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Ageed A, Khan M. Eliminating Trachoma in Africa: The Importance of Environmental Interventions. Cureus 2024; 16:e52358. [PMID: 38234389 PMCID: PMC10792353 DOI: 10.7759/cureus.52358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2024] [Indexed: 01/19/2024] Open
Abstract
Subsequent to the failure of the World Health Organisation (WHO) of achieving their target to eliminate trachoma by the year 2020, the most effective strategy in eliminating trachoma must be re-examined to accomplish the new target of eradication by the year 2030. Whilst antibiotic therapy is a core foundation of this elimination strategy, another important factor is the state of the environmental conditions in trachoma endemic countries. This manuscript aimed to identify the impact of environmental improvement strategies on the prevalence of trachoma and the significance of environmental improvement alongside the use of antibiotic treatment to achieve trachoma elimination. Two independent literature searches were conducted up until the 5th of July 2021. Two main databases were used to carry out these literature searches, namely, Ovid EMBASE and Ovid MEDLINE. All of the relevant references were found using MeSH and free text terms. Key terms used were 'trachoma', 'water', 'sanitation', 'hygiene' and 'environmental Improvement'. The exclusion criteria included non-African-based studies, review papers, protocols and case reports. A total of 17 studies were included for this review. Living within a close range of a water source was significantly associated with reduced risk of trachoma infection. Water obtained from piped water sources was associated with the lowest rates of active trachoma. Studies on facial cleanliness evidenced a strong association with reduced prevalence of trachoma. Whilst the provision of latrine facilities found was significantly associated with reduced prevalence of trachoma, there was no significant difference between the use of private latrine facilities over communal latrine facilities. The use of repeated scheduled antibiotic treatments over single-use antibiotic distribution had a greater impact both short term and long term on the prevalence rates of trachoma. Nonetheless, prevalence rates increased again following the commencement of treatment. Mass antibiotic treatment has been proven to have a greater impact on lowering the prevalence of trachoma initially, but this impact is not sustainable due to the rise in prevalence rates following the completion of treatment. A holistic approach, therefore, must be implemented with evidence showing that an emphasis on longer-term environmental methods should be implemented to compliment antibiotic distribution. Prioritisation of specific interventional measures should be tailored according to local epidemiology; nonetheless, these measures form the backbone of a trachoma elimination strategy to eliminate trachoma by the year 2030.
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Affiliation(s)
- Ahmed Ageed
- Hospital Medicine, University Hospitals of Leicester NHS Trust, Leicester, GBR
| | - Maaz Khan
- Medical Education, Royal Surrey County Hospital, Guildford, GBR
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Maciel AMS, Ramos AN, Gomes VDS, Ferreira AF, de Almeida NMGS, Gómez DVF, Favacho JDFR, Maciel MMS, Delerino AL, Pires RDJ. Epidemiology and control of trachoma in the state of Ceará, Northeast Brazil, 2007-2021. Rev Soc Bras Med Trop 2023; 56:S0037-86822023000100302. [PMID: 36700599 PMCID: PMC9870276 DOI: 10.1590/0037-8682-0207-2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 08/24/2022] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND To analyze the epidemiology, surveillance, and control strategies for trachoma in the state of Ceará, northeast Brazil, from 2007 to 2021. METHODS This ecological study was based on secondary data from the Information System on Notifiable Diseases of the Secretary of Health of the state of Ceará. Data from school and home surveys for trachoma detection obtained during the study period were analyzed, the percentage of positivity was estimated, and sociodemographic and clinico-epidemiological factors were investigated. RESULTS The coverage of trachoma surveillance and control actions in Ceará municipalities increased from 12.5% in 2007 to 55.9% in 2019, but with an average restriction of 8.0% during the COVID-19 pandemic. The estimated trachoma positivity (mean overall positivity) was less than 5.0% (2.76%, 95% CI 1.2-5.2), with a higher proportion of cases in the 5-9-year age group (45.0%, 95% CI 44.6-45.4), in females (53.2%, 95% CI 52.8-53.6), and rural areas (52.6%, 95% CI 52.2-53.0). Positivity above 10.0% was observed in the Litoral Leste/Jaguaribe and Sertão Central regions, with a higher occurrence of the follicular inflammatory clinical form (98.1%, 95% CI 98.0-98.2). CONCLUSIONS Trachoma remains in the state of Ceará and is likely underreported. Despite recent advances, the fragility of health surveillance activities compromises the recognition of the actual magnitude and distribution of trachoma in the state. Accurate information is fundamental for planning, monitoring, and evaluating surveillance and disease control.
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Affiliation(s)
- Adjoane Maurício Silva Maciel
- Universidade Federal do Ceará, Faculdade de Medicina, Programa de pós-graduação em Saúde Pública, Fortaleza, CE, Brasil.,Secretária Municipal de Saúde, Russas, CE, Brasil
| | - Alberto Novaes Ramos
- Universidade Federal do Ceará, Faculdade de Medicina, Programa de pós-graduação em Saúde Pública, Fortaleza, CE, Brasil.,Universidade Federal do Ceará, Faculdade de Medicina, Departamento de Saúde Comunitária, Fortaleza, CE, Brasil
| | - Vivian da Silva Gomes
- Universidade Federal do Ceará, Faculdade de Medicina, Programa de pós-graduação em Saúde Pública, Fortaleza, CE, Brasil.,Secretaria de Estado da Saúde, Fortaleza, CE, Brasil
| | - Anderson Fuentes Ferreira
- Universidade Federal do Ceará, Faculdade de Medicina, Programa de pós-graduação em Saúde Pública, Fortaleza, CE, Brasil
| | | | | | | | | | | | - Roberto da Justa Pires
- Universidade Federal do Ceará, Faculdade de Medicina, Programa de pós-graduação em Saúde Pública, Fortaleza, CE, Brasil.,Universidade Federal do Ceará, Faculdade de Medicina, Departamento de Saúde Comunitária, Fortaleza, CE, Brasil
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Balters L, Reichl S. 3D bioprinting of corneal models: A review of the current state and future outlook. J Tissue Eng 2023; 14:20417314231197793. [PMID: 37719307 PMCID: PMC10504850 DOI: 10.1177/20417314231197793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 08/13/2023] [Indexed: 09/19/2023] Open
Abstract
The cornea is the outermost layer of the eye and serves to protect the eye and enable vision by refracting light. The need for cornea organ donors remains high, and the demand for an artificial alternative continues to grow. 3D bioprinting is a promising new method to create artificial organs and tissues. 3D bioprinting offers the precise spatial arrangement of biomaterials and cells to create 3D constructs. As the cornea is an avascular tissue which makes it more attractive for 3D bioprinting, it could be one of the first tissues to be made fully functional via 3D bioprinting. This review discusses the most common 3D bioprinting technologies and biomaterials used for 3D bioprinting corneal models. Additionally, the current state of 3D bioprinted corneal models, especially specific characteristics such as light transmission, biomechanics, and marker expression, and in vivo studies are discussed. Finally, the current challenges and future prospects are presented.
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Affiliation(s)
- Leon Balters
- Institute of Pharmaceutical Technology and Biopharmaceutics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Stephan Reichl
- Institute of Pharmaceutical Technology and Biopharmaceutics, Technische Universität Braunschweig, Braunschweig, Germany
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Mekonnen J, Kassim J, Ahmed M, Gebeyehu N. Prevalence of active trachoma and associated factors among children 1-9 years old at Arsi Negele Town, West Arsi Zone, Oromia Regional State, Southern Ethiopia. PLoS One 2022; 17:e0273808. [PMID: 36206245 PMCID: PMC9543983 DOI: 10.1371/journal.pone.0273808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 08/15/2022] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Trachoma is a public health issue in more than 50 nations worldwide, mainly in Sub-Saharan Africa, where hundreds of millions of people are considered blind. Ethiopia is projected to have 30% of the global active trachoma burden. The frequency of Trachoma Folliculitis in children aged 1 to 9 years old is 30% in the Oromia Region. Therefore, the aim of this study was to assess the prevalence of active trachoma and associated variables among children aged 1 to 9 years old in Arsi Negele Town, West Arsi Zone, Oromia Regional State, Southern Ethiopia, December 24-26, 2019. METHODS A community-based cross-sectional study was conducted in the Arsi Negele town community on December 24-26, 2019. A total of 178 study volunteers were recruited using a single population proportion formula and assigned to families in the town's three kebeles in proportion. A simple random selection procedure was used to choose study participants from the identified households. Madda Walabu University provided ethical approval, and different government structures provided letters of permission. Pre-tested structured questionnaires and binocular loupes X 2.5 were used to collect data from either mothers or fathers of eligible children for eye examination; torches with bottles of alcohol were used to gather data from either mothers or fathers of eligible children for eye examination. For analysis, data was entered into (IBM, SPSS) version 22. To assess factors associated with active trachoma, bivariate and multivariable logistic regressions were used. The crude and adjusted odds ratios with 95% confidence intervals were calculated to investigate the degree of association between the independent variables and active trachoma. Multivariate logistic regression was used to find connections between dependent and independent variables with a p≤ 0.05 confidence levels and a 95% confidence interval. RESULT The prevalence of active trachoma was determined to be 21.91% TF among 178 children aged 1 to 9 years. Flies on children's faces (AOR = 3.427; 95 percent CI: 1.432-8.171), unclean children's faces (AOR = 3.99; 95 percent CI: 1.427-11.158), face washing habits (AOR = 3.064; 95 percent CI: 1.273-7.373), and not using soap while face washing (AOR = 4.564; 95 percent CI 1.561-13.342) were found to be statistically significant associated factors with the prevalence of active trachoma. CONCLUSION The prevalence of active trachoma was found to be relatively high. Face washing practices and the lack of soap use while washing faces were found as associated factors requiring optimal interventions to prevent trachoma infection among children aged 1-9 years in Arsi Negele town.
