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Franco JR, Cecchi G, Paone M, Diarra A, Grout L, Kadima Ebeja A, Simarro PP, Zhao W, Argaw D. The elimination of human African trypanosomiasis: Achievements in relation to WHO road map targets for 2020. PLoS Negl Trop Dis 2022; 16:e0010047. [PMID: 35041668 PMCID: PMC8765662 DOI: 10.1371/journal.pntd.0010047] [Citation(s) in RCA: 50] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 12/02/2021] [Indexed: 11/19/2022] Open
Abstract
Background In the 20th century, epidemics of human African trypanosomiasis (HAT) ravaged communities in a number of African countries. The latest surge in disease transmission was recorded in the late 1990s, with more than 35,000 cases reported annually in 1997 and 1998. In 2013, after more than a decade of sustained control efforts and steady progress, the World Health Assembly resolved to target the elimination of HAT as a public health problem by 2020. We report here on recent progress towards this goal. Methodology/principal findings With 992 and 663 cases reported in 2019 and 2020 respectively, the first global target was amply achieved (i.e. fewer than 2,000 HAT cases/year). Areas at moderate or higher risk of HAT, where more than 1 case/10,000 people/year are reported, shrunk to 120,000 km2 for the five-year period 2016–2020. This reduction of 83% from the 2000–2004 baseline (i.e. 709,000 km2) is slightly below the target (i.e. 90% reduction). As a result, the second global target for HAT elimination as a public health problem cannot be considered fully achieved yet. The number of health facilities able to diagnose and treat HAT expanded (+9.6% compared to a 2019 survey), thus reinforcing the capacity for passive detection and improving epidemiological knowledge of the disease. Active surveillance for gambiense HAT was sustained. In particular, 2.8 million people were actively screened in 2019 and 1.6 million in 2020, the decrease in 2020 being mainly caused by COVID-19-related restrictions. Togo and Côte d’Ivoire were the first countries to be validated for achieving elimination of HAT as a public health problem at the national level; applications from three additional countries are under review by the World Health Organization (WHO). Conclusions/significance The steady progress towards the elimination of HAT is a testament to the power of multi-stakeholder commitment and coordination. At the end of 2020, the World Health Assembly endorsed a new road map for 2021–2030 that set new bold targets for neglected tropical diseases. While rhodesiense HAT remains among the diseases targeted for elimination as a public health problem, gambiense HAT is targeted for elimination of transmission. The goal for gambiense HAT is expected to be particularly arduous, as it might be hindered by cryptic reservoirs and a number of other challenges (e.g. further integration of HAT surveillance and control into national health systems, availability of skilled health care workers, development of more effective and adapted tools, and funding for and coordination of elimination efforts). Human African trypanosomiasis (HAT) is a lethal neglected tropical disease (NTD) transmitted by the bite of infected tsetse flies. The disease is also known as “sleeping sickness”. During the 20th century it caused enormous suffering in the endemic areas in sub-Saharan Africa. HAT transmission last soared in the late 1990s, triggering a renewed, coordinated and very successful control effort. In this paper, we present achievements towards HAT elimination, with a focus on the WHO road map targets for 2020. In particular, reported cases continue to decline, from over 30,000 cases per year at the turn of the century to 663 cases in 2020. Despite the impact of the COVID-19 pandemic, HAT surveillance was largely sustained, and the network of health facilities able to diagnose and treat the disease further expanded. Looking to the future, the World Health Organization (WHO) set bold new targets for HAT in its 2021–2030 road map for NTDs, namely: the elimination of transmission of gambiense HAT, which occurs in western and central Africa, and the elimination as a public health problem of rhodesiense HAT, which is found in eastern and southern Africa. The strong commitment of national health authorities and the international community will be essential if these goals are to be achieved.
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Affiliation(s)
- Jose R. Franco
- World Health Organization, Control of Neglected Tropical Diseases, Prevention Treatment and Care, Geneva, Switzerland
- * E-mail:
| | - Giuliano Cecchi
- Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Rome, Italy
| | - Massimo Paone
- Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Rome, Italy
| | - Abdoulaye Diarra
- World Health Organization, Regional Office for Africa, Communicable Disease Unit, Brazzaville, Congo
| | - Lise Grout
- World Health Organization, Control of Neglected Tropical Diseases, Prevention Treatment and Care, Geneva, Switzerland
| | - Augustin Kadima Ebeja
- World Health Organization, Regional Office for Africa, Communicable Disease Unit, Brazzaville, Congo
| | - Pere P. Simarro
- Consultant, World Health Organization, Control of Neglected Tropical Diseases, Innovative and Intensified Disease Management, Geneva, Switzerland
| | - Weining Zhao
- Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Rome, Italy
| | - Daniel Argaw
- World Health Organization, Control of Neglected Tropical Diseases, Prevention Treatment and Care, Geneva, Switzerland
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Bessell PR, Esterhuizen J, Lehane MJ, Longbottom J, Mugenyi A, Selby R, Tirados I, Torr SJ, Waiswa C, Wamboga C, Hope A. Estimating the impact of Tiny Targets in reducing the incidence of Gambian sleeping sickness in the North-west Uganda focus. Parasit Vectors 2021; 14:410. [PMID: 34407867 PMCID: PMC8371857 DOI: 10.1186/s13071-021-04889-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 07/22/2021] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Riverine species of tsetse (Glossina) transmit Trypanosoma brucei gambiense, which causes Gambian human African trypanosomiasis (gHAT), a neglected tropical disease. Uganda aims to eliminate gHAT as a public health problem through detection and treatment of human cases and vector control. The latter is being achieved through the deployment of 'Tiny Targets', insecticide-impregnated panels of material which attract and kill tsetse. We analysed the spatial and temporal distribution of cases of gHAT in Uganda during the period 2010-2019 to assess whether Tiny Targets have had an impact on disease incidence. METHODS To quantify the deployment of Tiny Targets, we mapped the rivers and their associated watersheds in the intervention area. We then categorised each of these on a scale of 0-3 according to whether Tiny Targets were absent (0), present only in neighbouring watersheds (1), present in the watersheds but not all neighbours (2), or present in the watershed and all neighbours (3). We overlaid all cases that were diagnosed between 2000 and 2020 and assessed whether the probability of finding cases in a watershed changed following the deployment of targets. We also estimated the number of cases averted through tsetse control. RESULTS We found that following the deployment of Tiny Targets in a watershed, there were fewer cases of HAT, with a sampled error probability of 0.007. We estimate that during the intervention period 2012-2019 we should have expected 48 cases (95% confidence intervals = 40-57) compared to the 36 cases observed. The results are robust to a range of sensitivity analyses. CONCLUSIONS Tiny Targets have reduced the incidence of gHAT by 25% in north-western Uganda.
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Affiliation(s)
| | - Johan Esterhuizen
- Liverpool School of Tropical Medicine (LSTM), Pembroke Place, Liverpool, UK
| | - Michael J. Lehane
- Liverpool School of Tropical Medicine (LSTM), Pembroke Place, Liverpool, UK
| | - Joshua Longbottom
- Liverpool School of Tropical Medicine (LSTM), Pembroke Place, Liverpool, UK
| | - Albert Mugenyi
- Coordinating Office for Control of Trypanosomiasis in Uganda (COCTU), Kampala, Uganda
| | - Richard Selby
- Liverpool School of Tropical Medicine (LSTM), Pembroke Place, Liverpool, UK
| | - Inaki Tirados
- Liverpool School of Tropical Medicine (LSTM), Pembroke Place, Liverpool, UK
| | - Steve J. Torr
- Liverpool School of Tropical Medicine (LSTM), Pembroke Place, Liverpool, UK
| | - Charles Waiswa
- Coordinating Office for Control of Trypanosomiasis in Uganda (COCTU), Kampala, Uganda
| | | | - Andrew Hope
- Liverpool School of Tropical Medicine (LSTM), Pembroke Place, Liverpool, UK
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Abstract
Trypanosomiasis has been recognized as a scourge in sub-Saharan Africa for centuries. The disease, caused by protozoan parasites of the Trypanosoma genus, is a major cause of mortality and morbidity in animals and man. Human African trypanosomiasis (HAT), or sleeping sickness, results from infections with T. brucei (b.) gambiense or T. b. rhodesiense with T. b. gambiense accounting for over 95% of infections. Historically there have been major epidemics of the infection, followed by periods of relative disease control. As a result of concerted disease surveillance and treatment programmes, implemented over the last two decades, there has been a significant reduction in the number of cases of human disease reported. However, the recent identification of asymptomatic disease carriers gives cause for some concern. The parasites evade the host immune system by switching their surface coat, comprised of variable surface glycoprotein (VSG). In addition, they have evolved a variety of strategies, including the production of serum resistance associated protein (SRA) and T. b. gambiense-specific glycoprotein (TgsGP) to counter host defense molecules. Infection with either disease variant results in an early haemolymphatic-stage followed by a late encephalitic-stage when the parasites migrate into the CNS. The clinical features of HAT are diverse and non-specific with early-stage symptoms common to several infections endemic within sub-Saharan Africa which may result in a delayed or mistaken diagnosis. Migration of the parasites into the CNS marks the onset of late-stage disease. Diverse neurological manifestations can develop accompanied by a neuroinflammatory response, comprised of astrocyte activation, and inflammatory cell infiltration. However, the transition between the early and late-stage is insidious and accurate disease staging, although crucial to optimize chemotherapy, remains problematic with neurological symptoms and neuroinflammatory changes recorded in early-stage infections. Further research is required to develop better diagnostic and staging techniques as well as safer more efficacious drug regimens. Clearer information is also required concerning disease pathogenesis, specifically regarding asymptomatic carriers and the mechanisms employed by the trypanosomes to facilitate progression to the CNS and precipitate late-stage disease. Without progress in these areas it may prove difficult to maintain current control over this historically episodic disease.
