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Rajaonarifara E, Roche B, Chesnais CB, Rabenantoandro H, Evans M, Garchitorena A. Heterogeneity in elimination efforts could increase the risk of resurgence of lymphatic filariasis in Madagascar. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2024; 120:105589. [PMID: 38548211 DOI: 10.1016/j.meegid.2024.105589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 03/19/2024] [Accepted: 03/20/2024] [Indexed: 04/02/2024]
Abstract
BACKGROUND Progress in lymphatic filariasis (LF) elimination is spatially heterogeneous in many endemic countries, which may lead to resurgence in areas that have achieved elimination. Understanding the drivers and consequences of such heterogeneity could help inform strategies to reach global LF elimination goals by 2030. This study assesses whether differences in age-specific compliance with mass drug administration (MDA) could explain LF prevalence patterns in southeastern Madagascar and explores how spatial heterogeneity in prevalence and age-specific MDA compliance may affect the risk of LF resurgence after transmission interruption. METHODOLOGY We used LYMFASIM model with parameters in line with the context of southeastern Madagascar and explored a wide range of scenarios with different MDA compliance for adults and children (40-100%) to estimate the proportion of elimination, non-elimination and resurgence events associated with each scenario. Finally, we evaluated the risk of resurgence associated with different levels of migration (2-6%) from surrounding districts combined with varying levels of LF microfilaria (mf) prevalence (0-24%) during that same study period. RESULTS Differences in MDA compliance between adults and children better explained the observed heterogeneity in LF prevalence for these age groups than differences in exposure alone. The risk of resurgence associated with differences in MDA compliance scenarios ranged from 0 to 19% and was highest when compliance was high for children (e.g. 90%) and low for adults (e.g. 50%). The risk of resurgence associated with migration was generally higher, exceeding 60% risk for all the migration levels explored (2-6% per year) when mf prevalence in the source districts was between 9% and 20%. CONCLUSION Gaps in the implementation of LF elimination programme can increase the risk of resurgence and undermine elimination efforts. In Madagascar, districts that have not attained elimination pose a significant risk for those that have achieved it. More research is needed to help guide LF elimination programme on the optimal strategies for surveillance and control that maximize the chances to sustain elimination and avoid resurgence.
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Affiliation(s)
- Elinambinina Rajaonarifara
- UMR 224 MIVEGEC, Univ. Montpellier, IRD, CNRS, Montpellier, France; NGO Pivot, Ifanadiana, Madagascar; Sciences & Ingénierie, Sorbonne Université, Paris, France.
| | - Benjamin Roche
- UMR 224 MIVEGEC, Univ. Montpellier, IRD, CNRS, Montpellier, France
| | | | - Holivololona Rabenantoandro
- Service de Lutte contre les Maladies Epidémiques et Négligées - Ministère de la Santé Publique, Antananarivo, Madagascar
| | - Michelle Evans
- NGO Pivot, Ifanadiana, Madagascar; Departement of Global Health and Social Medicine, Blavatnik Institute at Harvard Medical School, Boston, MA, USA
| | - Andres Garchitorena
- UMR 224 MIVEGEC, Univ. Montpellier, IRD, CNRS, Montpellier, France; NGO Pivot, Ifanadiana, Madagascar
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Touloupou P, Fronterre C, Cano J, Prada JM, Smith M, Kontoroupis P, Brown P, Rivera RC, de Vlas SJ, Gunawardena S, Irvine MA, Njenga SM, Reimer L, Seife F, Sharma S, Michael E, Stolk WA, Pulan R, Spencer SEF, Hollingsworth TD. An Ensemble Framework for Projecting the Impact of Lymphatic Filariasis Interventions Across Sub-Saharan Africa at a Fine Spatial Scale. Clin Infect Dis 2024; 78:S108-S116. [PMID: 38662704 PMCID: PMC11045016 DOI: 10.1093/cid/ciae071] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024] Open
Abstract
BACKGROUND Lymphatic filariasis (LF) is a neglected tropical disease targeted for elimination as a public health problem by 2030. Although mass treatments have led to huge reductions in LF prevalence, some countries or regions may find it difficult to achieve elimination by 2030 owing to various factors, including local differences in transmission. Subnational projections of intervention impact are a useful tool in understanding these dynamics, but correctly characterizing their uncertainty is challenging. METHODS We developed a computationally feasible framework for providing subnational projections for LF across 44 sub-Saharan African countries using ensemble models, guided by historical control data, to allow assessment of the role of subnational heterogeneities in global goal achievement. Projected scenarios include ongoing annual treatment from 2018 to 2030, enhanced coverage, and biannual treatment. RESULTS Our projections suggest that progress is likely to continue well. However, highly endemic locations currently deploying strategies with the lower World Health Organization recommended coverage (65%) and frequency (annual) are expected to have slow decreases in prevalence. Increasing intervention frequency or coverage can accelerate progress by up to 5 or 6 years, respectively. CONCLUSIONS While projections based on baseline data have limitations, our methodological advancements provide assessments of potential bottlenecks for the global goals for LF arising from subnational heterogeneities. In particular, areas with high baseline prevalence may face challenges in achieving the 2030 goals, extending the "tail" of interventions. Enhancing intervention frequency and/or coverage will accelerate progress. Our approach facilitates preimplementation assessments of the impact of local interventions and is applicable to other regions and neglected tropical diseases.
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Affiliation(s)
| | | | - Jorge Cano
- Expanded Special Project for Elimination of Neglected Tropical Diseases (ESPEN), WHO Regional Office for Africa, Brazzaville, Democratic Republic of the Congo
| | - Joaquin M Prada
- School of Veterinary Medicine, University of Surrey, Guildford, United Kingdom
| | - Morgan Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | | | - Paul Brown
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
| | - Rocio Caja Rivera
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, USA
| | - Sake J de Vlas
- Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | | | - Michael A Irvine
- Data and Analytic Services, British Columbia Centre for Disease Control, Vancouver, Canada
| | - Sammy M Njenga
- Eastern and Southern Africa Centre of International Parasite Control, Kenya Medical Research Institute (KEMRI), Nairobi, Kenya
| | - Lisa Reimer
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Fikre Seife
- Disease Prevention and Control Directorate, Federal Ministry of Health, Addis Ababa, Ethiopia
| | - Swarnali Sharma
- Department of Mathematics, Vijaygarh Jyotish Ray College, Kolkata, India
| | - Edwin Michael
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, USA
| | - Wilma A Stolk
- Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Rachel Pulan
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Simon E F Spencer
- Zeeman Institute for Systems Biology and Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
| | - T Déirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
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James A, Coffeng LE, Blok DJ, King JD, de Vlas SJ, Stolk WA. Predictive Value of Microfilariae-Based Stop-MDA Thresholds After Triple Drug Therapy With IDA Against Lymphatic Filariasis in Treatment-Naive Indian Settings. Clin Infect Dis 2024; 78:S131-S137. [PMID: 38662696 PMCID: PMC11045019 DOI: 10.1093/cid/ciae019] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024] Open
Abstract
Mass drug administration (MDA) of antifilarial drugs is the main strategy for the elimination of lymphatic filariasis (LF). Recent clinical trials indicated that the triple-drug therapy with ivermectin, diethylcarbamazine, and albendazole (IDA) is much more effective against LF than the widely used two-drug combinations (albendazole plus either ivermectin or diethylcarbamazine). For IDA-based MDA, the stop-MDA decision is made based on microfilariae (mf) prevalence in adults. In this study, we assess how the probability of eventually reaching elimination of transmission depends on the critical threshold used in transmission assessment surveys (TAS-es) to define whether transmission was successfully suppressed and triple-drug MDA can be stopped. This analysis focuses on treatment-naive Indian settings. We do this for a range of epidemiological and programmatic contexts, using the established LYMFASIM model for transmission and control of LF. Based on our simulations, a single TAS, one year after the last MDA round, provides limited predictive value of having achieved suppressed transmission, while a higher MDA coverage increases elimination probability, thus leading to a higher predictive value. Every additional TAS, conditional on previous TAS-es being passed with the same threshold, further improves the predictive value for low values of stop-MDA thresholds. An mf prevalence threshold of 0.5% corresponding to TAS-3 results in ≥95% predictive value even when the MDA coverage is relatively low.
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Affiliation(s)
- Ananthu James
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - David J Blok
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Jonathan D King
- Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Prada JM, Touloupou P, Kebede B, Giorgi E, Sime H, Smith M, Kontoroupis P, Brown P, Cano J, Farkas H, Irvine M, Reimer L, Caja Rivera R, de Vlas SJ, Michael E, Stolk WA, Pulan R, Spencer SEF, Hollingsworth TD, Seife F. Subnational Projections of Lymphatic Filariasis Elimination Targets in Ethiopia to Support National Level Policy. Clin Infect Dis 2024; 78:S117-S125. [PMID: 38662702 PMCID: PMC11045027 DOI: 10.1093/cid/ciae072] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024] Open
Abstract
BACKGROUND Lymphatic filariasis (LF) is a debilitating, poverty-promoting, neglected tropical disease (NTD) targeted for worldwide elimination as a public health problem (EPHP) by 2030. Evaluating progress towards this target for national programmes is challenging, due to differences in disease transmission and interventions at the subnational level. Mathematical models can help address these challenges by capturing spatial heterogeneities and evaluating progress towards LF elimination and how different interventions could be leveraged to achieve elimination by 2030. METHODS Here we used a novel approach to combine historical geo-spatial disease prevalence maps of LF in Ethiopia with 3 contemporary disease transmission models to project trends in infection under different intervention scenarios at subnational level. RESULTS Our findings show that local context, particularly the coverage of interventions, is an important determinant for the success of control and elimination programmes. Furthermore, although current strategies seem sufficient to achieve LF elimination by 2030, some areas may benefit from the implementation of alternative strategies, such as using enhanced coverage or increased frequency, to accelerate progress towards the 2030 targets. CONCLUSIONS The combination of geospatial disease prevalence maps of LF with transmission models and intervention histories enables the projection of trends in infection at the subnational level under different control scenarios in Ethiopia. This approach, which adapts transmission models to local settings, may be useful to inform the design of optimal interventions at the subnational level in other LF endemic regions.
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Affiliation(s)
- Joaquin M Prada
- Department of Comparative Biomedical Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | | | - Biruck Kebede
- RTI International, 3040 E Cornwallis Rd, Research Triangle Park, North Carolina 27709, USA
| | | | - Heven Sime
- Malaria and Neglected Tropical Diseases Research Team, Bacterial, Parasitic and Zoonotic Disease Research Directorate, Ethiopian Public Health Institute, Addis Ababa, Ethiopia
| | - Morgan Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | | | - Paul Brown
- Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
| | - Jorge Cano
- Expanded Special Project for Elimination of Neglected Tropical Diseases (ESPEN), WHO Regional Office for Africa, Brazzaville, Democratic Republic of the Congo
| | - Hajnal Farkas
- Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
| | - Mike Irvine
- Faculty of Science, BC Centre for Disease Control, Vancouver, Canada
| | - Lisa Reimer
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Rocio Caja Rivera
- College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Sake J de Vlas
- Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Edwin Michael
- College of Public Health, University of South Florida, Tampa, Florida, USA
| | - Wilma A Stolk
- Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Rachel Pulan
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Simon E F Spencer
- Zeeman Institute for Systems Biology & Infectious Disease Epidemiology Research, University of Warwick, Coventry, United Kingdom
| | - T Déirdre Hollingsworth
- Nuffield Department of Medicine, Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Fikre Seife
- Disease Prevention and Control Directorate, Federal Ministry of Health, Addis Ababa, Ethiopia
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Kura K, Stolk WA, Basáñez MG, Collyer BS, de Vlas SJ, Diggle PJ, Gass K, Graham M, Hollingsworth TD, King JD, Krentel A, Anderson RM, Coffeng LE. How Does the Proportion of Never Treatment Influence the Success of Mass Drug Administration Programs for the Elimination of Lymphatic Filariasis? Clin Infect Dis 2024; 78:S93-S100. [PMID: 38662701 PMCID: PMC11045024 DOI: 10.1093/cid/ciae021] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024] Open
Abstract
BACKGROUND Mass drug administration (MDA) is the cornerstone for the elimination of lymphatic filariasis (LF). The proportion of the population that is never treated (NT) is a crucial determinant of whether this goal is achieved within reasonable time frames. METHODS Using 2 individual-based stochastic LF transmission models, we assess the maximum permissible level of NT for which the 1% microfilaremia (mf) prevalence threshold can be achieved (with 90% probability) within 10 years under different scenarios of annual MDA coverage, drug combination and transmission setting. RESULTS For Anopheles-transmission settings, we find that treating 80% of the eligible population annually with ivermectin + albendazole (IA) can achieve the 1% mf prevalence threshold within 10 years of annual treatment when baseline mf prevalence is 10%, as long as NT <10%. Higher proportions of NT are acceptable when more efficacious treatment regimens are used. For Culex-transmission settings with a low (5%) baseline mf prevalence and diethylcarbamazine + albendazole (DA) or ivermectin + diethylcarbamazine + albendazole (IDA) treatment, elimination can be reached if treatment coverage among eligibles is 80% or higher. For 10% baseline mf prevalence, the target can be achieved when the annual coverage is 80% and NT ≤15%. Higher infection prevalence or levels of NT would make achieving the target more difficult. CONCLUSIONS The proportion of people never treated in MDA programmes for LF can strongly influence the achievement of elimination and the impact of NT is greater in high transmission areas. This study provides a starting point for further development of criteria for the evaluation of NT.