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Affiliation(s)
- Jemal Mekonnen
- Department of Malaria Prevention & Control, West Arsi Zone Health Office, Shashemene, Ethiopia
| | - Jeylan Kassim
- Department of Public Health, Madda Walabu University Goba Referral Hospital, Bale Goba, Ethiopia
| | - Muluneh Ahmed
- Department of Nursing, School of Health Science, Madda Walabu University, Shashemene campus, Shashemene, Ethiopia
| | - Negeso Gebeyehu
- Department of Midwifery, School of Health Science, Madda Walabu University, Shashemene Campus, Shashemene, Ethiopia
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Global progress toward the elimination of active trachoma: an analysis of 38 countries. Lancet Glob Health 2022; 10:e491-e500. [PMID: 35303459 DOI: 10.1016/s2214-109x(22)00050-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 01/27/2022] [Accepted: 02/03/2022] [Indexed: 11/21/2022]
Abstract
BACKGROUND Global elimination of trachoma as a public health problem was targeted for 2020. We reviewed progress towards the elimination of active trachoma by country and geographical group. METHODS In this retrospective analysis of national survey and implementation data, all countries ever known to be endemic for trachoma that had either implemented at least one trachoma impact survey shown in the publicly available Trachoma Atlas, or are in Africa were invited to participate in this study. Scale-up was described according to the number of known endemic implementation units and mass drug administration implementation over time. The prevalence of active trachoma-follicular among children aged 1-9 years (TF1-9) from baseline, impact, and surveillance surveys was categorised and used to show programme progress towards reaching the elimination threshold (TF1-9 <5%) using dot maps, spaghetti plots, and boxplots. FINDINGS We included data until Nov 10, 2021, for 38 countries, representing 2097 ever-endemic implementation units. Of these, 1923 (91·7%) have had mass drug administration. Of 1731 implementation units with a trachoma impact survey, the prevalence of TF1-9 had reduced by at least 50% in 1465 (84·6%) implementation units and 1182 (56·4%) of 2097 ever-endemic implementation units had reached the elimination threshold. 2 years after reaching a TF1-9 prevalence below 5%, most implementation units sustained this target; however, 58 (56·3%) of 103 implementation units in Ethiopia showed recrudescence. INTERPRETATION Global elimination of trachoma as a public health problem by 2020 was not possible, but this finding masks the great progress achieved. Implementation units in high baseline categories and recrudescent TF1-9 might prolong the attainment of elimination of active trachoma. Elimination is delayed but, with an understanding of the patterns and timelines to reaching elimination targets and a commitment toward meeting future targets, global elimination can still be achieved by 2030. FUNDING None.
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Blumberg S, Borlase A, Prada JM, Solomon AW, Emerson P, Hooper PJ, Deiner MS, Amoah B, Hollingsworth TD, Porco TC, Lietman TM. Implications of the COVID-19 pandemic in eliminating trachoma as a public health problem. Trans R Soc Trop Med Hyg 2021; 115:222-228. [PMID: 33449114 PMCID: PMC7928550 DOI: 10.1093/trstmh/traa170] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 11/07/2020] [Accepted: 01/09/2021] [Indexed: 11/13/2022] Open
Abstract
Background Progress towards elimination of trachoma as a public health problem has been substantial, but the coronavirus disease 2019 (COVID-19) pandemic has disrupted community-based control efforts. Methods We use a susceptible-infected model to estimate the impact of delayed distribution of azithromycin treatment on the prevalence of active trachoma. Results We identify three distinct scenarios for geographic districts depending on whether the basic reproduction number and the treatment-associated reproduction number are above or below a value of 1. We find that when the basic reproduction number is <1, no significant delays in disease control will be caused. However, when the basic reproduction number is >1, significant delays can occur. In most districts, 1 y of COVID-related delay can be mitigated by a single extra round of mass drug administration. However, supercritical districts require a new paradigm of infection control because the current strategies will not eliminate disease. Conclusions If the pandemic can motivate judicious, community-specific implementation of control strategies, global elimination of trachoma as a public health problem could be accelerated.
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Affiliation(s)
- Seth Blumberg
- Francis I Proctor Foundation, University of California, San Francisco, San Francisco, CA, USA
| | | | - Joaquin M Prada
- Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK
| | - Anthony W Solomon
- Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
| | - Paul Emerson
- International Trachoma Initiative, Task Force for Global Health, Decatur, GA, USA
| | - Pamela J Hooper
- International Trachoma Initiative, Task Force for Global Health, Decatur, GA, USA
| | - Michael S Deiner
- Francis I Proctor Foundation, University of California, San Francisco, San Francisco, CA, USA
| | - Benjamin Amoah
- Lancaster Medical School, Lancaster University, Bailrigg, Lancaster, UK
| | | | - Travis C Porco
- Francis I Proctor Foundation, University of California, San Francisco, San Francisco, CA, USA.,Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA
| | - Thomas M Lietman
- Francis I Proctor Foundation, University of California, San Francisco, San Francisco, CA, USA.,Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA.,Institute for Global Health Sciences, University of California, San Francisco, San Francisco, CA, USA.,Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
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7
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Silva EJD, Pereira DP, Ambrózio JOAM, Barboza LM, Fonseca VL, Caldeira AP. Prevalence of trachoma and associated factors in students from the Jequitinhonha Valley, Minas Gerais, Brazil. Rev Soc Bras Med Trop 2020; 53:e20200056. [PMID: 33111907 PMCID: PMC7580275 DOI: 10.1590/0037-8682-0056-2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Accepted: 07/27/2020] [Indexed: 11/22/2022] Open
Abstract
INTRODUCTION: Trachoma is the leading cause of blindness in the world, especially in undeveloped countries, due to its association with poor socioeconomic and sanitation conditions. This study aimed to estimate the prevalence of trachoma among students from the Jequitinhonha Valley, Minas Gerais, one of the poorest regions in Brazil, and to identify associated factors. METHODS: This is a cross-sectional study that utilized clinical evaluation and a socioeconomic questionnaire applied to a random and representative sample of elementary school students from the Jequitinhonha Valley, Minas Gerais, Brazil. Participants underwent conjunctival scraping and direct immunofluorescence was used to confirm the presence of the bacteria. Five or more elementary bodies in the conjunctival scrape was considered a positive result. In the study, 36.6% positive samples were detected. A culture of the conjunctival scrape, considered to be the "gold standard", was not performed due to cost and complexity. Bivariate analyses were performed, followed by binary logistic regression analysis to define the associated variables. RESULTS: In the present study, 478 students comprised the sample. The prevalence of trachoma was 6.3% and was higher among students who lived in unfinished houses (no plastering, painting, flooring, and unfinished bathrooms) (OR, 2.27; 95% CI, 1.12-6.48) without sewage systems (OR = 9.49; 95% CI = 3.52-25.60) and studied in rural areas (OR, 3.37; 95% CI, 1.53-7.35). CONCLUSIONS: The prevalence of trachoma among the students aged 7 to 16 years old, from public and private schools, is not negligible and is especially associated with inadequate living conditions.
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Affiliation(s)
- Evanildo José da Silva
- Universidade Federal dos Vales do Jequitinhonha e Mucuri, Departamento de Medicina, Diamantina, MG, Brasil
| | - Daniela Porto Pereira
- Universidade Federal dos Vales do Jequitinhonha e Mucuri, Departamento de Medicina, Diamantina, MG, Brasil
| | | | - Laiara Morais Barboza
- Universidade Federal dos Vales do Jequitinhonha e Mucuri, Departamento de Medicina, Diamantina, MG, Brasil
| | - Vivian Ladeira Fonseca
- Universidade Federal dos Vales do Jequitinhonha e Mucuri, Departamento de Medicina, Diamantina, MG, Brasil
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Nasir MA, Elsawy F, Omar A, Haque SO, Nadir R. Eliminating Trachoma by 2020: Assessing Progress in Nigeria. Cureus 2020; 12:e9450. [PMID: 32760636 PMCID: PMC7392186 DOI: 10.7759/cureus.9450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Trachoma is a neglected tropical disease that causes an eye infection which can lead to blindness if left untreated. In 1998, the World Health Organisation (WHO) launched a new goal to eradicate trachoma by 2020. Over the years, in partnership with the WHO, an effective strategy plan was devised to help tackle and control the disease. This involved surgery for trichiasis, antibiotic treatment, facial cleanliness, and environmental improvement (SAFE). Consequently, the number of people affected by trachoma has significantly decreased in recent times. Despite this, trachoma remains a major public health concern in 44 countries worldwide, including Nigeria. Although improvements have been seen throughout Nigeria, the disjointed application of the SAFE strategy has delayed progress compared to other countries. Providing quality treatment to those with trachoma, in addition to improving preventative measures are challenges faced throughout the country. However, a multi-pronged approach emulating the methods of other countries is recommended to achieve trachoma elimination. This review aims to evaluate the progress and challenges faced in Nigeria with regards to eliminating trachoma.