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Affiliation(s)
- Peter G. E. Kennedy
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Jean Rodgers
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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Kaboré J, Camara O, Koffi M, Sanou D, Ilboudo H, Sakandé H, Camara M, De Meeûs T, Ravel S, Belem AMG, MacLeod A, Bucheton B, Jamonneau V, Thévenon S. Differences in pathogenicity and virulence of Trypanosoma brucei gambiense field isolates in experimentally infected Balb/C mice. Infect Genet Evol 2018; 63:269-276. [PMID: 29807131 DOI: 10.1016/j.meegid.2018.05.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 05/21/2018] [Accepted: 05/22/2018] [Indexed: 11/29/2022]
Abstract
Trypanosoma brucei gambiense (T. b. gambiense) is the major causative agent of human African trypanosomiasis (HAT). A great variety of clinical outcomes have been observed in West African foci, probably due to complex host-parasite interactions. In order to separate the roles of parasite genetic diversity and host variability, we have chosen to precisely characterize the pathogenicity and virulence of T. b. gambiense field isolates in a mouse model. Thirteen T. b. gambiense strains were studied in experimental infections, with 20 Balb/C infected mice per isolate. Mice were monitored for 30 days, in which mortality, parasitemia, anemia, and weight were recorded. Mortality rate, prepatent period, and maximum parasitemia were estimated, and a survival analysis was performed to compare strain pathogenicity. Mixed models were used to assess parasitemia dynamics, weight, and changes in Packed Cell Volume (PCV). Finally, a multivariate analysis was performed to infer relationships between all variables. A large phenotypic diversity was observed. Pathogenicity was highly variable, ranging from strains that kill their host within 9 days to a non-pathogenic strain (no deaths during the experiment). Virulence was also variable, with maximum parasitemia values ranging from 42 million to 1 billion trypanosomes/ml. Reduced PCV and weight occurred in the first two weeks of the infection, with the exception of two strains. Finally, the global analysis highlighted three groups of strains: a first group with highly pathogenic strains showing an early mortality associated with a short prepatent period; a second group of highly virulent strains with intermediate pathogenicity; and a third group of isolates characterized by low pathogenicity and virulence patterns. Such biological differences could be related to the observed clinical diversity in HAT. A better understanding of the biological pathways underlying the observed phenotypic diversity could thus help to clarify the complex nature of the host-parasite interactions that determine the resistance/susceptibility status to T. brucei gambiense.
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Affiliation(s)
- Jacques Kaboré
- Centre International de Recherche-Développement sur l'Elevage en zone Subhumide (CIRDES), 01 BP 454, Bobo-Dioulasso 01, Burkina Faso; Université NAZI BONI de Bobo-Dioulasso, UFR Sciences et Techniques, 01 BP 1091, Bobo-Dioulasso 01, Burkina Faso.
| | - Oumou Camara
- Programme National de Lutte contre la THA, BP 851, Conakry, Guinea.
| | - Mathurin Koffi
- Université Jean Lorougnon Guédé, UFR Environnement, BP 150, Daloa, Côte d'Ivoire.
| | - Djénéba Sanou
- Université NAZI BONI de Bobo-Dioulasso, UFR Sciences et Techniques, 01 BP 1091, Bobo-Dioulasso 01, Burkina Faso.
| | - Hamidou Ilboudo
- Programme National de Lutte contre la THA, BP 851, Conakry, Guinea.
| | - Hassane Sakandé
- Centre International de Recherche-Développement sur l'Elevage en zone Subhumide (CIRDES), 01 BP 454, Bobo-Dioulasso 01, Burkina Faso.
| | - Mamadou Camara
- Programme National de Lutte contre la THA, BP 851, Conakry, Guinea.
| | | | - Sophie Ravel
- INTERTRYP, Univ Montpellier, CIRAD, IRD, Montpellier, France.
| | - Adrien Marie Gaston Belem
- Université NAZI BONI de Bobo-Dioulasso, UFR Sciences et Techniques, 01 BP 1091, Bobo-Dioulasso 01, Burkina Faso.
| | - Annette MacLeod
- Wellcome Center for Molecular Parasitology, University of Glasgow, 464 Bearsden Road, Glasgow G60 1QH, UK.
| | - Bruno Bucheton
- INTERTRYP, Univ Montpellier, CIRAD, IRD, Montpellier, France.
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Devlin R, Marques CA, McCulloch R. Does DNA replication direct locus-specific recombination during host immune evasion by antigenic variation in the African trypanosome? Curr Genet 2017; 63:441-449. [PMID: 27822899 PMCID: PMC5422504 DOI: 10.1007/s00294-016-0662-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 10/26/2016] [Accepted: 10/27/2016] [Indexed: 12/14/2022]
Abstract
All pathogens must survive host immune attack and, amongst the survival strategies that have evolved, antigenic variation is a particularly widespread reaction to thwart adaptive immunity. Though the reactions that underlie antigenic variation are highly varied, recombination by gene conversion is a widespread approach to immune survival in bacterial and eukaryotic pathogens. In the African trypanosome, antigenic variation involves gene conversion-catalysed movement of a huge number of variant surface glycoprotein (VSG) genes into a few telomeric sites for VSG expression, amongst which only a single site is actively transcribed at one time. Genetic evidence indicates VSG gene conversion has co-opted the general genome maintenance reaction of homologous recombination, aligning the reaction strategy with targeted rearrangements found in many organisms. What is less clear is how gene conversion might be initiated within the locality of the VSG expression sites. Here, we discuss three emerging models for VSG switching initiation and ask how these compare with processes for adaptive genome change found in other organisms.
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Affiliation(s)
- Rebecca Devlin
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
| | - Catarina A Marques
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK
- Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, UK
| | - Richard McCulloch
- The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
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Wamwiri FN, Changasi RE. Tsetse Flies (Glossina) as Vectors of Human African Trypanosomiasis: A Review. Biomed Res Int 2016; 2016:6201350. [PMID: 27034944 PMCID: PMC4789378 DOI: 10.1155/2016/6201350] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 02/02/2016] [Accepted: 02/04/2016] [Indexed: 11/18/2022]
Abstract
Human African Trypanosomiasis (HAT) transmitted by the tsetse fly continues to be a public health issue, despite more than a century of research. There are two types of the disease, the chronic gambiense and the acute rhodesiense-HAT. Fly abundance and distribution have been affected by changes in land-use patterns and climate. However, disease transmission still continues. Here, we review some aspects of HAT ecoepidemiology in the context of altered infestation patterns and maintenance of the transmission cycle as well as emerging options in disease and vector control.
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Affiliation(s)
- Florence Njeri Wamwiri
- Kenya Agricultural and Livestock Research Organisation, Biotechnology Research Institute, P.O. Box 362, Muguga 00902, Kenya
| | - Robert Emojong Changasi
- Kenya Agricultural and Livestock Research Organisation, Biotechnology Research Institute, P.O. Box 362, Muguga 00902, Kenya
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Sutherland CS, Yukich J, Goeree R, Tediosi F. A literature review of economic evaluations for a neglected tropical disease: human African trypanosomiasis ("sleeping sickness"). PLoS Negl Trop Dis 2015; 9:e0003397. [PMID: 25654605 PMCID: PMC4318581 DOI: 10.1371/journal.pntd.0003397] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Human African trypanosomiasis (HAT) is a disease caused by infection with the parasite Trypanosoma brucei gambiense or T. b. rhodesiense. It is transmitted to humans via the tsetse fly. Approximately 70 million people worldwide were at risk of infection in 1995, and approximately 20,000 people across Africa are infected with HAT. The objective of this review was to identify existing economic evaluations in order to summarise cost-effective interventions to reduce, control, or eliminate the burden of HAT. The studies included in the review were compared and critically appraised in order to determine if there were existing standardised methods that could be used for economic evaluation of HAT interventions or if innovative methodological approaches are warranted. A search strategy was developed using keywords and was implemented in January 2014 in several databases. The search returned a total of 2,283 articles. After two levels of screening, a total of seven economic evaluations were included and underwent critical appraisal using the Scottish Intercollegiate Guidelines Network (SIGN) Methodology Checklist 6: Economic Evaluations. Results from the existing studies focused on the cost-effectiveness of interventions for the control and reduction of disease transmission. Modelling was a common method to forecast long-term results, and publications focused on interventions by category, such as case detection, diagnostics, drug treatments, and vector control. Most interventions were considered cost-effective based on the thresholds described; however, the current treatment, nifurtomix-eflornithine combination therapy (NECT), has not been evaluated for cost-effectiveness, and considerations for cost-effective strategies for elimination have yet to be completed. Overall, the current evidence highlights the main components that play a role in control; however, economic evaluations of HAT elimination strategies are needed to assist national decision makers, stakeholders, and key funders. These analyses would be of use, as HAT is currently being prioritized as a neglected tropical disease (NTD) to reach elimination by 2020.