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Affiliation(s)
- Klodeta Kura
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, London, United Kingdom
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Maria-Gloria Basáñez
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, London, United Kingdom
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Benjamin S Collyer
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, London, United Kingdom
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Peter J Diggle
- Centre for Health Informatics, Computing and Statistics, Lancaster University, Lancaster, United Kingdom
| | - Katherine Gass
- Neglected Tropical Diseases Support Center, Task Force for Global Health, Decatur, Georgia, USA
| | - Matthew Graham
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
- Centre for Mathematical Modelling of Infectious Disease, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - T Déirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Jonathan D King
- Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
| | - Alison Krentel
- Bruyère Research Institute, Canada
- School of Epidemiology and Public Health, Faculty of Medicine, University of Ottawa, Canada
| | - Roy M Anderson
- London Centre for Neglected Tropical Disease Research, London, United Kingdom
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, London, United Kingdom
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Luc E Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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Stolk WA, Coffeng LE, Bolay FK, Eneanya OA, Fischer PU, Hollingsworth TD, Koudou BG, Méité A, Michael E, Prada JM, Caja Rivera RM, Sharma S, Touloupou P, Weil GJ, de Vlas SJ. Comparing antigenaemia- and microfilaraemia as criteria for stopping decisions in lymphatic filariasis elimination programmes in Africa. PLoS Negl Trop Dis 2022; 16:e0010953. [PMID: 36508458 PMCID: PMC9779720 DOI: 10.1371/journal.pntd.0010953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 12/22/2022] [Accepted: 11/14/2022] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Mass drug administration (MDA) is the main strategy towards lymphatic filariasis (LF) elimination. Progress is monitored by assessing microfilaraemia (Mf) or circulating filarial antigenaemia (CFA) prevalence, the latter being more practical for field surveys. The current criterion for stopping MDA requires <2% CFA prevalence in 6- to 7-year olds, but this criterion is not evidence-based. We used mathematical modelling to investigate the validity of different thresholds regarding testing method and age group for African MDA programmes using ivermectin plus albendazole. METHODOLGY/PRINCIPAL FINDINGS We verified that our model captures observed patterns in Mf and CFA prevalence during annual MDA, assuming that CFA tests are positive if at least one adult worm is present. We then assessed how well elimination can be predicted from CFA prevalence in 6-7-year-old children or from Mf or CFA prevalence in the 5+ or 15+ population, and determined safe (>95% positive predictive value) thresholds for stopping MDA. The model captured trends in Mf and CFA prevalences reasonably well. Elimination cannot be predicted with sufficient certainty from CFA prevalence in 6-7-year olds. Resurgence may still occur if all children are antigen-negative, irrespective of the number tested. Mf-based criteria also show unfavourable results (PPV <95% or unpractically low threshold). CFA prevalences in the 5+ or 15+ population are the best predictors, and post-MDA threshold values for stopping MDA can be as high as 10% for 15+. These thresholds are robust for various alternative assumptions regarding baseline endemicity, biological parameters and sampling strategies. CONCLUSIONS/SIGNIFICANCE For African areas with moderate to high pre-treatment Mf prevalence that have had 6 or more rounds of annual ivermectin/albendazole MDA with adequate coverage, we recommend to adopt a CFA threshold prevalence of 10% in adults (15+) for stopping MDA. This could be combined with Mf testing of CFA positives to ensure absence of a significant Mf reservoir for transmission.
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Affiliation(s)
- Wilma A. Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
- * E-mail:
| | - Luc E. Coffeng
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Fatorma K. Bolay
- National Public Health Institute of Liberia (NPHIL), Monrovia, Liberia
| | - Obiora A. Eneanya
- Infectious Diseases Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Peter U. Fischer
- Infectious Diseases Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - T. Déirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, Oxford, United Kingdom
| | - Benjamin G. Koudou
- Centre Suisse de Recherches Scientifiques en Côte d’Ivoire, Abidjan, Abidjan, Côte d’Ivoire
- Laboratoire de Cytologie et Biologie Animale, UFR Science de la Nature, Université Nangui Abrogoua Abidjan, Abidjan, Côte d’Ivoire
| | - Aboulaye Méité
- Programme National de Lutte contre les Maladies Tropicales Négligées à Chimiothérapie Préventive, Abidjan, Côte d’Ivoire
| | - Edwin Michael
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida, United States of America
| | - Joaquin M. Prada
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Rocio M. Caja Rivera
- Center for Global Health Infectious Disease Research, University of South Florida, Tampa, Florida, United States of America
| | - Swarnali Sharma
- Department of Biological Sciences, University of Notre Dame, South Bend, Indiana, United States of America
- Christian Medical College, IDA Scudder Rd, Vellore, Tamil Nadu, India
| | - Panayiota Touloupou
- Department of Statistics, University of Warwick, Coventry, United Kingdom
- School of Mathematics, University of Birmingham, Birmingham, United Kingdom
| | - Gary J. Weil
- Infectious Diseases Division, Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Sake J. de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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The Domestic Dog as a Laboratory Host for Brugia malayi. Pathogens 2022; 11:pathogens11101073. [PMID: 36297129 PMCID: PMC9607614 DOI: 10.3390/pathogens11101073] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 09/07/2022] [Accepted: 09/19/2022] [Indexed: 11/21/2022] Open
Abstract
Of the three nematodes responsible for lymphatic filariasis in humans, only Brugia malayi is actively maintained in research settings owing to its viability in small animal hosts, principal among which is the domestic cat. While the microfilaremic feline host is necessary for propagation of parasites on any significant scale, this system is plagued by a number of challenges not as pronounced in canine filarial models. For this reason, we investigated the capacity in which dogs may serve as competent laboratory hosts for B. malayi. We infected a total of 20 dogs by subcutaneous injection of 500 B. malayi third-stage larvae (L3) in either a single (n = 10) or repeated infection events (125 L3 per week for four weeks; n = 10). Within each group, half of the individuals were injected in the inguinal region and half in the dorsum of the hind paw. To track the course of microfilaremia in this host, blood samples were examined by microscopy biweekly for two years following infection. Additionally, to identify cellular responses with potential value as predictors of patency, we measured peripheral blood leukocyte counts for the first year of infection. A total of 10 of 20 dogs developed detectable microfilaremia. Peak microfilaria density varied but attained levels useful for parasite propagation (median = 1933 mL−1; range: 33–9950 mL−1). Nine of these dogs remained patent at 104 weeks. A two-way ANOVA revealed no significant differences between infection groups in lifetime microfilaria production (p = 0.42), nor did regression analysis reveal any likely predictive relationships to leukocyte values. The results of this study demonstrate the competence of the dog as a host for B. malayi and its potential to serve in the laboratory role currently provided by the cat, while also clarifying the potential for zoonosis in filariasis-endemic regions.
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Evans CC, Burkman EJ, Dzimianski MT, Garner B, Moorhead AR. The Course of Brugia malayi Microfilaremia in Experimentally Infected Cats. Vector Borne Zoonotic Dis 2021; 21:586-592. [PMID: 34129397 DOI: 10.1089/vbz.2020.2761] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
As one of the causative agents of lymphatic filariasis in humans, Brugia malayi has been established as the laboratory model of choice for studying this infection owing to its viability in small animal hosts, with the domestic cat being significant among these. The usefulness of individual feline infections is highly dependent on the levels of circulating microfilariae in the blood; thus, characterizing the course of microfilaremia benefits our understanding of this model. In B. malayi-endemic regions, cats are also known reservoirs of infection, and describing microfilaremia in a controlled setting may improve transmission modeling. We followed the course of B. malayi infection in 10 experimentally infected cats from inoculation to ultimate resolution. Seven cats developed patency, with a peak microfilaria concentration of 6525/mL. In addition, to identify cellular responses with potential value as predictors of patency, we measured the peripheral blood leukocyte counts during the first 8 months of infection and tested for correlations with lifelong microfilaria production. No strong relationships were observed, though cell values did appear to shift with the maturation phases of the parasite. The data we present reflect the course of microfilaremia in an important laboratory model under controlled conditions.
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Affiliation(s)
- Christopher C Evans
- Department of Infectious Diseases and College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Erica J Burkman
- Department of Infectious Diseases and College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Michael T Dzimianski
- Department of Infectious Diseases and College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Bridget Garner
- Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Andrew R Moorhead
- Department of Infectious Diseases and College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
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Santoso, Yahya, Supranelfy Y, Suryaningtyas NH, Taviv Y, Yenni A, Arisanti M, Mayasari R, Mahdalena V, Nurmaliani R, Marini, Krishnamoorthy K, Pangaribuan HU. Risk of Recrudescence of Lymphatic Filariasis after Post-MDA Surveillance in Brugia malayi Endemic Belitung District, Indonesia. THE KOREAN JOURNAL OF PARASITOLOGY 2021; 58:627-634. [PMID: 33412766 PMCID: PMC7806434 DOI: 10.3347/kjp.2020.58.6.627] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 12/01/2020] [Indexed: 11/23/2022]
Abstract
Belitung district in Bangka-Belitung Province, Indonesia with a population of 0.27 million is endemic for Brugia malayi and 5 rounds of mass drug administration (MDA) were completed by 2010. Based on the results of 3 transmission assessment surveys (TAS), the district is declared as achieving elimination of lymphatic filariasis (LF) in 2017. The findings of an independent survey conducted by the National Institute of Health Research and Development (NIHRD) in the same year showed microfilaria (Mf) prevalence of 1.3% in this district. In 2019, NIHRD conducted microfilaria survey in 2 villages in Belitung district. Screening of 311 and 360 individuals in Lasar and Suak Gual villages showed Mf prevalence of 5.1% and 2.2% with mean Mf density of 120 and 354 mf/ml in the respective villages. Mf prevalence was significantly higher among farmers and fishermen compared to others and the gender specific difference was not significant. The results of a questionnaire based interview showed that 62.4% of the respondents reported to have participated in MDA in Lasar while it was 57.7% in Suak Gual village. About 42% of the Mf positive cases did not participate in MDA. Environmental surveys identified many swampy areas supporting the breeding of Mansonia vector species. Persistence of infection is evident and in the event of successful TAS3 it is necessary to monitor the situation and plan for focal MDA. Appropriate surveillance strategies including xenomonitoring in post-MDA situations need to be developed to prevent resurgence of infection. Possible role of animal reservoirs is discussed.