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Affiliation(s)
| | - Fayez Elsawy
- Medicine, Manchester University, Manchester, GBR
| | | | - Shah O Haque
- Medicine, Manchester University, Manchester, GBR
| | - Rans Nadir
- Medicine, Imperial College London, London, GBR
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The functional ClpXP protease of Chlamydia trachomatis requires distinct clpP genes from separate genetic loci. Sci Rep 2019; 9:14129. [PMID: 31575885 PMCID: PMC6773864 DOI: 10.1038/s41598-019-50505-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Accepted: 09/13/2019] [Indexed: 12/15/2022] Open
Abstract
Clp proteases play a central role in bacterial physiology and, for some bacterial species, are even essential for survival. Also due to their conservation among bacteria including important human pathogens, Clp proteases have recently attracted considerable attention as antibiotic targets. Here, we functionally reconstituted and characterized the ClpXP protease of Chlamydia trachomatis (ctClpXP), an obligate intracellular pathogen and the causative agent of widespread sexually transmitted diseases in humans. Our in vitro data show that ctClpXP is formed by a hetero-tetradecameric proteolytic core, composed of two distinct homologs of ClpP (ctClpP1 and ctClpP2), that associates with the unfoldase ctClpX via ctClpP2 for regulated protein degradation. Antibiotics of the ADEP class interfere with protease functions by both preventing the interaction of ctClpX with ctClpP1P2 and activating the otherwise dormant proteolytic core for unregulated proteolysis. Thus, our results reveal molecular insight into ctClpXP function, validating this protease as an antibacterial target.
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Favacho J, Alves da Cunha AJL, Gomes STM, Freitas FB, Queiroz MAF, Vallinoto ACR, Ishak R, Ishak MDOG. Prevalence of trachoma in school children in the Marajó Archipelago, Brazilian Amazon, and the impact of the introduction of educational and preventive measures on the disease over eight years. PLoS Negl Trop Dis 2018; 12:e0006282. [PMID: 29447155 PMCID: PMC5831641 DOI: 10.1371/journal.pntd.0006282] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Revised: 02/28/2018] [Accepted: 01/30/2018] [Indexed: 11/25/2022] Open
Abstract
Trachoma is the leading infectious cause of blindness in the world and is associated with precarious living conditions in developing countries. The aim of the present study was to evaluate the prevalence of trachoma in three municipalities of the Marajó Archipelago, located in the state of Pará, Brazil. In 2008, 2,054 schoolchildren from the public primary school system of the urban area of the region and their communicants were clinically examined; in 2016, 1,502 schoolchildren were examined. The positive cases seen during the clinical evaluation were confirmed by direct immunofluorescence (DIF) laboratory tests. The presence of antibodies against the genus Chlamydia was evaluated by indirect immunofluorescence (IIF), and the serotypes were determined by microimmunofluorescence (MIF). In 2008, the prevalence of trachoma among schoolchildren was 3.4% (69 cases) and it was more frequent in children between six and nine years of age and in females; among the communicants, a prevalence of 16.5% was observed. In 2016, three cases of trachoma were diagnosed (prevalence of 0.2%), found only in the municipality of Soure. The results of the present study showed that in 2008, trachoma had a low prevalence (3.4%) among schoolchildren in the urban area of Marajó Archipelago; eight years after the first evaluation and the introduction of control and prevention measures (SAFE strategy), there was a drastic reduction in the number of cases (0.2%), demonstrating the need for constant monitoring and effective measures for the elimination of trachoma. Trachoma is one of the main neglected infectious diseases and carry a considerable burden to human health as a consequence of the clinical severity of the disease which may evolve to blindness. The lack of hygiene, education and other indicators of low social and economic markers occurring in developing and underdeveloped countries favour the spread of Chlamydia trachomatis, the bacterium causing trachoma. Although there is an easy, cheap and available treatment, reinfections are common and transmission is a consequence of bad hygienic habits and the various serotypes of the bacterium. The Marajó territory, in the North of the Amazon region of Brazil, is a large area with an ill educated, poor population, with almost no access to health resources and with almost no chance of transportation to major urban centers. Trachoma was detected a long time ago in the island and now, for the first time, a clear effort was produced during an eight year period in order to improve health hygienic habits among children and their relatives. The number of new cases following an initial diagnosis, was significantly reduced by the application of the WHO SAFE (Surgery, Antibiotics, Facial hygiene and Education for better habits) strategy.
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Affiliation(s)
- Joana Favacho
- Health Surveillance Department, Evandro Chagas Institute, Bélem, Pará, Brasil
| | | | | | | | | | | | - Ricardo Ishak
- Biological Sciences Institute, Federal University of Pará, Belém, Pará, Brasil
- * E-mail:
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Pinsent A, Gambhir M. Improving our forecasts for trachoma elimination: What else do we need to know? PLoS Negl Trop Dis 2017; 11:e0005378. [PMID: 28182664 PMCID: PMC5321453 DOI: 10.1371/journal.pntd.0005378] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 02/22/2017] [Accepted: 02/01/2017] [Indexed: 11/20/2022] Open
Abstract
The World Health Organization (WHO) has targeted trachoma for elimination as a public health concern by 2020. Mathematical modelling is used for a range of infectious diseases to assess the impact of different intervention strategies on the prevalence of infection or disease. Here we evaluate the performance of four different mechanistic mathematical models that could all realistically represent trachoma transmission. We fit the four different mechanistic models of trachoma transmission to cross-sectional age-specific Polymerase Chain Reaction (PCR) and Trachomatous inflammation, follicular (TF) prevalence data. We estimate 4 or 3 parameters within each model, including the duration of an individual's infection and disease episode using Markov Chain Monte Carlo. We assess the performance of each models fit to the data by calculating the deviance information criterion. We then model the implementation of different interventions for each model structure to assess the feasibility of elimination of trachoma with different model structures. A model structure which allowed some re-infection in the disease state (Model 2) was statistically the most well performing model. All models struggled to fit to the very high prevalence of active disease in the youngest age group. Our simulations suggested that for Model 3, with annual antibiotic treatment and transmission reduction, the chance of reducing active disease prevalence to < 5% within 5 years was very low, while Model 2 and 4 could ensure that active disease prevalence was reduced within 5 years. Model 2 here fitted to the data best of the models evaluated. The appropriate level of susceptibility to re-infection was, however, challenging to identify given the amount and kind of data available. We demonstrate that the model structure assumed can lead to different end points following the implementation of the same interventions. Our findings are likely to extend beyond trachoma and should be considered when modelling other neglected tropical diseases.
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Affiliation(s)
- Amy Pinsent
- Department of Epidemiology and Preventive Medicine, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia
| | - Manoj Gambhir
- Department of Epidemiology and Preventive Medicine, Faculty of Medicine, Nursing and Health Sciences, Monash University, Melbourne, Victoria, Australia
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12
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Liu T, Liang Q, Hu A, Feng G, Wang N, Peng X, Baudouin C, Labbé A. Elimination of blinding trachoma in China. J Fr Ophtalmol 2016; 39:836-842. [PMID: 27865692 DOI: 10.1016/j.jfo.2016.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 09/28/2016] [Accepted: 10/04/2016] [Indexed: 10/20/2022]
Abstract
OBJECTIVE To present the change in the prevalence of blindness caused by trachoma between 1987 and 2006 by secondary data analysis based on two China National Sample Surveys on Disability (CNSSD). METHODS Secondary data analysis was performed on two China National Sample Surveys on Disability (CNSSD), which were national representative household surveys conducted in 1987 and 2006. The prevalence of blindness caused by trachoma was estimated by 10-year age group. In addition, the proportion of various causes of blindness was evaluated. The geographical distribution of blindness caused by trachoma both in 1987 and 2006 was analyzed in order to visualize the hot spots of blinding trachoma in China. RESULTS The prevalence of blindness caused by trachoma in China decreased from 51.5/100,000 in 1987 to 17.6/100,000 in 2006. In addition, the proportion of blindness attributed to trachoma also decreased from 10.1% (1987) to 0.9% (2006). Moreover, the prevalence of blindness caused by trachoma was over 200/100,000 in 2.2% of sampled counties in 2006 as compared to 8.6% in 1987. The hot spots of blinding trachoma were shown to be limited to underdeveloped mountain areas in Hubei and Guizhou provinces. CONCLUSION Although blinding trachoma is no longer the leading cause of blindness in China since the 2000's, the prevalence of trachoma should still be monitored in some underdeveloped mountain areas. Therefore, health organization must continue to fight against blinding trachoma in underdeveloped areas.