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Affiliation(s)
- C. Simone Sutherland
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- * E-mail:
| | - Joshua Yukich
- Department of Global Health Systems and Development, Tulane University School of Public Health and Tropical Medicine, New Orleans, Louisiana, United States of America
| | - Ron Goeree
- Programs for Assessment of Technology in Health (PATH) Research Institute, St. Joseph’s Healthcare Hamilton, Hamilton, Ontario, Canada
- Department of Clinical Epidemiology & Biostatistics, McMaster University, Hamilton, Ontario, Canada
| | - Fabrizio Tediosi
- Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Centre for Research on Health and Social Care Management (CERGAS), Università Bocconi, Milano, Italy
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Capewell P, Clucas C, DeJesus E, Kieft R, Hajduk S, Veitch N, Steketee PC, Cooper A, Weir W, MacLeod A. The TgsGP gene is essential for resistance to human serum in Trypanosoma brucei gambiense. PLoS Pathog 2013; 9:e1003686. [PMID: 24098129 PMCID: PMC3789759 DOI: 10.1371/journal.ppat.1003686] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 08/22/2013] [Indexed: 11/25/2022] Open
Abstract
Trypanosoma brucei gambiense causes 97% of all cases of African sleeping sickness, a fatal disease of sub-Saharan Africa. Most species of trypanosome, such as T. b. brucei, are unable to infect humans due to the trypanolytic serum protein apolipoprotein-L1 (APOL1) delivered via two trypanosome lytic factors (TLF-1 and TLF-2). Understanding how T. b. gambiense overcomes these factors and infects humans is of major importance in the fight against this disease. Previous work indicated that a failure to take up TLF-1 in T. b. gambiense contributes to resistance to TLF-1, although another mechanism is required to overcome TLF-2. Here, we have examined a T. b. gambiense specific gene, TgsGP, which had previously been suggested, but not shown, to be involved in serum resistance. We show that TgsGP is essential for resistance to lysis as deletion of TgsGP in T. b. gambiense renders the parasites sensitive to human serum and recombinant APOL1. Deletion of TgsGP in T. b. gambiense modified to uptake TLF-1 showed sensitivity to TLF-1, APOL1 and human serum. Reintroducing TgsGP into knockout parasite lines restored resistance. We conclude that TgsGP is essential for human serum resistance in T. b. gambiense. Trypanosoma brucei gambiense causes 97% of all cases of African sleeping sickness, a fatal disease of sub-Saharan Africa. Most species of trypanosome, such as T. b. brucei, are unable to infect humans due to trypanolytic factors in human serum. Understanding how T. b. gambiense overcomes these factors and infects humans is of major importance in the fight against this disease. Previous work indicated that a failure to take up some trypanolytic factors by T. b. gambiense contributes to resistance, although other mechanisms are involved. Here, we have examined a T. b. gambiense specific gene, TgsGP, for involvement in resistance to human serum. We show that TgsGP is essential for resistance to lysis as deletion of TgsGP in T. b. gambiense renders the parasites sensitive to most trypanolytic factors. TgsGP deletion in T. b. gambiense modified to overcome the sub-species trait to reduce uptake of some trypanolytic factors resulted in sensitivity to all trypanolytic factors. Reintroducing TgsGP into these knockout parasite lines restored resistance. We conclude that TgsGP is essential for human serum resistance in T. b. gambiense.
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Affiliation(s)
- Paul Capewell
- Wellcome Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Caroline Clucas
- Wellcome Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Eric DeJesus
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Rudo Kieft
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Stephen Hajduk
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Nicola Veitch
- Wellcome Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Pieter C. Steketee
- Wellcome Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Anneli Cooper
- Wellcome Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - William Weir
- Wellcome Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Annette MacLeod
- Wellcome Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- * E-mail:
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Tiberti N, Lejon V, Hainard A, Courtioux B, Robin X, Turck N, Kristensson K, Matovu E, Enyaru JC, Mumba Ngoyi D, Krishna S, Bisser S, Ndung′u JM, Büscher P, Sanchez JC. Neopterin is a cerebrospinal fluid marker for treatment outcome evaluation in patients affected by Trypanosoma brucei gambiense sleeping sickness. PLoS Negl Trop Dis 2013; 7:e2088. [PMID: 23469311 PMCID: PMC3585011 DOI: 10.1371/journal.pntd.0002088] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 01/19/2013] [Indexed: 11/30/2022] Open
Abstract
Background Post-therapeutic follow-up is essential to confirm cure and to detect early treatment failures in patients affected by sleeping sickness (HAT). Current methods, based on finding of parasites in blood and cerebrospinal fluid (CSF) and counting of white blood cells (WBC) in CSF, are imperfect. New markers for treatment outcome evaluation are needed. We hypothesized that alternative CSF markers, able to diagnose the meningo-encephalitic stage of the disease, could also be useful for the evaluation of treatment outcome. Methodology/Principal findings Cerebrospinal fluid from patients affected by Trypanosoma brucei gambiense HAT and followed for two years after treatment was investigated. The population comprised stage 2 (S2) patients either cured or experiencing treatment failure during the follow-up. IgM, neopterin, B2MG, MMP-9, ICAM-1, VCAM-1, CXCL10 and CXCL13 were first screened on a small number of HAT patients (n = 97). Neopterin and CXCL13 showed the highest accuracy in discriminating between S2 cured and S2 relapsed patients (AUC 99% and 94%, respectively). When verified on a larger cohort (n = 242), neopterin resulted to be the most efficient predictor of outcome. High levels of this molecule before treatment were already associated with an increased risk of treatment failure. At six months after treatment, neopterin discriminated between cured and relapsed S2 patients with 87% specificity and 92% sensitivity, showing a higher accuracy than white blood cell numbers. Conclusions/Significance In the present study, neopterin was highlighted as a useful marker for the evaluation of the post-therapeutic outcome in patients suffering from sleeping sickness. Detectable levels of this marker in the CSF have the potential to shorten the follow-up for HAT patients to six months after the end of the treatment. The reduction of the number of lumbar punctures performed during the follow-up of patients affected by sleeping sickness (HAT) is considered a research priority. Follow-up, consisting of the examination of cerebrospinal fluid (CSF) for presence of parasites and for the number of leukocytes, is necessary to assess treatment outcome. However, diagnosis of treatment failure is still imperfect and WHO encourages improvements in defining criteria. Many studies have attempted to standardize actual methods and to define a cut-off for the number of white blood cells in CSF to define relapses, while only few have proposed alternatives to current practice. Here we show that neopterin, already proven to be a powerful marker for staging T. b. gambiense HAT, is also useful in evaluating post-therapeutic outcome. The measurement of neopterin concentration in CSF during the follow-up may allow reduction in the number of lumbar punctures from five to three for the majority of cured patients.
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Affiliation(s)
- Natalia Tiberti
- Translational Biomarker Group, Department of Human Protein Sciences, University of Geneva, Geneva, Switzerland
| | - Veerle Lejon
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Alexandre Hainard
- Translational Biomarker Group, Department of Human Protein Sciences, University of Geneva, Geneva, Switzerland
| | - Bertrand Courtioux
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1094, Tropical Neuroepidemiology, Limoges, France
- Institute of Neuroepidemiology and Tropical Neurology, School of Medicine, CNRS FR 3503 GEIST, University of Limoges, Limoges, France
| | - Xavier Robin
- Translational Biomarker Group, Department of Human Protein Sciences, University of Geneva, Geneva, Switzerland
| | - Natacha Turck
- Translational Biomarker Group, Department of Human Protein Sciences, University of Geneva, Geneva, Switzerland
| | | | - Enock Matovu
- Department of Veterinary Parasitology and Microbiology, School of Veterinary Medicine, Makerere University, Kampala, Uganda
| | - John Charles Enyaru
- Department of Biochemistry, College of Natural Sciences, Makerere University, Kampala, Uganda
| | - Dieudonné Mumba Ngoyi
- Department of Parasitology, Institut National de Recherche Biomédicale, Kinshasa, D. R. Congo
| | - Sanjeev Krishna
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's, University of London, London, United Kingdom
| | - Sylvie Bisser
- Institut National de la Santé et de la Recherche Médicale (INSERM), UMR1094, Tropical Neuroepidemiology, Limoges, France
- Institute of Neuroepidemiology and Tropical Neurology, School of Medicine, CNRS FR 3503 GEIST, University of Limoges, Limoges, France
| | | | - Philippe Büscher
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Jean-Charles Sanchez
- Translational Biomarker Group, Department of Human Protein Sciences, University of Geneva, Geneva, Switzerland
- * E-mail:
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10
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World Health Organization. Control and surveillance of human African trypanosomiasis. World Health Organ Tech Rep Ser 2013;:1-237. [PMID: 24552089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In the 1960s, it appeared that human African trypanosomiasis (HAT) could be effectively controlled, but by the beginning of the twenty-first century several decades of neglect had led to alarming numbers of reported new cases, with an estimated 300 000 people infected. The World Health Organization (WHO) responded with a series of initiatives aimed at bringing HAT under control again. Since 2001, the pharmaceutical companies that produce drugs for HAT have committed themselves to providing them free of charge to WHO for distribution for the treatment of patients. In addition, funds have been provided to WHO to support national sleeping sickness control programmes to boost control and surveillance of the disease. That, coupled with bilateral cooperation and the work of nongovernmental organizations, helped reverse the upward trend in HAT prevalence. By 2012, the number of reported cases was fewer than 8000. This success in bringing HAT under control led to its inclusion in the WHO Roadmap for eradication, elimination and control of neglected tropical diseases, with a target set to eliminate the disease as a public health problem by 2020. A further target has been set, by countries in which HAT is endemic, to eliminate gambiense HAT by reducing the incidence of infection to zero in a defined geographical area. This report provides information about new diagnostic approaches, new therapeutic regimens and better understanding of the distribution of the disease with high-quality mapping. The roles of human and animal reservoirs and the tsetse fly vectors that transmit the parasites are emphasized. The new information has formed the basis for an integrated strategy with which it is hoped that elimination of gambiense HAT will be achieved. The report also contains recommendations on the approaches that will lead to elimination of the disease.