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Affiliation(s)
- Santoso
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Yahya
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Yanelza Supranelfy
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Nungki Hapsari Suryaningtyas
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Yulian Taviv
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Aprioza Yenni
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Maya Arisanti
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Rika Mayasari
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Vivin Mahdalena
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Rizki Nurmaliani
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - Marini
- Baturaja Unit for Health Research and Development, National Institute of Health Research and Development (NIHRD), Ministry of Health of Indonesia, South Sumatera, Indonesia
| | - K Krishnamoorthy
- Vector Control Research Centre (VCRC), Medical Complex, Indira Nagar, Puducherry, India
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Potential strategies for strengthening surveillance of lymphatic filariasis in American Samoa after mass drug administration: Reducing 'number needed to test' by targeting older age groups, hotspots, and household members of infected persons. PLoS Negl Trop Dis 2020; 14:e0008916. [PMID: 33370264 PMCID: PMC7872281 DOI: 10.1371/journal.pntd.0008916] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 02/09/2021] [Accepted: 10/26/2020] [Indexed: 12/12/2022] Open
Abstract
Under the Global Programme to Eliminate Lymphatic Filariasis (LF), American Samoa conducted mass drug administration (MDA) from 2000-2006. Despite passing Transmission Assessment Surveys (TAS) in 2011/2012 and 2015, American Samoa failed TAS-3 in 2016, with antigen (Ag) prevalence of 0.7% (95%CI 0.3-1.8%) in 6-7 year-olds. A 2016 community survey (Ag prevalence 6.2% (95%CI 4.4-8.5%) in age ≥8 years) confirmed resurgence. Using data from the 2016 survey, this study aims to i) investigate antibody prevalence in TAS-3 and the community survey, ii) identify risk factors associated with being seropositive for Ag and anti-filarial antibodies, and iii) compare the efficiency of different sampling strategies for identifying seropositive persons in the post-MDA setting. Antibody prevalence in TAS-3 (n = 1143) were 1.6% for Bm14 (95%CI 0.9-2.9%), 7.9% for Wb123 (95%CI 6.4-9.6%), and 20.2% for Bm33 (95%CI 16.7-24.3%); and in the community survey (n = 2507), 13.9% for Bm14 (95%CI 11.2-17.2%), 27.9% for Wb123 (95%CI 24.6-31.4%), and 47.3% for Bm33 (95%CI 42.1-52.6%). Multivariable logistic regression was used to identify risk factors for being seropositive for Ag and antibodies. Higher Ag prevalence was found in males (adjusted odds ratio [aOR] 3.01), age ≥18 years (aOR 2.18), residents of Fagali'i (aOR 15.81), and outdoor workers (aOR 2.61). Ag prevalence was 20.7% (95%CI 9.7-53.5%) in households of Ag-positive children identified in TAS-3. We used NNTestav (average number needed to test to identify one positive) to compare the efficiency of the following strategies for identifying persons who were seropositive for Ag and each antibody: i) TAS of 6-7 year-old children, ii) population representative surveys of older age groups, and iii) targeted surveillance of subpopulations at higher risk of being seropositive (older ages, householders of Ag-positive TAS children, and known hotspots). For Ag, NNTestav ranged from 142.5 for TAS, to <5 for households of index children. NNTestav was lower in older ages, and highest for Ag, followed by Bm14, Wb123 and Bm33 antibodies. We propose a multi-stage surveillance strategy, starting with population-representative sampling (e.g. TAS or population representative survey of older ages), followed by strategies that target subpopulations and/or locations with low NNTestav. This approach could potentially improve the efficiency of identifying remaining infected persons and residual hotspots. Surveillance programs should also explore the utility of antibodies as indicators of transmission.
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11
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Collyer BS, Irvine MA, Hollingsworth TD, Bradley M, Anderson RM. Defining a prevalence level to describe the elimination of Lymphatic Filariasis (LF) transmission and designing monitoring & evaluating (M&E) programmes post the cessation of mass drug administration (MDA). PLoS Negl Trop Dis 2020; 14:e0008644. [PMID: 33044958 PMCID: PMC7549789 DOI: 10.1371/journal.pntd.0008644] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 07/27/2020] [Indexed: 12/23/2022] Open
Abstract
The global decline in prevalence of lymphatic filariasis has been one of the major successes of the WHO's NTD programme. The recommended strategy of intensive, community-wide mass drug administration, aims to break localised transmission by either reducing the prevalence of microfilaria positive infections to below 1%, or antigen positive infections to below 2%. After the threshold is reached, and mass drug administration is stopped, geographically defined evaluation units must pass Transmission Assessment Surveys to demonstrate that transmission has been interrupted. In this study, we use an empirically parameterised stochastic transmission model to investigate the appropriateness of 1% microfilaria-positive prevalence as a stopping threshold, and statistically evaluate how well various monitoring prevalence-thresholds predict elimination or disease resurgence in the future by calculating their predictive value. Our results support the 1% filaremia prevalence target as appropriate stopping criteria. However, because at low prevalence-levels random events dominate the transmission dynamics, we find single prevalence measurements have poor predictive power for predicting resurgence, which suggests alternative criteria for restarting MDA may be beneficial.
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Affiliation(s)
- Benjamin S. Collyer
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, St Mary’s Campus, Imperial College London, London, United Kingdom
| | - Michael A. Irvine
- Institute of Applied Mathematics, University of British Columbia, Vancouver, Canada
| | - T. Deidre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Mark Bradley
- Global Health Program, GlaxoSmithKline (GSK), Brentford, United Kingdom
| | - Roy M. Anderson
- Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, St Mary’s Campus, Imperial College London, London, United Kingdom
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12
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Stolk WA, Prada JM, Smith ME, Kontoroupis P, de Vos AS, Touloupou P, Irvine MA, Brown P, Subramanian S, Kloek M, Michael E, Hollingsworth TD, de Vlas SJ. Are Alternative Strategies Required to Accelerate the Global Elimination of Lymphatic Filariasis? Insights From Mathematical Models. Clin Infect Dis 2019; 66:S260-S266. [PMID: 29860286 PMCID: PMC5982795 DOI: 10.1093/cid/ciy003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Background With the 2020 target year for elimination of lymphatic filariasis (LF) approaching, there is an urgent need to assess how long mass drug administration (MDA) programs with annual ivermectin + albendazole (IA) or diethylcarbamazine + albendazole (DA) would still have to be continued, and how elimination can be accelerated. We addressed this using mathematical modeling. Methods We used 3 structurally different mathematical models for LF transmission (EPIFIL, LYMFASIM, TRANSFIL) to simulate trends in microfilariae (mf) prevalence for a range of endemic settings, both for the current annual MDA strategy and alternative strategies, assessing the required duration to bring mf prevalence below the critical threshold of 1%. Results Three annual MDA rounds with IA or DA and good coverage (≥65%) are sufficient to reach the threshold in settings that are currently at mf prevalence <4%, but the required duration increases with increasing mf prevalence. Switching to biannual MDA or employing triple-drug therapy (ivermectin, diethylcarbamazine, and albendazole [IDA]) could reduce program duration by about one-third. Optimization of coverage reduces the time to elimination and is particularly important for settings with a history of poorly implemented MDA (low coverage, high systematic noncompliance). Conclusions Modeling suggests that, in several settings, current annual MDA strategies will be insufficient to achieve the 2020 LF elimination targets, and programs could consider policy adjustment to accelerate, guided by recent monitoring and evaluation data. Biannual treatment and IDA hold promise in reducing program duration, provided that coverage is good, but their efficacy remains to be confirmed by more extensive field studies.
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Affiliation(s)
- Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Centre Rotterdam, The Netherlands
| | - Joaquin M Prada
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Morgan E Smith
- Department of Biological Sciences, University of Notre Dame, South Bend, Indiana
| | - Periklis Kontoroupis
- Department of Public Health, Erasmus MC, University Medical Centre Rotterdam, The Netherlands
| | - Anneke S de Vos
- Department of Public Health, Erasmus MC, University Medical Centre Rotterdam, The Netherlands
| | | | - Michael A Irvine
- University of British Columbia and British Columbia Centre for Disease Control, Vancouver, Canada
| | - Paul Brown
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Swaminathan Subramanian
- Vector Control Research Centre, Indian Council of Medical Research, Indira Nagar, Puducherry
| | - Marielle Kloek
- Department of Public Health, Erasmus MC, University Medical Centre Rotterdam, The Netherlands
| | - E Michael
- Department of Biological Sciences, University of Notre Dame, South Bend, Indiana
| | | | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Centre Rotterdam, The Netherlands
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13
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The roadmap towards elimination of lymphatic filariasis by 2030: insights from quantitative and mathematical modelling. Gates Open Res 2019; 3:1538. [PMID: 31728440 PMCID: PMC6833911 DOI: 10.12688/gatesopenres.13065.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2019] [Indexed: 01/26/2023] Open
Abstract
The Global Programme to Eliminate Lymphatic Filariasis was launched in 2000 to eliminate lymphatic filariasis (LF) as a public health problem by 1) interrupting transmission through mass drug administration (MDA) and 2) offering basic care to those suffering from lymphoedema or hydrocele due to the infection. Although impressive progress has been made, the initial target year of 2020 will not be met everywhere. The World Health Organization recently proposed 2030 as the new target year for elimination of lymphatic filariasis (LF) as a public health problem. In this letter, LF modelers of the Neglected Tropical Diseases (NTDs) Modelling Consortium reflect on the proposed targets for 2030 from a quantitative perspective. While elimination as a public health problem seems technically and operationally feasible, it is uncertain whether this will eventually also lead to complete elimination of transmission. The risk of resurgence needs to be mitigated by strong surveillance after stopping interventions and sometimes perhaps additional interventions.
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14
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Davis EL, Reimer LJ, Pellis L, Hollingsworth TD. Evaluating the Evidence for Lymphatic Filariasis Elimination. Trends Parasitol 2019; 35:860-869. [PMID: 31506245 PMCID: PMC7413036 DOI: 10.1016/j.pt.2019.08.003] [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: 06/24/2019] [Revised: 08/19/2019] [Accepted: 08/19/2019] [Indexed: 12/01/2022]
Abstract
In the global drive for elimination of lymphatic filariasis (LF), 15 countries have achieved validation of elimination as a public health problem (EPHP). Recent empirical evidence has demonstrated that EPHP does not always lead to elimination of transmission (EOT). Here we show how the probability of elimination explicitly depends on key biological parameters, many of which have been poorly characterized, leading to a poor evidence base for the elimination threshold. As more countries progress towards EPHP it is essential that this process is well-informed, as prematurely halting treatment and surveillance programs could pose a serious threat to global progress. We highlight that refinement of the weak empirical evidence base is vital to understand drivers of elimination and inform long-term policy.