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Affiliation(s)
- T Liu
- Department of epidemiology and biostatistics, school of public health, Capital medical university, No.10, Xitoutiao, 100069 You An Men, Beijing, China
| | - Q Liang
- Beijing institute of ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Key laboratory of ophthalmology and visual sciences, 100005 Beijing, China
| | - A Hu
- Beijing institute of ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Key laboratory of ophthalmology and visual sciences, 100005 Beijing, China
| | - G Feng
- Center of clinical epidemiology & evidence-based medicine, Beijing children's hospital, capital medical university, Beijing, China
| | - N Wang
- Beijing institute of ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Key laboratory of ophthalmology and visual sciences, 100005 Beijing, China
| | - X Peng
- Department of epidemiology and biostatistics, school of public health, Capital medical university, No.10, Xitoutiao, 100069 You An Men, Beijing, China; Center of clinical epidemiology & evidence-based medicine, Beijing children's hospital, capital medical university, Beijing, China.
| | - C Baudouin
- Beijing institute of ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Key laboratory of ophthalmology and visual sciences, 100005 Beijing, China; Quinze-Vingts national ophthalmology hospital, 75012 Paris, France; Versailles Saint-Quentin-en-Yvelines university, 78000 Versailles, France; Inserm, U968, 75012 Paris, France; UPMC Université Paris 06, UMR_S 968, institut de la vision, 75012 Paris, France; CNRS, UMR_7210, 75012 Paris, France
| | - A Labbé
- Beijing institute of ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Key laboratory of ophthalmology and visual sciences, 100005 Beijing, China; Quinze-Vingts national ophthalmology hospital, 75012 Paris, France; Versailles Saint-Quentin-en-Yvelines university, 78000 Versailles, France; Inserm, U968, 75012 Paris, France; UPMC Université Paris 06, UMR_S 968, institut de la vision, 75012 Paris, France; CNRS, UMR_7210, 75012 Paris, France
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Pinsent A, Blake IM, Basáñez MG, Gambhir M. Mathematical Modelling of Trachoma Transmission, Control and Elimination. ADVANCES IN PARASITOLOGY 2016; 94:1-48. [PMID: 27756453 DOI: 10.1016/bs.apar.2016.06.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The World Health Organization has targeted the elimination of blinding trachoma by the year 2020. To this end, the Global Elimination of Blinding Trachoma (GET, 2020) alliance relies on a four-pronged approach, known as the SAFE strategy (S for trichiasis surgery; A for antibiotic treatment; F for facial cleanliness and E for environmental improvement). Well-constructed and parameterized mathematical models provide useful tools that can be used in policy making and forecasting in order to help to control trachoma and understand the feasibility of this large-scale elimination effort. As we approach this goal, the need to understand the transmission dynamics of infection within areas of different endemicities, to optimize available resources and to identify which strategies are the most cost-effective becomes more pressing. In this study, we conducted a review of the modelling literature for trachoma and identified 23 articles that included a mechanistic or statistical model of the transmission, dynamics and/or control of (ocular) Chlamydia trachomatis. Insights into the dynamics of trachoma transmission have been generated through both deterministic and stochastic models. A large body of the modelling work conducted to date has shown that, to varying degrees of effectiveness, antibiotic administration can reduce or interrupt trachoma transmission. However, very little analysis has been conducted to consider the effect of nonpharmaceutical interventions (and particularly the F and E components of the SAFE strategy) in helping to reduce transmission. Furthermore, very few of the models identified in the literature review included a structure that permitted tracking of the prevalence of active disease (in the absence of active infection) and the subsequent progression to disease sequelae (the morbidity associated with trachoma and ultimately the target of GET 2020 goals). This represents a critical gap in the current trachoma modelling literature, which makes it difficult to reliably link infection and disease. In addition, it hinders the application of modelling to assist the public health community in understanding whether trachoma programmes are on track to reach the GET goals by 2020. Another gap identified in this review was that of the 23 articles examined, only one considered the cost-effectiveness of the interventions implemented. We conclude that although good progress has been made towards the development of modelling frameworks for trachoma transmission, key components of disease sequelae representation and economic evaluation of interventions are currently missing from the available literature. We recommend that rapid advances in these areas should be urgently made to ensure that mathematical models for trachoma transmission can robustly guide elimination efforts and quantify progress towards GET 2020.
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Affiliation(s)
- A Pinsent
- Monash University, Melbourne, VIC, Australia
| | - I M Blake
- Imperial College London, London, United Kingdom
| | - M G Basáñez
- Imperial College London, London, United Kingdom
| | - M Gambhir
- Monash University, Melbourne, VIC, Australia
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Gambhir M, Grassly NC, Burton MJ, Solomon AW, Taylor HR, Mabey DC, Blake IM, Basáñez MG. Estimating the Future Impact of a Multi-Pronged Intervention Strategy on Ocular Disease Sequelae Caused by Trachoma: A Modeling Study. Ophthalmic Epidemiol 2016; 22:394-402. [PMID: 26653262 PMCID: PMC4841017 DOI: 10.3109/09286586.2015.1081249] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Purpose: Trachoma control programs are underway in endemic regions worldwide. They are based on the SAFE strategy (Surgery for trichiasis, Antibiotic distribution, Facial cleanliness, and Environmental improvement). Although much is known about the effect of community-wide treatment with antibiotics on the prevalence of Chlamydia trachomatis, the impact of the SAFE strategy on severe ocular disease sequelae (the main focus of the Global Elimination of blinding Trachoma by 2020 program) remains largely unknown. Methods: We use a mathematical model to explore the impact of each of the components of the SAFE strategy, individually and together, on disease sequelae, arising from repeat infection and subsequent conjunctival scarring. We ask whether two elimination goals, to reduce the prevalence of trachomatous trichiasis to 1 per 1000 persons, and the incidence of corneal opacity to 1 per 10,000 persons per annum, are achievable, and which combinations of interventions have the greatest impact on these indicators. Results: In high prevalence communities (here, >20% infection of children aged 1–9 years), a combination of efforts is needed to bring down sustainably the prevalence and incidence of ocular disease sequelae. Conclusion: The mass delivery of antibiotics is highly beneficial for the clearance of infection, inflammation and prevention of subsequent scarring, but needs to be supplemented with sustained reductions in transmission and surgery to consider realistically the elimination of blindness by the year 2020.
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Affiliation(s)
- Manoj Gambhir
- a Department of Epidemiology and Preventive Medicine , Monash University , Melbourne , Victoria , Australia
| | - Nicholas C Grassly
- b Department of Infectious Disease Epidemiology , Imperial College London , London, UK .,c MRC Centre for Outbreak Analysis and Modelling , Department of Infectious Disease Epidemiology, Imperial College London , London, UK
| | - Matthew J Burton
- d Clinical Research Department , Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine , London , UK , and
| | - Anthony W Solomon
- d Clinical Research Department , Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine , London , UK , and
| | - Hugh R Taylor
- e Indigenous Eye Health Unit, Melbourne School of Population Health, The University of Melbourne , East Melbourne, Victoria, Australia
| | - David C Mabey
- d Clinical Research Department , Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine , London , UK , and
| | - Isobel M Blake
- b Department of Infectious Disease Epidemiology , Imperial College London , London, UK .,c MRC Centre for Outbreak Analysis and Modelling , Department of Infectious Disease Epidemiology, Imperial College London , London, UK
| | - María-Gloria Basáñez
- b Department of Infectious Disease Epidemiology , Imperial College London , London, UK
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Pinsent A, Burton MJ, Gambhir M. Enhanced antibiotic distribution strategies and the potential impact of facial cleanliness and environmental improvements for the sustained control of trachoma: a modelling study. BMC Med 2016; 14:71. [PMID: 27194136 PMCID: PMC4872360 DOI: 10.1186/s12916-016-0614-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 04/05/2016] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Despite some success in controlling trachoma with repeated mass drug administration (MDA), some hyperendemic regions are not responding as fast as anticipated. Available data suggests that individuals with higher bacterial infection loads are less likely to resolve infection following a single dose of treatment, and thus remain a source of re-emergent infection following treatment. We assessed the potential impact of a new double-dose antibiotic distribution strategy in addition to enhanced facial cleanliness (F) and environmental improvements (E). METHODS Using a within-community mathematical model of trachoma transmission we assessed the impact of a new double-dose antibiotic distribution strategy given 2 weeks apart, with and without enhanced F&E. We compared the annual double-dose strategy to single-dose annual MDA treatment in hyper-, meso- and hypoendemic settings, and to biannual MDA at 6-monthly intervals in hyperendemic communities. RESULTS The findings from our mathematical model suggest that implementing the new double-dose strategy for 5 years or less was predicted to control infection more successfully than annual or 6-monthly treatment. Infection was controlled more readily if treatment was combined with enhanced F&E. The results appeared robust to variation in a number of key epidemiological parameters. To have long-term impact on transmission, enhanced F&E is essential for high transmission settings. CONCLUSION Our current findings are based on simualtion modelling only, due to lack of epidemilogical data, however they do suggest that the annual double-dose treatment strategy is encouraging for trachoma control. In high transmission settings, both MDA and enhanced F&E are needed for sustained control.