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Simarro PP, Cecchi G, Franco JR, Paone M, Diarra A, Ruiz-Postigo JA, Fèvre EM, Mattioli RC, Jannin JG. Estimating and mapping the population at risk of sleeping sickness. PLoS Negl Trop Dis 2012; 6:e1859. [PMID: 23145192 PMCID: PMC3493382 DOI: 10.1371/journal.pntd.0001859] [Citation(s) in RCA: 230] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 08/29/2012] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND Human African trypanosomiasis (HAT), also known as sleeping sickness, persists as a public health problem in several sub-Saharan countries. Evidence-based, spatially explicit estimates of population at risk are needed to inform planning and implementation of field interventions, monitor disease trends, raise awareness and support advocacy. Comprehensive, geo-referenced epidemiological records from HAT-affected countries were combined with human population layers to map five categories of risk, ranging from "very high" to "very low," and to estimate the corresponding at-risk population. RESULTS Approximately 70 million people distributed over a surface of 1.55 million km(2) are estimated to be at different levels of risk of contracting HAT. Trypanosoma brucei gambiense accounts for 82.2% of the population at risk, the remaining 17.8% being at risk of infection from T. b. rhodesiense. Twenty-one million people live in areas classified as moderate to very high risk, where more than 1 HAT case per 10,000 inhabitants per annum is reported. DISCUSSION Updated estimates of the population at risk of sleeping sickness were made, based on quantitative information on the reported cases and the geographic distribution of human population. Due to substantial methodological differences, it is not possible to make direct comparisons with previous figures for at-risk population. By contrast, it will be possible to explore trends in the future. The presented maps of different HAT risk levels will help to develop site-specific strategies for control and surveillance, and to monitor progress achieved by ongoing efforts aimed at the elimination of sleeping sickness.
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Affiliation(s)
- Pere P Simarro
- Control of Neglected Tropical Diseases, Innovative and Intensified Disease Management, World Health Organization, Geneva, Switzerland.
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12
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Abstract
Sleeping sickness describes two diseases, both fatal if left untreated: (i) Gambian sleeping sickness caused by Trypanosoma brucei gambiense, a chronic disease with average infection lasting around 3 years, and (ii) Rhodesian sleeping sickness caused by T. b. rhodesiense, an acute disease with death occurring within weeks of infection. Control of Gambian sleeping sickness is based on case detection and treatment involving serological screening, followed by diagnostic confirmation and staging. In stage I, patients can remain asymptomatic as trypanosomes multiply in tissues and body fluids; in stage II, trypanosomes cross the blood-brain barrier, enter the central nervous system and, if left untreated, death follows. Staging is crucial as it defines the treatment that is prescribed; for both forms of disease, stage II involves the use of the highly toxic drug melarsoprol or, in the case of Gambian sleeping sickness, the use of complex and very expensive drug regimes. Case detection of T. b. gambiense sleeping sickness is known to be inefficient but could be improved by the identification of parasites using molecular tools that are, as yet, rarely used in the field. Diagnostics are not such a problem in relation to T. b. rhodesiense sleeping sickness, but the high level of under-reporting of this disease suggests that current strategies, reliant on self-reporting, are inefficient. Sleeping sickness is one of the 'neglected tropical diseases' that attracts little attention from donors or policymakers. Proper quantification of the burden of sleeping sickness matters, as the primary reason for its 'neglect' is that the true impact of the disease is unknown, largely as a result of under-reporting. Certainly, elimination will not be achieved without vast improvements in field diagnostics for both forms of sleeping sickness especially if there is a hidden reservoir of 'chronic carriers'. Mass screening would be a desirable aim for Gambian sleeping sickness and could be handled on a national scale in the endemic countries - perhaps by piggybacking on programmes committed to other diseases. As well as improved diagnostics, the search for non-toxic drugs for stage II treatment should remain a research priority. There is good evidence that thorough active case finding is sufficient to control T. b. gambiense sleeping sickness, as there is no significant animal reservoir. Trypanosoma brucei rhodesiense sleeping sickness is a zoonosis and control involves interrupting the fly-animal-human cycle, so some form of tsetse control and chemotherapy of the animal reservoir must be involved. The restricted application of insecticide to cattle is the most promising, affordable and sustainable technique to have emerged for tsetse control. Animal health providers can aid disease control by treating cattle and, when allied with innovative methods of funding (e.g. public-private partnerships) not reliant on the public purse, this approach may prove more sustainable. Sleeping sickness incidence for the 36 endemic countries has shown a steady decline in recent years and we should take advantage of the apparent lull in incidence and aim for elimination. This is feasible in some sleeping sickness foci but must be planned and paid for increasingly by the endemic countries themselves. The control and elimination of T. b. gambiense sleeping sickness may be seen as a public good, as appropriate strategies depend on local health services for surveillance and treatment, but public-private funding mechanisms should not be excluded. It is timely to take up the tools available and invest in new tools - including novel financial instruments - to eliminate this disease from Africa.
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Affiliation(s)
- Susan C Welburn
- Division of Pathway Medicine and Centre for Infectious Diseases, School of Biomedical Sciences, College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, UK
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Symula RE, Beadell JS, Sistrom M, Agbebakun K, Balmer O, Gibson W, Aksoy S, Caccone A. Trypanosoma brucei gambiense group 1 is distinguished by a unique amino acid substitution in the HpHb receptor implicated in human serum resistance. PLoS Negl Trop Dis 2012; 6:e1728. [PMID: 22802982 PMCID: PMC3393672 DOI: 10.1371/journal.pntd.0001728] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2012] [Accepted: 05/22/2012] [Indexed: 11/18/2022] Open
Abstract
Trypanosoma brucei rhodesiense (Tbr) and T. b. gambiense (Tbg), causative agents of Human African Trypanosomiasis (sleeping sickness) in Africa, have evolved alternative mechanisms of resisting the activity of trypanosome lytic factors (TLFs), components of innate immunity in human serum that protect against infection by other African trypanosomes. In Tbr, lytic activity is suppressed by the Tbr-specific serum-resistance associated (SRA) protein. The mechanism in Tbg is less well understood but has been hypothesized to involve altered activity and expression of haptoglobin haemoglobin receptor (HpHbR). HpHbR has been shown to facilitate internalization of TLF-1 in T.b. brucei (Tbb), a member of the T. brucei species complex that is susceptible to human serum. By evaluating the genetic variability of HpHbR in a comprehensive geographical and taxonomic context, we show that a single substitution that replaces leucine with serine at position 210 is conserved in the most widespread form of Tbg (Tbg group 1) and not found in related taxa, which are either human serum susceptible (Tbb) or known to resist lysis via an alternative mechanism (Tbr and Tbg group 2). We hypothesize that this single substitution contributes to reduced uptake of TLF and thus may play a key role in conferring serum resistance to Tbg group 1. In contrast, similarity in HpHbR sequence among isolates of Tbg group 2 and Tbb/Tbr provides further evidence that human serum resistance in Tbg group 2 is likely independent of HpHbR function.
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Affiliation(s)
- Rebecca E Symula
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States of America.
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14
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Jamonneau V, Ilboudo H, Kaboré J, Kaba D, Koffi M, Solano P, Garcia A, Courtin D, Laveissière C, Lingue K, Büscher P, Bucheton B. Untreated human infections by Trypanosoma brucei gambiense are not 100% fatal. PLoS Negl Trop Dis 2012; 6:e1691. [PMID: 22720107 PMCID: PMC3373650 DOI: 10.1371/journal.pntd.0001691] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 04/30/2012] [Indexed: 02/04/2023] Open
Abstract
The final outcome of infection by Trypanosoma brucei gambiense, the main agent of sleeping sickness, has always been considered as invariably fatal. While scarce and old reports have mentioned cases of self-cure in untreated patients, these studies suffered from the lack of accurate diagnostic tools available at that time. Here, using the most specific and sensitive tools available to date, we report on a long-term follow-up (15 years) of a cohort of 50 human African trypanosomiasis (HAT) patients from the Ivory Coast among whom 11 refused treatment after their initial diagnosis. In 10 out of 11 subjects who continued to refuse treatment despite repeated visits, parasite clearance was observed using both microscopy and polymerase chain reaction (PCR). Most of these subjects (7/10) also displayed decreasing serological responses, becoming progressively negative to trypanosome variable antigens (LiTat 1.3, 1.5 and 1.6). Hence, in addition to the “classic” lethal outcome of HAT, we show that alternative natural progressions of HAT may occur: progression to an apparently aparasitaemic and asymptomatic infection associated with strong long-lasting serological responses and progression to an apparently spontaneous resolution of infection (with negative results in parasitological tests and PCR) associated with a progressive drop in antibody titres as observed in treated cases. While this study does not precisely estimate the frequency of the alternative courses for this infection, it is noteworthy that in the field national control programs encounter a significant proportion of subjects displaying positive serologic test results but negative results in parasitological testing. These findings demonstrate that a number of these subjects display such infection courses. From our point of view, recognising that trypanotolerance exists in humans, as is now widely accepted for animals, is a major step forward for future research in the field of HAT. The existence of a diversity of infection outcomes – ranging from self-cure to asymptomatic, severe or fatal cases – is now widely recognised for most parasitic and infectious diseases. The dogma concerning sleeping sickness, however, is still that infection is 100% fatal. Here we describe a 15-year follow-up of patients diagnosed with human African trypanosomiasis (HAT) in the Ivory Coast but who refused treatment. Our results, based on clinical, serological, molecular, and parasitological investigations, combining diagnostic tools for the field and highly specific and sensitive laboratory tests, constitute the most comprehensive study on the natural evolution of Trypanosoma brucei gambiense infection in its human host. At least two alternative natural progressions of HAT to the “classic” fatal disease were identified: a progression to an apparently aparasitaemic and asymptomatic infection and a progression to an apparently spontaneous resolution of infection. We believe that recognising that trypanotolerance exists in humans is a major step forward for future research aimed at identifying human-specific defence and immune mechanisms involved in the control of T.b. gambiense infection and thus new candidate therapeutic or prophylactic targets.
