middle-income countries. To reduce infection-associated morbidity, WHO has published guidelines for control of schistosomiasis based on targeted mass drug administration (MDA) and, in 2017, on supplemental snail control. We compared the current WHO guideline-based strategies from 2012 to an alternative, adaptive decision making framework for control in heterogeneous environments, to estimate their predicted relative effectiveness and time to achievement of defined public health goals. Methods In this model-based comparison study, we adapted an established transmission model for Schistosoma infection that couples local human and snail populations and includes aspects of snail ecology and parasite biology. We calibrated the model using data from high-risk, moderate-risk, and lower-risk rural villages in Kenya, and then simulated control via MDA. We compared 2012 WHO guidelines with a modified adaptive strategy that tested a lower-prevalence threshold for MDA and shorter intervals between implementation, evaluation, and modification. We also explored the addition of snail control to this modified strategy. The primary outcomes were the proportion of simulations that achieved the WHO targets in children aged 5–14 years of less than 5% (2020 morbidity control goal) and less than 1% (2025 elimination as a public health problem goal) heavy infection and the mean duration of treatment required to achieve these goals. Findings In high-risk communities (80% baseline prevalence), current WHO strategies for MDA were not predicted to achieve morbidity control (<5% prevalence of heavy infections) in 80% of simulations over a 10-year period, whereas the modified adaptive strategy was predicted to achieve this goal in over 50% of simulations within 5 years. In low-risk and moderate-risk communities, current WHO guidelines from 2012 were predicted to achieve morbidity control in most simulations (96% in low-risk and 41% for moderate-risk), although the proposed adaptive strategy reached this goal in a shorter period (mean reduction of 5 years). The model predicted that the addition of snail control to the proposed adaptive strategy would achieve morbidity control in all high-risk communities, and 54% of communities could reach the goal for elimination as a public health problem (<1% heavy infection) within 7 years. Interpretation The modified adaptive decision making framework is predicted to be more effective than the current WHO guidelines in reaching 2025 public health goals, especially for high-prevalence regions. Modifications in current guidelines could reduce the time and resources needed for countries who are currently working on achieving public health goals against schistosomiasis. Funding University of Georgia Research Foundation, The Bill & Melinda Gates Foundation, and the Medical Scientist Training Program at Stanford University School of Medicine.
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Affiliation(s)
- Emily Y Li
- School of Medicine, Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA.
| | - David Gurarie
- Department of Mathematics, Applied Mathematics, and Statistics, Case Western Reserve University, Cleveland, OH, USA
| | - Nathan C Lo
- Department of Medicine, University of California, San Francisco, San Francisco, CA, USA
| | - Xuewei Zhu
- Department of Mathematics, Applied Mathematics, and Statistics, Case Western Reserve University, Cleveland, OH, USA
| | - Charles H King
- School of Medicine, Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA
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15
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Tushabe JV, Lubyayi L, Sserubanja J, Kabuubi P, Abayo E, Kiwanuka S, Nassuuna J, Kaweesa J, Corstjens P, van Dam G, Sanya RE, Ssenyonga W, Tukahebwa EM, Kabatereine NB, Elliott AM, Webb EL. Does Intensive Treatment Select for Praziquantel Resistance in High-Transmission Settings? Parasitological Trends and Treatment Efficacy Within a Cluster-Randomized Trial. Open Forum Infect Dis 2020; 7:ofaa091. [PMID: 32296727 PMCID: PMC7148002 DOI: 10.1093/ofid/ofaa091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 03/10/2020] [Indexed: 11/14/2022] Open
Abstract
Background Praziquantel mass drug administration (MDA) is recommended in schistosomiasis-endemic areas. Animal models demonstrate Schistosoma parasite resistance to praziquantel after repeated exposure. Methods We conducted a parasitological survey in 26 fishing communities in Uganda after 4 years of quarterly (13 communities) or annual (13 communities) praziquantel MDA, with Schistosoma infection detected by single-stool-sample Kato-Katz. A test of cure was done in participants who were positive on both urine circulating cathodic antigen test and 3-sample Kato-Katz. We calculated cure rates (CRs) and egg reduction rates (ERRs) based on 3-sample Kato-Katz and infection intensity using worm-specific circulating anodic antigen (CAA) in blood, comparing these between quarterly and annually treated participants. Results Single-sample Kato-Katz Schistosoma mansoni prevalence was 22% in 1,056 quarterly treated participants and 34% in 1,030 annually treated participants (risk ratio, 0.62; 95% confidence interval [CI], 0.40 to 0.94). Among 110 test-of-cure participants, CRs were 65% and 51% in annually and quarterly treated villages, respectively (odds ratio, 0.65; 95% CI, 0.27 to 1.58); ERRs were 94% and 81% (difference, –13%; 95% CI, –48% to 2%). There was no impact of quarterly vs annual praziquantel on S. mansoni by CAA. Conclusions In this schistosomiasis hot spot, there was little evidence of decreased praziquantel efficacy. However, in the absence of alternative therapies, there remains a need for continued vigilance of praziquantel efficacy in the MDA era.
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Affiliation(s)
- John Vianney Tushabe
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda.,Wellcome Sanger Institute, Wellcome Trust Genome Campus, Hinxton, United Kingdom
| | - Lawrence Lubyayi
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda.,Department of Epidemiology and Biostatistics, School of Public Health, University of the Witwatersrand, Johannesburg, South Africa
| | - Joel Sserubanja
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda
| | - Prossy Kabuubi
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda
| | - Elson Abayo
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda
| | - Samuel Kiwanuka
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda
| | - Jacent Nassuuna
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda
| | - James Kaweesa
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | - Paul Corstjens
- Leiden University Medical Center, Leiden, the Netherlands
| | - Govert van Dam
- Leiden University Medical Center, Leiden, the Netherlands
| | - Richard E Sanya
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda.,Department of Internal Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
| | - William Ssenyonga
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda
| | | | | | - Alison M Elliott
- Immunomodulation and Vaccines Research Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe, Uganda.,Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, UK
| | - Emily L Webb
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
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16
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Michael E, Smith ME, Singh BK, Katabarwa MN, Byamukama E, Habomugisha P, Lakwo T, Tukahebwa E, Richards FO. Data-driven modelling and spatial complexity supports heterogeneity-based integrative management for eliminating Simulium neavei-transmitted river blindness. Sci Rep 2020; 10:4235. [PMID: 32144362 PMCID: PMC7060237 DOI: 10.1038/s41598-020-61194-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Accepted: 02/24/2020] [Indexed: 11/28/2022] Open
Abstract
Concern is emerging regarding the challenges posed by spatial complexity for modelling and managing the area-wide elimination of parasitic infections. While this has led to calls for applying heterogeneity-based approaches for addressing this complexity, questions related to spatial scale, the discovery of locally-relevant models, and its interaction with options for interrupting parasite transmission remain to be resolved. We used a data-driven modelling framework applied to infection data gathered from different monitoring sites to investigate these questions in the context of understanding the transmission dynamics and efforts to eliminate Simulium neavei- transmitted onchocerciasis, a macroparasitic disease that causes river blindness in Western Uganda and other regions of Africa. We demonstrate that our Bayesian-based data-model assimilation technique is able to discover onchocerciasis models that reflect local transmission conditions reliably. Key management variables such as infection breakpoints and required durations of drug interventions for achieving elimination varied spatially due to site-specific parameter constraining; however, this spatial effect was found to operate at the larger focus level, although intriguingly including vector control overcame this variability. These results show that data-driven modelling based on spatial datasets and model-data fusing methodologies will be critical to identifying both the scale-dependent models and heterogeneity-based options required for supporting the successful elimination of S. neavei-borne onchocerciasis.
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Affiliation(s)
- Edwin Michael
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.
| | - Morgan E Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Brajendra K Singh
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Moses N Katabarwa
- The Carter Center, One Copenhill, 453 Freedom Parkway, Atlanta, GA, 30307, USA
| | - Edson Byamukama
- The Carter Center, Uganda, 15 Bombo Road, P.O. Box, 12027, Kampala, Uganda
| | - Peace Habomugisha
- The Carter Center, Uganda, 15 Bombo Road, P.O. Box, 12027, Kampala, Uganda
| | - Thomson Lakwo
- Vector Control Division, Ministry of Health, 15 Bombo Road, P.O. Box, 1661, Kampala, Uganda
| | - Edridah Tukahebwa
- Vector Control Division, Ministry of Health, 15 Bombo Road, P.O. Box, 1661, Kampala, Uganda
| | - Frank O Richards
- The Carter Center, One Copenhill, 453 Freedom Parkway, Atlanta, GA, 30307, USA
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17
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Vale N, Gouveia MJ, Gärtner F. Current and Novel Therapies Against Helminthic Infections: The Potential of Antioxidants Combined with Drugs. Biomolecules 2020; 10:E350. [PMID: 32106428 PMCID: PMC7175190 DOI: 10.3390/biom10030350] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/02/2020] [Accepted: 02/21/2020] [Indexed: 12/11/2022] Open
Abstract
Infections caused by Schistosoma haematobium and Opisthorchisviverrini are classified as Group 1 biological carcinogen and it has been postulated that parasites produce oxysterol and estrogen-like metabolites that might be considered as initiators of infection-associated carcinogenesis. Chemotherapy for these helminthic infections relies on a single drug, praziquantel, (PZQ) that mainly targets the parasite. Additionally, PZQ has some major drawbacks as inefficacy against juvenile form and alone it is not capable to counteract pathologies associated to infections or prevent carcinogenesis. There is an urgent need to develop novel therapeutic approaches that not only target the parasite but also improve the pathologies associated to infection, and ultimately, counteract or/and prevent the carcinogenesis processes. Repurposing the drug in combination of compounds with different modes of action is a promising strategy to find novel therapeutics approaches against these helminthic infections and its pathologies. Here, we emphasized that using antioxidants either alone or combined with anthelmintic drugs could ameliorate tissue damage, infection-associated complications, moreover, could prevent the development of cancer associated to infections. Hence, antioxidants represent a potential adjuvant approach during treatment to reduce morbidity and mortality. Despite the success of some strategies, there is a long way to go to implement novel therapies for schistosomiasis.
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Affiliation(s)
- Nuno Vale
- Laboratory of Pharmacology, Department of Drug Sciences, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
- i3S, Instituto de Investigação e Inovação em Saúde, University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal;
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Rua Júlio Amaral de Carvalho 45, 4200-135 Porto, Portugal
- Department of Molecular Pathology and Immunology, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal;
| | - Maria João Gouveia
- Department of Molecular Pathology and Immunology, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal;
- Center for the Study in Animal Science (CECA/ICETA), University of Porto, Rua de D. Manuel II, Apt 55142, 4051-401 Porto, Portugal
| | - Fátima Gärtner
- i3S, Instituto de Investigação e Inovação em Saúde, University of Porto, Rua Alfredo Allen 208, 4200-135 Porto, Portugal;
- Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP), Rua Júlio Amaral de Carvalho 45, 4200-135 Porto, Portugal
- Department of Molecular Pathology and Immunology, Institute of Biomedical Sciences Abel Salazar (ICBAS), University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal;
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18
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Betson M, Alonte AJI, Ancog RC, Aquino AMO, Belizario VY, Bordado AMD, Clark J, Corales MCG, Dacuma MG, Divina BP, Dixon MA, Gourley SA, Jimenez JRD, Jones BP, Manalo SMP, Prada JM, van Vliet AHM, Whatley KCL, Paller VGV. Zoonotic transmission of intestinal helminths in southeast Asia: Implications for control and elimination. ADVANCES IN PARASITOLOGY 2020; 108:47-131. [PMID: 32291086 DOI: 10.1016/bs.apar.2020.01.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Intestinal helminths are extremely widespread and highly prevalent infections of humans, particularly in rural and poor urban areas of low and middle-income countries. These parasites have chronic and often insidious effects on human health and child development including abdominal problems, anaemia, stunting and wasting. Certain animals play a fundamental role in the transmission of many intestinal helminths to humans. However, the contribution of zoonotic transmission to the overall burden of human intestinal helminth infection and the relative importance of different animal reservoirs remains incomplete. Moreover, control programmes and transmission models for intestinal helminths often do not consider the role of zoonotic reservoirs of infection. Such reservoirs will become increasingly important as control is scaled up and there is a move towards interruption and even elimination of parasite transmission. With a focus on southeast Asia, and the Philippines in particular, this review summarises the major zoonotic intestinal helminths, risk factors for infection and highlights knowledge gaps related to their epidemiology and transmission. Various methodologies are discussed, including parasite genomics, mathematical modelling and socio-economic analysis, that could be employed to improve understanding of intestinal helminth spread, reservoir attribution and the burden associated with infection, as well as assess effectiveness of interventions. For sustainable control and ultimately elimination of intestinal helminths, there is a need to move beyond scheduled mass deworming and to consider animal and environmental reservoirs. A One Health approach to control of intestinal helminths is proposed, integrating interventions targeting humans, animals and the environment, including improved access to water, hygiene and sanitation. This will require coordination and collaboration across different sectors to achieve best health outcomes for all.