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Affiliation(s)
- Amy Pinsent
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
| | - Matthew J Burton
- International Centre for Eye Health, Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK
| | - Manoj Gambhir
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
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Liu F, Porco TC, Amza A, Kadri B, Nassirou B, West SK, Bailey RL, Keenan JD, Lietman TM. Short-term forecasting of the prevalence of clinical trachoma: utility of including delayed recovery and tests for infection. Parasit Vectors 2015; 8:535. [PMID: 26489933 PMCID: PMC4618840 DOI: 10.1186/s13071-015-1115-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Accepted: 09/28/2015] [Indexed: 12/03/2022] Open
Abstract
Background The World Health Organization aims to control blinding trachoma by 2020. Decisions on whether to start and stop mass treatments and when to declare that control has been achieved are currently based on clinical examination data generated in population-based surveys. Thresholds are based on the district-level prevalence of trachomatous inflammation–follicular (TF) in children aged 1–9 years. Forecasts of which districts may and may not meet TF control goals by the 2020 target date could affect resource allocation in the next few years. Methods We constructed a hidden Markov model fit to the prevalence of two clinical signs of trachoma and PCR data in 24 communities from the recent PRET-Niger trial. The prevalence of TF in children in each community at 36 months was forecast given data from earlier time points. Forecasts were scored by the likelihood of the observed results. We assessed whether use of TF with additional TI and PCR data rather than just the use of TF alone improves forecasts, and separately whether incorporating a delay in TF recovery is beneficial. Results Including TI and PCR data did not significantly improve forecasts of TF. Forecasts of TF prevalence at 36 months by the model with the delay in TF recovery were significantly better than forecasts by the model without the delay in TF recovery (p = 0.003). A zero-inflated truncated normal observation model was better than a truncated normal observation model, and better than a sensitivity-specificity observation model. Conclusion The results in this study suggest that future studies could consider using just TF data for forecasting, and should include a delay in TF recovery. Trial registration Clinicaltrials.gov NCT00792922 Electronic supplementary material The online version of this article (doi:10.1186/s13071-015-1115-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Fengchen Liu
- F.I. Proctor Foundation, University of California San Francisco, 513 Parnassus, Medical Sciences 309A, San Francisco, CA, 94143-0944, USA.
| | - Travis C Porco
- F.I. Proctor Foundation, University of California San Francisco, 513 Parnassus, Medical Sciences 309A, San Francisco, CA, 94143-0944, USA. .,Department of Ophthalmology, University of California San Francisco, San Francisco, CA, USA. .,Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA.
| | - Abdou Amza
- Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger.
| | - Boubacar Kadri
- Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger.
| | - Baido Nassirou
- Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger.
| | - Sheila K West
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA.
| | - Robin L Bailey
- Clinical Research Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
| | - Jeremy D Keenan
- F.I. Proctor Foundation, University of California San Francisco, 513 Parnassus, Medical Sciences 309A, San Francisco, CA, 94143-0944, USA. .,Department of Ophthalmology, University of California San Francisco, San Francisco, CA, USA.
| | - Thomas M Lietman
- F.I. Proctor Foundation, University of California San Francisco, 513 Parnassus, Medical Sciences 309A, San Francisco, CA, 94143-0944, USA. .,Department of Ophthalmology, University of California San Francisco, San Francisco, CA, USA. .,Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA.
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Gambhir M, Pinsent A. Possible changes in the transmissibility of trachoma following MDA and transmission reduction: implications for the GET2020 goals. Parasit Vectors 2015; 8:530. [PMID: 26490436 PMCID: PMC4618927 DOI: 10.1186/s13071-015-1133-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 10/02/2015] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND The role of mass drug administration (MDA) and the implementation of transmission reduction measures are essential to successfully control and eliminate a wide range of NTDs, including the ocular disease trachoma. Immunity to trachoma infection acts by reducing the duration of an individual's infectious period and by reducing their infectivity with each successive infection. METHODS In this study, we use a model of trachoma infection, which includes population immunity, to explore the impact of treatment and transmission reduction measures on trachoma prevalence. Specifically, we investigate the possibility of increasing transmissibility of trachoma arising as MDA and transmission reduction measures are scaled up in endemic settings. RESULTS We demonstrate this increase in transmissibility by calculating the effective reproduction number during several simulated control programmes and show that it is related to a decrease in the level of immunity in the population. CONCLUSIONS This effect should be studied in the field by measuring the rate of return of infection and disease in at least two separate age groups. If the decline of population immunity is operating, it should be accounted for when planning for the GET2020 goal of eliminating blinding trachoma by 2020.
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Affiliation(s)
- Manoj Gambhir
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia.
| | - Amy Pinsent
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
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Craig AP, Gray RT, Edwards JL, Apicella MA, Jennings MP, Wilson DP, Seib KL. The potential impact of vaccination on the prevalence of gonorrhea. Vaccine 2015; 33:4520-4525. [PMID: 26192351 PMCID: PMC4743649 DOI: 10.1016/j.vaccine.2015.07.015] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 07/02/2015] [Accepted: 07/07/2015] [Indexed: 11/23/2022]
Abstract
Gonorrhea, one of the most common sexually transmitted infections worldwide, can lead to serious sequelae, including infertility and increased HIV transmission. Recently, untreatable, multidrug-resistant Neisseria gonorrhoeae strains have been reported. In the absence of new antibiotics, and given the speed with which resistance has emerged to all previously used antibiotics, development of a vaccine would be the ideal solution to this public health emergency. Understanding the desired characteristics, target population, and expected impact of an anti-gonococcal vaccine is essential to facilitate vaccine design, assessment and implementation. The modeling presented herein aims to fill these conceptual gaps, and inform future gonococcal vaccine development. Using an individual-based, epidemiological simulation model, gonococcal prevalence was simulated in a heterosexual population of 100,000 individuals after the introduction of vaccines with varied efficacy (10-100%) and duration of protection (2.5-20 years). Model simulations predict that gonococcal prevalence could be reduced by at least 90% after 20 years, if all 13-year-olds were given a non-waning vaccine with 50% efficacy, or a vaccine with 100% efficacy that wanes after 7.5 years. A 40% reduction in prevalence is achievable with a non-waning vaccine of only 20% efficacy. We conclude that a vaccine of moderate efficacy and duration could have a substantive impact on gonococcal prevalence, and disease sequelae, if coverage is high and protection lasts over the highest risk period (i.e., most sexual partner change) among young people.
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Affiliation(s)
- Andrew P. Craig
- The Kirby Institute, UNSW Australia, Sydney 2052, NSW, Australia
| | - Richard T. Gray
- The Kirby Institute, UNSW Australia, Sydney 2052, NSW, Australia
| | - Jennifer L. Edwards
- Center for Microbial Pathogenesis, The Research Institute at Nationwide Children's Hospital, and The Ohio State University Department of Pediatrics, Columbus, OH, USA
| | | | | | - David P. Wilson
- The Kirby Institute, UNSW Australia, Sydney 2052, NSW, Australia
| | - Kate L. Seib
- Institute for Glycomics, Griffith University, Southport, QLD, Australia
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Liu F, Porco TC, Amza A, Kadri B, Nassirou B, West SK, Bailey RL, Keenan JD, Solomon AW, Emerson PM, Gambhir M, Lietman TM. Short-term Forecasting of the Prevalence of Trachoma: Expert Opinion, Statistical Regression, versus Transmission Models. PLoS Negl Trop Dis 2015; 9:e0004000. [PMID: 26302380 PMCID: PMC4547743 DOI: 10.1371/journal.pntd.0004000] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 07/21/2015] [Indexed: 11/17/2022] Open
Abstract
Background Trachoma programs rely on guidelines made in large part using expert opinion of what will happen with and without intervention. Large community-randomized trials offer an opportunity to actually compare forecasting methods in a masked fashion. Methods The Program for the Rapid Elimination of Trachoma trials estimated longitudinal prevalence of ocular chlamydial infection from 24 communities treated annually with mass azithromycin. Given antibiotic coverage and biannual assessments from baseline through 30 months, forecasts of the prevalence of infection in each of the 24 communities at 36 months were made by three methods: the sum of 15 experts’ opinion, statistical regression of the square-root-transformed prevalence, and a stochastic hidden Markov model of infection transmission (Susceptible-Infectious-Susceptible, or SIS model). All forecasters were masked to the 36-month results and to the other forecasts. Forecasts of the 24 communities were scored by the likelihood of the observed results and compared using Wilcoxon’s signed-rank statistic. Findings Regression and SIS hidden Markov models had significantly better likelihood than community expert opinion (p = 0.004 and p = 0.01, respectively). All forecasts scored better when perturbed to decrease Fisher’s information. Each individual expert’s forecast was poorer than the sum of experts. Interpretation Regression and SIS models performed significantly better than expert opinion, although all forecasts were overly confident. Further model refinements may score better, although would need to be tested and compared in new masked studies. Construction of guidelines that rely on forecasting future prevalence could consider use of mathematical and statistical models. Forecasts of infectious diseases are rarely made in a falsifiable manner. Trachoma trials offer an opportunity to actually compare forecasting methods in a masked fashion. The World Health Organization recommends at least three annual antibiotic mass drug administrations where the prevalence of trachoma is greater than 10% in children aged 1–9 years, with coverage at least at 80%. The Program for the Rapid Elimination of Trachoma trials estimated longitudinal prevalence of ocular chlamydial infection from 24 communities treated annually with mass azithromycin. Here, we compared forecasts of the prevalence of infection in each of the 24 communities at 36 months (given antibiotic coverage and biannual assessments from baseline through 30 months, and masked to the 36-month assessments) made by experts, statistical regression, and a transmission model. The transmission model was better than regression, with both far better than experts’ opinion. Construction of guidelines that rely on forecasting future prevalence could consider use of mathematical and statistical models.