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Affiliation(s)
| | - Lisa J Reimer
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Lorenzo Pellis
- University of Manchester, Oxford Road, Manchester M13 9PL, UK
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15
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Quantifying the value of surveillance data for improving model predictions of lymphatic filariasis elimination. PLoS Negl Trop Dis 2018; 12:e0006674. [PMID: 30296266 PMCID: PMC6175292 DOI: 10.1371/journal.pntd.0006674] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 07/09/2018] [Indexed: 12/27/2022] Open
Abstract
Background Mathematical models are increasingly being used to evaluate strategies aiming to achieve the control or elimination of parasitic diseases. Recently, owing to growing realization that process-oriented models are useful for ecological forecasts only if the biological processes are well defined, attention has focused on data assimilation as a means to improve the predictive performance of these models. Methodology and principal findings We report on the development of an analytical framework to quantify the relative values of various longitudinal infection surveillance data collected in field sites undergoing mass drug administrations (MDAs) for calibrating three lymphatic filariasis (LF) models (EPIFIL, LYMFASIM, and TRANSFIL), and for improving their predictions of the required durations of drug interventions to achieve parasite elimination in endemic populations. The relative information contribution of site-specific data collected at the time points proposed by the WHO monitoring framework was evaluated using model-data updating procedures, and via calculations of the Shannon information index and weighted variances from the probability distributions of the estimated timelines to parasite extinction made by each model. Results show that data-informed models provided more precise forecasts of elimination timelines in each site compared to model-only simulations. Data streams that included year 5 post-MDA microfilariae (mf) survey data, however, reduced each model’s uncertainty most compared to data streams containing only baseline and/or post-MDA 3 or longer-term mf survey data irrespective of MDA coverage, suggesting that data up to this monitoring point may be optimal for informing the present LF models. We show that the improvements observed in the predictive performance of the best data-informed models may be a function of temporal changes in inter-parameter interactions. Such best data-informed models may also produce more accurate predictions of the durations of drug interventions required to achieve parasite elimination. Significance Knowledge of relative information contributions of model only versus data-informed models is valuable for improving the usefulness of LF model predictions in management decision making, learning system dynamics, and for supporting the design of parasite monitoring programmes. The present results further pinpoint the crucial need for longitudinal infection surveillance data for enhancing the precision and accuracy of model predictions of the intervention durations required to achieve parasite elimination in an endemic location. Although parasite transmission models offer powerful tools for predicting the impacts of interventions, there is growing realization that these models can be useful for this purpose only if their governing biological processes are well defined. Recently, model-data assimilation has been applied to address this problem and improve the performance of process-oriented models for ecological forecasting. Here, we developed an analytical framework that allowed the sequential coupling of the three existing lymphatic filariasis (LF) models with longitudinal infection monitoring data collected in field sites undergoing mass drug administrations (MDAs) to examine the relative value of such data for parameterizing these models and for improving their predictions of the required durations of drug interventions to break parasite transmission. We found that data-informed models provided more precise and reliable forecasts of elimination timelines in the study sites compared to model-only predictions, and that data collected up to 5 years post-MDA reduced each model’s predictive uncertainty most. We also found that this improved performance may be intriguingly related to temporal changes in system dynamics. Our results underscore the significance of sequential model-data fusion for enhancing the understanding of LF transmission dynamics, design of surveillance, and generation of reliable model predictions for management decision making.
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16
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Smith ME, Singh BK, Irvine MA, Stolk WA, Subramanian S, Hollingsworth TD, Michael E. Predicting lymphatic filariasis transmission and elimination dynamics using a multi-model ensemble framework. Epidemics 2018; 18:16-28. [PMID: 28279452 PMCID: PMC5340857 DOI: 10.1016/j.epidem.2017.02.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 02/01/2017] [Accepted: 02/01/2017] [Indexed: 11/28/2022] Open
Abstract
No single mathematical model captures all features of parasite transmission dynamics. Multi-model ensemble modelling can overcome biases of single models. A multi-model ensemble of three lymphatic filariasis models is proposed and evaluated. The multi-model ensemble outperformed the single models in predicting infection. The ensemble approach may improve use of models to inform disease control policy.
Mathematical models of parasite transmission provide powerful tools for assessing the impacts of interventions. Owing to complexity and uncertainty, no single model may capture all features of transmission and elimination dynamics. Multi-model ensemble modelling offers a framework to help overcome biases of single models. We report on the development of a first multi-model ensemble of three lymphatic filariasis (LF) models (EPIFIL, LYMFASIM, and TRANSFIL), and evaluate its predictive performance in comparison with that of the constituents using calibration and validation data from three case study sites, one each from the three major LF endemic regions: Africa, Southeast Asia and Papua New Guinea (PNG). We assessed the performance of the respective models for predicting the outcomes of annual MDA strategies for various baseline scenarios thought to exemplify the current endemic conditions in the three regions. The results show that the constructed multi-model ensemble outperformed the single models when evaluated across all sites. Single models that best fitted calibration data tended to do less well in simulating the out-of-sample, or validation, intervention data. Scenario modelling results demonstrate that the multi-model ensemble is able to compensate for variance between single models in order to produce more plausible predictions of intervention impacts. Our results highlight the value of an ensemble approach to modelling parasite control dynamics. However, its optimal use will require further methodological improvements as well as consideration of the organizational mechanisms required to ensure that modelling results and data are shared effectively between all stakeholders.
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Affiliation(s)
- 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
| | - Michael A Irvine
- School of Life Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
| | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
| | - Swaminathan Subramanian
- Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Pondicherry 650 006, India
| | - T Déirdre Hollingsworth
- School of Life Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK; Mathematics Institute, University of Warwick, Gibbet Hill Road, CV4 7AL Coventry, UK
| | - Edwin Michael
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
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17
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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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18
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Irvine MA, Stolk WA, Smith ME, Subramanian S, Singh BK, Weil GJ, Michael E, Hollingsworth TD. Effectiveness of a triple-drug regimen for global elimination of lymphatic filariasis: a modelling study. THE LANCET. INFECTIOUS DISEASES 2016; 17:451-458. [PMID: 28012943 DOI: 10.1016/s1473-3099(16)30467-4] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 09/26/2016] [Accepted: 10/17/2016] [Indexed: 10/20/2022]
Abstract
BACKGROUND Lymphatic filariasis is targeted for elimination as a public health problem by 2020. The principal approach used by current programmes is annual mass drug administration with two pairs of drugs with a good safety profile. However, one dose of a triple-drug regimen (ivermectin, diethylcarbamazine, and albendazole) has been shown to clear the transmissible stage of the helminth completely in treated individuals. The aim of this study was to use modelling to assess the potential value of mass drug administration with the triple-drug regimen for accelerating elimination of lymphatic filariasis in different epidemiological settings. METHODS We used three different transmission models to compare the number of rounds of mass drug administration needed to achieve a prevalence of microfilaraemia less than 1% with the triple-drug regimen and with current two-drug regimens. FINDINGS In settings with a low baseline prevalence of lymphatic filariasis (5%), the triple-drug regimen reduced the number of rounds of mass drug administration needed to reach the target prevalence by one or two rounds, compared with the two-drug regimen. For areas with higher baseline prevalence (10-40%), the triple-drug regimen strikingly reduced the number of rounds of mass drug administration needed, by about four or five, but only at moderate-to-high levels of population coverage (>65%) and if systematic non-adherence to mass drug administration was low. INTERPRETATION Simulation modelling suggests that the triple-drug regimen has potential to accelerate the elimination of lymphatic filariasis if high population coverage of mass drug administration can be achieved and if systematic non-adherence with mass drug administration is low. Future work will reassess these estimates in light of more clinical trial data and to understand the effect on an individual country's programme. FUNDING Bill & Melinda Gates Foundation.
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Affiliation(s)
| | - Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, Rotterdam, Netherlands
| | - Morgan E Smith
- Department of Biological Sciences, University of Notre Dame, Notre Dame, South Bend, IN, USA
| | - Swaminathan Subramanian
- Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Puducherry, India
| | - Brajendra K Singh
- Department of Biological Sciences, University of Notre Dame, Notre Dame, South Bend, IN, USA
| | - Gary J Weil
- Washington University School of Medicine, St Louis, MO, USA
| | - Edwin Michael
- Department of Biological Sciences, University of Notre Dame, Notre Dame, South Bend, IN, USA
| | - T Deirdre Hollingsworth
- School of Life Sciences, University of Warwick, Coventry, UK; Mathematics Institute, University of Warwick, Coventry, UK.
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19
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Mary KA, Krishnamoorthy K, Hoti SL. Scope of detectability of circulating antigens of human lymphatic filarial parasite Wuchereria bancrofti with smaller amount of serum by Og4C3 assay: its application in lymphatic filariasis elimination programme. J Parasit Dis 2016; 40:1622-1626. [PMID: 27876997 PMCID: PMC5118297 DOI: 10.1007/s12639-015-0671-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 02/26/2015] [Indexed: 11/25/2022] Open
Abstract
Filarial antigen detection is an appropriate epidemiological indicator for mapping lymphatic filariasis and impact evaluation of filariasis elimination programme in view of low sensitivity of parasite detection. Monoclonal antibody-based Og4C3 immunological test requires 100 µl serum, which is difficult to collect by finger prick method during community based surveys. Hence, we tested lesser volume of serum compared to standard volume of 100 µl to compare its sensitivity and specificity in detecting the circulating filarial antigens. Blood samples were collected from individuals who tested positive [with titer groups 4 (border line positives), 6 (medium positives), and 8 (high positives)] and negative (titre group 3) for Og4C3 assay. Different volumes of serum samples were used to make-up required volume (100 µl) with appropriate dilutions and subjected to Og4C3 assay. The results showed that known negative samples tested negative at all the serum volumes tested. All positives (titer groups 6 and 8) showed positivity at all reduced volumes of serum sample. However one of the medium positive sample showed negative reaction in 5 µl volume of serum and two of the border line positives showed negative at all the serum volume tested. The results thus showed as less as 15 µl serum is adequate for use in Og4C3 assay. So the test can be performed without losing its sensitivity even with 5 µl serum samples at high titre of antigen (titre group 8) and 15 µl for other groups and this method has scope in programme evaluation.
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Affiliation(s)
- K. Athisaya Mary
- Unit of Microbiology and Immunology, Vector Control Research Centre (Indian Council of Medical Research and Department of Health Research), Indira Nagar, Puducherry, 605 006 India
| | - K. Krishnamoorthy
- Unit of Epidemiology and Operational Research, Vector Control Research Centre (Indian Council of Medical Research and Department of Health Research), Indira Nagar, Puducherry, 605 006 India
| | - S. L. Hoti
- Unit of Microbiology and Immunology, Vector Control Research Centre (Indian Council of Medical Research and Department of Health Research), Indira Nagar, Puducherry, 605 006 India
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Irvine MA, Njenga SM, Gunawardena S, Njeri Wamae C, Cano J, Brooker SJ, Hollingsworth TD. Understanding the relationship between prevalence of microfilariae and antigenaemia using a model of lymphatic filariasis infection. Trans R Soc Trop Med Hyg 2016; 110:118-24. [PMID: 26822604 PMCID: PMC4731003 DOI: 10.1093/trstmh/trv096] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Background Lymphatic filariasis is a debilitating neglected tropical disease that affects impoverished communities. Rapid diagnostic tests of antigenaemia are a practical alternative to parasitological tests of microfilaraemia for mapping and surveillance. However the relationship between these two methods of measuring burden has previously been difficult to interpret. Methods A statistical model of the distribution of worm burden and microfilariae (mf) and resulting antigenaemic and mf prevalence was developed and fitted to surveys of two contrasting sentinel sites undergoing interventions. The fitted model was then used to explore the relationship in various pre- and post-intervention scenarios. Results The model had good quantitative agreement with the data and provided estimates of the reduction in mf output due to treatment. When extrapolating the results to a range of prevalences there was good qualitative agreement with published data. Conclusions The observed relationship between antigenamic and mf prevalence is a natural consequence of the relationship between prevalence and intensity of adult worms and mf production. The method described here allows the estimation of key epidemiological parameters and consequently gives insight into the efficacy of an intervention programme.
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Affiliation(s)
- Michael A Irvine
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Sammy M Njenga
- Kenya Medical Research Institute (KEMRI), P.O. Box 54840, Post Code 00200, Nairobi, Kenya
| | - Shamini Gunawardena
- School of Health Sciences, Mount Kenya University, P.O. Box 342-01000, Thika, Kenya
| | - Claire Njeri Wamae
- School of Health Sciences, Mount Kenya University, P.O. Box 342-01000, Thika, Kenya
| | - Jorge Cano
- London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Simon J Brooker
- London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - T Deirdre Hollingsworth
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK Mathematics Institute, University of Warwick, Coventry, CV4 7AL, UK
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Lessons Learned From Developing an Eradication Investment Case for Lymphatic Filariasis. ADVANCES IN PARASITOLOGY 2016; 94:393-417. [PMID: 27756458 DOI: 10.1016/bs.apar.2016.08.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In the last few years, the concepts of disease elimination and eradication have again gained consideration from the global health community, with Guinea worm disease (dracunculiasis) on track to become the first parasitic disease to be eradicated. Given the many complex and interlinking issues involved in committing to a disease eradication initiative, such commitments must be based on a solid assessment of a broad range of factors. In this chapter, we discuss the value and implications of undertaking a systematic and fact-based analysis of the overall situation prior to embarking on an elimination or eradication programme. As an example, we draw upon insights gained from a series of lymphatic filariasis (LF) studies from our research group that adopted an eradication investment case (EIC) framework. The justification for EICs, and related epidemiological, geospatial and other mathematical/operational research modelling, stems from the necessity for proper planning prior to committing to disease eradication. Across all considerations for LF eradication, including: time, treatments, level of investments necessary, health impact, cost-effectiveness, and broader economic benefits, scaling-up mass drug administration coverage to all endemic communities immediately provided the most favourable results. The coherent and consistent pursuit of eradication goals, operationally tailored to a given socioecological system and based on integrated measures of available tools will lead relatively rapidly to elimination in many parts of endemic areas and provide the cornerstone towards eradication.