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Affiliation(s)
- Martha Betson
- University of Surrey, Guildford, Surrey, United Kingdom.
| | | | - Rico C Ancog
- University of the Philippines Los Baños, Laguna, Philippines
| | | | | | | | - Jessica Clark
- University of Surrey, Guildford, Surrey, United Kingdom
| | | | | | - Billy P Divina
- University of the Philippines Los Baños, Laguna, Philippines
| | | | | | | | - Ben P Jones
- University of Surrey, Guildford, Surrey, United Kingdom
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19
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Differential impact of mass and targeted praziquantel delivery on schistosomiasis control in school-aged children: A systematic review and meta-analysis. PLoS Negl Trop Dis 2019; 13:e0007808. [PMID: 31603895 PMCID: PMC6808504 DOI: 10.1371/journal.pntd.0007808] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 10/23/2019] [Accepted: 09/25/2019] [Indexed: 02/07/2023] Open
Abstract
Background Schistosomiasis is a widespread public health concern in the poorest regions of the world. The principal control strategy is regular praziquantel administration to school-aged children in endemic areas. With calls for the elimination of schistosomiasis as a public health problem, expanding praziquantel delivery to all community members has been advocated. This systematic review and meta-analysis compares the impact of community-wide and child-targeted praziquantel distribution on schistosomiasis prevalence and intensity in school-aged children. Methodology/Principal findings We searched MEDLINE, Embase and Web of Science to identify papers that reported schistosome prevalence before and after praziquantel administration, either to children only or to all community members. Extracted data included Schistosoma species, drug administration strategy, number of treatment rounds, follow-up interval and prevalence and intensity before and after treatment. We used inverse variance weighted generalised linear models to examine the impact of mass versus targeted drug administration on prevalence reduction, and weighted boxplots to examine the impact on infection intensity reduction. This study is registered with PROSPERO, number CRD42018095377. In total, 34 articles were eligible for systematic review and 28 for meta-analysis. Schistosoma mansoni was reported in 20 studies; Schistosoma haematobium in 19 studies, and Schistosoma japonicum in two studies. Results of generalised linear models showed no detectable difference between mass and targeted treatment strategies on prevalence reduction in school-aged children for S. mansoni (odds ratio 0.47, 95%CI 0.13–1.68, p = 0.227) and S. haematobium (0.41, 95%CI 0.06–3.03, p = 0.358). Box plots also showed no apparent differences in intensity reduction between the two treatment strategies. Conclusions/Significance The results of this meta-analysis do not support the hypothesis that community-wide treatment is more effective than targeted treatment at reducing schistosomiasis infections in children. This may be due to the relatively small number of included studies, insufficient treatment coverage, persistent infection hotspots and unmeasured confounders. Further field-based studies comparing mass and targeted treatment are required. Schistosomiasis is a neglected tropical disease, caused by parasitic worms, that affects more than 143 million people worldwide. Chronic infections can lead to significant morbidity including kidney damage, anaemia, malnutrition, infertility and growth impairment. School-aged children between six and 15 years are often targeted for regular treatment with praziquantel in large-scale drug delivery programs, because they suffer a disproportionate burden of morbidity. On the other hand, a mass drug delivery strategy that treats all members of the community has been suggested in a move towards elimination of schistosomiasis as a public health problem. In this systematic review, we assess the impact of community-wide versus children-only praziquantel distribution in reducing schistosomiasis infections in school-aged children. We did not detect a difference between mass and targeted treatment strategies, possibly due to factors including insufficient treatment coverage and persistent sources of reinfection. Addressing these factors may assist in optimising control programs.
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20
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Sanya RE, Nkurunungi G, Hoek Spaans R, Nampijja M, O’Hara G, Kizindo R, Oduru G, Kabuubi Nakawungu P, Niwagaba E, Abayo E, Kabagenyi J, Zziwa C, Tumusiime J, Nakazibwe E, Kaweesa J, Muwonge Kakooza F, Akello M, Lubyayi L, Verweij J, Nash S, van Ree R, Mpairwe H, Tukahebwa E, Webb EL, Elliott AM. The Impact of Intensive Versus Standard Anthelminthic Treatment on Allergy-related Outcomes, Helminth Infection Intensity, and Helminth-related Morbidity in Lake Victoria Fishing Communities, Uganda: Results From the LaVIISWA Cluster-randomized Trial. Clin Infect Dis 2019; 68:1665-1674. [PMID: 30202872 PMCID: PMC6495012 DOI: 10.1093/cid/ciy761] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 09/03/2018] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND The prevalence of allergy-related diseases is increasing in low-income countries. Parasitic helminths, common in these settings, may be protective. We hypothesized that intensive, community-wide, anthelminthic mass drug administration (MDA) would increase allergy-related diseases, while reducing helminth-related morbidity. METHODS In an open, cluster-randomized trial (ISRCTN47196031), we randomized 26 high-schistosomiasis-transmission fishing villages in Lake Victoria, Uganda, in a 1:1 ratio to receive community-wide intensive (quarterly single-dose praziquantel plus albendazole daily for 3 days) or standard (annual praziquantel plus 6 monthly single-dose albendazole) MDA. Primary outcomes were recent wheezing, skin prick test positivity (SPT), and allergen-specific immunoglobulin E (asIgE) after 3 years of intervention. Secondary outcomes included helminths, haemoglobin, and hepatosplenomegaly. RESULTS The outcome survey comprised 3350 individuals. Intensive MDA had no effect on wheezing (risk ratio [RR] 1.11, 95% confidence interval [CI] 0.64-1.93), SPT (RR 1.10, 95% CI 0.85-1.42), or asIgE (RR 0.96, 95% CI 0.82-1.12). Intensive MDA reduced Schistosoma mansoni infection intensity: the prevalence from Kato Katz examinations of single stool samples from each patient was 23% versus 39% (RR 0.70, 95% CI 0.55-0.88), but the urine circulating cathodic antigen test remained positive in 85% participants in both trial arms. Hookworm prevalence was 8% versus 11% (RR 0.55, 95% CI 0.31-1.00). There were no differences in anemia or hepatospenomegaly between trial arms. CONCLUSIONS Despite reductions in S. mansoni intensity and hookworm prevalence, intensive MDA had no effect on atopy, allergy-related diseases, or helminth-related pathology. This could be due to sustained low-intensity infections; thus, a causal link between helminths and allergy outcomes cannot be discounted. Intensive community-based MDA has a limited impact in high-schistosomiasis-transmission fishing communities, in the absence of other interventions. CLINICAL TRIALS REGISTRATION ISRCTN47196031.
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Affiliation(s)
- Richard E Sanya
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
- Department of Internal Medicine, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Gyaviira Nkurunungi
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Remy Hoek Spaans
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Margaret Nampijja
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Geraldine O’Hara
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Robert Kizindo
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Gloria Oduru
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Prossy Kabuubi Nakawungu
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Emmanuel Niwagaba
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Elson Abayo
- Entebbe Hospital, Wakiso District Local Government, Uganda
| | - Joyce Kabagenyi
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Christopher Zziwa
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | | | | | - James Kaweesa
- Vector Control Division, Ministry of Health, Kampala, Uganda
| | | | - Mirriam Akello
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Lawrence Lubyayi
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | - Jaco Verweij
- Laboratory for Medical Microbiology and Immunology, St Elisabeth Hospital, Tilburg, The Netherlands
| | - Stephen Nash
- Medical Research Council Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Ronald van Ree
- Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
| | - Harriet Mpairwe
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
| | | | - Emily L Webb
- Medical Research Council Tropical Epidemiology Group, Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Alison M Elliott
- Immunomodulation and Vaccines Programme, Medical Research Council/Uganda Virus Research Institute and London School of Hygiene and Tropical Medicine Uganda Research Unit, Entebbe
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, United Kingdom
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21
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A Call for Systems Epidemiology to Tackle the Complexity of Schistosomiasis, Its Control, and Its Elimination. Trop Med Infect Dis 2019; 4:tropicalmed4010021. [PMID: 30699922 PMCID: PMC6473336 DOI: 10.3390/tropicalmed4010021] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 01/22/2019] [Accepted: 01/24/2019] [Indexed: 12/20/2022] Open
Abstract
Ever since the first known written report of schistosomiasis in the mid-19th century, researchers have aimed to increase knowledge of the parasites, their hosts, and the mechanisms contributing to infection and disease. This knowledge generation has been paramount for the development of improved intervention strategies. Yet, despite a broad knowledge base of direct risk factors for schistosomiasis, there remains a paucity of information related to more complex, interconnected, and often hidden drivers of transmission that hamper intervention successes and sustainability. Such complex, multidirectional, non-linear, and synergistic interdependencies are best understood by looking at the integrated system as a whole. A research approach able to address this complexity and find previously neglected causal mechanisms for transmission, which include a wide variety of influencing factors, is needed. Systems epidemiology, as a holistic research approach, can integrate knowledge from classical epidemiology, with that of biology, ecology, social sciences, and other disciplines, and link this with informal, tacit knowledge from experts and affected populations. It can help to uncover wider-reaching but difficult-to-identify processes that directly or indirectly influence exposure, infection, transmission, and disease development, as well as how these interrelate and impact one another. Drawing on systems epidemiology to address persisting disease hotspots, failed intervention programmes, and systematically neglected population groups in mass drug administration programmes and research studies, can help overcome barriers in the progress towards schistosomiasis elimination. Generating a comprehensive view of the schistosomiasis system as a whole should thus be a priority research agenda towards the strategic goal of morbidity control and transmission elimination.
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22
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Truscott JE, Gurarie D, Alsallaq R, Toor J, Yoon N, Farrell SH, Turner HC, Phillips AE, Aurelio HO, Ferro J, King CH, Anderson RM. A comparison of two mathematical models of the impact of mass drug administration on the transmission and control of schistosomiasis. Epidemics 2018; 18:29-37. [PMID: 28279453 PMCID: PMC5340850 DOI: 10.1016/j.epidem.2017.02.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/02/2017] [Accepted: 02/03/2017] [Indexed: 11/24/2022] Open
Abstract
This paper compares two mathematical models describing the transmission dynamics of schistosome infection and the impact of mass drug administration. The models differ structurally in a number of ways, including the dynamics of the intermediate snail host and the treatment of adult worms within the human host. The models are validated against data taken from a mass-drug administration trial in Mozambique. The differences between the model predictions and the data are discussed in the context of the structural differences between the models.
The predictions of two mathematical models describing the transmission dynamics of schistosome infection and the impact of mass drug administration are compared. The models differ in their description of the dynamics of the parasites within the host population and in their representation of the stages of the parasite lifecycle outside of the host. Key parameters are estimated from data collected in northern Mozambique from 2011 to 2015. This type of data set is valuable for model validation as treatment prior to the study was minimal. Predictions from both models are compared with each other and with epidemiological observations. Both models have difficulty matching both the intensity and prevalence of disease in the datasets and are only partially successful at predicting the impact of treatment. The models also differ from each other in their predictions, both quantitatively and qualitatively, of the long-term impact of 10 years’ school-based mass drug administration. We trace the dynamical differences back to basic assumptions about worm aggregation, force of infection and the dynamics of the parasite in the snail population in the two models and suggest data which could discriminate between them. We also discuss limitations with the datasets used and ways in which data collection could be improved.