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Affiliation(s)
- Fengchen Liu
- Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America
| | - Travis C Porco
- Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America; Department of Ophthalmology, University of California San Francisco, San Francisco, California, United States of America; Department of Epidemiology & Biostatistics, University of California San Francisco, San Francisco, California, United States of America
| | - Abdou Amza
- Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger
| | - Boubacar Kadri
- Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger
| | - Baido Nassirou
- Programme FSS/Université Abdou Moumouni de Niamey, Programme National de Santé Oculaire, Niamey, Niger
| | - Sheila K West
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Robin L Bailey
- Clinical Research Unit, Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Jeremy D Keenan
- Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America; Department of Ophthalmology, University of California San Francisco, San Francisco, California, United States of America
| | - Anthony W Solomon
- Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
| | - Paul M Emerson
- International Trachoma Initiative, Atlanta, Georgia, United States of America
| | - Manoj Gambhir
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
| | - Thomas M Lietman
- Francis I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America; Department of Ophthalmology, University of California San Francisco, San Francisco, California, United States of America; Department of Epidemiology & Biostatistics, University of California San Francisco, San Francisco, California, United States of America
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Jimenez V, Gelderblom HC, Mann Flueckiger R, Emerson PM, Haddad D. Mass drug administration for trachoma: how long is not long enough? PLoS Negl Trop Dis 2015; 9:e0003610. [PMID: 25799168 PMCID: PMC4370651 DOI: 10.1371/journal.pntd.0003610] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 02/09/2015] [Indexed: 11/20/2022] Open
Abstract
Background Blinding trachoma is targeted for elimination by 2020 using the SAFE strategy (Surgery, Antibiotics, Facial cleanliness, and Environmental improvements). Annual mass drug administration (MDA) with azithromycin is a cornerstone of this strategy. If baseline prevalence of clinical signs of trachomatous inflammation – follicular among 1-9 year-olds (TF1-9) is ≥10% but <30%, the World Health Organization guidelines are for at least 3 annual MDAs; if ≥30%, 5. We assessed the likelihood of achieving the global elimination target of TF1-9 <5% at 3 and 5 year evaluations using program reports. Methodology/Principal Findings We used the International Trachoma Initiative’s prevalence and treatment database. Of 283 cross-sectional survey pairs with baseline and follow-up data, MDA was conducted in 170 districts. Linear and logistic regression modeling was applied to these to investigate the effect of MDA on baseline prevalence. Reduction to <5% was less likely, though not impossible, at higher baseline TF1-9 prevalences. Increased number of annual MDAs, as well as no skipped MDAs, were significant predictors of reduced TF1-9 at follow-up. The probability of achieving the <5% target was <50% for areas with ≥30% TF1-9 prevalence at baseline, even with 7 or more continuous annual MDAs. Conclusions Number of annual MDAs alone appears insufficient to predict program progress; more information on the effects of baseline prevalence, coverage, and underlying environmental and hygienic conditions is needed. Programs should not skip MDAs, and at prevalences >30%, 7 or more annual MDAs may be required to achieve the target. There are five years left before the 2020 deadline to eliminate blinding trachoma. Low endemic settings are poised to succeed in their elimination goals. However, newly-identified high prevalence districts warrant immediate inclusion in the global program. Intensified application of the SAFE strategy is needed in order to guarantee blinding trachoma elimination by 2020. Trachoma, the world’s leading infectious cause of blindness, is scheduled for elimination by 2020. Reaching this elimination target depends on successful implementation of the SAFE strategy (Surgery, Antibiotics, Facial cleanliness, and Environmental improvements). Annual mass antibiotic distributions are key to breaking the cycle of transmission in a community. However, it is not clear how many annual mass treatments need to be carried out in order to achieve elimination. Our study analyzes the effect of mass antibiotic distribution on different baseline prevalence levels of trachoma, in order to assess factors that affect the success of reaching elimination goals. We find that the prevailing belief, which suggests that 3 annual mass treatments can achieve local elimination of trachoma at prevalences between 10–30%, and 5 annual mass treatments for districts above this benchmark, is probably incorrect. In fact, much longer intervals may be required with “business as usual” programmatic strategies, which often include skipped years of treatment. Districts with high prevalence levels may require more intense treatment strategies to eliminate trachoma. Intensified recommendations must be implemented without delay in order to reach the 2020 elimination deadline.
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Affiliation(s)
- Violeta Jimenez
- Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America
- International Trachoma Initiative, Task Force for Global Health, Emory University, Atlanta, Georgia, United States of America
- Global Ophthalmology Emory, Emory Eye Center, Emory University School of Medicine, Atlanta, Georgia, United States of America
| | - Huub C. Gelderblom
- International Trachoma Initiative, Task Force for Global Health, Emory University, Atlanta, Georgia, United States of America
| | - Rebecca Mann Flueckiger
- International Trachoma Initiative, Task Force for Global Health, Emory University, Atlanta, Georgia, United States of America
| | - Paul M. Emerson
- International Trachoma Initiative, Task Force for Global Health, Emory University, Atlanta, Georgia, United States of America
| | - Danny Haddad
- Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America
- Global Ophthalmology Emory, Emory Eye Center, Emory University School of Medicine, Atlanta, Georgia, United States of America
- * E-mail:
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Gambhir M, Singh BK, Michael E. The Allee effect and elimination of neglected tropical diseases: a mathematical modelling study. ADVANCES IN PARASITOLOGY 2015; 87:1-31. [PMID: 25765192 DOI: 10.1016/bs.apar.2014.12.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Elimination and control programmes for neglected tropical diseases (NTDs) are underway around the world, yet they are generally informed by epidemiological modelling only to a rudimentary degree. Chief among the modelling-derived predictors of disease emergence or controllability is the basic reproduction number R0. The ecological systems of several of the NTDs include density-dependent processes--which alter the rate of e.g. parasite establishment or fecundity--that complicate the calculation of R0. Here we show how the forms of the density-dependent functions for a model of the NTD lymphatic filariasis affect the effective reproduction number Reff. We construct infection transmission models containing various density-dependent functions and show how they alter the shape of the Reff profile, affecting two important epidemiological outcome variables that relate to elimination and control programmes: the parasite transmission breakpoint (or extinction threshold) and the reproduction fitness, as measured by Reff. The current drive to control, eliminate or eradicate several parasitic infections would be substantially aided by the existence of ecological Allee effects. For these control programmes, the findings of this paper are encouraging, since a single positive density dependency (DD) can introduce a reasonable chance of achieving elimination; however, there are diminishing returns to additional positive DDs.