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Affiliation(s)
- Vincent Jamonneau
- Institut de Recherche pour le Développement, Unité Mixte de Recherche IRD-CIRAD 177, Campus International de Baillarguet, Montpellier, France.
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15
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Priotto G, Chappuis F, Bastard M, Flevaud L, Etard JF. Early prediction of treatment efficacy in second-stage gambiense human African trypanosomiasis. PLoS Negl Trop Dis 2012; 6:e1662. [PMID: 22701752 PMCID: PMC3367996 DOI: 10.1371/journal.pntd.0001662] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Accepted: 04/12/2012] [Indexed: 11/28/2022] Open
Abstract
Background Human African trypanosomiasis is fatal without treatment. The long post-treatment follow-up (24 months) required to assess cure complicates patient management and is a major obstacle in the development of new therapies. We analyzed individual patient data from 12 programs conducted by Médecins Sans Frontières in Uganda, Sudan, Angola, Central African Republic, Republic of Congo and Democratic Republic of Congo searching for early efficacy indicators. Methodology/Principal Findings Patients analyzed had confirmed second-stage disease with complete follow-up and confirmed outcome (cure or relapse), and had CSF leucocytes counts (CSFLC) performed at 6 months post-treatment. We excluded patients with uncertain efficacy outcome: incomplete follow-up, death, relapse diagnosed with CSFLC below 50/µL and no trypanosomes. We analyzed the 6-month CSFLC via receiver-operator-characteristic curves. For each cut-off value we calculated sensitivity, specificity and likelihood ratios (LR+ and LR−). We assessed the association of the optimal cut-off with the probability of relapsing via random-intercept logistic regression. We also explored two-step (6 and 12 months) composite algorithms using the CSFLC. The most accurate cut-off to predict outcome was 10 leucocytes/µL (n = 1822, 76.2% sensitivity, 80.4% specificity, 3.89 LR+, 0.29 LR−). Multivariate analysis confirmed its association with outcome (odds ratio = 17.2). The best algorithm established cure at 6 months with < = 5 leucocytes/µL and relapse with > = 50 leucocytes/µL; patients between these values were discriminated at 12 months by a 20 leucocytes/µL cut-off (n = 2190, 87.4% sensitivity, 97.7% specificity, 37.84 LR+, 0.13 LR−). Conclusions/Significance The 6-month CSFLC can predict outcome with some limitations. Two-step algorithms enhance the accuracy but impose 12-month follow-up for some patients. For early estimation of efficacy in clinical trials and for individual patients in the field, several options exist that can be used according to priorities. Because Human African trypanosomiasis is fatal, it is crucial for the patient to determine if curative treatment has been effective. Unfortunately this is not possible without a 24-month laboratory follow-up, which is problematic and largely unaccomplished in the field reality. Studies that assessed early indicators have used small cohorts, yielding limited statistical power plus potential bias because of including patients with equivocal outcome. We tackled this problem by pooling a large dataset which allowed for selecting cases providing strictly unequivocal information, still numerous enough to produce sound statistical evidence. We studied predictors based on the CSF leucocytes count, a laboratory technique already available in the field, evaluating their predictive power at 6 and 12 months post-treatment. We found a predictor at 6 months (10 leucocytes/µL of CSF) that has sub-optimal accuracy but may be valuable in some particular situations, plus two-step algorithms at 6 and 12 months that offer sufficient confidence to shorten the patients' follow-up. Until better biomarkers are identified, these findings represent a significant advance for this neglected disease. Benefits are foreseen both for patients and for overburdened treatment facilities. In addition, research for new treatments can be accelerated by using early predictors.
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Affiliation(s)
| | - François Chappuis
- Operational Centre Geneva, Médecins sans Frontiéres, Geneva University Hospitals, Geneva, Switzerland
| | | | - Laurence Flevaud
- Operational Centre Barcelona-Athens, Médecins sans Frontiéres, Barcelona, Spain
| | - Jean-François Etard
- Epicentre, Paris, France
- Institut de Recherche pour le Développement/UMI 233, Montpellier, France
- * E-mail: (GP); (JE)
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16
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Simarro PP, Cecchi G, Paone M, Franco JR, Diarra A, Ruiz JA, Fèvre EM, Courtin F, Mattioli RC, Jannin JG. The Atlas of human African trypanosomiasis: a contribution to global mapping of neglected tropical diseases. Int J Health Geogr 2010; 9:57. [PMID: 21040555 PMCID: PMC2988709 DOI: 10.1186/1476-072x-9-57] [Citation(s) in RCA: 253] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 11/01/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Following World Health Assembly resolutions 50.36 in 1997 and 56.7 in 2003, the World Health Organization (WHO) committed itself to supporting human African trypanosomiasis (HAT)-endemic countries in their efforts to remove the disease as a public health problem. Mapping the distribution of HAT in time and space has a pivotal role to play if this objective is to be met. For this reason WHO launched the HAT Atlas initiative, jointly implemented with the Food and Agriculture Organization of the United Nations, in the framework of the Programme Against African Trypanosomosis. RESULTS The distribution of HAT is presented for 23 out of 25 sub-Saharan countries having reported on the status of sleeping sickness in the period 2000-2009. For the two remaining countries, i.e. Angola and the Democratic Republic of the Congo, data processing is ongoing. Reports by National Sleeping Sickness Control Programmes (NSSCPs), Non-Governmental Organizations (NGOs) and Research Institutes were collated and the relevant epidemiological data were entered in a database, thus incorporating (i) the results of active screening of over 2.2 million people, and (ii) cases detected in health care facilities engaged in passive surveillance. A total of over 42 000 cases of HAT and 6 000 different localities were included in the database. Various sources of geographic coordinates were used to locate the villages of epidemiological interest. The resulting average mapping accuracy is estimated at 900 m. CONCLUSIONS Full involvement of NSSCPs, NGOs and Research Institutes in building the Atlas of HAT contributes to the efficiency of the mapping process and it assures both the quality of the collated information and the accuracy of the outputs. Although efforts are still needed to reduce the number of undetected and unreported cases, the comprehensive, village-level mapping of HAT control activities over a ten-year period ensures a detailed and reliable representation of the known geographic distribution of the disease. Not only does the Atlas serve research and advocacy, but, more importantly, it provides crucial evidence and a valuable tool for making informed decisions to plan and monitor the control of sleeping sickness.
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Affiliation(s)
- Pere P Simarro
- World Health Organization, Control of Neglected Tropical Diseases, Innovative and Intensified Disease Management, 1211 Geneva 27, Switzerland
| | - Giuliano Cecchi
- Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Viale delle Terme di Caracalla, 00153, Rome, Italy
| | - Massimo Paone
- Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Viale delle Terme di Caracalla, 00153, Rome, Italy
| | - José R Franco
- World Health Organization, Control of Neglected Tropical Diseases, Innovative and Intensified Disease Management, 1211 Geneva 27, Switzerland
| | - Abdoulaye Diarra
- World Health Organization, Regional Office for Africa, Brazzaville, Congo
| | - José A Ruiz
- World Health Organization, Regional Office for the Eastern Mediterranean, Cairo 11371, Egypt
| | - Eric M Fèvre
- Centre for Infectious Diseases, University of Edinburgh, Ashworth Laboratories, Kings Buildings, West Mains Road, Edinburgh EH9 3JT, UK
| | - Fabrice Courtin
- Institut de Recherche pour le Développement - UMR 177, Centre International de Recherche Développement sur l'Elevage en zone Subhumide, Bobo-Dioulasso, Burkina Faso
| | - Raffaele C Mattioli
- Food and Agriculture Organization of the United Nations, Animal Production and Health Division, Viale delle Terme di Caracalla, 00153, Rome, Italy
| | - Jean G Jannin
- World Health Organization, Control of Neglected Tropical Diseases, Innovative and Intensified Disease Management, 1211 Geneva 27, Switzerland
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17
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Abstract
Human African trypanosomiasis (sleeping sickness) occurs in sub-Saharan Africa. It is caused by the protozoan parasite Trypanosoma brucei, transmitted by tsetse flies. Almost all cases are due to Trypanosoma brucei gambiense, which is indigenous to west and central Africa. Prevalence is strongly dependent on control measures, which are often neglected during periods of political instability, thus leading to resurgence. With fewer than 12 000 cases of this disabling and fatal disease reported per year, trypanosomiasis belongs to the most neglected tropical diseases. The clinical presentation is complex, and diagnosis and treatment difficult. The available drugs are old, complicated to administer, and can cause severe adverse reactions. New diagnostic methods and safe and effective drugs are urgently needed. Vector control, to reduce the number of flies in existing foci, needs to be organised on a pan-African basis. WHO has stated that if national control programmes, international organisations, research institutes, and philanthropic partners engage in concerted action, elimination of this disease might even be possible.
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Affiliation(s)
- Reto Brun
- Swiss Tropical Institute, Basel, Switzerland.