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Affiliation(s)
- J E Truscott
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, St. Mary's Campus, London, UK.
| | - D Gurarie
- Department of Mathematics, Case Western Reserve University, 10900 Euclid Avenue LC: 4983, Cleveland, OH 44106, United States
| | - R Alsallaq
- Department of Mathematics, Case Western Reserve University, 10900 Euclid Avenue LC: 4983, Cleveland, OH 44106, United States
| | - J Toor
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, St. Mary's Campus, London, UK
| | - N Yoon
- Center for Global Health and Diseases, Case Western Reserve University, 10900 Euclid Avenue LC: 4983, Cleveland, OH 44106, United States
| | - S H Farrell
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, St. Mary's Campus, London, UK
| | - H C Turner
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, St. Mary's Campus, London, UK
| | - A E Phillips
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, St. Mary's Campus, London, UK
| | - H O Aurelio
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, St. Mary's Campus, London, UK
| | - J Ferro
- Universidade Catholica de Moçambique, Beira, Mozambique
| | - C H King
- Center for Global Health and Diseases, Case Western Reserve University, 10900 Euclid Avenue LC: 4983, Cleveland, OH 44106, United States
| | - R M Anderson
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, St. Mary's Campus, London, UK
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23
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Elliott AM, Roestenberg M, Wajja A, Opio C, Angumya F, Adriko M, Egesa M, Gitome S, Mfutso-Bengo J, Bejon P, Kapulu M, Seager Z, Lutalo T, Nazziwa WB, Muwumuza A, Yazdanbakhsh M, Kaleebu P, Kabatereine N, Tukahebwa E. Ethical and scientific considerations on the establishment of a controlled human infection model for schistosomiasis in Uganda: report of a stakeholders' meeting held in Entebbe, Uganda. AAS Open Res 2018; 1:2. [PMID: 30714021 PMCID: PMC6358001 DOI: 10.12688/aasopenres.12841.2] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/01/2018] [Indexed: 02/02/2023] Open
Abstract
Controlled human infection (CHI) models are gaining recognition as an approach to accelerating vaccine development, for use in both non-endemic and endemic populations: they can facilitate identification of the most promising candidate vaccines for further trials and advance understanding of protective immunity. Helminths present a continuing health burden in sub-Saharan Africa. Vaccine development for these complex organisms is particularly challenging, partly because protective responses are akin to mechanisms of allergy. A CHI model for Schistosoma mansoni (CHI-S) has been developed at Leiden University Medical Centre, the Netherlands. However, responses to schistosome infections, and candidate vaccines, are likely to be different among people from endemic settings compared to schistosome-naïve Dutch volunteers. Furthermore, among volunteers from endemic regions who have acquired immune responses through prior exposure, schistosome challenge can be used to define responses associated with clinical protection, and thus to guide vaccine development. To explore the possibility of establishing the CHI-S in Uganda, a Stakeholders' Meeting was held in Entebbe in 2017. Regulators, community members, researchers and policy-makers discussed implementation challenges and recommended preparatory steps: risk assessment; development of infrastructure and technical capacity to produce the infectious challenge material in Uganda; community engagement from Parliamentary to grass-roots level; pilot studies to establish approaches to assuring fully informed consent and true voluntariness, and strategies for selection of volunteers who can avoid natural infection during the 12-week CHI-S; the building of regulatory capacity; and the development of study protocols and a product dossier in close consultation with ethical and regulatory partners. It was recommended that, on completion, the protocol and product dossier be reviewed for approval in a joint meeting combining ethical, regulatory and environment management authorities. Most importantly, representatives of schistosomiasis-affected communities emphasised the urgent need for an effective vaccine and urged the research community not to delay in the development process.
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Affiliation(s)
- Alison M. Elliott
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda,
| | - Meta Roestenberg
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Anne Wajja
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda
| | - Christopher Opio
- Department of Medicine, College of Health Sciences, Makerere University, Kampala, P.O. Box 7072, Uganda
| | - Francis Angumya
- Department of Medicine, College of Health Sciences, Makerere University, Kampala, P.O. Box 7072, Uganda
| | - Moses Adriko
- Vector Control Division, Ministry of Health of Uganda, Kampala, Uganda
| | - Moses Egesa
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda,Department of Medical Microbiology, School of Biomedical Sciences, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Serah Gitome
- Kenya Medical Research Institute (KEMRI), Nairobi, Kenya
| | - Joseph Mfutso-Bengo
- Centre for Bioethics for Eastern and Southern Africa, School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | - Tom Lutalo
- Uganda Virus Research Institute, Entebbe, Uganda
| | | | | | - Maria Yazdanbakhsh
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Pontiano Kaleebu
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda,Uganda Virus Research Institute, Entebbe, Uganda
| | - Narcis Kabatereine
- Vector Control Division, Ministry of Health of Uganda, Kampala, Uganda,Schistosomiasis Control Initiative, Faculty of Medicine, School of Public Health, Imperial College London, London, UK
| | - Edridah Tukahebwa
- Vector Control Division, Ministry of Health of Uganda, Kampala, Uganda
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24
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Elliott AM, Roestenberg M, Wajja A, Opio C, Angumya F, Adriko M, Egesa M, Gitome S, Mfutso-Bengo J, Bejon P, Kapulu M, Seager Z, Lutalo T, Nazziwa WB, Muwumuza A, Yazdanbakhsh M, Kaleebu P, Kabatereine N, Tukahebwa E. Ethical and scientific considerations on the establishment of a controlled human infection model for schistosomiasis in Uganda: report of a stakeholders' meeting held in Entebbe, Uganda. AAS Open Res 2018; 1:2. [PMID: 30714021 PMCID: PMC6358001 DOI: 10.12688/aasopenres.12841.1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Controlled human infection (CHI) models are gaining recognition as an approach to accelerating vaccine development, for use in both non-endemic and endemic populations: they can facilitate identification of the most promising candidate vaccines for further trials and advance understanding of protective immunity. Helminths present a continuing health burden in sub-Saharan Africa. Vaccine development for these complex organisms is particularly challenging, partly because protective responses are akin to mechanisms of allergy. A CHI model for Schistosoma mansoni (CHI-S) has been developed at Leiden University Medical Centre, the Netherlands. However, responses to schistosome infections, and candidate vaccines, are likely to be different among people from endemic settings compared to schistosome-naïve Dutch volunteers. Furthermore, among volunteers from endemic regions who have acquired immune responses through prior exposure, schistosome challenge can be used to define responses associated with clinical protection, and thus to guide vaccine development. To explore the possibility of establishing the CHI-S in Uganda, a Stakeholders' Meeting was held in Entebbe in 2017. Regulators, community members, researchers and policy-makers discussed implementation challenges and recommended preparatory steps: risk assessment; development of infrastructure and technical capacity to produce the infectious challenge material in Uganda; community engagement from Parliamentary to grass-roots level; pilot studies to establish approaches to assuring fully informed consent and true voluntariness, and strategies for selection of volunteers who can avoid natural infection during the 12-week CHI-S; the building of regulatory capacity; and the development of study protocols and a product dossier in close consultation with ethical and regulatory partners. It was recommended that, on completion, the protocol and product dossier be reviewed for approval in a joint meeting combining ethical, regulatory and environment management authorities. Most importantly, representatives of schistosomiasis-affected communities emphasised the urgent need for an effective vaccine and urged the research community not to delay in the development process.
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Affiliation(s)
- Alison M. Elliott
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda,
| | - Meta Roestenberg
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Anne Wajja
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda
| | - Christopher Opio
- Department of Medicine, College of Health Sciences, Makerere University, Kampala, P.O. Box 7072, Uganda
| | - Francis Angumya
- Department of Medicine, College of Health Sciences, Makerere University, Kampala, P.O. Box 7072, Uganda
| | - Moses Adriko
- Vector Control Division, Ministry of Health of Uganda, Kampala, Uganda
| | - Moses Egesa
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda,Department of Medical Microbiology, School of Biomedical Sciences, College of Health Sciences, Makerere University, Kampala, Uganda
| | - Serah Gitome
- Kenya Medical Research Institute (KEMRI), Nairobi, Kenya
| | - Joseph Mfutso-Bengo
- Centre for Bioethics for Eastern and Southern Africa, School of Public Health and Family Medicine, College of Medicine, University of Malawi, Blantyre, Malawi
| | - Philip Bejon
- KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya
| | | | | | - Tom Lutalo
- Uganda Virus Research Institute, Entebbe, Uganda
| | | | | | - Maria Yazdanbakhsh
- Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Pontiano Kaleebu
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine (MRC/UVRI and LSHTM) Uganda Research Unit, Entebbe, P.O. Box 49, Uganda,Uganda Virus Research Institute, Entebbe, Uganda
| | - Narcis Kabatereine
- Vector Control Division, Ministry of Health of Uganda, Kampala, Uganda,Schistosomiasis Control Initiative, Faculty of Medicine, School of Public Health, Imperial College London, London, UK
| | - Edridah Tukahebwa
- Vector Control Division, Ministry of Health of Uganda, Kampala, Uganda
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Inobaya MT, Chau TN, Ng SK, MacDougall C, Olveda RM, Tallo VL, Landicho JM, Malacad CM, Aligato MF, Guevarra JB, Ross AG. Mass drug administration and the sustainable control of schistosomiasis: an evaluation of treatment compliance in the rural Philippines. Parasit Vectors 2018; 11:441. [PMID: 30064469 PMCID: PMC6069569 DOI: 10.1186/s13071-018-3022-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Accepted: 07/17/2018] [Indexed: 12/22/2022] Open
Abstract
Background Preventive chemotherapy is the current global control strategy for schistosomiasis. The WHO target coverage rate is at least 75% for school-aged children. In the Philippines, the reported national coverage rate (43.5%) is far below the WHO target. This study examined the factors associated with non-compliance to mass drug administration. Methods A cross-sectional survey was conducted in 2015 among 2189 adults in the province of Northern Samar, the Philippines using a structured face-to-face survey questionnaire. Results The overall rate of non-compliance to mass drug administration (MDA) in the last treatment round was 27%. Females (aOR = 1.67, P = 0.033) were more likely to be non-compliant. Respondents who believed that schistosomiasis was acquired by open defecation and poor sanitation (aOR = 1.41, P = 0.015), and by drinking unclean water (aOR = 2.09, P = 0.001) were more likely to refuse treatment. Uncertainties on whether schistosomiasis can be treated (aOR = 2.39, P = 0.033), their fear of adverse reactions to praziquantel (aOR = 1.94, P = 0.021), misconceptions about alternative forms of treatment (aOR = 1.45, P = 0.037), and that praziquantel is used for purposes other than deworming (aOR = 2.15, P = 0.021) were all associated with a higher odd of non-compliance. In contrary, being a farmer (aOR = 0.62, P =0.038), participation in past MDA (aOR = 0.30, P < 0.001), informed about impending MDA (aOR = 0.08, P < 0.001), and having heard of schistosomiasis (aOR = 0.22, P = 0.045) were all significantly associated with reduced non-compliance. Conclusions To improve drug compliance for schistosomiasis there is an urgent need for intensive health education campaigns before conducting MDA that would not only provide disease specific information, but also deal with prevailing misconceptions about transmission, prevention, treatment, and drug side-effects.
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Affiliation(s)
- Marianette T Inobaya
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia.,Department of Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines
| | - Thao N Chau
- Discipline of Public Health, School of Health Sciences, Flinders University, Adelaide, Australia
| | - Shu-Kay Ng
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
| | - Colin MacDougall
- Discipline of Public Health, School of Health Sciences, Flinders University, Adelaide, Australia
| | - Remigio M Olveda
- Department of Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines
| | - Veronica L Tallo
- Department of Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines
| | - Jhoys M Landicho
- Department of Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines
| | - Carol M Malacad
- Department of Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines
| | - Mila F Aligato
- Department of Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines
| | - Jerric B Guevarra
- Department of Health, Research Institute for Tropical Medicine, Muntinlupa City, Philippines
| | - Allen G Ross
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia.