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Affiliation(s)
- Manoj Gambhir
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, VIC, Australia
| | - Brajendra K Singh
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Edwin Michael
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
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Vickers DM, Osgood ND. The arrested immunity hypothesis in an immunoepidemiological model of Chlamydia transmission. Theor Popul Biol 2014; 93:52-62. [PMID: 24513099 DOI: 10.1016/j.tpb.2014.01.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2011] [Revised: 01/29/2014] [Accepted: 01/30/2014] [Indexed: 01/07/2023]
Abstract
For curable infectious diseases, public health strategies such as treatment can effectively shorten an individual's infectious period, and thus limit their role in transmission. However, because treatment effectively eliminates antigen impingement, these types of control strategies may also paradoxically impair the development of adaptive immune responses. For sexually transmitted Chlamydia trachomatis infections, this latter effect has been coined the arrested immunity hypothesis, and is discussed to carry significant epidemiological implications for those individuals who return to similar sexual networks with similar sexual behavior. Here, we examine the effect of antibiotic treatment on the spread of Chlamydia infection through a simple immunoepidemiological framework that characterizes the population as a collection of dynamically evolving individuals in small, paradigmatic networks. Within each individual there is an explicit representation of pathogen replication, accumulation and persistence of an immune response, followed by a gradual waning of that response once the infection is cleared. Individuals are then nested in networks, allowing the variability in the life history of their infection to be functions of both individual immune dynamics as well as their position in the network. Model results suggest that the timing and coverage of treatment are important contributors to the development of immunity and reinfection. In particular, the impact of treatment on the spread of infection between individuals can be beneficial, have no effect, or be deleterious depending on who is treated and when. Although we use sexually transmitted Chlamydia infection as an example, the observed results arise endogenously from a basic model structure, and thus warrant consideration to understanding the interaction of infection, treatment, and spread of other infectious diseases.
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Affiliation(s)
- David M Vickers
- Infection, Prevention, and Control, Alberta Health Services, Calgary, AB, Canada; Computational Epidemiology and Public Health Informatics Laboratory, University of Saskatchewan, Saskatoon, SK, Canada.
| | - Nathaniel D Osgood
- Computational Epidemiology and Public Health Informatics Laboratory, University of Saskatchewan, Saskatoon, SK, Canada; Department of Computer Science, University of Saskatchewan, Saskatoon, SK, Canada; School of Public Health, University of Saskatchewan, Saskatoon, SK, Canada
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The burden of trachoma in South Sudan: assessing the health losses from a condition of graded severity. PLoS Negl Trop Dis 2012; 6:e1538. [PMID: 22413025 PMCID: PMC3295813 DOI: 10.1371/journal.pntd.0001538] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 12/24/2011] [Indexed: 11/19/2022] Open
Abstract
Introduction Trachoma is a disease that can lead to visual impairment and ultimately blindness. Previous estimates of health losses from trachoma using the Global Burden of Disease methodology have not, however, included the stage prior to visual impairment. We estimated the burden of all stages of trachoma in South Sudan and assessed the uncertainty associated with the severity and duration of stages of trachoma prior to full blindness. Methods The prevalence of trachoma with normal vision, low vision and blindness in the Republic of South Sudan has been estimated previously. These estimates were used to model the incidence and duration of the different stages employing DISMOD II. Different assumptions about disability weights and duration were used to estimate the Years Lived with Disability (YLD). Results We have estimated the total burden of trachoma in South Sudan to be between 136,562 and 163,695 YLD and trichiasis with normal vision contributes between 5% and 21% of the total depending on the disability weight applied. Women experience more of this burden than men. The sensitivity of the results to different assumptions about the disability weights is partly dependent upon the assumed duration of the different disease states. Interpretation A better understanding of the natural history of trachoma is critical for a more accurate burden estimate. Trachoma is an infectious disease that is endemic to the Republic of South Sudan. In the absence of appropriate treatment recurrent re-infection in an individual will lead to progressively severe states of trachoma, eventually leading to the loss of visual acuity and finally blindness. Here we distinguish between three separate states of disease: trachoma with normal vision, trachoma with low vision and trachoma with blindness. The first of these states, trachoma with normal vision, is the least severe and the impact of this state on a population has not been well investigated. Trachoma, even before any loss of vision, comes with a great deal of pain and social consequences, and thus disability. In this study we employ data from South Sudan and estimate the burden caused by trachoma with normal vision for the first time. In doing so, we also reveal the extent of the gaps in our knowledge surrounding the natural history of trachoma and highlight areas of research that require urgent attention.
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Gouda HN, Critchley J, Powles J, Capewell S. Why choice of metric matters in public health analyses: a case study of the attribution of credit for the decline in coronary heart disease mortality in the US and other populations. BMC Public Health 2012; 12:88. [PMID: 22284813 PMCID: PMC3305465 DOI: 10.1186/1471-2458-12-88] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Accepted: 01/28/2012] [Indexed: 11/16/2022] Open
Abstract
Background Reasons for the widespread declines in coronary heart disease (CHD) mortality in high income countries are controversial. Here we explore how the type of metric chosen for the analyses of these declines affects the answer obtained. Methods The analyses we reviewed were performed using IMPACT, a large Excel based model of the determinants of temporal change in mortality from CHD. Assessments of the decline in CHD mortality in the USA between 1980 and 2000 served as the central case study. Results Analyses based in the metric of number of deaths prevented attributed about half the decline to treatments (including preventive medications) and half to favourable shifts in risk factors. However, when mortality change was expressed in the metric of life-years-gained, the share attributed to risk factor change rose to 65%. This happened because risk factor changes were modelled as slowing disease progression, such that the hypothetical deaths averted resulted in longer average remaining lifetimes gained than the deaths averted by better treatments. This result was robust to a range of plausible assumptions on the relative effect sizes of changes in treatments and risk factors. Conclusions Time-based metrics (such as life years) are generally preferable because they direct attention to the changes in the natural history of disease that are produced by changes in key health determinants. The life-years attached to each death averted will also weight deaths in a way that better reflects social preferences.
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Affiliation(s)
- Hebe N Gouda
- Institute of Public Health, Forvie Site, Robinson Way, University of Cambridge, Cambridge CB2 1SP, UK.
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Mitchell KM, Mutapi F, Savill NJ, Woolhouse MEJ. Explaining observed infection and antibody age-profiles in populations with urogenital schistosomiasis. PLoS Comput Biol 2011; 7:e1002237. [PMID: 22028640 PMCID: PMC3197645 DOI: 10.1371/journal.pcbi.1002237] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 09/04/2011] [Indexed: 01/05/2023] Open
Abstract
Urogenital schistosomiasis is a tropical disease infecting more than 100 million people in sub-Saharan Africa. Individuals in endemic areas endure repeated infections with long-lived schistosome worms, and also encounter larval and egg stages of the life cycle. Protective immunity against infection develops slowly with age. Distinctive age-related patterns of infection and specific antibody responses are seen in endemic areas, including an infection 'peak shift' and a switch in the antibody types produced. Deterministic models describing changing levels of infection and antibody with age in homogeneously exposed populations were developed to identify the key mechanisms underlying the antibody switch, and to test two theories for the slow development of protective immunity: that (i) exposure to dying (long-lived) worms, or (ii) experience of a threshold level of antigen, is necessary to stimulate protective antibody. Different model structures were explored, including alternative stages of the life cycle as the main antigenic source and the principal target of protective antibody, different worm survival distributions, antigen thresholds and immune cross-regulation. Models were identified which could reproduce patterns of infection and antibody consistent with field data. Models with dying worms as the main source of protective antigen could reproduce all of these patterns, but so could some models with other continually-encountered life stages acting as the principal antigen source. An antigen threshold enhanced the ability of the model to replicate these patterns, but was not essential for it to do so. Models including either non-exponential worm survival or cross-regulation were more likely to be able to reproduce field patterns, but neither of these was absolutely required. The combination of life cycle stage stimulating, and targeted by, antibody was found to be critical in determining whether models could successfully reproduce patterns in the data, and a number of combinations were excluded as being inconsistent with field data.
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Affiliation(s)
- Kate M Mitchell
- Centre for Immunology, Infection and Evolution, Institute of Immunology & Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom.
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Savy M, Hennig BJ, Doherty CP, Fulford AJ, Bailey R, Holland MJ, Sirugo G, Rockett KA, Kwiatkowski DP, Prentice AM, Cox SE. Haptoglobin and sickle cell polymorphisms and risk of active trachoma in Gambian children. PLoS One 2010; 5:e11075. [PMID: 20552021 PMCID: PMC2884021 DOI: 10.1371/journal.pone.0011075] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2010] [Accepted: 05/20/2010] [Indexed: 11/04/2022] Open
Abstract
Background Susceptibility and resistance to trachoma, the leading infectious cause of blindness, have been associated with a range of host genetic factors. In vitro studies of the causative organism, Chlamydia trachomatis, demonstrate that iron availability regulates its growth, suggesting that host genes involved in regulating iron status and/or availability may modulate the risk of trachoma. The objective was to investigate whether haptoglobin (Hp) haplotypes constructed from the functional polymorphism (Hp1/Hp2) plus the functional promoter SNPs -61A-C (rs5471) and -101C-G (rs5470), or sickle cell trait (HbAS, rs334) were associated with risk of active trachoma when stratified by age and sex, in rural Gambian children. Methodology and Principal Findings In two cross sectional surveys of children aged 6–78 months (n = 836), the prevalence of the clinical signs of active trachoma was 21.4%. Within boys, haplotype E (-101G, -61A, Hp1), containing the variant allele of the -101C-G promoter SNP, was associated with a two-fold increased risk of active trachoma (OR = 2.0 [1.17–3.44]). Within girls, an opposite association was non-significant (OR = 0.58 [0.32–1.04]; P = 0.07) and the interaction by sex was statistically significant (P = 0.001). There was no association between trachoma and HbAS. Conclusions These data indicate that genetic variation in Hp may affect susceptibility to active trachoma differentially by sex in The Gambia.