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18
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Sindato C, Malele II, Mwalimu C, Nyingilili HS, Kaboya S, Kombe E, Msumary C, Manoza A. Seasonal variation in human African trypanosomiasis in Tarangire National Park in Babati district, Tanzania. Tanzan Health Res Bull 2007; 9:136-9. [PMID: 17722418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A survey was carried out to determine seasonal epidemiological variation of human African trypanosomiasis (HAT) in Tarangire National Park and villages around it in Babati District, Tanzania. Concentration and Field's stain techniques were employed to examine the presence of trypanosomes in human blood samples. Tsetse flies were collected using traps and dissected under light microscope to examine for presence of trypanosomes. Retrospective data on HAT were sought from health facilities. Blood samples were collected from a total 509 individuals (306 during the dry and 203 during wet seasons). None of the individuals was infected with trypanosomes in the area. A total of 766 tsetse flies were collected. Of these, Glossina swynnertoni accounted for 94.6% and G. pallidipes for 5.4% of the total collection. The largest proportion (63.8%) of the tsetse flies was collected during the wet season. Glossina swynnertoni was most abundant tsetse species during both wet and dry seasons. Salivary gland examination revealed the presence of Trypanosoma brucei type of infection in 3.2% of tsetse flies collected. All infective trypanosomes were found during the dry season. This study concludes that the transmission and prevalence of HAT among human population in Tarangire National Pars and its surrounding villages is low despite the recent reports on tourists acquiring the infection during their visits to the Park. However, disease surveillance needs to be strengthened to monitor any impending epidemic.
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Affiliation(s)
- C Sindato
- National Institute for Medical Research, P.O. Box 482, Tabora, Tanzania.
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19
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Abstract
Trypanosoma brucei rhodesiense and T. b. gambiense are the causative agents of sleeping sickness, a fatal disease that affects 36 countries in sub-Saharan Africa. Nevertheless, only a handful of clinically useful drugs are available. These drugs suffer from severe side-effects. The situation is further aggravated by the alarming incidence of treatment failures in several sleeping sickness foci, apparently indicating the occurrence of drug-resistant trypanosomes. Because of these reasons, and since vaccination does not appear to be feasible due to the trypanosomes' ever changing coat of variable surface glycoproteins (VSGs), new drugs are needed urgently. The entry of Trypanosoma brucei into the post-genomic age raises hopes for the identification of novel kinds of drug targets and in turn new treatments for sleeping sickness. The pragmatic definition of a drug target is, a protein that is essential for the parasite and does not have homologues in the host. Such proteins are identified by comparing the predicted proteomes of T. brucei and Homo sapiens, then validated by large-scale gene disruption or gene silencing experiments in trypanosomes. Once all proteins that are essential and unique to the parasite are identified, inhibitors may be found by high-throughput screening. However powerful, this functional genomics approach is going to miss a number of attractive targets. Several current, successful parasiticides attack proteins that have close homologues in the human proteome. Drugs like DFMO or pyrimethamine inhibit parasite and host enzymes alike--a therapeutic window is opened only by subtle differences in the regulation of the targets, which cannot be recognized in silico. Working against the post-genomic approach is also the fact that essential proteins tend to be more highly conserved between species than non-essential ones. Here we advocate drug targeting, i.e. uptake or activation of a drug via parasite-specific pathways, as a chemotherapeutic strategy to selectively inhibit enzymes that have equally sensitive counterparts in the host. The T. brucei purine salvage machinery offers opportunities for both metabolic and transport-based targeting: unusual nucleoside and nucleobase permeases may be exploited for selective import, salvage enzymes for selective activation of purine antimetabolites.
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Affiliation(s)
- A Lüscher
- University of Bern, Institute of Cell Biology, Bern, Switzerland
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20
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Ravel S, Patrel D, Koffi M, Jamonneau V, Cuny G. Cyclical transmission of Trypanosoma brucei gambiense in Glossina palpalis gambiensis displays great differences among field isolates. Acta Trop 2006; 100:151-5. [PMID: 17069743 DOI: 10.1016/j.actatropica.2006.09.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 09/19/2006] [Accepted: 09/21/2006] [Indexed: 10/24/2022]
Abstract
Six sets of teneral Glossina palpalis gambiensis (Diptera: Glossinidae) were fed on mice infected with six different isolates of Trypanosoma brucei gambiense (each mouse was infected with one of the isolates), previously isolated from patients in the sleeping sickness focus of Bonon, Côte d'Ivoire and in Makoua, Congo. All the tsetse flies were dissected 42 days post-infection and midgut and salivary glands were examined for trypanosomes by microscopical examination. No infection was observed with the reference stock whereas each of the five recently isolated trypanosome isolates was able to infect tsetse flies, with rates of infection varying between 9.7 and 18.2% depending on the isolate. Three isolates displayed only immature infections with 9.7, 17.3 and 18% of the flies showing trypanosomes in their midgut. One isolate gave both immature (12.1%) and mature infections (6.1%). Finally, the last isolate involved only mature infections in 9.7% of the Glossina species examined. These substantial differences in the cyclical transmission of T. b. gambiense in the same fly species could have important implications for the epidemiology of the transmission of Human African Trypanosomiasis.
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Affiliation(s)
- S Ravel
- IRD, UR177, Laboratoire de Recherche et de Coordination sur les Trypanosomoses, IRD-CIRAD, TA 207/G, Campus International de Baillarguet, 34398 Montpellier Cedex 5, France.
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21
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Abstract
Human African trypanosomiasis or sleeping sickness is caused by infection with two subspecies of the tsetse-fly-vectored haemoflagellate parasite Trypanosoma brucei. Historically, epidemic sleeping sickness has caused massive loss of life, and related animal diseases have had a crucial impact on development in sub-Saharan Africa. After a period of moderately successful control during the mid-part of the 20th century, sleeping sickness incidence is currently rising, and control is hampered by a combination of factors, including civil unrest and the possible development of drug resistance by the parasites. The prevailing view is that the disease is invariably fatal without anti-trypanosomal drug treatment. However, there have also been intriguing reports of wide variations in disease severity as well as evidence of asymptomatic carriers of trypanosomes. These differences in the presentation of the disease will be discussed in the context of our knowledge of the immunology of trypanosomiasis. The impact of dysregulated inflammatory responses in both systemic and CNS pathology will be examined and the potential for host genotype variation in disease severity and control will be discussed.
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Affiliation(s)
- J M Sternberg
- Zoology Building, School of Biological Sciences, University of Aberdeen, UK.
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22
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Magez S, Stijlemans B, Baral T, De Baetselier P. VSG-GPI anchors of African trypanosomes: their role in macrophage activation and induction of infection-associated immunopathology. Microbes Infect 2002; 4:999-1006. [PMID: 12106794 DOI: 10.1016/s1286-4579(02)01617-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
African trypanosomes express a glycosylphosphatidyl inositol (GPI)-anchored variant-specific surface glycoprotein (VSG) as a protective coat. During infection, large amounts of VSG molecules are released into the circulation. Their interaction with various cells of the immune system underlies the severe infection-associated pathology. Recent results have shown that anti-GPI vaccination can prevent the occurrence of this pathology.
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Affiliation(s)
- Stefan Magez
- Laboratory of Cellular Immunology, Free University of Brussels/Flemish Interuniversity, Institute for Biotechnology, Paardenstraat 65, Sint Genesius Rode, Belgium.
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23
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Abstract
Recent progress in understanding the neuropathological mechanisms of sleeping sickness reveals a complex relationship between the trypanosome parasite that causes this disease and the host nervous system. The pathology of late-stage sleeping sickness, in which the central nervous system is involved, is complicated and is associated with disturbances in the circadian rhythm of sleep. The blood-brain barrier, which separates circulating blood from the central nervous system, regulates the flow of materials to and from the brain. During the course of disease, the integrity of the blood-brain barrier is compromised. Dysfunction of the nervous system may be exacerbated by factors of trypanosomal origin or by host responses to parasites. Microscopic examination of cerebrospinal fluid remains the best way to confirm late-stage sleeping sickness, but this necessitates a risky lumbar puncture. Most drugs, including many trypanocides, do not cross the blood-brain barrier efficiently. Improved diagnostic and therapeutic approaches are thus urgently required. The latter might benefit from approaches which manipulate the blood-brain barrier to enhance permeability or to limit drug efflux. This review summarizes our current understanding of the neurological aspects of sleeping sickness, and envisages new research into blood-brain barrier models that are necessary to understand the interactions between trypanosomes and drugs active against them within the host nervous system.
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Affiliation(s)
- B Enanga
- Institute of Biomedical and Life Sciences, Division of Infection and Immunity, University of Glasgow, Scotland, United Kingdom
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24
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Abstract
The accurate identification of each of the three subspecies of Trypanosoma brucei remains a challenging problem in the epidemiology of sleeping sickness. Advances in molecular characterization have revealed a much greater degree of heterogeneity within the species than previously supposed. Only group 1 T. b. gambiense stands out as a separate entity, defined by several molecular markers. T. b. rhodesiense is generally too similar to sympatric T. b. brucei strains to be distinguished from them by any particular molecular markers. Nevertheless, characterization of trypanosome isolates from humans and other animals has allowed the identification of potential reservoir hosts of T. b. rhodesiense. The recent discovery of a gene for human serum resistance may provide a useful marker for T. b. rhodesiense in the future. There have been few attempts to find associations between genetic markers and other biological characters, except human infectivity. However, virulence or fly transmissibility have been correlated with molecular markers in some instances.
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Affiliation(s)
- W Gibson
- School of Biological Sciences, University of Bristol, Bristol, UK.