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Coulibaly JT, Ouattara M, Barda B, Utzinger J, N'Goran EK, Keiser J. A Rapid Appraisal of Factors Influencing Praziquantel Treatment Compliance in Two Communities Endemic for Schistosomiasis in Côte d'Ivoire. Trop Med Infect Dis 2018; 3:tropicalmed3020069. [PMID: 30274465 PMCID: PMC6073597 DOI: 10.3390/tropicalmed3020069] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 05/09/2018] [Accepted: 06/14/2018] [Indexed: 01/12/2023] Open
Abstract
Over the past decade, a significant reduction in the prevalence of schistosomiasis has been achieved, partially explained by the large-scale administration of praziquantel. Yet, the burden of schistosomiasis remains considerable, and factors influencing intervention coverage are important. This study aimed to deepen the understanding of low treatment coverage rates observed in two schistosomiasis-endemic villages in Côte d’Ivoire. The research was conducted in August 2015, in Moronou and Bigouin, two villages of Côte d’Ivoire that are endemic for Schistosoma haematobium and S. mansoni, respectively. After completion of a clinical trial, standard praziquantel treatment (single 40 mg/kg oral dose) was offered to all village inhabitants by community health workers using a house-to-house approach. Factors influencing treatment coverage were determined by a questionnaire survey, randomly selecting 405 individuals. The overall treatment coverage rate was only 47.6% (2730/5733) with considerable intervillage heterogeneity (27.7% in Bigouin (302/1091) versus 52.3% in Moronou (2428/4642)). Among the 200 individuals interviewed in Moronou, 50.0% were administered praziquantel, while only 19.5% of the 205 individuals interviewed in Bigouin received praziquantel. The main reasons for low treatment coverage were work-related (agricultural activities), the bitter taste of praziquantel and previous experiences with adverse events. The most suitable period for treatment campaigns was reported to be the dry season. More than three-quarter of the interviewees who had taken praziquantel (overall, 116/140; Moronou, 84/100; Bigouin, 32/40) declared that they would not participate in future treatments (p < 0.001). In order to enhance praziquantel treatment coverage, careful consideration should be given to attitudes and practices, such as prior or perceived adverse events and taste of praziquantel, and appropriate timing, harmonized with agricultural activities. Without such understanding, breaking the transmission of schistosomiasis remains a distant goal.
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Affiliation(s)
- Jean T Coulibaly
- Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
- University of Basel, P.O. Box, CH-4001 Basel, Switzerland.
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 01 BP 770, Abidjan 01, Côte d'Ivoire.
- Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire.
| | - Mamadou Ouattara
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 01 BP 770, Abidjan 01, Côte d'Ivoire.
- Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire.
| | - Beatrice Barda
- Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
- University of Basel, P.O. Box, CH-4001 Basel, Switzerland.
| | - Jürg Utzinger
- Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
- University of Basel, P.O. Box, CH-4001 Basel, Switzerland.
| | - Eliézer K N'Goran
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, 01 BP 770, Abidjan 01, Côte d'Ivoire.
- Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, 01 BP 1303, Abidjan 01, Côte d'Ivoire.
| | - Jennifer Keiser
- Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland.
- University of Basel, P.O. Box, CH-4001 Basel, Switzerland.
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Freer JB, Bourke CD, Durhuus GH, Kjetland EF, Prendergast AJ. Schistosomiasis in the first 1000 days. THE LANCET. INFECTIOUS DISEASES 2018; 18:e193-e203. [PMID: 29170089 DOI: 10.1016/s1473-3099(17)30490-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 07/02/2017] [Accepted: 07/13/2017] [Indexed: 12/29/2022]
Abstract
Infections during the first 1000 days-the period from conception to a child's second birthday-can have lifelong effects on health, because this is a crucial phase of growth and development. There is increasing recognition of the burden and potential effects of schistosomiasis in women of reproductive age and young children. Exposure to schistosomes during pregnancy can modulate infant immune development and schistosomiasis can occur from early infancy, such that the high disease burden found in adolescents is often due to accumulation of infections with long-lived schistosomes from early life. Women of reproductive age and young children are largely neglected in mass drug administration programmes, but early treatment could avert subsequent disease. We evaluate the evidence that early schistosomiasis has adverse effects on birth, growth, and development. We also discuss the case for expanding public health interventions for schistosomiasis in women of reproductive age and preschool-age children, and the need for further research to evaluate the potential of treating women pre-conception to maximise health across the life course.
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Affiliation(s)
- Joseph B Freer
- Zvitambo Institute for Maternal and Child Health Research, Harare, Zimbabwe; Blizard Institute, Queen Mary University of London, London, UK.
| | - Claire D Bourke
- Blizard Institute, Queen Mary University of London, London, UK
| | - Gunn H Durhuus
- Department of Internal Medicine, Sorlandet Hospital, Kristiansand, Norway
| | - Eyrun F Kjetland
- Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital, Oslo, Norway; Discipline of Public Health Medicine, Nelson R Mandela School of Medicine, College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Andrew J Prendergast
- Zvitambo Institute for Maternal and Child Health Research, Harare, Zimbabwe; Blizard Institute, Queen Mary University of London, London, UK
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Lothe A, Zulu N, Øyhus AO, Kjetland EF, Taylor M. Treating schistosomiasis among South African high school pupils in an endemic area, a qualitative study. BMC Infect Dis 2018; 18:239. [PMID: 29801483 PMCID: PMC5970489 DOI: 10.1186/s12879-018-3102-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Accepted: 04/17/2018] [Indexed: 12/02/2022] Open
Abstract
Background Schistosomiasis, a neglected tropical disease caused by parasites that infest open water sources such as rivers and dams may increase susceptibility to HIV. Mass-treatment with praziquantel tablets, recommended by the World Health Organization reduces the prevalence of schistosomiasis. The goal in endemic areas is 75% treatment participation in every treatment round (e.g. yearly). However, in rural Ugu district, KwaZulu-Natal, South-Africa there was low participation among pupils in a Department of Health Mass-Treatment Campaign for schistosomiasis. Methods Nested in a large study on schistosomiasis the study was conducted in 2012 over 4 months using qualitative methods with the Health Belief Model as the conceptual framework. Purposive sampling was done. Focus Group Discussions were undertaken at six schools in grades 10–12. Individual in-depth interviews were held with one teacher and two pupils at each school. In addition three traditional healers and a community health worker were interviewed. Results The severity of schistosomiasis was not recognised and neither was the pupils’ susceptibility. Barriers to treatment included confusing S, haematobium symptoms with sexually transmitted infections, teasing and stigma. Conclusions Increased knowledge, health literacy for treatment, and correct understanding about the severity of schistosomiasis may provide cues to action. The study indicates that comprehensive information may increase pupil participation in mass-treatment and decrease schistosomiasis prevalence. Trial registration This study was registered with clinicaltrials.gov registry database and the registration number is NCT01154907 30 June 2011.
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Affiliation(s)
- Andrea Lothe
- Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital, 0424, Oslo, Norway.,Institute for Global Development and Planning, University of Agder, 4630, Kristiansand, Norway
| | - Nqobile Zulu
- Centre for Communication, Media and Society, University of KwaZulu-Natal, Durban, 4001, South Africa
| | - Arne Olav Øyhus
- Institute for Global Development and Planning, University of Agder, 4630, Kristiansand, Norway
| | - Eyrun Floerecke Kjetland
- Norwegian Centre for Imported and Tropical Diseases, Department of Infectious Diseases Ullevaal, Oslo University Hospital, 0424, Oslo, Norway.,Discipline of Public Health Medicine, Howard College Campus, University of KwaZulu-Natal, Room 219, George Campbell Building, Science Drive, Durban, 4001, South Africa
| | - Myra Taylor
- Discipline of Public Health Medicine, Howard College Campus, University of KwaZulu-Natal, Room 219, George Campbell Building, Science Drive, Durban, 4001, South Africa.
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29
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Gurarie D, Lo NC, Ndeffo-Mbah ML, Durham DP, King CH. The human-snail transmission environment shapes long term schistosomiasis control outcomes: Implications for improving the accuracy of predictive modeling. PLoS Negl Trop Dis 2018; 12:e0006514. [PMID: 29782500 PMCID: PMC5983867 DOI: 10.1371/journal.pntd.0006514] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Revised: 06/01/2018] [Accepted: 05/09/2018] [Indexed: 11/25/2022] Open
Abstract
INTRODUCTION Schistosomiasis is a chronic parasitic trematode disease that affects over 240 million people worldwide. The Schistosoma lifecycle is complex, involving transmission via specific intermediate-host freshwater snails. Predictive mathematical models of Schistosoma transmission have often chosen to simplify or ignore the details of environmental human-snail interaction in their analyses. Schistosome transmission models now aim to provide better precision for policy planning of elimination of transmission. This heightens the importance of including the environmental complexity of vector-pathogen interaction in order to make more accurate projections. METHODOLOGY AND PRINCIPAL FINDINGS We propose a nonlinear snail force of infection (FOI) that takes into account an intermediate larval stage (miracidium) and snail biology. We focused, in particular, on the effects of snail force of infection (FOI) on the impact of mass drug administration (MDA) in human communities. The proposed (modified) model was compared to a conventional model in terms of their predictions. A longitudinal dataset generated in Kenya field studies was used for model calibration and validation. For each sample community, we calibrated modified and conventional model systems, then used them to model outcomes for a range of MDA regimens. In most cases, the modified model predicted more vigorous post-MDA rebound, with faster relapse to baseline levels of infection. The effect was pronounced in higher risk communities. When compared to observed data, only the modified system was able to successfully predict persistent rebound of Schistosoma infection. CONCLUSION AND SIGNIFICANCE The observed impact of varying location-specific snail inputs sheds light on the diverse MDA response patterns noted in operational research on schistosomiasis control, such as the recent SCORE project. Efficiency of human-to-snail transmission is likely to be much higher than predicted by standard models, which, in practice, will make local elimination by implementation of MDA alone highly unlikely, even over a multi-decade period.
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Affiliation(s)
- David Gurarie
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, Ohio, United States of America
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
- Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, Georgia, United States of America
| | - Nathan C Lo
- Division of Epidemiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Martial L Ndeffo-Mbah
- Yale School of Public Health, Yale University, New Haven, Connecticut, United States of America
| | - David P Durham
- Yale School of Public Health, Yale University, New Haven, Connecticut, United States of America
| | - Charles H King
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
- Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, Georgia, United States of America
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30
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Tanser F, Azongo DK, Vandormael A, Bärnighausen T, Appleton C. Impact of the scale-up of piped water on urogenital schistosomiasis infection in rural South Africa. eLife 2018; 7:33065. [PMID: 29460779 PMCID: PMC5819946 DOI: 10.7554/elife.33065] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 01/31/2018] [Indexed: 12/31/2022] Open
Abstract
Recent work has estimated that sub-Saharan Africa could lose US$3.5 billion of economic productivity every year as a result of schistosomiasis and soil-transmitted helminthiasis. One of the main interventions to control schistosomiasis is the provision of safe water to limit the contact with infected water bodies and break the cycle of transmission. To date, a rigorous quantification of the impact of safe water supplies on schistosomiasis is lacking. Using data from one of Africa's largest population-based cohorts, we establish the impact of the scale-up of piped water in a typical rural South African population over a seven-year time horizon. High coverage of piped water in the community decreased a child's risk of urogenital schistosomiasis infection eight-fold (adjusted odds ratio = 0.12, 95% CI 0.06-0.26, p<0.001). The provision of safe water could drive levels of urogenital schistosomiasis infection to low levels of endemicity in rural African settings.