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Jambulingam P, Subramanian S, de Vlas SJ, Vinubala C, Stolk WA. Mathematical modelling of lymphatic filariasis elimination programmes in India: required duration of mass drug administration and post-treatment level of infection indicators. Parasit Vectors 2016; 9:501. [PMID: 27624157 PMCID: PMC5022201 DOI: 10.1186/s13071-016-1768-y] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 08/22/2016] [Indexed: 12/03/2022] Open
Abstract
Background India has made great progress towards the elimination of lymphatic filariasis. By 2015, most endemic districts had completed at least five annual rounds of mass drug administration (MDA). The next challenge is to determine when MDA can be stopped. We performed a simulation study with the individual-based model LYMFASIM to help clarify this. Methods We used a model-variant for Indian settings. We considered different hypotheses on detectability of antigenaemia (Ag) in relation to underlying adult worm burden, choosing the most likely hypothesis by comparing the model predicted association between community-level microfilaraemia (Mf) and antigenaemia (Ag) prevalence levels to observed data (collated from literature). Next, we estimated how long MDA must be continued in order to achieve elimination in different transmission settings and what Mf and Ag prevalence may still remain 1 year after the last required MDA round. The robustness of key-outcomes was assessed in a sensitivity analysis. Results Our model matched observed data qualitatively well when we assumed an Ag detection rate of 50 % for single worm infections, which increases with the number of adult worms (modelled by relating detection to the presence of female worms). The required duration of annual MDA increased with higher baseline endemicity and lower coverage (varying between 2 and 12 rounds), while the remaining residual infection 1 year after the last required treatment declined with transmission intensity. For low and high transmission settings, the median residual infection levels were 1.0 % and 0.4 % (Mf prevalence in the 5+ population), and 3.5 % and 2.0 % (Ag prevalence in 6–7 year-old children). Conclusion To achieve elimination in high transmission settings, MDA must be continued longer and infection levels must be reduced to lower levels than in low-endemic communities. Although our simulations were for Indian settings, qualitatively similar patterns are also expected in other areas. This should be taken into account in decision algorithms to define whether MDA can be interrupted. Transmission assessment surveys should ideally be targeted to communities with the highest pre-control transmission levels, to minimize the risk of programme failure. Electronic supplementary material The online version of this article (doi:10.1186/s13071-016-1768-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Purushothaman Jambulingam
- Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Puducherry, 605006, India
| | - Swaminathan Subramanian
- Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Puducherry, 605006, India.
| | - S J de Vlas
- Department of Public Health, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Chellasamy Vinubala
- Vector Control Research Centre (Indian Council of Medical Research), Indira Nagar, Puducherry, 605006, India
| | - W A Stolk
- Department of Public Health, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands
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Pineda MA, Eason RJ, Harnett MM, Harnett W. From the worm to the pill, the parasitic worm product ES-62 raises new horizons in the treatment of rheumatoid arthritis. Lupus 2015; 24:400-11. [PMID: 25801883 DOI: 10.1177/0961203314560004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Evidence from human studies suggests that parasitic worm infection can protect humans against rheumatoid arthritis (RA) and this idea is strengthened by data generated in model systems. Although therapeutic use of parasitic worms is currently being explored, there are obvious benefits in pursuing drug development through identification and isolation of the 'active ingredients'. ES-62 is a secreted glycoprotein of the filarial nematode Acanthocheilonema viteae, which we have found to protect against the development of collagen-induced arthritis (CIA) in mice. ES-62 activity is dependent on the inflammatory phenotype of the local environment and protection arises via inhibition of Th17- and γδT cell-dependent IL-17 production. At the same time, NK and NK T cell IL-17 production is left intact, and such selectivity suggests that ES-62 might make a particularly attractive therapeutic for RA. However, as a potentially immunogenic protein, ES-62 is unsuitable for development as a drug. Nevertheless, ES-62 activity is dependent on covalently attached phosphorylcholine (PC) residues and we have therefore produced a library of PC-based drug-like ES-62 small-molecule analogues (SMAs) as an alternative therapeutic strategy. Screening this library, we have found an ES-62 SMA that mirrors ES-62 in protecting against CIA and by the same IL-17-dependent mechanism of action.
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Affiliation(s)
- M A Pineda
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | - R J Eason
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | - M M Harnett
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
| | - W Harnett
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
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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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Irvine MA, Reimer LJ, Njenga SM, Gunawardena S, Kelly-Hope L, Bockarie M, Hollingsworth TD. Modelling strategies to break transmission of lymphatic filariasis--aggregation, adherence and vector competence greatly alter elimination. Parasit Vectors 2015; 8:547. [PMID: 26489753 PMCID: PMC4618540 DOI: 10.1186/s13071-015-1152-3] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 10/06/2015] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND With ambitious targets to eliminate lymphatic filariasis over the coming years, there is a need to identify optimal strategies to achieve them in areas with different baseline prevalence and stages of control. Modelling can assist in identifying what data should be collected and what strategies are best for which scenarios. METHODS We develop a new individual-based, stochastic mathematical model of the transmission of lymphatic filariasis. We validate the model by fitting to a first time point and predicting future timepoints from surveillance data in Kenya and Sri Lanka, which have different vectors and different stages of the control programme. We then simulate different treatment scenarios in low, medium and high transmission settings, comparing once yearly mass drug administration (MDA) with more frequent MDA and higher coverage. We investigate the potential impact that vector control, systematic non-compliance and different levels of aggregation have on the dynamics of transmission and control. RESULTS In all settings, increasing coverage from 65 to 80 % has a similar impact on control to treating twice a year at 65 % coverage, for fewer drug treatments being distributed. Vector control has a large impact, even at moderate levels. The extent of aggregation of parasite loads amongst a small portion of the population, which has been estimated to be highly variable in different settings, can undermine the success of a programme, particularly if high risk sub-communities are not accessing interventions. CONCLUSION Even moderate levels of vector control have a large impact both on the reduction in prevalence and the maintenance of gains made during MDA, even when parasite loads are highly aggregated, and use of vector control is at moderate levels. For the same prevalence, differences in aggregation and adherence can result in very different dynamics. The novel analysis of a small amount of surveillance data and resulting simulations highlight the need for more individual level data to be analysed to effectively tailor programmes in the drive for elimination.
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Affiliation(s)
- M A Irvine
- School of Life Sciences, University of Warwick, Gibbet Hill Road, CV4 7AL, Coventry, UK.
| | - L J Reimer
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - S M Njenga
- Kenya Medical Research Institute (KEMRI), P.O. Box 54840, 00200, Nairobi, Kenya
| | - S Gunawardena
- Faculty of Medicine, University of Colombo, Colombo, Sri Lanka
| | - L Kelly-Hope
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - M Bockarie
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - T D Hollingsworth
- School of Life Sciences, University of Warwick, Gibbet Hill Road, CV4 7AL, Coventry, UK
- Mathematics Institute, University of Warwick, Gibbet Hill Road, CV4 7AL, Coventry, UK
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26
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Winter AD, Gillan V, Maitland K, Emes RD, Roberts B, McCormack G, Weir W, Protasio AV, Holroyd N, Berriman M, Britton C, Devaney E. A novel member of the let-7 microRNA family is associated with developmental transitions in filarial nematode parasites. BMC Genomics 2015; 16:331. [PMID: 25896062 PMCID: PMC4428239 DOI: 10.1186/s12864-015-1536-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 04/13/2015] [Indexed: 12/18/2022] Open
Abstract
Background Filarial nematodes are important pathogens in the tropics transmitted to humans via the bite of blood sucking arthropod vectors. The molecular mechanisms underpinning survival and differentiation of these parasites following transmission are poorly understood. microRNAs are small non-coding RNA molecules that regulate target mRNAs and we set out to investigate whether they play a role in the infection event. Results microRNAs differentially expressed during the early post-infective stages of Brugia pahangi L3 were identified by microarray analysis. One of these, bpa-miR-5364, was selected for further study as it is upregulated ~12-fold at 24 hours post-infection, is specific to clade III nematodes, and is a novel member of the let-7 family, which are known to have key developmental functions in the free-living nematode Caenorhabditis elegans. Predicted mRNA targets of bpa-miR-5364 were identified using bioinformatics and comparative genomics approaches that relied on the conservation of miR-5364 binding sites in the orthologous mRNAs of other filarial nematodes. Finally, we confirmed the interaction between bpa-miR-5364 and three of its predicted targets using a dual luciferase assay. Conclusions These data provide new insight into the molecular mechanisms underpinning the transmission of third stage larvae of filarial nematodes from vector to mammal. This study is the first to identify parasitic nematode mRNAs that are verified targets of specific microRNAs and demonstrates that post-transcriptional control of gene expression via stage-specific expression of microRNAs may be important in the success of filarial infection. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1536-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alan D Winter
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
| | - Victoria Gillan
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
| | - Kirsty Maitland
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
| | - Richard D Emes
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Leicestershire, LE12 5RD, UK. .,Advanced Data Analysis Centre, University of Nottingham, Nottingham, UK.
| | - Brett Roberts
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
| | - Gillian McCormack
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
| | - William Weir
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
| | - Anna V Protasio
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, CB10 1SA, UK.
| | - Nancy Holroyd
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, CB10 1SA, UK.
| | - Matthew Berriman
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, CB10 1SA, UK.
| | - Collette Britton
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
| | - Eileen Devaney
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Garscube Estate, Bearsden Road, Glasgow, G61 1QH, UK.
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Stolk WA, Stone C, de Vlas SJ. Modelling lymphatic filariasis transmission and control: modelling frameworks, lessons learned and future directions. ADVANCES IN PARASITOLOGY 2015; 87:249-91. [PMID: 25765197 DOI: 10.1016/bs.apar.2014.12.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Mathematical modelling provides a useful tool for policy making and planning in lymphatic filariasis control programmes, by providing trend forecasts based on sound scientific knowledge and principles. This is now especially true, in view of the ambitious target to eliminate lymphatic filariasis as a public health problem globally by the year 2020 and the short remaining timeline to achieve this. To meet this target, elimination programmes need to be accelerated, requiring further optimization of strategies and tailoring to local circumstances. Insights from epidemiological transmission models provide a useful basis. Two general models of lymphatic filariasis transmission and control are nowadays in use to support decision-making, namely a population-based deterministic model (EPIFIL) and an individual-based stochastic model (LYMFASIM). Model predictions confirm that lymphatic filariasis transmission can be interrupted by annual mass drug administration (MDA), but this may need to be continued much longer than the initially suggested 4-6 years in areas with high transmission intensity or poor treatment coverage. However, the models have not been validated against longitudinal data describing the impact of MDA programmes. Some critical issues remain to be incorporated in one or both of the models to make predictions on elimination more realistic, including the possible occurrence of systematic noncompliance, the risk of emerging parasite resistance to anthelmintic drugs, and spatial heterogeneities. Rapid advances are needed to maximize the utility of models in decision-making for the ongoing ambitious lymphatic filariasis elimination programmes.