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25
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Inoue N, Narumi D, Mbati PA, Hirumi K, Situakibanza NT, Hirumi H. Susceptibility of severe combined immuno-deficient (SCID) mice to Trypanosoma brucei gambiense and T. b. rhodesiense. Trop Med Int Health 1998; 3:408-12. [PMID: 9623947 DOI: 10.1046/j.1365-3156.1998.00245.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Susceptibility of severe combined immunodeficient (SCID) mice to 7 isolates of Trypanosoma brucei gambiense and 2 isolates of T. b. rhodesiense was examined in terms of their infectivity, course of parasitaemia, packed cell volume (PCV) and survival period in comparison with that of normal immunocompetent (BALB/c) mice. All isolates of T. b. gambiense and T. b. rhodesiense caused high (> 1 x 10(8) parasites/ml) parasitaemia in the SCID mice, the survival periods ranged from 5 to 47 days. On the other hand, 5 of 7 isolates of T. b. gambiense developed chronic infection in the BALB/c mice with sporadic but persistent parasitaemia with less than 5 x 10(6) parasites/ml. All the mice tested in this group survived more than 60 days after infection. In contrast, the 2 remaining isolates of T. b. gambiense and both isolates of T. b. rhodesiense showed high virulence in the BALB/c mice and killed all of them within 30 days after infection. The results demonstrate that the SCID mice, in which functional B- and T-cell-mediated immunities are congenitally lacking, are highly susceptible for 'low-virulence' T. b. gambiense. This makes SCID mice useful tools for the isolation of parasites from T. b. gambiense sleeping sickness patients and the propagation of large amounts of such parasites.
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Affiliation(s)
- N Inoue
- The Research Centre for Protozoan Molecular Immunology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro Hokkaido, Japan
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26
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Truc P, Formenty P, Diallo PB, Komoin-Oka C, Lauginie F. Confirmation of two distinct classes of zymodemes of Trypanosoma brucei infecting man and wild mammals in Côte d'Ivoire: suspected difference in pathogenicity. Ann Trop Med Parasitol 1997; 91:951-6. [PMID: 9579216 DOI: 10.1080/00034989760356] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- P Truc
- Laboratoire de Biologie des Parasites et Vecteurs, Institut Pierre Richet/OCCGE, Bouaké, Côte d'Ivoire.
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27
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Otigbuo IN, Oyerinde JP. A modified medium for the in vitro cultivation of trypanosomes. Afr J Med Med Sci 1993; 22:63-71. [PMID: 7839932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A modified medium (ME-99) for the in vitro cultivation of trypanosomes was developed and evaluated in our laboratory. The medium comprised of Eagle MEM as a base and various components of medium 199 not found in MEM. Trypanosoma brucei brucei, T. b. gambiense and T. vivax were grown in ME-99 and various other media combinations such as MEM/RPMI 1640, MEM/BCM, MEM/199, RPMI 1640/BCM, RPMI 1640/199, BCM/199 for comparison. Both growth and infectivity of these parasites were compared in these media. Parasites grew better and maintained their infectivity for longer periods in ME-99 than in any other medium or combination of media.
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Affiliation(s)
- I N Otigbuo
- Department of Medical Microbiology and Parasitology College of Medicine, University of Lagos
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28
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Tibayrenc M, Neubauer K, Barnabé C, Guerrini F, Skarecky D, Ayala FJ. Genetic characterization of six parasitic protozoa: parity between random-primer DNA typing and multilocus enzyme electrophoresis. Proc Natl Acad Sci U S A 1993; 90:1335-9. [PMID: 8433991 PMCID: PMC45867 DOI: 10.1073/pnas.90.4.1335] [Citation(s) in RCA: 230] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
We have assayed genetic polymorphisms in several species of parasitic protozoa by means of random amplified polymorphic DNA (RAPD). One goal was to ascertain the suitability of RAPD markers for investigating genetic and evolutionary problems, particularly in organisms, such as the parasitic protozoa, unsuitable for traditional methods of genetic analysis. Another goal was to test certain hypotheses concerning Trypanosoma cruzi, and other protozoa, that have been established by multilocus enzyme electrophoresis. The RAPD results corroborate the hypothesis that the population structure of T. cruzi is clonal and yield a phylogeny of the clonal lineages in agreement with the one obtained by enzyme electrophoresis. This parity between the two sets of results confirms that RAPD markers are reliable genetic markers. The RAPD markers are also suitable for reconstructing species phylogenies and as diagnostic characters of species and subspecific lineages. The number of DNA polymorphisms that can be detected by the RAPD method seems virtually unlimited, since the number of primers can be increased effectively at will. The RAPD method is well suited for investigating genetic and evolutionary questions in certain organisms, because it is cost effective and demands no previous genetic knowledge about the organism.
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Affiliation(s)
- M Tibayrenc
- Department of Ecology and Evolutionary Biology, University of California, Irvine 92917
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29
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Kageruka P, Mangus E, Bajyana Songa E, Nantulya V, Jochems M, Hamers R, Mortelmans J. Infectivity of Trypanosoma (Trypanozoon) brucei gambiense for baboons (Papio hamadryas, Papio papio). Ann Soc Belg Med Trop 1991; 71:39-46. [PMID: 2042999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
In order to study sensitivity or resistance of T.b. gambiense to baboon serum, two species of baboons, P. hamadryas and P. papio were inoculated with T.b. gambiense clone LiTat 1.1. Both species were receptive to infection but, parasitological and immunological parameters showed that P. papio was more trypanotolerant than P. hamadryas. The VAT-specific trypanolysis test and the ELISA, using MoAb for circulating antigen detection may be appropriate for the diagnosis of human trypanosomiasis due to T.b. gambiense.
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Affiliation(s)
- P Kageruka
- Institute of Tropical Medicine, Antwerpen, Belgium
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30
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Dukes P, Kaukas A, Hudson KM, Asonganyi T, Gashumba JK. A new method for isolating Trypanosoma brucei gambiense from sleeping sickness patients. Trans R Soc Trop Med Hyg 1989; 83:636-9. [PMID: 2617625 DOI: 10.1016/0035-9203(89)90379-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Low infectivity to laboratory mammals and low virulence make Trypanosoma brucei gambiense difficult to isolate and grow in amounts sufficient for biochemical characterization. We report the isolation of T.b. gambiense by feeding cryopreserved primary isolates to laboratory-reared Glossina morsitans morsitans, followed by rapid cultivation in vitro of procyclic forms dissected from infected tsetse fly midguts. This technique allows the characterization of hitherto unsampled populations and avoids selection due to long-term subpassage. Of 16 primary isolates from trypanosomiasis patients of the Fontem focus in Cameroon, 12 (75%) produced infections in tsetse whereas only 4 (25%) infected rats. Ten isolates were subsequently cultivated as procyclic forms in vitro; 2 failed to grow owing to bacterial contamination. In addition, 2 primary isolates from Côte d'Ivoire patients and a stock of low virulence from the Congo Republic were similarly grown. Only one primary isolate produced tsetse salivary gland infections, an observation consistent with the hypothesis that some populations of T.b. gambiense are intrinsically incompatible with G.m. morsitans.
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Affiliation(s)
- P Dukes
- Tsetse Research Laboratory, University of Bristol, Langford, UK
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31
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Noireau F, Paindavoine P, Lemesre JL, Toudic A, Pays E, Gouteux JP, Steinert M, Frezil JL. The epidemiological importance of the animal reservoir of Trypanosoma brucei gambiense in the Congo. 2. Characterization of the Trypanosoma brucei complex. Trop Med Parasitol 1989; 40:9-11. [PMID: 2740734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Biological and biochemical characterization of 36 human and 5 animal congolese stocks of Trypanosoma brucei were performed. One human and all the animal stocks showed a quick adaptation to rodent host whereas the other 35 human stocks were characterized by a low virulence degree (Group 1 of T. gambiense). The virulent stocks showed hybridization patterns specific to the gambiense subspecies. Our results confirm the absence of the T. b. brucei subspecies in the Congo and the low prevalence of domestic animals infected with T. b. gambiense (0.5%). Two cycles of human trypanosomiasis may thus occur in Central Africa: a predominant man-to-man cycle with group 1 trypanosomes and a minor cycle involving an animal reservoir.
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Affiliation(s)
- F Noireau
- ORSTOM, Centre de Brazzaville, Congo
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32
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Yabu Y, Takayanagi T, Sato S. Long-term culture and cloning system for Trypanosoma brucei gambiense bloodstream forms in semi-defined medium in vitro. Parasitol Res 1989; 76:93-7. [PMID: 2616571 DOI: 10.1007/bf00930828] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A new semi-defined medium extremely useful for the long-term cultivation and cloning of Trypanosoma b. gambiense (Wellcome strain) bloodstream forms is described. Bloodstream forms could be continuously grown in 25 mM HEPES-buffered D-MEM supplemented with 10 microM bathocuproine sulfonate (BCS), 100 microM cysteine, and 20% heat-inactivated fetal calf serum at 37 degrees C in vitro. Under these culture conditions, T. b. gambiense bloodstream forms increased in number up to 2-3 x 10(6) trypanosomes/ml by day 3 after initiation of the culture. The trypanosomes maintained in this culture system for 200 days retained their infectivity for mice. Morphologically, they were long and slender, and a surface coat was evident on the cell surface and flagellar membrane. In vitro cloning with single bloodstream forms of T. b. gambiense could be achieved with high efficiency.