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Affiliation(s)
- Frank Tanser
- Africa Health Research Institute, KwaZulu-Natal, South Africa.,School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South Africa.,Centre for the AIDS Programme of Research in South Africa (CAPRISA), University of KwaZulu-Natal, Durban, South Africa.,Institute of Epidemiology and Health Care, University College London, London, United Kingdom
| | - Daniel K Azongo
- Navrongo Health Research Centre, Ghana Health Service, Navrongo, Upper East Region, Ghana
| | - Alain Vandormael
- Africa Health Research Institute, KwaZulu-Natal, South Africa.,School of Nursing and Public Health, University of KwaZulu-Natal, Durban, South Africa.,KwaZulu-Natal Research Innovation and Sequencing Platform (KRISP), College of Health Sciences, University of KwaZulu-Natal, Durban, South Africa
| | - Till Bärnighausen
- Africa Health Research Institute, KwaZulu-Natal, South Africa.,Institute of Epidemiology and Health Care, University College London, London, United Kingdom.,Department of Global Health and Population, Harvard T.H. Chan School of Public Health, Boston, United States.,Institute for Public Health, University of Heidelberg, Heidelberg, Germany
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31
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Phillips AE, Gazzinelli-Guimarães PH, Aurelio HO, Dhanani N, Ferro J, Nala R, Deol A, Fenwick A. Urogenital schistosomiasis in Cabo Delgado, northern Mozambique: baseline findings from the SCORE study. Parasit Vectors 2018; 11:30. [PMID: 29316983 PMCID: PMC5761122 DOI: 10.1186/s13071-017-2592-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Accepted: 12/13/2017] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND The results presented here are part of a five-year cluster-randomised intervention trial that was implemented to understand how best to gain and sustain control of schistosomiasis through different preventive chemotherapy strategies. This paper presents baseline data that were collected in ten districts of Cabo Delgado province, northern Mozambique, before treatment. METHODS A cross-sectional study of 19,039 individuals was sampled from 144 villages from May to September 2011. In each village prevalence and intensity of S. haematobium were investigated in 100 children first-year students (aged 5-8 years), 100 school children aged 9-12 years (from classes 2 to 7) and 50 adults (20-55 years). Prevalence and intensity of S. haematobium infection were evaluated microscopically by two filtrations, each of 10 ml, from a single urine specimen. Given that individual and community perceptions of schistosomiasis influence control efforts, community knowledge and environmental risk factors were collected using a face-to-face interview. Data were entered onto mobile phones using EpiCollect. Data summary was made using descriptive statistics. Chi-square and logistic regression were used to determine the association between dependent and independent variables. RESULTS The overall prevalence of urogenital schistosomiasis was 60.4% with an arithmetic mean intensity of infection of 55.8 eggs/10 ml of urine. Heavy infections were detected in 17.7%, of which 235 individuals (6.97%) had an egg count of 1000 eggs/10 ml or more. There was a significantly higher likelihood of males being infected than females across all ages (62% vs 58%; P < 0.0005). Adolescents aged 9-12 years had a higher prevalence (66.6%) and mean infection intensity (71.9 eggs/10 ml) than first-year students (63.1%; 58.2 eggs/10 ml). This is the first study in Mozambique looking at infection rates among adults. Although children had higher levels of infection, it was found here that adults had a high average prevalence and intensity of infection (44.5%; 23.9 eggs/10 ml). Awareness of schistosomiasis was relatively high (68.6%); however, correct knowledge of how schistosomiasis is acquired was low (23.2%) among those who had heard of the disease. Schistosomiasis risk behaviour such as washing (91.3%) and bathing (86.7%) in open water sources likely to be infested with host snails was high. CONCLUSIONS Urogenital schistosomiasis is widespread in Cabo Delgado. In addition, poor community knowledge about the causes of schistosomiasis and how to prevent it increases the significant public health challenge for the national control program. This was the first study in Mozambique that examined infection levels among adults, where results showed that S. haematobium infection was also extremely high. Given that this controlled trial aims to understand the impact of different combinations of schistosomiasis control through treatment of communities, schools, and treatment holidays over a five-year period, these findings highlight the importance of examining the impact of different treatment approaches also in adults. TRIAL REGISTRATION The trials have been registered with the International Standard Randomised Controlled Trial registry under ISRCT 14117624 Mozambique (14 December 2015).
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Affiliation(s)
- Anna E. Phillips
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, W2 1PG, London, UK
| | - Pedro H. Gazzinelli-Guimarães
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, W2 1PG, London, UK
| | - Herminio O. Aurelio
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, W2 1PG, London, UK
- Faculdade of Health Sciences, Universidade Católica de Moçambique (UCM), Beira, Mozambique
| | - Neerav Dhanani
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, W2 1PG, London, UK
| | - Josefo Ferro
- Faculdade of Health Sciences, Universidade Católica de Moçambique (UCM), Beira, Mozambique
| | | | - Arminder Deol
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, W2 1PG, London, UK
| | - Alan Fenwick
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, W2 1PG, London, UK
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Impact and cost-effectiveness of snail control to achieve disease control targets for schistosomiasis. Proc Natl Acad Sci U S A 2018; 115:E584-E591. [PMID: 29301964 PMCID: PMC5789907 DOI: 10.1073/pnas.1708729114] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Schistosomiasis is an infectious disease that affects over 240 million people living in low- and middle-income countries, and is caused by parasitic worms that require snail hosts to complete its lifecycle. To improve public health control of this disease, there is growing interest in using chemical-based snail control that kills snail populations in environmental water sources, which will reduce infection rate in people. We modeled transmission of schistosomiasis and cost-effectiveness of various strategies with data from low- and high-prevalence rural Kenyan communities. Adding snail control alongside conventional mass treatment programs (instead of mass treatment programs alone) was found to be cost-effective, especially in settings with high disease burden and nonparticipation in mass treatment programs. Schistosomiasis is a parasitic disease that affects over 240 million people globally. To improve population-level disease control, there is growing interest in adding chemical-based snail control interventions to interrupt the lifecycle of Schistosoma in its snail host to reduce parasite transmission. However, this approach is not widely implemented, and given environmental concerns, the optimal conditions for when snail control is appropriate are unclear. We assessed the potential impact and cost-effectiveness of various snail control strategies. We extended previously published dynamic, age-structured transmission and cost-effectiveness models to simulate mass drug administration (MDA) and focal snail control interventions against Schistosoma haematobium across a range of low-prevalence (5–20%) and high-prevalence (25–50%) rural Kenyan communities. We simulated strategies over a 10-year period of MDA targeting school children or entire communities, snail control, and combined strategies. We measured incremental cost-effectiveness in 2016 US dollars per disability-adjusted life year and defined a strategy as optimally cost-effective when maximizing health gains (averted disability-adjusted life years) with an incremental cost-effectiveness below a Kenya-specific economic threshold. In both low- and high-prevalence settings, community-wide MDA with additional snail control reduced total disability by an additional 40% compared with school-based MDA alone. The optimally cost-effective scenario included the addition of snail control to MDA in over 95% of simulations. These results support inclusion of snail control in global guidelines and national schistosomiasis control strategies for optimal disease control, especially in settings with high prevalence, “hot spots” of transmission, and noncompliance to MDA.
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Phillips AE, Gazzinelli-Guimaraes PH, Aurelio HO, Ferro J, Nala R, Clements M, King CH, Fenwick A, Fleming FM, Dhanani N. Assessing the benefits of five years of different approaches to treatment of urogenital schistosomiasis: A SCORE project in Northern Mozambique. PLoS Negl Trop Dis 2017; 11:e0006061. [PMID: 29220347 PMCID: PMC5745126 DOI: 10.1371/journal.pntd.0006061] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 12/27/2017] [Accepted: 10/21/2017] [Indexed: 12/22/2022] Open
Abstract
Background In Mozambique, schistosomiasis is highly endemic across the whole country. The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) coordinates a five-year study that has been implemented in various African countries, including Mozambique. The overall goal of SCORE was to better understand how to best apply preventive chemotherapy with praziquantel (PZQ) for schistosomiasis control by evaluating the impact of alternative treatment approaches. Methods This was a cluster-randomised trial that compared the impact of different treatment strategies in study areas with prevalence among school children of ≥21% S. haematobium infection by urine dipstick. Each village was randomly allocated to one of six possible combinations of community-wide treatment (CWT), school-based treatment (SBT), and/or drug holidays over a period of four years, followed by final data collection in the fifth year. The most intense intervention arm involved four years of CWT, while the least intensive arm involved two years of SBT followed by two consecutive years of PZQ holiday. Each study arm included 25 villages randomly assigned to one of the six treatment arms. The primary outcome of interest was change in prevalence and intensity of S. haematobium among 100 children aged 9-to-12-years that were sampled each year in every village. In addition to children aged 9-to-12 years, 100 children aged 5–8 years in their first-year of school and 50 adults (aged 20–55 years) were tested in the first and final fifth year of the study. Prevalence and intensity of S. haematobium infection was evaluated by two filtrations, each of 10mL, from a single urine specimen. Principal findings In total, data was collected from 81,167 individuals across 149 villages in ten districts of Cabo Delgado province, Northern Mozambique. Overall PZQ treatment resulted in a significant reduction in the prevalence of S. haematobium infection from Year 1 to Year 5, where the average prevalence went from 60.5% to 38.8%, across all age groups and treatment arms. The proportion of those heavily infected also reduced from 17.6% to 11.9% over five years. There was a significantly higher likelihood of males being infected than females at baseline, but no significant difference between the sexes in their response to treatment. The only significant response based on a study arm was seen in both the 9-to-12-year-old and first-year cross sections, where two consecutive treatment holidays resulted in a significantly higher final prevalence of S. haematobium than no treatment holidays. When the arms were grouped together, four rounds of treatment (regardless of whether it was CWT or SBT), however, did result in a significantly greater reduction in S. haematobium prevalence than two rounds of treatment (i.e. with two intermittent or consecutive holiday years) over a five-year period. Conclusions Although PC was successful in reducing the burden of active infection, even among those heavily infected, annual CWT did not have a significantly greater impact on disease prevalence or intensity than less intense treatment arms. This may be due to extremely high starting prevalence and intensity in the study area, with frequent exposure to reinfection, or related to challenges in achieving high treatment coverage More frequent treatment had a greater impact on prevalence and intensity of infection when arms were grouped by number of treatments, however, cost efficiency was greater in arms only receiving two treatments. Finally, a significant reduction in prevalence of S. haematobium was seen in adults even in the SBT arms implying the rate of transmission in the community had been decreased, even where only school children have been treated, which has significant logistical and cost-saving implications for a national control programme in justifying CWT. Urogenital schistosomiasis is highly endemic in Mozambique. This study was part of a multi-country trial, including Mozambique, designed to understand the impact of different schistosomiasis treatment strategies involving community-wide treatment (CWT), school-based (SBT), and treatment holidays over a five-year period. Results from Mozambique showed that although preventive chemotherapy was successful in reducing the prevalence of Schistosoma haematobium over five-years, the most intense treatment approach, annual CWT, did not have a significantly greater impact than less intense treatment strategies, such as bi-annual SBT. Infection rates were higher among males, but there was no difference in response to treatment by gender. Four rounds of treatment (regardless of whether it was given in the community or school) did result in a significantly greater reduction of S. haematobium prevalence than two rounds of treatment over a five-year period. There was, however, a resurgent increase in prevalence and intensity of S. haematobium infection shown after two consecutive treatment-holiday years, implying a bounce back in infection after a two year pause in treatment. Interestingly and unexpectedly, there was a significant reduction in prevalence of schistosomiasis in adults even in communities that had received SBT implying the force of transmission in the community had been decreased, even where only school children had been treated. These findings provide an evidence-base with significant logistical and cost-saving implications for programmatic decisions on how best to gain control of Schistosoma haematobium.
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Affiliation(s)
- Anna E. Phillips
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
- * E-mail:
| | - Pedro H. Gazzinelli-Guimaraes
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Herminio O. Aurelio
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
- Faculdade of Health Sciences, Universidade Católica de Moçambique (UCM) Beira, Moçambique
| | - Josefo Ferro
- Faculdade of Health Sciences, Universidade Católica de Moçambique (UCM) Beira, Moçambique
| | - Rassul Nala
- Laboratório de Parasitologia Intestinal e Vesical do Instituto Nacional de Saúde de Moçambique, Ministerio da Saúde, Maputo, Moçambique
| | - Michelle Clements
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Charles H. King
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Euclid Avenue, Cleveland, Ohio, United States of America
- Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, Georgia, United States of America
| | - Alan Fenwick
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Fiona M. Fleming
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Neerav Dhanani
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
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Michael E, Singh BK, Mayala BK, Smith ME, Hampton S, Nabrzyski J. Continental-scale, data-driven predictive assessment of eliminating the vector-borne disease, lymphatic filariasis, in sub-Saharan Africa by 2020. BMC Med 2017; 15:176. [PMID: 28950862 PMCID: PMC5615442 DOI: 10.1186/s12916-017-0933-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Accepted: 08/16/2017] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND There are growing demands for predicting the prospects of achieving the global elimination of neglected tropical diseases as a result of the institution of large-scale nation-wide intervention programs by the WHO-set target year of 2020. Such predictions will be uncertain due to the impacts that spatial heterogeneity and scaling effects will have on parasite transmission processes, which will introduce significant aggregation errors into any attempt aiming to predict the outcomes of interventions at the broader spatial levels relevant to policy making. We describe a modeling platform that addresses this problem of upscaling from local settings to facilitate predictions at regional levels by the discovery and use of locality-specific transmission models, and we illustrate the utility of using this approach to evaluate the prospects for eliminating the vector-borne disease, lymphatic filariasis (LF), in sub-Saharan Africa by the WHO target year of 2020 using currently applied or newly proposed intervention strategies. METHODS AND RESULTS: We show how a computational platform that couples site-specific data discovery with model fitting and calibration can allow both learning of local LF transmission models and simulations of the impact of interventions that take a fuller account of the fine-scale heterogeneous transmission of this parasitic disease within endemic countries. We highlight how such a spatially hierarchical modeling tool that incorporates actual data regarding the roll-out of national drug treatment programs and spatial variability in infection patterns into the modeling process can produce more realistic predictions of timelines to LF elimination at coarse spatial scales, ranging from district to country to continental levels. Our results show that when locally applicable extinction thresholds are used, only three countries are likely to meet the goal of LF elimination by 2020 using currently applied mass drug treatments, and that switching to more intensive drug regimens, increasing the frequency of treatments, or switching to new triple drug regimens will be required if LF elimination is to be accelerated in Africa. The proportion of countries that would meet the goal of eliminating LF by 2020 may, however, reach up to 24/36 if the WHO 1% microfilaremia prevalence threshold is used and sequential mass drug deliveries are applied in countries. CONCLUSIONS We have developed and applied a data-driven spatially hierarchical computational platform that uses the discovery of locally applicable transmission models in order to predict the prospects for eliminating the macroparasitic disease, LF, at the coarser country level in sub-Saharan Africa. We show that fine-scale spatial heterogeneity in local parasite transmission and extinction dynamics, as well as the exact nature of intervention roll-outs in countries, will impact the timelines to achieving national LF elimination on this continent.