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Affiliation(s)
- Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands
| | - Chris Stone
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands
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Pineda MA, Al-Riyami L, Harnett W, Harnett MM. Lessons from helminth infections: ES-62 highlights new interventional approaches in rheumatoid arthritis. Clin Exp Immunol 2014; 177:13-23. [PMID: 24666108 PMCID: PMC4089150 DOI: 10.1111/cei.12252] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/06/2013] [Indexed: 12/19/2022] Open
Abstract
Parasitic worms are able to survive in their mammalian host for many years due to their ability to manipulate the immune response by secreting immunomodulatory products. It is increasingly clear that, reflecting the anti-inflammatory actions of such worm-derived immunomodulators, there is an inverse correlation between helminth infection and autoimmune diseases in the developing world. As the decrease in helminth infections due to increased sanitation has correlated with an alarming increase in prevalence of such disorders in industrialized countries, this ‘hygiene hypothesis’ has led to the proposal that worms and their secreted products offer a novel platform for the development of safe and effective strategies for the treatment of autoimmune disorders. In this study we review the anti-inflammatory effects of one such immunomodulator, ES-62 on innate and adaptive immune responses and the mechanisms it exploits to afford protection in the murine collagen-induced arthritis (CIA) model of rheumatoid arthritis (RA). As its core mechanism involves targeting of interleukin (IL)-17 responses, which despite being pathogenic in RA are important for combating infection, we discuss how its selective targeting of IL-17 production by T helper type 17 (Th17) and γδ T cells, while leaving that of CD49b+ natural killer (NK and NK T) cells intact, reflects the ability of helminths to modulate the immune system without immunocompromising the host. Exploiting helminth immunomodulatory mechanisms therefore offers the potential for safer therapies than current biologicals, such as ‘IL-17 blockers’, that are not able to discriminate sources of IL-17 and hence present adverse effects that limit their therapeutic potential.
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Affiliation(s)
- M A Pineda
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, UK
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Pineda MA, Lumb F, Harnett MM, Harnett W. ES-62, a therapeutic anti-inflammatory agent evolved by the filarial nematode Acanthocheilonema viteae. Mol Biochem Parasitol 2014; 194:1-8. [PMID: 24671112 DOI: 10.1016/j.molbiopara.2014.03.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 03/07/2014] [Accepted: 03/12/2014] [Indexed: 01/29/2023]
Abstract
Filarial nematodes cause long-term infections in hundreds of millions of people. A significant proportion of those affected develop a number of debilitating health problems but, remarkably, such infections are often unnoticed for many years. It is well known that parasitic worms modulate, yet do not completely inhibit, host immunological pathways, promoting their survival by limiting effective immune mechanisms. Such immunoregulation largely depends on molecules released by the worms, termed excretory-secretory products (ES). One of these products is the molecule ES-62, which is actively secreted by the rodent filarial nematode Acanthocheilonema viteae. ES-62 has been shown to exert anti-inflammatory actions thorough its phosphorylcholine (PC)-containing moiety on a variety of cells of the immune system, affecting intracellular signalling pathways associated with antigen receptor- and TLR-dependent responses. We summarise here how ES-62 modulates key signal transduction elements and how such immunomodulation confers protection to mice subjected to certain experimental models of inflammatory disease. Finally, we discuss recent results showing that it is possible to synthetise small molecule analogues (SMAs) that mimic the anti-inflammatory properties of ES-62, opening an exciting new drug development field in translational medicine.
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Affiliation(s)
- Miguel A Pineda
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow G12 8TA, UK
| | - Felicity Lumb
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0NR, UK
| | - Margaret M Harnett
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow G12 8TA, UK
| | - William Harnett
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0NR, UK.
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Gillan V, O'Neill K, Maitland K, Sverdrup FM, Devaney E. A repurposing strategy for Hsp90 inhibitors demonstrates their potency against filarial nematodes. PLoS Negl Trop Dis 2014; 8:e2699. [PMID: 24551261 PMCID: PMC3923716 DOI: 10.1371/journal.pntd.0002699] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 01/02/2014] [Indexed: 02/03/2023] Open
Abstract
Novel drugs are required for the elimination of infections caused by filarial worms, as most commonly used drugs largely target the microfilariae or first stage larvae of these infections. Previous studies, conducted in vitro, have shown that inhibition of Hsp90 kills adult Brugia pahangi. As numerous small molecule inhibitors of Hsp90 have been developed for use in cancer chemotherapy, we tested the activity of several novel Hsp90 inhibitors in a fluorescence polarization assay and against microfilariae and adult worms of Brugia in vitro. The results from all three assays correlated reasonably well and one particular compound, NVP-AUY922, was shown to be particularly active, inhibiting Mf output from female worms at concentrations as low as 5.0 nanomolar after 6 days exposure to drug. NVP-AUY922 was also active on adult worms after a short 24 h exposure to drug. Based on these in vitro data, NVP-AUY922 was tested in vivo in a mouse model and was shown to significantly reduce the recovery of both adult worms and microfilariae. These studies provide proof of principle that the repurposing of currently available Hsp90 inhibitors may have potential for the development of novel agents with macrofilaricidal properties.
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Affiliation(s)
- Victoria Gillan
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Kerry O'Neill
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Kirsty Maitland
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Francis M. Sverdrup
- Center for World Health & Medicine, Saint Louis University, Saint Louis, Missouri, United States of America
| | - Eileen Devaney
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
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Nematode-derived proteins suppress proliferation and cytokine production of antigen-specific T cells via induction of cell death. PLoS One 2013; 8:e68380. [PMID: 23861729 PMCID: PMC3693813 DOI: 10.1371/journal.pone.0068380] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 05/28/2013] [Indexed: 01/08/2023] Open
Abstract
In order to establish long-lasting infections in their mammalian host, filarial
nematodes have developed sophisticated strategies to dampen their host’s immune
response. Proteins that are actively secreted by the parasites have been shown
to induce the expansion of regulatory T cells and to directly interfere with
effector T cell function. Here, we analyze the suppressive capacity of
Onchocercavolvulus-derived excreted/secreted
proteins. Addition of two recombinant O. volvulus proteins, abundant larval
transcript-2 (OvALT-2) and novel larval transcript-1
(OvNLT-1) to cell cultures of T cell receptor transgenic
CD4+ and CD8+ T cells suppressed antigen-specific
stimulation in vitro. Ovalbumin-specific CD4+
DO11.10 and OT-II T cells that had been stimulated with their cognate antigen in
the presence of OvALT-2 or OvNLT-1 displayed
reduced DNA synthesis quantified by 3H-thymidine incorporation and
reduced cell division quantified by CFSE dilution. Furthermore, the IL-2 and
IFN-γ response of ovalbumin-specific CD8+ OT-I T cells was suppressed
by OvALT-2 and OvNLT-1. In contrast, another
recombinant O.
volvulus protein,
microfilariae surface-associated antigen (Ov103), did not
modulate T cell activation, thus serving as internal control for
non-ESP-mediated artifacts. Suppressive capacity of the identified ESP was
associated with induction of apoptosis in T cells demonstrated by increased
exposure of phosphatidylserine on the plasma membrane. Of note, the digestion of
recombinant proteins with proteinase K did not abolish the suppression of
antigen-specific proliferation although the suppressive capacity of the
identified excreted/secreted products was not mediated by low molecular weight
contaminants in the undigested preparations. In summary, we identified two
suppressive excreted/secreted products from O. volvulus, which interfere with the
function of antigen-specific T cells in vitro.
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Ramaiah KD, Vanamail P. Surveillance of lymphatic filariasis after stopping ten years of mass drug administration in rural communities in south India. Trans R Soc Trop Med Hyg 2013; 107:293-300. [PMID: 23442572 DOI: 10.1093/trstmh/trt011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND While various studies provided insight into the impact of mass drug administration (MDA), information on the dynamics of the post-MDA threshold level lymphatic filariasis (LF) infection facilitates understanding its disappearance pattern and determining the duration of post-MDA monitoring and evaluation. METHODS The changes in microfilaraemia (Mf) prevalence and vector infection rates were monitored for four (2005-2008) and six years (2005-2010) respectively after stopping ten rounds of annual mass diethylcarbamazine (DEC) administration in a group of five villages located in South India. Four years after stopping MDA, circulating filarial antigenaemia (Ag) status among children and adults was also assessed in two villages. RESULTS Overall Mf prevalence (n = 700) and vector infection rates (n=803-3520) showed a declining trend. Two villages maintained zero Mf status in each of the four years, vector infection rate was zero from the third year onwards and Ag prevalence in adults was 0.4% (n = 226). In two other villages despite persistence of Mf and vector infection there was zero vector infectivity rate during the third to sixth year and Ag prevalence among children (n = 50) was nil. In the fifth village Mf prevailed at <1.0% and Ag prevalence among 1-7 year old children was 4.6% (n = 44) and vector infectivity rate during the sixth year was 0.1% (n = 852). CONCLUSION The incidence of sporadic new infections is evident in highly endemic communities such as the fifth village. However, there is uncertainty on the potential of the Ag positive children to reestablish infection. Six years of post-MDA monitoring and evaluation appears to be adequate to discern the status of transmission interruption and appropriate decision making.
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Affiliation(s)
- K D Ramaiah
- Vector Control Research Centre, Indian Council of Medical Research, Medical Complex, Indira Nagar, Pondicherry 605006, India
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Modeling the impact and costs of semiannual mass drug administration for accelerated elimination of lymphatic filariasis. PLoS Negl Trop Dis 2013; 7:e1984. [PMID: 23301115 PMCID: PMC3536806 DOI: 10.1371/journal.pntd.0001984] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 11/07/2012] [Indexed: 11/25/2022] Open
Abstract
The Global Program to Eliminate Lymphatic Filariasis (LF) has a target date of 2020. This program is progressing well in many countries. However, progress has been slow in some countries, and others have not yet started their mass drug administration (MDA) programs. Acceleration is needed. We studied how increasing MDA frequency from once to twice per year would affect program duration and costs by using computer simulation modeling and cost projections. We used the LYMFASIM simulation model to estimate how many annual or semiannual MDA rounds would be required to eliminate LF for Indian and West African scenarios with varied pre-control endemicity and coverage levels. Results were used to estimate total program costs assuming a target population of 100,000 eligibles, a 3% discount rate, and not counting the costs of donated drugs. A sensitivity analysis was done to investigate the robustness of these results with varied assumptions for key parameters. Model predictions suggested that semiannual MDA will require the same number of MDA rounds to achieve LF elimination as annual MDA in most scenarios. Thus semiannual MDA programs should achieve this goal in half of the time required for annual programs. Due to efficiency gains, total program costs for semiannual MDA programs are projected to be lower than those for annual MDA programs in most scenarios. A sensitivity analysis showed that this conclusion is robust. Semiannual MDA is likely to shorten the time and lower the cost required for LF elimination in countries where it can be implemented. This strategy may improve prospects for global elimination of LF by the target year 2020. The Global Program to Eliminate Lymphatic Filariasis (LF) employs annual mass drug administration (MDA) of antifilarial drugs to reduce infection rates in populations and interrupt transmission. While this program is working well in many countries, progress has been slow in others, and some countries have not yet started MDA programs. We used computer simulation modeling and cost projections to study how increasing MDA frequency from once to twice per year would affect program duration and costs. Our results suggest that semiannual MDA is likely to reduce the time required to eliminate LF by 50% and reduce total program costs (excluding the cost of donated drugs) in most situations. For these and other reasons, we expect semiannual MDA to be superior to annual MDA in most endemic settings. Semiannual MDA should be considered as a means of accelerating LF elimination in areas where it can be implemented, because this may improve prospects for global elimination of LF by the target year 2020.