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Affiliation(s)
- Y Yabu
- Department of Medical Zoology, Nagoya City University, Medical School, Japan
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33
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Diffley P, Scott JO, Mama K, Tsen TN. The rate of proliferation among African trypanosomes is a stable trait that is directly related to virulence. Am J Trop Med Hyg 1987; 36:533-40. [PMID: 3578651 DOI: 10.4269/ajtmh.1987.36.533] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The relationship between the growth rate of Trypanosoma brucei gambiense and its virulence was investigated. A cloned, monomorphic, slow growing, and relatively avirulent line of T. b. gambiense was serially passaged at 3- to 5-day intervals through immunosuppressed mice. The growth rate measured within the first 2 patent days of infection did not vary significantly through the first 25 passages but by passage 50 had decreased significantly from 11.9 +/- 1.1 hr to 9.0 +/- 0.7 hr. A clone from passage 50 and three different second peak heterologous variants all had statistically similar growth rates, indicating that the rate of proliferation was a stable trait. With the faster rate of proliferation there was a corresponding increase in virulence. The inoculum necessary to kill 50% of normal outbred mice in the first peak of parasitemia (LD50) dropped significantly from 3 X 10(6) first passage parasites to 4 X 10(5) passage 50 parasites. The lethal load for both fast and slow growing organisms was the same (greater than 2 X 10(9) trypanosomes/ml of blood). To further link virulence and growth rate, a strong correlation (r = 0.89) was measured when generation times of 10 closely related lines of T. b. gambiense, and 2 lines of pleomorphic T. b. rhodesiense were compared to their LD50 values. While the rate of trypanosomal proliferation was similar between the day of inoculation through the second patent day, it slowed to 64% of that level once parasitemias exceeded 3 X 10(8) organisms/ml of host blood.(ABSTRACT TRUNCATED AT 250 WORDS)
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Abstract
Thirty-two isolates from man in known areas of Gambian trypanosomiasis, in the Sudan, Kenya, Zaire, Nigeria, Ivory Coast, Burkina Faso, Liberia and Senegal, were examined by isoenzyme electrophoresis of 11 enzymes. Comparisons were also made with our previously published results on 23 other stocks of similar origins, which had been examined in the same manner. All those stocks of low initial virulence to laboratory rodents, which thus conform to the accepted view of the behaviour of Trypanosoma brucei gambiense can be identified by characteristic combinations of enzyme patterns, especially certain aminotransferase markers. A limited study of superoxide dismutase polymorphism suggested a further marker of value. The isolates of high initial virulence to rodents, which are thus behaviourally akin to T. b. rhodesiense, did not share these characteristics. We conclude that there exists a homogeneous group of trypanosomes of wide dispersion throughout tropical Africa, characterized by certain isoenzyme combinations and low initial virulence to rodents, which corresponds to the classical concept of T. b. gambiense. The features of limited antigenic repertoire, high resistance to normal human serum and restriction fragment length polymorphisms of the genes for certain variant surface glycoproteins also appear to be characteristic of this group.
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35
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Gigase PL, Wéry M. [Too sensitive a diagnosis or too toxic a treatment?]. Ann Soc Belg Med Trop 1986; 66:197-8. [PMID: 3827348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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36
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Abstract
Comparative analyses were made to define the immunogenic role in mice of the variant surface coat glycoprotein (VSG) of African trypanosomes. Less than 10 micrograms of the glycoprotein fixed to trypanosomes or covalently linked to sheep erythrocytes were 100 times more immunogenic than soluble VSG. Therefore, although VSG is present on the parasites and in the blood of infected hosts, the cell-bound form most likely elicits immunity. Intravenous administration of soluble or cell-bound VSG was a better route of immunization than the subcutaneous route. Therefore, although parasites grow at the site of infection, in tissue spaces, and in the blood, control of blood parasitemia is best developed if the antigen is introduced to the vascular bed. Full protection against homologous challenge occurred by 4 days and was maintained through 30 days. Trypanosome-agglutinating antibody titers could be measured at 3 days, peaked at 5 days, and remained high through 14 days after immunization. Therefore, mice immunized with an optimal dosage of VSG, 2 days before challenge, should have had ample time to elicit a protective response. Most of these mice, however, developed patent infections, and one-third died during the first peak of parasitemia at about the same time as untreated control mice. This indicates that active infection inhibits the early phases of induction of immunity. Mice, suboptimally immunized against and challenged with an avirulent isolate of Trypanosoma brucei gambiense, survived at higher rates than mice immunized and challenged with a virulent clone of T. b. rhodesiense. Cell-fixed and soluble VSG from both parasites elicited similar agglutinating-antibody titers, indicating that the two trypanosomes were equally antigenic. Results from neutralization tests, however, revealed that, per unit of immune mouse serum, 400 times more T. b. gambiense became noninfective than T. b. rhodesiense. Apparently, virulence is related to relative sensitivity of the trypanosomes to immunological assault.
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37
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Hall JE, Seed JR, Sechelski JB. Multiple alpha-keto aciduria in Microtus montanus chronically infected with Trypanosoma brucei gambiense. Comp Biochem Physiol B 1985; 82:73-8. [PMID: 3902349 DOI: 10.1016/0305-0491(85)90130-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Microtus montanus chronically infected with a monomorphic strain of Trypanosoma brucei gambiense excreted in urine greatly elevated quantities of not only the aromatic alpha-keto acids, phenylpyruvic and 4-hydroxyphenylpyruvic acids, but also two aliphatic alpha-keto acids, pyruvic and alpha-ketoglutaric acids. Elevated keto acid excretion began approximately midway through infection and quantities remained elevated until death. Daily keto acid excretion did not correlate with daily parasitemia. Thus, a large metabolic disturbance exists in laboratory animals infected with African trypanosomes. The multiple alpha-keto aciduria potentially contributes to the pathogenesis of chronic African trypanosomiasis.
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Büngener W, Mehlitz D. Histopathological findings in mini-pigs infected with different strains of Trypanosoma brucei. Tropenmed Parasitol 1984; 35:109-14. [PMID: 6464185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Two pigs infected with Trypanosoma brucei gambiense developed low parasitemia which became undetectable after 6 months; on autopsy 13 months after infection they showed no histopathological alterations. --Five of six pigs infected with a Trypanosoma brucei brucei strain from the Ivory Coast developed low parasitemia (up to about antilog 6.5 per ml of blood) which became progressively lower but was detectable up to one year after infection. On autopsy they showed interstitial myocarditis and meningo-encephalitis; during the course of the infection, the first became milder, the second more intense; no trypanosomes were seen in the tissues. One of these pigs developed a parasitemia of up to antilog 8 and died 172 days after infection from bacterial pneumonia, histologically it had severe myocarditis with many trypanosomes in the tissue and mild meningo-encephalitis. --Three pigs infected with a Trypanosoma brucei brucei strain from the Serengeti died 47, 68, 130 days after infection. The first dying pig had a high terminal parasitemia, in the others, the parasitemia was low until the end, being only detectable by the hematocrit centrifugation technique or by mouse passage. At autopsy, all showed massive myocarditis and interstitial nephritis with masses of extravascular trypanosomes, moderate meningo-encephalitis with very few trypanosomes, and widespread colonization of other organs and tissues by trypanosomes, still without marked cellular infiltrations.
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39
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Joshua RA, Magaji Y, Kayit YS. Isolation of human serum resistant Trypanozoon from cattle in Nigeria. Tropenmed Parasitol 1983; 34:201-2. [PMID: 6636302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Four trypanosome stocks of the subgenus Trypanozoon were isolated from a herd of cattle in the Jos Plateau of Nigerian during a study on the epizootiology of trypanosomiasis. One of the stocks was repeatedly highly resistant to normal human serum (Blood Incubation Infectivity Test), indicating potential human infectivity. These observations suggest that the domestic cattle might act as reservoir hosts for the causative agent of human trypanosomiasis.
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40
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Babiker EA, Le Ray D. Adaptation of low virulence stocks of Trypanosoma brucei gambiense to rat and mouse. Ann Soc Belg Med Trop 1981; 61:15-29. [PMID: 7294922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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41
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Princewill TJ. Effect of storage in ice on pathogenicity of salivarian trypanosomes. Bull Anim Health Prod Afr 1980; 28:115-29. [PMID: 7437543] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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42
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Beckers A, Wéry M, Van Marck E, Gigase P. Experimental infections of laboratory rodents with recently isolated stocks of Trypanosoma brucei gambiense. 1. Parasitological investigations. Z Parasitenkd 1980; 64:285-96. [PMID: 6971541 DOI: 10.1007/bf00927376] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Albino rats and white mice were infected with populations of Trypanosoma brucei gambiense isolated from patients in four different areas in Central Africa. Differences in virulence as shown by the level of parasitaemia, number of relapses, and length of survival time, were observed amongst the stocks according to their geographical origin and secondarily to the degree of adaptation to the rodents. All the stocks are pathogenic for the laboratory rodents, and the presence of extravascular trypanosomes in the brain was confirmed in all infected animals. Spleen, liver, and kidneys were less constantly found to be positive. The morphology of the extravascular parasites was highly variable, ranging from long slender trypomastigotes to spheromastigotes and even amastigotes.
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43
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Gray AR. Variable agglutinogenic antigens of Trypanosoma gambiense and their distribution among isolates of the trypanosome collected in different places in Nigeria. Trans R Soc Trop Med Hyg 1972; 66:263-84. [PMID: 5048793 DOI: 10.1016/0035-9203(72)90158-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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44
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Molyneux DH. Isolation of Trypanosoma (Trypanozoon) brucei gambiense by the intratesticular inoculation technique and the biology of the parasites after isolation. Trans R Soc Trop Med Hyg 1972; 66:338-9. [PMID: 5048844 DOI: 10.1016/0035-9203(72)90219-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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45
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