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Affiliation(s)
- Edwin Michael
- Department of Biological Sciences, University of Notre Dame, Galvin Life Science Center, Notre Dame, IN, 46556, USA.
| | - Brajendra K Singh
- Department of Biological Sciences, University of Notre Dame, Galvin Life Science Center, Notre Dame, IN, 46556, USA
| | - Benjamin K Mayala
- Department of Biological Sciences, University of Notre Dame, Galvin Life Science Center, Notre Dame, IN, 46556, USA
| | - Morgan E Smith
- Department of Biological Sciences, University of Notre Dame, Galvin Life Science Center, Notre Dame, IN, 46556, USA
| | - Scott Hampton
- Center for Research Computing, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Jaroslaw Nabrzyski
- Center for Research Computing, University of Notre Dame, Notre Dame, IN, 46556, USA
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The Interdependence between Schistosome Transmission and Protective Immunity. Trop Med Infect Dis 2017; 2:tropicalmed2030042. [PMID: 30270899 PMCID: PMC6082113 DOI: 10.3390/tropicalmed2030042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 08/02/2017] [Accepted: 08/08/2017] [Indexed: 01/14/2023] Open
Abstract
Mass drug administration (MDA) for control of schistosomiasis is likely to affect transmission dynamics through a combination of passive vaccination and reduction of local transmission intensity. This is indicated in phenomenological models of immunity and the impact of MDA, yet immunity parameters in these models are not validated by empirical data that reflects protective immunity to reinfection. There is significant empirical evidence supporting the role of IgE in acquired protective immunity. This is proposed to be a form of delayed concomitant immunity, driven at least in part by protective IgE responses to the tegument allergen-like (TAL) family of proteins. Specific questions have arisen from modeling studies regarding the strength and duration of the protective immune response. At present, field studies have not been specifically designed to address these questions. There is therefore a need for field studies that are explicitly designed to capture epidemiological effects of acquired immunity to elucidate these immunological interactions. In doing so, it is important to address the discourse between theoretical modelers and immuno-epidemiologists and develop mechanistic models that empirically define immunity parameters. This is of increasing significance in a climate of potential changing transmission dynamics following long-term implementation of MDA.
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Egesa M, Hoffmann KF, Hokke CH, Yazdanbakhsh M, Cose S. Rethinking Schistosomiasis Vaccine Development: Synthetic Vesicles. Trends Parasitol 2017; 33:918-921. [PMID: 28818406 DOI: 10.1016/j.pt.2017.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 07/15/2017] [Accepted: 07/17/2017] [Indexed: 12/26/2022]
Abstract
There is currently no vaccine against schistosomiasis. With few Schistosoma vaccine candidates in clinical trials, unexplored antigens from the vulnerable schistosomulum should be considered as possible vaccine candidates. In addition, we suggest developing synthetic vesicles as a new delivery vehicle and adjuvant for immunoprophylactic schistosomula vaccine candidates.
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Affiliation(s)
- Moses Egesa
- Department of Medical Microbiology, School of Biomedical Sciences, Makerere University College of Health Sciences, Kampala, Uganda; Medical Research Council/Uganda Virus Research Institute Uganda Research Unit on AIDS, Entebbe, Uganda
| | - Karl F Hoffmann
- Institute of Biological, Environmental and Rural Sciences (IBERS), Edward Llwyd Building, Room 3-31, Aberystwyth University, Ceredigion, SY23 3DA, UK
| | - Cornelis H Hokke
- Department of Parasitology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
| | - Maria Yazdanbakhsh
- Department of Parasitology, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
| | - Stephen Cose
- Medical Research Council/Uganda Virus Research Institute Uganda Research Unit on AIDS, Entebbe, Uganda; Department of Clinical Research, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
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Turner HC, Truscott JE, Bettis AA, Farrell SH, Deol AK, Whitton JM, Fleming FM, Anderson RM. Evaluating the variation in the projected benefit of community-wide mass treatment for schistosomiasis: Implications for future economic evaluations. Parasit Vectors 2017; 10:213. [PMID: 28454578 PMCID: PMC5410074 DOI: 10.1186/s13071-017-2141-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 04/18/2017] [Indexed: 12/14/2022] Open
Abstract
Background The majority of schistosomiasis control programmes focus on targeting school-aged children. Expanding the use of community-wide mass treatment to reach more adults is under consideration. However, it should be noted that this would require a further increase in programmatic resources, international aid, and commitment for the provision of praziquantel. Consequently, it is important to understand (i) where a change of strategy would have the greatest benefit, and (ii) how generalisable the conclusions of field trials and analytical studies based on mathematical models investigating the impact of community-wide mass treatment, are to a broad range of settings. Methods In this paper, we employ a previously described deterministic fully age-structured schistosomiasis transmission model and evaluate the benefit of community-wide mass treatment both in terms of controlling morbidity and eliminating transmission for Schistosoma mansoni, across a wide range of epidemiological settings and programmatic scenarios. This included variation in the baseline relative worm pre-control burden in adults, the overall level of transmission in defined settings, choice of effectiveness metric (basing morbidity calculations on prevalence or intensity), the level of school enrolment and treatment compliance. Results Community-wide mass treatment was found to be more effective for controlling the transmission of schistosome parasites than using a school-based programme only targeting school-aged children. However, in the context of morbidity control, the potential benefit of switching to community-wide mass treatment was highly variable across the different scenarios analysed. In contrast, for areas where the goal is to eliminate transmission, the projected benefit of community-wide mass treatment was more consistent. Conclusion Whether community-wide mass treatment is appropriate will depend on the local epidemiological setting (i.e. the relative pre-control burden in adults and transmission intensity), and whether the goal is morbidity control or eliminating transmission. This has important implications regarding the generalisability of cost-effectiveness analyses of schistosomiasis interventions. Our results indicate that areas with poor school-enrolment/coverage could benefit more from community-wide treatment of praziquantel and should potentially be prioritised for any change in strategy. This work highlights the importance of not over-generalising conclusions and policy in this area, but of basing decisions on high quality epidemiological data and quantitative analyses of the impact of interventions in a range of settings. Electronic supplementary material The online version of this article (doi:10.1186/s13071-017-2141-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hugo C Turner
- London Centre for Neglected Tropical Disease Research, London, UK. .,Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, St Marys Campus, Imperial College London, Norfolk Place, London, W2 1PG, UK. .,Oxford University Clinical Research Unit, Wellcome Trust Major Overseas Programme, Ho Chi Minh City, Vietnam. .,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, UK.
| | - James E Truscott
- London Centre for Neglected Tropical Disease Research, London, UK.,Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, St Marys Campus, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Alison A Bettis
- London Centre for Neglected Tropical Disease Research, London, UK.,Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, St Marys Campus, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Sam H Farrell
- London Centre for Neglected Tropical Disease Research, London, UK.,Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, St Marys Campus, Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Arminder K Deol
- London Centre for Neglected Tropical Disease Research, London, UK.,Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St. Mary's Campus), Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Jane M Whitton
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St. Mary's Campus), Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Fiona M Fleming
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine (St. Mary's Campus), Imperial College London, Norfolk Place, London, W2 1PG, UK
| | - Roy M Anderson
- London Centre for Neglected Tropical Disease Research, London, UK.,Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, St Marys Campus, Imperial College London, Norfolk Place, London, W2 1PG, UK
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King CH. The evolving schistosomiasis agenda 2007-2017-Why we are moving beyond morbidity control toward elimination of transmission. PLoS Negl Trop Dis 2017; 11:e0005517. [PMID: 28426653 PMCID: PMC5398522 DOI: 10.1371/journal.pntd.0005517] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Charles H. King
- Center for Global Health and Diseases and WHO Collaborating Centre for Research and Training for Schistosomiasis Elimination, Case Western Reserve University, Cleveland, Ohio, United States of America
- Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, Georgia, United States of America
- * E-mail:
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Quantitative assessment of the impact of partially protective anti-schistosomiasis vaccines. PLoS Negl Trop Dis 2017; 11:e0005544. [PMID: 28410369 PMCID: PMC5406007 DOI: 10.1371/journal.pntd.0005544] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 04/26/2017] [Accepted: 04/03/2017] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Mass drug administration (MDA) of praziquantel has been the intervention of choice against schistosomiasis but with limited success in interrupting the transmission. The development of anti-Schistosoma vaccines is underway. Our objective is to quantify the population-level impact of anti-Schistosoma vaccines when administered alone and in combination with mass drug administration (MDA) and determine factors in vaccine design and public health implementation that optimize vaccination role in schistosomiasis control and elimination. METHODS AND FINDINGS We developed a deterministic compartmental model simulation of schistosomiasis transmission in a high-risk Kenyan community, including stratification by age, parasite burden, and vaccination status. The modeled schistosomiasis vaccines differed in terms of vaccine duration of protection (durability) and three biological efficacies. These are vaccine susceptibility effect (SE) of reducing person's susceptibility to Schistosoma acquisition, vaccine mortality effect (ME) of reducing established worm burden and vaccine fecundity effect (FE) of reducing egg release by mature worms. We quantified the population-level impact of vaccination over two decades under diverse vaccination schemes (childhood vs. mass campaigns), with different age-targeting scenarios, different risk settings, and with combined intervention with MDA. We also assessed the sensitivity of our predictions to uncertainties in model parameters. Over two decades, our base case vaccine with 80% SE, FE, and ME efficacies, 10 years' durability, provided by mass vaccination every 10 years, reduced host prevalence, mean intensity, incidence, and patent snail prevalence to 31%, 20 eggs/10-ml sample/person, 0.87 worm/person-year, and 0.74%, from endemic-state values of 71%, 152, 3.3, and 0.98%, respectively. Lower impact was found when coverage did not encompass all potential contaminators, and childhood-only vaccination schemes showed delayed and lower impact. In lower prevalence settings, the base case vaccine generated a proportionately smaller impact. A substantially larger vaccine program effect was generated when MDA + mass vaccination was provided every 5 years, which could be achieved by an MDA-only program only if drug was offered annually. Vaccine impact on schistosomiasis transmission was sensitive to a number of parameters including vaccine efficacies, human contact rates with water, human density, patent snails' rate of patency and lifespan, and force of infection to snails. CONCLUSIONS To be successful a vaccine-based control strategy will need a moderately to highly effective formulation combined with early vaccination of potential contaminators and aggressive coverage in repeated rounds of mass vaccination. Compared to MDA-only program, vaccination combined with MDA accelerates and prolongs the impact by reducing the acquisition of new worms and reducing egg release from residual worms.