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Abstract
The planning and evaluation of parasitic control programmes are complicated by the many interacting population dynamic and programmatic factors that determine infection trends under different control options. A key need is quantification about the status of the parasite system state at any one given timepoint and the dynamic change brought upon that state as an intervention program proceeds. Here, we focus on the control and elimination of the vector-borne disease, lymphatic filariasis, to show how mathematical models of parasite transmission can provide a quantitative framework for aiding the design of parasite elimination and monitoring programs by their ability to support (1) conducting rational analysis and definition of endpoints for different programmatic aims or objectives, including transmission endpoints for disease elimination, (2) undertaking strategic analysis to aid the optimal design of intervention programs to meet set endpoints under different endemic settings and (3) providing support for performing informed evaluations of ongoing programs, including aiding the formation of timely adaptive management strategies to correct for any observed deficiencies in program effectiveness. The results also highlight how the use of a model-based framework will be critical to addressing the impacts of ecological complexities, heterogeneities and uncertainties on effective parasite management and thereby guiding the development of strategies to resolve and overcome such real-world complexities. In particular, we underscore how this approach can provide a link between ecological science and policy by revealing novel tools and measures to appraise and enhance the biological controllability or eradicability of parasitic diseases. We conclude by emphasizing an urgent need to develop and apply flexible adaptive management frameworks informed by mathematical models that are based on learning and reducing uncertainty using monitoring data, apply phased or sequential decision-making to address extant uncertainty and focus on developing ecologically resilient management strategies, in ongoing efforts to control or eliminate filariasis and other parasitic diseases in resource-poor communities.
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Meyrowitsch DW, Simonsen PE, Garred P, Dalgaard M, Magesa SM, Alifrangis M. Association between mannose-binding lectin polymorphisms and Wuchereria bancrofti infection in two communities in North-Eastern Tanzania. Am J Trop Med Hyg 2010; 82:115-20. [PMID: 20065005 DOI: 10.4269/ajtmh.2010.09-0342] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The association between selected mannose-binding lectin (MBL) genotype polymorphisms and Wuchereria bancrofti infection status was assessed among individuals whose infection status had been monitored for three decades. Blood samples were collected in 2006 and examined for polymorphisms in the mbl-2 gene and for W. bancrofti-specific circulating filarial antigen (CFA) status. Logistic regression analysis showed a significant association between MBL genotype and CFA status, with low-expression MBL genotype individuals being almost three times more likely to be CFA positive than high-expression MBL genotype individuals (odds ratio [OR] = 2.90). When individuals' filarial infection (microfilaria) status in 1975 was included in the analyses, the gain of new infections between the two examination points was almost 10 times higher among individuals with low than among those with high MBL expression genotype (OR = 9.51). The susceptibility to W. bancrofti infection thus appears to be significantly affected by the MBL expression genotype of the host.
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Affiliation(s)
- Dan W Meyrowitsch
- Section of Health Services Research, Department of Public Health, University of Copenhagen, Denmark.
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Harnett MM, Melendez AJ, Harnett W. The therapeutic potential of the filarial nematode-derived immunodulator, ES-62 in inflammatory disease. Clin Exp Immunol 2009; 159:256-67. [PMID: 19968663 DOI: 10.1111/j.1365-2249.2009.04064.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The dramatic recent rise in the incidence of allergic or autoimmune inflammatory diseases in the West has been proposed to reflect the lack of appropriate priming of the immune response by infectious agents such as parasitic worms during childhood. Consistent with this, there is increasing evidence supporting an inverse relationship between worm infection and T helper type 1/17 (Th1/17)-based inflammatory disorders such as rheumatoid arthritis, inflammatory bowel disease, type 1 diabetes and multiple sclerosis. Perhaps more surprisingly, given that such worms often induce strong Th2-type immune responses, there also appears to be an inverse correlation between parasite load and atopy. These findings therefore suggest that the co-evolution of helminths with hosts, which has resulted in the ability of worms to modulate inflammatory responses to promote parasite survival, has also produced the benefit of protecting the host from pathological lesions arising from aggressive proinflammatory responses to infection or, indeed, aberrant inflammatory responses underlying autoimmune and allergic disorders. By focusing upon the properties of the filarial nematode-derived immunomodulatory molecule, ES-62, in this review we shall discuss the potential of exploiting the immunomodulatory products of parasitic worms to identify and develop novel therapeutics for inflammation.
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Affiliation(s)
- M M Harnett
- Division of Immunology, Infection and Inflammation, Glasgow Biomedical Centre, University of Glasgow, Glasgow, UK.
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Grabitzki J, Lochnit G. Immunomodulation by phosphocholine--biosynthesis, structures and immunological implications of parasitic PC-epitopes. Mol Immunol 2009; 47:149-63. [PMID: 19864025 DOI: 10.1016/j.molimm.2009.09.035] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 09/24/2009] [Indexed: 11/28/2022]
Abstract
Phosphocholine (PC) as a small haptenic molecule present on antigens of parasites can provoke various effects on immune cells leading to immunomodulation of the host's immune system. This immunomodulation not only allows long-term persistence but also prevents severe pathology due to down-regulation of cellular immune responses. Additionally, PC plays an important role for development and fertility of the parasites. To fully understand the mechanisms of immunomodulation the detailed knowledge of the biosynthesis of the PC-epitopes, their molecular structure and biological function has to be elucidated. The implication of parasite-specific transferases in the biosynthesis of the PC-epitopes and the sensitivity of parasites towards disruption of the choline metabolism offers new perspectives for the development of anti-parasitic drugs and therapies. Furthermore, the immunomodulation provoked by PC-epitopes preventing inflammatory reactions may be useful in the treatment of inflammatory diseases. This review summarizes the current knowledge on the biosynthesis of PC-epitopes, their structures and immunological implications.
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Affiliation(s)
- Julia Grabitzki
- Institute of Biochemistry, Faculty of Medicine, University of Giessen, Germany
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Immunomodulatory activity and therapeutic potential of the filarial nematode secreted product, ES-62. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 666:88-94. [PMID: 20054977 DOI: 10.1007/978-1-4419-1601-3_7] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
ES-62 is a protein that is actively secreted by filarial nematodes during parasitism of the vertebrate host. The molecule is able to directly interact with a number of cells of the immune system including B-lymphocytes, dendritic cells, macrophages and mast cells. Interaction appears to be dependent on complexing with TLR4 and results in modulation of the activity of a number of signal transduction molecules including MAP kinases, PI-3 kinase and NF-kappaB. Immunomodulatory activity of ES-62 appears to be largely due to the presence of phosphorylcholine (PC) moieties covalently attached to N-type glycans. The net effect of ES-62's interaction with the immune system is the generation of an anti-inflammatory immunological phenotype. As a consequence of this, ES-62 demonstrates striking drug-like activity in models of disease associated with aberrant inflammation, in particular those associated with autoimmunity and allergy.
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LYMFASIM, a simulation model for predicting the impact of lymphatic filariasis control: quantification for African villages. Parasitology 2008; 135:1583-98. [PMID: 19006602 DOI: 10.1017/s0031182008000437] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
LYMFASIM is a simulation model for lymphatic filariasis transmission and control. We quantified its parameters to simulate Wuchereria bancrofti transmission by Anopheles mosquitoes in African villages, using a wide variety of reported data. The developed model captures the general epidemiological patterns, but also the differences between communities. It was calibrated to represent the relationship between mosquito biting rate and the prevalence of microfilariae (mf) in the human population, the age-pattern in mf prevalence, and the relation between mf prevalence and geometric mean mf intensity. Explorative simulations suggest that the impact of mass treatment depends strongly on the mosquito biting rate and on the assumed coverage, compliance and efficacy. Our sensitivity analysis showed that some biological parameters strongly influence the predicted equilibrium pre-treatment mf prevalence (e.g. the lifespan of adult worms and mf). Other parameters primarily affect the post-treatment trends (e.g. severity of density dependence in the mosquito uptake of infection from the human blood, between-person variability in exposure to mosquito bites). The longitudinal data, which are being collected for evaluation of ongoing elimination programmes, can help to further validate the model. The model can help to assess when ongoing elimination activities in African populations can be stopped and to design surveillance schemes. It can be a valuable tool for decision making in the Global Programme to Eliminate Lymphatic Filariasis.
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Abstract
Incidence of allergic diseases such as asthma has increased at an alarming rate in Western countries in the past few decades. However, in parts of the world in which parasitic nematode infections are highly prevalent, allergy remains uncommon. Hence, it has been postulated that nematodes offer humans protection against this type of disease. This article reviews the evidence to support this idea, considering data from human studies and results from investigations into the protective effects of nematodes in animal models of allergic disease. The evidence strongly favors a protective role for nematodes; thus, the search is on to find the molecules involved, with a view toward using them for therapeutic purposes. The article also describes the nature and mode of action of recently characterized nematode-derived molecules with antiallergic properties and highlights their therapeutic efficacy in allergy models.
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41
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HARNETT W, HARNETT MM. Lymphocyte hyporesponsiveness during filarial nematode infection. Parasite Immunol 2008; 30:447-53. [DOI: 10.1111/j.1365-3024.2008.01045.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
There has been an alarming increase in the incidence of autoimmune and allergic diseases in Western countries in the past few decades. However, in countries endemic for parasitic helminth infections, such diseases remain relatively rare. Hence, it has been hypothesised that helminths may protect against the development of autoimmunity and allergy. This article reviews the evidence supporting this idea with respect to helminths of the phylum Nematoda (nematodes), considering data from human studies and animal models of inflammatory disease. The nature and mode of action of nematode-derived molecules with immunomodulatory properties are considered, and their therapeutic efficacy in models of autoimmunity and allergy described. The recent and future use of nematodes and their products in treating human disease are also discussed.
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Affiliation(s)
- William Harnett
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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Harnett W, Harnett MM. Filarial nematode secreted product ES-62 is an anti-inflammatory agent: therapeutic potential of small molecule derivatives and ES-62 peptide mimetics. Clin Exp Pharmacol Physiol 2007; 33:511-8. [PMID: 16700887 DOI: 10.1111/j.1440-1681.2006.04400.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
1. The 'hygiene hypothesis' postulates that the recent increased incidence of allergic or autoimmune diseases (e.g. asthma, type I diabetes) in the West reflects an absence of appropriate priming of the immune response by infectious agents, such as parasitic worms, during childhood. 2. Consistent with this, it has long been recognized that several autoimmune disorders, such as rheumatoid arthritis (RA), a T helper (Th) 1-mediated autoimmune disease characterized by excess production of pro-inflammatory cytokines, such as tumour necrosis factor-alpha, exhibit reduced incidence and severity in geographical regions with high parasite load, suggesting that environmental factors may subtly alter disease progression. 3. Infection with worms also appears to suppress Th2-biased inflammatory disorders, such as asthma, because there also appears to be an inverse correlation between parasite load and atopy. This is perhaps more surprising, given that helminths often induce strong Th2-type immune responses characterized by release of specific cytokines, such as interleukin (IL)-4, IL-5 and IL-13. 4. Therefore, these findings suggest that the co-evolution of helminths with hosts, which has resulted in the ability of worms to modulate inflammatory responses in order to promote parasite survival, may also have generated a predisposition for the host to develop autoimmunity and allergy in the absence of infection. 5. The mechanisms underlying such immunomodulation are not clear, but appear to involve the release of parasite-derived molecules that allow the worms to modulate or evade the host immune response by a number of mechanisms, including skewing of cytokine responses and the induction of T regulatory cells. 6. In the present review we discuss the properties of one such filarial nematode-derived immunomodulatory molecule, namely ES-62, its anti-inflammatory action and the therapeutic potential of small molecule derivatives and peptides that mimic its action.
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Affiliation(s)
- William Harnett
- Department of Immunology, University of Strathclyde, Glasgow, UK.
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Ramaiah KD, Vanamail P, Das PK. Changes in Wuchereria bancrofti infection in a highly endemic community following 10 rounds of mass administration of diethylcarbamazine. Trans R Soc Trop Med Hyg 2007; 101:250-5. [PMID: 16890256 DOI: 10.1016/j.trstmh.2006.05.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 05/09/2006] [Accepted: 05/09/2006] [Indexed: 11/21/2022] Open
Abstract
Mass drug administration (MDA) is the principal strategy of the programme to eliminate lymphatic filariasis (LF). Evaluation of MDA in highly endemic 'sentinel' communities is necessary to understand its impact on LF infection. This study examined the changes in Wuchereria bancrofti infection following 10 rounds of annual mass administration of diethylcarbamazine (DEC) in a highly endemic community. The mean number of DEC treatments received per adult in the community was 7.4+/-2.0. Following 10 rounds of DEC administration, the number of microfilaria (mf) carriers fell from 565 to 55. None of the pre-MDA amicrofilaraemic individuals showed circulating filarial antigen (CFA). However, 54.5% of the pre-MDA microfilaraemic individuals were positive for CFA. All the pre-MDA high intensity mf carriers continued to be positive for CFA, and some of them also showed blood mf. These patients are the most difficult to be cured by MDA and were distributed in 8.2% of the households. All the children born during the last 7 years of the MDA programme were negative for CFA. The study suggests that six to seven DEC treatments per individual suppresses microfilaraemia, except in some people with heavy infection, and repeated MDA has very good potential to prevent infection in children.
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Affiliation(s)
- K D Ramaiah
- Vector Control Research Centre (Indian Council of Medical Research), Medical Complex, Indira Nagar, Pondicherry 605006, India.
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Hise AG, Daehnel K, Gillette-Ferguson I, Cho E, McGarry HF, Taylor MJ, Golenbock DT, Fitzgerald KA, Kazura JW, Pearlman E. Innate Immune Responses to EndosymbioticWolbachiaBacteria inBrugia malayiandOnchocerca volvulusAre Dependent on TLR2, TLR6, MyD88, and Mal, but Not TLR4, TRIF, or TRAM. THE JOURNAL OF IMMUNOLOGY 2007; 178:1068-76. [PMID: 17202370 DOI: 10.4049/jimmunol.178.2.1068] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The discovery that endosymbiotic Wolbachia bacteria play an important role in the pathophysiology of diseases caused by filarial nematodes, including lymphatic filariasis and onchocerciasis (river blindness) has transformed our approach to these disabling diseases. Because these parasites infect hundreds of millions of individuals worldwide, understanding host factors involved in the pathogenesis of filarial-induced diseases is paramount. However, the role of early innate responses to filarial and Wolbachia ligands in the development of filarial diseases has not been fully elucidated. To determine the role of TLRs, we used cell lines transfected with human TLRs and macrophages from TLR and adaptor molecule-deficient mice and evaluated macrophage recruitment in vivo. Extracts of Brugia malayi and Onchocerca volvulus, which contain Wolbachia, directly stimulated human embryonic kidney cells expressing TLR2, but not TLR3 or TLR4. Wolbachia containing filarial extracts stimulated cytokine production in macrophages from C57BL/6 and TLR4(-/-) mice, but not from TLR2(-/-) or TLR6(-/-) mice. Similarly, macrophages from mice deficient in adaptor molecules Toll/IL-1R domain-containing adaptor-inducing IFN-beta and Toll/IL-1R domain-containing adaptor-inducing IFN-beta-related adaptor molecule produced equivalent cytokines as wild-type cells, whereas responses were absent in macrophages from MyD88(-/-) and Toll/IL-1R domain-containing adaptor protein (TIRAP)/MyD88 adaptor-like (Mal) deficient mice. Isolated Wolbachia bacteria demonstrated similar TLR and adaptor molecule requirements. In vivo, macrophage migration to the cornea in response to filarial extracts containing Wolbachia was dependent on TLR2 but not TLR4. These results establish that the innate inflammatory pathways activated by endosymbiotic Wolbachia in B. malayi and O. volvulus filaria are dependent on TLR2-TLR6 interactions and are mediated by adaptor molecules MyD88 and TIRAP/Mal.
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Affiliation(s)
- Amy G Hise
- Center for Global Health and Diseases and Department of Ophthalmology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA.
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de Kraker MEA, Stolk WA, van Oortmarssen GJ, Habbema JDF. Model-based analysis of trial data: microfilaria and worm-productivity loss after diethylcarbamazine-albendazole or ivermectin-albendazole combination therapy against Wuchereria bancrofti. Trop Med Int Health 2006; 11:718-28. [PMID: 16640625 DOI: 10.1111/j.1365-3156.2006.01606.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVES To determine the efficacies of combinations of ivermectin or diethylcarbamazine and albendazole, which are recommended for use in mass treatment programmes against lymphatic filariasis. METHOD Review of published trends in microfilarial (mf) intensities after treatment with these combination therapies. By fitting a mathematical model of treatment effects to the trial data, we quantified the efficacy of treatment, distinguishing between the killing of mf (mf loss) and a reduction in mf production by adult worms (worm-productivity loss). After diethylcarbamazine-albendazole treatment mf density dropped immediately, then slowly but steadily decreased further (four trials). After ivermectin-albendazole treatment, mf densities immediately dropped to near-zero levels, followed by a small increase (five trials). For diethylcarbamazine-albendazole treatment the average mf loss was approximately 83% (ranging from 54% to 100% in the different studies) and worm-productivity loss was 100% (in all studies). For ivermectin-albendazole treatment, average mf loss was 100% (ranging from 98% to 100%) and worm productivity loss was 96% (ranging from 83% to 100%). The effects were dose-dependent. Sensitivity analysis showed that the estimates did not depend on assumptions on worm lifespan or premature period and little on assumptions on mf lifespan. CONCLUSION The two therapies differ with respect to their direct effect on mf, but both are highly effective against adult worms. If mass treatment with these combination therapies achieves high coverage, they can have a large impact on lymphatic filariasis transmission.
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Affiliation(s)
- Marlieke E A de Kraker
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, The Netherlands
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47
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Stolk WA, de Vlas SJ, Habbema JDF. Advances and challenges in predicting the impact of lymphatic filariasis elimination programmes by mathematical modelling. FILARIA JOURNAL 2006; 5:5. [PMID: 16569234 PMCID: PMC1448203 DOI: 10.1186/1475-2883-5-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Accepted: 03/28/2006] [Indexed: 11/17/2022]
Abstract
Mathematical simulation models for transmission and control of lymphatic filariasis are useful tools for studying the prospects of lymphatic filariasis elimination. Two simulation models are currently being used. The first, EPIFIL, is a population-based, deterministic model that simulates average trends in infection intensity over time. The second, LYMFASIM, is an individual-based, stochastic model that simulates acquisition and loss of infection for each individual in the simulated population, taking account of individual characteristics. For settings like Pondicherry (India), where Wuchereria bancrofti infection is transmitted by Culex quinquefasciatus, the models give similar predictions of the coverage and number of treatment rounds required to bring microfilaraemia prevalence below a level of 0.5%. Nevertheless, published estimates of the duration of mass treatment required for elimination differed, due to the use of different indicators for elimination (EPIFIL: microfilaraemia prevalence < 0.5% after the last treatment; LYMFASIM: reduction of microfilaraemia prevalence to zero, within 40 years after the start of mass treatment). The two main challenges for future modelling work are: 1) quantification and validation of the models for other regions, for investigation of elimination prospects in situations with other vector-parasite combinations and endemicity levels than in Pondicherry; 2) application of the models to address a range of programmatic issues related to the monitoring and evaluation of ongoing control programmes. The models' usefulness could be enhanced by several extensions; inclusion of different diagnostic tests and natural history of disease in the models is of particular relevance.
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Affiliation(s)
- Wilma A Stolk
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - Sake J de Vlas
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | - J Dik F Habbema
- Department of Public Health, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
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Dreyer G, Addiss D, Norões J. Does longevity of adult Wuchereria bancrofti increase with decreasing intensity of parasite transmission? Insights from clinical observations. Trans R Soc Trop Med Hyg 2005; 99:883-92. [PMID: 16165175 DOI: 10.1016/j.trstmh.2005.05.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2005] [Revised: 05/05/2005] [Accepted: 05/26/2005] [Indexed: 10/25/2022] Open
Abstract
To interrupt transmission of Wuchereria bancrofti, a parasite that causes lymphatic filariasis, mass treatment of at-risk populations with antifilarial drugs is recommended for 4-6 years, the minimum estimated adult worm lifespan. Factors associated with adult worm longevity are unknown. In Recife, Brazil, we conducted a retrospective cohort study of 57 men whose adult W. bancrofti were not sensitive to diethylcarbamazine and who were followed with semi-annual physical examinations (to detect intrascrotal nodules, indicative of adult worm death) and ultrasound examinations (to detect the 'filaria dance sign' (FDS), indicative of living adult worms). After 5 years, the FDS remained detectable in 10 (24.4%) of 41 adult worm nests in 25 men from areas of high filariasis transmission intensity and in 30 (90.9%) of 33 nests in 32 men from areas of low transmission (P<0.001). New nodules and adult worm nests were detected only in men from high-transmission areas. Of 30 men who were microfilaria-positive initially and whose FDS remained detectable after 5 years of follow-up, 19 (63.3%) remained microfilaria-positive in 5 ml blood (mean density, 0.4 per ml). In conclusion, survival of adult W. bancrofti is inversely associated with transmission intensity. These findings have implications for filariasis elimination and research.
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Affiliation(s)
- Gerusa Dreyer
- Centro de Pesquisas Aggeu Magalhães, FIOCRUZ, and NEPAF, Hospital das Clínicas, Universidade Federal de Pernambuco, Av. Prof. Moraes Rego s/n, Cidade Universitária, CEP 50670-420, Recife PE, Brazil.
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Harnett W, Goodridge HS, Harnett MM. Subversion of immune cell signal transduction pathways by the secreted filarial nematode product, ES-62. Parasitology 2005; 130 Suppl:S63-8. [PMID: 16281993 DOI: 10.1017/s0031182005008164] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Filarial nematodes achieve longevity within the infected host by suppressing and modulating the host immune response. To do this, the worms actively secrete products that have been demonstrated to possess immunomodulatory properties. In this article we discuss the immunomodulatory effects of the phosphorylcholine-containing filarial nematode secreted glycoprotein ES-62. In particular we describe how it modulates intracellular signal transduction pathways in a number of different cells of the immune system, in particular B-lymphocytes, T-lymphocytes, macrophages and dendritic cells.
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Affiliation(s)
- W Harnett
- Department of Immunology, University of Strathclyde, Glasgow, UK.
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Egan CA, Houston KM, Alcocer MJC, Solovyova A, Tate R, Lochnit G, McInnes IB, Harnett MM, Geyer R, Byron O, Harnett W. Lack of immunological cross-reactivity between parasite-derived and recombinant forms of ES-62, a secreted protein of Acanthocheilonema viteae. Parasitology 2005; 132:263-74. [PMID: 16216137 DOI: 10.1017/s0031182005009005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2005] [Revised: 08/23/2005] [Accepted: 08/24/2005] [Indexed: 11/05/2022]
Abstract
The longevity of filarial nematodes is dependent on secreted immunomodulatory products. Previous investigation of one such product, ES-62, has suggested a critical role for post-translationally attached phosphorylcholine (PC) moieties. In order to further investigate this, ES-62 lacking PC was produced, using the Pichia pastoris recombinant gene expression system. Unlike parasite-derived ES-62, which is tetrameric the recombinant material was found to consist of a mixture of apparently stable tetramers, dimers and monomers. Nevertheless, the recombinant protein was considered to be an adequate PC-free ES-62 as it was recognized by existing antisera against the parasite-derived protein. However, subsequent to this, recognition of parasite-derived ES-62 by antibodies produced against the recombinant protein was found to be absent. In an attempt to explain this, recombinant ES-62 was subjected to structural analysis and was found to (i) contain 3 changes in amino acid composition; (ii) demonstrate significant alterations in glycosylation; (iii) show major differences in protein secondary structure. The effects of these alterations in relation to the observed change in immunogenicity were investigated and are discussed. The data presented clearly show that recognition by existing antibodies is insufficient proof that recombinant proteins can be used to mimic parasite-derived material in studies on nematode immunology and vaccination.
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Affiliation(s)
- C A Egan
- Department of Immunology, University of Strathclyde, Glasgow G4 0NR, UK
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