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Mewabo AP, Moyou RS, Kouemeni LE, Ngogang JY, Kaptue L, Tambo E. Assessing the prevalence of urogenital schistosomaisis and transmission risk factors amongst school-aged children around Mapé dam ecological suburbs in Malantouen district, Cameroon. Infect Dis Poverty 2017; 6:40. [PMID: 28260525 PMCID: PMC5338087 DOI: 10.1186/s40249-017-0257-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 02/10/2017] [Indexed: 12/01/2022] Open
Abstract
Background Urogenital schistosomiasis is a parasitic infection of public health importance that affects over 112 million people worldwide. The study aimed at assessing the urogenital schistosomiasis prevalence and risk factors of transmission around Mape dam suburds in Malantouen district, West, Cameroon. Methods The study was conducted using semi-structured pretested questionnaires to collect socio-demographic and ecological data. Urine samples were also collected and used to confirm the prevalence of schistosomiasis in consented school-aged children in four primary schools between March – July 2014. Snails’ samples around the dam surburbs were also collected for taxonomy characterization and species identification. Data were compiled and quality control assessed and analysed using SPSS version 17 and Epiinfo data 3.1. P < 0.05 was considered statistical significance. Results Questionnaires were administered to 229 pupils, with gender ratio of 1.04 (m/f). The prevalence of schistosomiasis haematobium was 16.6%. Mambonko school site, which is the closest to the dam suburbs, registered the greatest prevalence rate of 40%. The age group beween 10–13 years was the most infected (18.3%) and boys were more infested than girls (21.0% vs. 15.5%). Haematuria, urination pain, school absentiesm and poor performance were the major recorded complications in 39.5 and 26.3% males to female respectively. Infection rate gender disparity documented is still poorly understood and Bulinus truncatus collected from Mambonko suburb as potential snail intermediate host requires further studies. Conclusions Authors advocated that schools and dam suburds sustained and innovative community-based surveillance and response targeted interventions implementation are needed to inform and support decision-making policy, but also in improving effective contextual behavioural communication changes and MDA improved uptake measures on national schistosomiasis control and elimination in Cameroon. Electronic supplementary material The online version of this article (doi:10.1186/s40249-017-0257-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Adeline P Mewabo
- Department Biochemistry, Higher Institute of Health Sciences, Université des Montagnes, Bangangté, Cameroon
| | - Roger S Moyou
- Institut de Recherches Médicales et d'Etudes des Plantes Médicinale-Centre de Recherches Médicales (IMPM-CRM), Yaoundé, Cameroon
| | - Lysette E Kouemeni
- Department Biochemistry, Higher Institute of Health Sciences, Université des Montagnes, Bangangté, Cameroon
| | - Jeanne Y Ngogang
- Department Biochemistry, Higher Institute of Health Sciences, Université des Montagnes, Bangangté, Cameroon
| | - Lazare Kaptue
- Department Biochemistry, Higher Institute of Health Sciences, Université des Montagnes, Bangangté, Cameroon
| | - Ernest Tambo
- Department Biochemistry, Higher Institute of Health Sciences, Université des Montagnes, Bangangté, Cameroon. .,Africa Disease Intelligence and Surveillance, Communication and Response (Africa DISCoR) Institute, Yaoundé, Cameroon.
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Dyson L, Stolk WA, Farrell SH, Hollingsworth TD. Measuring and modelling the effects of systematic non-adherence to mass drug administration. Epidemics 2017; 18:56-66. [PMID: 28279457 PMCID: PMC5340860 DOI: 10.1016/j.epidem.2017.02.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 02/01/2017] [Accepted: 02/02/2017] [Indexed: 11/18/2022] Open
Abstract
It is well understood that the success or failure of a mass drug administration campaign critically depends on the level of coverage achieved. To that end coverage levels are often closely scrutinised during campaigns and the response to underperforming campaigns is to attempt to improve coverage. Modelling work has indicated, however, that the quality of the coverage achieved may also have a significant impact on the outcome. If the coverage achieved is likely to miss similar people every round then this can have a serious detrimental effect on the campaign outcome. We begin by reviewing the current modelling descriptions of this effect and introduce a new modelling framework that can be used to simulate a given level of systematic non-adherence. We formalise the likelihood that people may miss several rounds of treatment using the correlation in the attendance of different rounds. Using two very simplified models of the infection of helminths and non-helminths, respectively, we demonstrate that the modelling description used and the correlation included between treatment rounds can have a profound effect on the time to elimination of disease in a population. It is therefore clear that more detailed coverage data is required to accurately predict the time to disease elimination. We review published coverage data in which individuals are asked how many previous rounds they have attended, and show how this information may be used to assess the level of systematic non-adherence. We note that while the coverages in the data found range from 40.5% to 95.5%, still the correlations found lie in a fairly narrow range (between 0.2806 and 0.5351). This indicates that the level of systematic non-adherence may be similar even in data from different years, countries, diseases and administered drugs.
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Affiliation(s)
- Louise Dyson
- Mathematics Institute, University of Warwick, Coventry, UK; School of Life Sciences, University of Warwick, Coventry, UK.
| | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Sam H Farrell
- London Centre for Neglected Tropical Disease Research, Department of Infectious Disease Epidemiology, St Mary's Campus, Imperial College London, London WC2 1PG, UK
| | - T Déirdre Hollingsworth
- Mathematics Institute, University of Warwick, Coventry, UK; School of Life Sciences, University of Warwick, Coventry, UK
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Mutapi F, Maizels R, Fenwick A, Woolhouse M. Human schistosomiasis in the post mass drug administration era. THE LANCET. INFECTIOUS DISEASES 2017; 17:e42-e48. [PMID: 27988094 PMCID: PMC7614913 DOI: 10.1016/s1473-3099(16)30475-3] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 09/30/2016] [Accepted: 10/05/2016] [Indexed: 11/16/2022]
Abstract
Profound changes are occurring in the epidemiology of schistosomiasis, a neglected tropical disease caused by a chronic infection with parasitic helminths of the genus Schistosoma. Schistosomiasis currently affects 240 million people worldwide, mostly in sub-Saharan Africa. The advent and proliferation of mass drug administration (MDA) programmes using the drug praziquantel is resulting in substantial increases in the number of people, mainly children aged 6-14 years, being effectively treated, approaching the point where most people in endemic areas will receive one or more treatments during their lifetimes. Praziquantel treatment not only cures infection but also frees the host from the powerful immunomodulatory action of the parasites. The treatment simultaneously enhances exposure to key parasite antigens, accelerating the development of protective acquired immunity, which would take many years to develop naturally. At a population level, these changes constitute a substantial alteration to schistosome ecology in that the parasites are more likely to be exposed not only to praziquantel directly but also to hosts with altered immune phenotypes. Here, we consider the consequences of this for schistosome biology, immunoepidemiology, and public health. We anticipate that there could be substantial effects on chronic pathology, natural immunity, vaccine development strategies, immune disorders, and drug efficacy. This makes for a complex picture that will only become apparent over decades. We recommend careful monitoring and assessment to accompany the roll-out of MDA programmes to ensure that the considerable health benefits to populations are achieved and sustained.
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Affiliation(s)
- Francisca Mutapi
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, UK; Centre for Infection, Immunity and Evolution, University of Edinburgh, Edinburgh, UK.
| | - Rick Maizels
- Institute of Immunology & Infection Research, University of Edinburgh, Edinburgh, UK; Centre for Infection, Immunity and Evolution, University of Edinburgh, Edinburgh, UK; Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunology and Inflammation, University of Glasgow, Glasgow UK
| | - Alan Fenwick
- Schistosomiasis Control Initiative, Department of Infectious Disease Epidemiology, Imperial College London, London, UK
| | - Mark Woolhouse
- Centre for Infection, Immunity and Evolution, University of Edinburgh, Edinburgh, UK; Usher Institute, University of Edinburgh, Edinburgh, UK
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Kariuki HC, Ivy JA, Muchiri EM, Sutherland LJ, King CH. Divergent Effects of Schistosoma haematobium Exposure on Intermediate-Host Snail Species Bulinus nasutus and Bulinus globosus from Coastal Kenya. Am J Trop Med Hyg 2017; 96:850-855. [PMID: 28115664 DOI: 10.4269/ajtmh.16-0614] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
AbstractSchistosoma haematobium infection causes urogenital schistosomiasis, a chronic inflammatory disease that is highly prevalent in many parts of sub-Saharan Africa. Bulinid snails are the obligate intermediate hosts in the transmission of this parasite. In the present study, Bulinus globosus and Bulinus nasutus snails from coastal Kenya were raised in the laboratory and exposed to miracidia derived from sympatric S. haematobium specimens to assess the species-specific impact of parasite contact and infection. The snails' subsequent patterns of survival, cercarial shedding, and reproduction were monitored for up to 3 months postexposure. Schistosoma haematobium exposure significantly decreased the survival of B. globosus, but not of B. nasutus. Although both species were capable of transmitting S. haematobium, the B. globosus study population had a greater cumulative incidence of cercarial shedders and a higher average number of cercariae shed per snail than did the B. nasutus population. The effects of prior parasite exposure on snail reproduction were different between the two species. These included more numerous production of egg masses by exposed B. nasutus (as compared with unexposed snails), contrasted to decreased overall egg mass production by parasite-exposed B. globosus. The interspecies differences in the response to and transmission of S. haematobium reflect clear differences in life histories for the two bulinid species when they interact with the parasite, which should be taken into account when planning control interventions aimed at reducing each host snails' contribution to local transmission of Schistosoma infection.
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Affiliation(s)
- H Curtis Kariuki
- Division of Vector Borne Diseases, Ministry of Health, Nairobi, Kenya
| | - Julianne A Ivy
- Center for Global Health and Diseases, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Eric M Muchiri
- Division of Vector Borne Diseases, Ministry of Health, Nairobi, Kenya
| | - Laura J Sutherland
- Center for Global Health and Diseases, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Charles H King
- Center for Global Health and Diseases, Case Western Reserve University School of Medicine, Cleveland, Ohio
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Ross AGP, Chau TN, Inobaya MT, Olveda RM, Li Y, Harn DA. A new global strategy for the elimination of schistosomiasis. Int J Infect Dis 2016; 54:130-137. [PMID: 27939558 DOI: 10.1016/j.ijid.2016.09.023] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 09/18/2016] [Indexed: 01/17/2023] Open
Abstract
Mass drug administration utilising a single oral dose of 40mg/kg of praziquantel (PZQ) has been endorsed and advocated by the World Health Organisation (WHO) for the global control and elimination of schistosomiasis. However, this strategy is failing primarily because the drugs are not getting to the people who need them the most. The current global coverage is 20%, the drug compliance rate is less than 50%, and the drug efficacy is approximately 50%. Thus in reality, only about 5% of the reservoir human population is actually receiving intermittent chemotherapy. Despite claims that more of the drug will soon be made available the current strategy is inherently flawed and will not lead to disease elimination. We discuss the many practical issues related to this global strategy, and advocate for an integrated control strategy targeting the life cycle and the most at-risk. Moreover, we discuss how an integrated control package for schistosomiasis should fit within a larger integrated health package for rural and remote villages in the developing world. A holistic health system approach is required to achieve sustainable control and ultimately disease elimination.
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Affiliation(s)
- Allen G P Ross
- Menzies Health Institute Queensland, Griffith University, Australia.
| | - Thao N Chau
- Discipline of Public Health, Flinders University, Australia
| | | | - Remigio M Olveda
- Research Institute for Tropical Medicine, Department of Health, the Philippines
| | - Yuesheng Li
- QIMR Berghofer Medical Research Institute, Australia; Hunan Institute of Parasitic Diseases, Peoples Republic of China
| | - Donald A Harn
- Centre for Tropical and Emerging Global Health Diseases, University of Georgia, USA
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45
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Lo NC, Addiss DG, Hotez PJ, King CH, Stothard JR, Evans DS, Colley DG, Lin W, Coulibaly JT, Bustinduy AL, Raso G, Bendavid E, Bogoch II, Fenwick A, Savioli L, Molyneux D, Utzinger J, Andrews JR. A call to strengthen the global strategy against schistosomiasis and soil-transmitted helminthiasis: the time is now. THE LANCET. INFECTIOUS DISEASES 2016; 17:e64-e69. [PMID: 27914852 DOI: 10.1016/s1473-3099(16)30535-7] [Citation(s) in RCA: 124] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 11/17/2016] [Accepted: 11/22/2016] [Indexed: 01/01/2023]
Abstract
In 2001, the World Health Assembly (WHA) passed the landmark WHA 54.19 resolution for global scale-up of mass administration of anthelmintic drugs for morbidity control of schistosomiasis and soil-transmitted helminthiasis, which affect more than 1·5 billion of the world's poorest people. Since then, more than a decade of research and experience has yielded crucial knowledge on the control and elimination of these helminthiases. However, the global strategy has remained largely unchanged since the original 2001 WHA resolution and associated WHO guidelines on preventive chemotherapy. In this Personal View, we highlight recent advances that, taken together, support a call to revise the global strategy and guidelines for preventive chemotherapy and complementary interventions against schistosomiasis and soil-transmitted helminthiasis. These advances include the development of guidance that is specific to goals of morbidity control and elimination of transmission. We quantify the result of forgoing this opportunity by computing the yearly disease burden, mortality, and lost economic productivity associated with maintaining the status quo. Without change, we estimate that the population of sub-Saharan Africa will probably lose 2·3 million disability-adjusted life-years and US$3·5 billion of economic productivity every year, which is comparable to recent acute epidemics, including the 2014 Ebola and 2015 Zika epidemics. We propose that the time is now to strengthen the global strategy to address the substantial disease burden of schistosomiasis and soil-transmitted helminthiasis.
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Affiliation(s)
- Nathan C Lo
- Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA, USA; Division of Epidemiology, Stanford University School of Medicine, Stanford, CA, USA.
| | - David G Addiss
- Children Without Worms, Task Force for Global Health, Decatur, GA, USA
| | - Peter J Hotez
- Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development, National School of Tropical Medicine at Baylor College of Medicine, Houston, TX, USA; Department of Biology, Baylor University, Waco, TX, USA; James A Baker III Institute for Public Policy, Rice University, Houston, TX, USA
| | - Charles H King
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, OH, USA
| | - J Russell Stothard
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Darin S Evans
- United States Agency for International Development, Global Health, Washington, DC, USA
| | - Daniel G Colley
- Center for Tropical and Emerging Global Diseases and the Department of Microbiology, University of Georgia, Athens, GA, USA
| | - William Lin
- Global Public Health, Johnson & Johnson, New Brunswick, NJ, USA
| | - Jean T Coulibaly
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët-Boigny, Abidjan, Côte d'Ivoire; Centre Suisse de Recherches Scientifiques en Côte d'Ivoire, Abidjan, Côte d'Ivoire; Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - Amaya L Bustinduy
- Clinical Research Department, London School of Hygiene & Tropical Medicine, London, UK
| | - Giovanna Raso
- Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - Eran Bendavid
- Division of General Medical Disciplines, Stanford University, Stanford, CA, USA; Center for Health Policy and the Center for Primary Care and Outcomes Research, Stanford University, Stanford, CA, USA
| | - Isaac I Bogoch
- Department of Medicine, University of Toronto, Toronto, ON, Canada; Division of Internal Medicine and Infectious Diseases, Toronto General Hospital, University Health Network, Toronto, ON, Canada
| | - Alan Fenwick
- Schistosomiasis Control Initiative, Imperial College London, London, UK
| | - Lorenzo Savioli
- Global Schistosomiasis Alliance, Chavannes de Bogis, Switzerland
| | - David Molyneux
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Jürg Utzinger
- Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland
| | - Jason R Andrews
- Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA, USA
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Gurarie D, King CH, Yoon N, Li E. Refined stratified-worm-burden models that incorporate specific biological features of human and snail hosts provide better estimates of Schistosoma diagnosis, transmission, and control. Parasit Vectors 2016; 9:428. [PMID: 27492409 PMCID: PMC4973538 DOI: 10.1186/s13071-016-1681-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 07/05/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Schistosoma parasites sustain a complex transmission process that cycles between a definitive human host, two free-swimming larval stages, and an intermediate snail host. Multiple factors modify their transmission and affect their control, including heterogeneity in host populations and environment, the aggregated distribution of human worm burdens, and features of parasite reproduction and host snail biology. Because these factors serve to enhance local transmission, their inclusion is important in attempting accurate quantitative prediction of the outcomes of schistosomiasis control programs. However, their inclusion raises many mathematical and computational challenges. To address these, we have recently developed a tractable stratified worm burden (SWB) model that occupies an intermediate place between simpler deterministic mean worm burden models and the very computationally-intensive, autonomous agent models. METHODS To refine the accuracy of model predictions, we modified an earlier version of the SWB by incorporating factors representing essential in-host biology (parasite mating, aggregation, density-dependent fecundity, and random egg-release) into demographically structured host communities. We also revised the snail component of the transmission model to reflect a saturable form of human-to-snail transmission. The new model allowed us to realistically simulate overdispersed egg-test results observed in individual-level field data. We further developed a Bayesian-type calibration methodology that accounted for model and data uncertainties. RESULTS The new model methodology was applied to multi-year, individual-level field data on S. haematobium infections in coastal Kenya. We successfully derived age-specific estimates of worm burden distributions and worm fecundity and crowding functions for children and adults. Estimates from the new SWB model were compared with those from the older, simpler SWB with some substantial differences noted. We validated our new SWB estimates in prediction of drug treatment-based control outcomes for a typical Kenyan community. CONCLUSIONS The new version of the SWB model provides a better tool to predict the outcomes of ongoing schistosomiasis control programs. It reflects parasite features that augment and perpetuate transmission, while it also readily incorporates differences in diagnostic testing and human sub-population differences in treatment coverage. Once extended to other Schistosoma species and transmission environments, it will provide a useful and efficient tool for planning control and elimination strategies.
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Affiliation(s)
- David Gurarie
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, USA.,Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio, USA
| | - Charles H King
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio, USA. .,Schistosomiasis Consortium for Operational Research and Evaluation, University of Georgia, Athens, Georgia, USA.
| | - Nara Yoon
- Department of Mathematics, Applied Mathematics and Statistics, Case Western Reserve University, Cleveland, USA
| | - Emily Li
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio, USA
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47
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Hydrology and density feedbacks control the ecology of intermediate hosts of schistosomiasis across habitats in seasonal climates. Proc Natl Acad Sci U S A 2016; 113:6427-32. [PMID: 27162339 DOI: 10.1073/pnas.1602251113] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report about field and theoretical studies on the ecology of the aquatic snails (Bulinus spp. and Biomphalaria pfeifferi) that serve as obligate intermediate hosts in the complex life cycle of the parasites causing human schistosomiasis. Snail abundance fosters disease transmission, and thus the dynamics of snail populations are critically important for schistosomiasis modeling and control. Here, we single out hydrological drivers and density dependence (or lack of it) of ecological growth rates of local snail populations by contrasting novel ecological and environmental data with various models of host demography. Specifically, we study various natural and man-made habitats across Burkina Faso's highly seasonal climatic zones. Demographic models are ranked through formal model comparison and structural risk minimization. The latter allows us to evaluate the suitability of population models while clarifying the relevant covariates that explain empirical observations of snail abundance under the actual climatic forcings experienced by the various field sites. Our results link quantitatively hydrological drivers to distinct population dynamics through specific density feedbacks, and show that statistical methods based on model averaging provide reliable snail abundance projections. The consistency of our ranking results suggests the use of ad hoc models of snail demography depending on habitat type (e.g., natural vs. man-made) and hydrological characteristics (e.g., ephemeral vs. permanent). Implications for risk mapping and space-time allocation of control measures in schistosomiasis-endemic contexts are discussed.
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48
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Anderson RM, Turner HC, Farrell SH, Truscott JE. Studies of the Transmission Dynamics, Mathematical Model Development and the Control of Schistosome Parasites by Mass Drug Administration in Human Communities. ADVANCES IN PARASITOLOGY 2016; 94:199-246. [PMID: 27756455 DOI: 10.1016/bs.apar.2016.06.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Schistosomiasis is global in extent within developing countries, but more than 90% of the at-risk population lives in sub-Saharan Africa. In total, 261 million people are estimated to require preventive treatment. However, with increasing drug availability through donation, the World Health Organization has set a goal of increasing coverage to 75% of at-risk children in endemic countries and elimination in some regions. In this chapter, we discuss key biological and epidemiological processes involved in the schistosome transmission cycle and review the history of modelling schistosomiasis and the impact of mass drug administration, including both deterministic and stochastic approaches. In particular, we look at the potential impact of the WHO 2020 schistosomiasis treatment goals.
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Affiliation(s)
- R M Anderson
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
| | - H C Turner
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
| | - S H Farrell
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
| | - J E Truscott
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
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49
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Hollingsworth TD, Adams ER, Anderson RM, Atkins K, Bartsch S, Basáñez MG, Behrend M, Blok DJ, Chapman LAC, Coffeng L, Courtenay O, Crump RE, de Vlas SJ, Dobson A, Dyson L, Farkas H, Galvani AP, Gambhir M, Gurarie D, Irvine MA, Jervis S, Keeling MJ, Kelly-Hope L, King C, Lee BY, Le Rutte EA, Lietman TM, Ndeffo-Mbah M, Medley GF, Michael E, Pandey A, Peterson JK, Pinsent A, Porco TC, Richardus JH, Reimer L, Rock KS, Singh BK, Stolk W, Swaminathan S, Torr SJ, Townsend J, Truscott J, Walker M, Zoueva A. Quantitative analyses and modelling to support achievement of the 2020 goals for nine neglected tropical diseases. Parasit Vectors 2015; 8:630. [PMID: 26652272 PMCID: PMC4674954 DOI: 10.1186/s13071-015-1235-1] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Accepted: 12/01/2015] [Indexed: 12/30/2022] Open
Abstract
Quantitative analysis and mathematical models are useful tools in informing strategies to control or eliminate disease. Currently, there is an urgent need to develop these tools to inform policy to achieve the 2020 goals for neglected tropical diseases (NTDs). In this paper we give an overview of a collection of novel model-based analyses which aim to address key questions on the dynamics of transmission and control of nine NTDs: Chagas disease, visceral leishmaniasis, human African trypanosomiasis, leprosy, soil-transmitted helminths, schistosomiasis, lymphatic filariasis, onchocerciasis and trachoma. Several common themes resonate throughout these analyses, including: the importance of epidemiological setting on the success of interventions; targeting groups who are at highest risk of infection or re-infection; and reaching populations who are not accessing interventions and may act as a reservoir for infection,. The results also highlight the challenge of maintaining elimination 'as a public health problem' when true elimination is not reached. The models elucidate the factors that may be contributing most to persistence of disease and discuss the requirements for eventually achieving true elimination, if that is possible. Overall this collection presents new analyses to inform current control initiatives. These papers form a base from which further development of the models and more rigorous validation against a variety of datasets can help to give more detailed advice. At the moment, the models' predictions are being considered as the world prepares for a final push towards control or elimination of neglected tropical diseases by 2020.
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Affiliation(s)
| | - Emily R Adams
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | | | - Katherine Atkins
- London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Sarah Bartsch
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | | | | | - David J Blok
- Erasmus University Medical Center, 3015 CE, Rotterdam, Netherlands
| | | | - Luc Coffeng
- Erasmus University Medical Center, 3015 CE, Rotterdam, Netherlands
| | | | - Ron E Crump
- University of Warwick, Coventry, CV4 7AL, UK
| | - Sake J de Vlas
- Erasmus University Medical Center, 3015 CE, Rotterdam, Netherlands
| | - Andy Dobson
- Princeton University, New Jersey, NJ, 08544, USA
| | | | | | | | | | - David Gurarie
- Case Western Reserve University, Cleveland, OH, 44106, USA
| | | | | | | | | | - Charles King
- Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Bruce Y Lee
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA
| | - Epke A Le Rutte
- Erasmus University Medical Center, 3015 CE, Rotterdam, Netherlands
| | - Thomas M Lietman
- University of California, San Francisco, San Francisco, CA, 94143, USA
| | | | - Graham F Medley
- London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
| | - Edwin Michael
- University of Notre Dame, South Bend, IN, 47556, USA
| | | | | | - Amy Pinsent
- Monash University, Melbourne, VIC, 3800, Australia
| | - Travis C Porco
- University of California, San Francisco, San Francisco, CA, 94143, USA
| | | | - Lisa Reimer
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
| | - Kat S Rock
- University of Warwick, Coventry, CV4 7AL, UK
| | | | - Wilma Stolk
- Erasmus University Medical Center, 3015 CE, Rotterdam, Netherlands
| | | | - Steve J Torr
- Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK
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