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Affiliation(s)
- Mathilde Savy
- MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Branwen J. Hennig
- MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | - Anthony J. Fulford
- MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Robin Bailey
- MRC Laboratories, Fajara, The Gambia
- Department of Infectious Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Martin J. Holland
- MRC Laboratories, Fajara, The Gambia
- Department of Infectious Tropical Diseases, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Giorgio Sirugo
- MRC Laboratories, Fajara, The Gambia
- Department of Medical Genetics, San Pietro Hospital, Rome, Italy
| | - Kirk A. Rockett
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
| | - Dominic P. Kwiatkowski
- Wellcome Trust Centre for Human Genetics, Oxford, United Kingdom
- Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, United Kingdom
| | - Andrew M. Prentice
- MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - Sharon E. Cox
- MRC International Nutrition Group, London School of Hygiene & Tropical Medicine, London, United Kingdom
- * E-mail:
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Hägi M, Schémann JF, Mauny F, Momo G, Sacko D, Traoré L, Malvy D, Viel JF. Active trachoma among children in Mali: Clustering and environmental risk factors. PLoS Negl Trop Dis 2010; 4:e583. [PMID: 20087414 PMCID: PMC2799671 DOI: 10.1371/journal.pntd.0000583] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Accepted: 12/01/2009] [Indexed: 10/29/2022] Open
Abstract
BACKGROUND Active trachoma is not uniformly distributed in endemic areas, and local environmental factors influencing its prevalence are not yet adequately understood. Determining whether clustering is a consistent phenomenon may help predict likely modes of transmission and help to determine the appropriate level at which to target control interventions. The aims of this study were, therefore, to disentangle the relative importance of clustering at different levels and to assess the respective role of individual, socio-demographic, and environmental factors on active trachoma prevalence among children in Mali. METHODOLOGY/PRINCIPAL FINDINGS We used anonymous data collected during the Mali national trachoma survey (1996-1997) at different levels of the traditional social structure (14,627 children under 10 years of age, 6,251 caretakers, 2,269 households, 203 villages). Besides field-collected data, environmental variables were retrieved later from various databases at the village level. Bayesian hierarchical logistic models were fit to these prevalence and exposure data. Clustering revealed significant results at four hierarchical levels. The higher proportion of the variation in the occurrence of active trachoma was attributable to the village level (36.7%), followed by household (25.3%), and child (24.7%) levels. Beyond some well-established individual risk factors (age between 3 and 5, dirty face, and flies on the face), we showed that caretaker-level (wiping after body washing), household-level (common ownership of radio, and motorbike), and village-level (presence of a women's association, average monthly maximal temperature and sunshine fraction, average annual mean temperature, presence of rainy days) features were associated with reduced active trachoma prevalence. CONCLUSIONS/SIGNIFICANCE This study clearly indicates the importance of directing control efforts both at children with active trachoma as well as those with close contact, and at communities. The results support facial cleanliness and environmental improvements (the SAFE strategy) as population-health initiatives to combat blinding trachoma.
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Affiliation(s)
- Mathieu Hägi
- CNRS UMR 6249 “Chrono-Environment”, Faculty of Medicine, Besançon, France
| | | | - Frédéric Mauny
- CNRS UMR 6249 “Chrono-Environment”, Faculty of Medicine, Besançon, France
| | - Germain Momo
- Institute of African Tropical Ophthalmology (IOTA), Bamako, Mali
| | - Doulaye Sacko
- West African Health Organization, Vision 2020 coordination group, Bobo-Dioulasso, Burkina Faso
| | - Lamine Traoré
- Institute of African Tropical Ophthalmology (IOTA), Bamako, Mali
| | - Denis Malvy
- University of Bordeaux 2 (EA 3677 and Centre René Labusquière), Bordeaux, France
| | - Jean-François Viel
- CNRS UMR 6249 “Chrono-Environment”, Faculty of Medicine, Besançon, France
- * E-mail:
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Kur LW, Picon D, Adibo O, Robinson E, Sabasio A, Edwards T, Ndyaba A, Rumunu J, Lewis K, Lado M, Kolaczinski J. Trachoma in Western Equatoria State, Southern Sudan: implications for national control. PLoS Negl Trop Dis 2009; 3:e492. [PMID: 19636366 PMCID: PMC2710503 DOI: 10.1371/journal.pntd.0000492] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 06/26/2009] [Indexed: 11/18/2022] Open
Abstract
Background Trachoma is thought to be common over large parts of Southern Sudan. However, many areas of the country, particularly west of the Nile, have not yet been surveyed. The aim of this study was to confirm whether trachoma extends into Western Equatoria State from neighboring Central Equatoria, where trachoma is highly prevalent, and whether intervention with the SAFE strategy is required. Methods and Findings Population-based cross-sectional surveys were conducted using a two-stage cluster random sampling method to select the study population. Subjects were examined for trachoma by experienced graders using the World Health Organization (WHO) simplified grading scheme. Two counties thought to be most likely to have trachoma were surveyed, Maridi and Mundri. In Maridi, prevalence of one of the signs of active trachoma (trachomatous inflammation-follicular (TF)) in children aged 1–9 years was 0.4% (95% confidence interval (CI), 0.0%–0.8%), while no children showing the other possible sign, trachomatous inflammation-intense (TI), were identified. No trachomatous trichiasis (TT) was found in those aged under 15, and prevalence was 0.1% (95% CI, 0.0%–0.4%) in those aged 15 years and above. In Mundri, active trachoma was also limited to signs of TF, with a prevalence of 4.1% (95% CI, 1.4%–6.9%) in children aged 1–9 years. Again, no TT was found in those aged under 15, and prevalence in those aged 15 years and above was 0.3% (95% CI, 0.0%–0.8%). Conclusion Trachoma prevalence in the east of Western Equatoria State is below the WHO recommended intervention threshold for mass drug administration of antibiotic treatment in all villages. However, the prevalence of TF and TT in some villages, particularly in Mundri County, is sufficiently high to warrant targeted interventions at the community level. These results demonstrate that trachoma is not a major public health problem throughout Southern Sudan. Further studies will be required to determine trachoma prevalence in other areas, particularly west of the Nile, but there are presently no resources to survey each county. Studies should thus be targeted to areas where collection of new data would be most informative. Baseline data on trachoma prevalence is a prerequisite for intervention. Prior to the present study, all surveys in Southern Sudan reported trachoma prevalences that exceeded the threshold for large-scale intervention. This gave rise to the notion that the disease may be endemic throughout the country. The present study was conducted under the auspices of the National Program for Integrated Control of Neglected Tropical Diseases, to verify whether prevalences in two counties west of the Nile exceeded the WHO recommended intervention threshold for mass drug administration (MDA) of antibiotic treatment. The results show that trachoma prevalence at county level was below this threshold. However, prevalences in some communities within the county were above the threshold, meaning that they should be targeted with MDA of antibiotics, as well as with other interventions such as trichiasis surgery, health promotion and improved water and sanitation. This finding reminds us of the need for geographical targeting of resources, both for surveys and subsequent intervention. Current resources are insufficient to conduct population-based prevalence surveys for trachoma throughout Southern Sudan. Further surveys should thus be conducted in areas where collection of additional information will be most informative. We propose that a combination of risk-mapping and rapid assessments is used to identify such areas.
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Affiliation(s)
- Lucia W. Kur
- Ministry of Health, Government of Southern Sudan, Juba, Southern Sudan
| | - Diana Picon
- Malaria Consortium – Southern Sudan Office, Juba, Southern Sudan
| | - Obec Adibo
- Ministry of Health, Government of Southern Sudan, Juba, Southern Sudan
| | - Emily Robinson
- Malaria Consortium – Africa Regional Office, Kampala, Uganda
| | - Anthony Sabasio
- Malaria Consortium – Southern Sudan Office, Juba, Southern Sudan
| | - Tansy Edwards
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Aggrey Ndyaba
- Malaria Consortium – Southern Sudan Office, Juba, Southern Sudan
| | - John Rumunu
- Ministry of Health, Government of Southern Sudan, Juba, Southern Sudan
| | - Karinya Lewis
- Christoffel-Blindenmission (CBM), Juba, Southern Sudan
| | - Mounir Lado
- Ministry of Health, Government of Southern Sudan, Juba, Southern Sudan
| | - Jan Kolaczinski
- Malaria Consortium – Africa Regional Office, Kampala, Uganda
- London School of Hygiene and Tropical Medicine, London, United Kingdom
- * E-mail:
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The development of an age-structured model for trachoma transmission dynamics, pathogenesis and control. PLoS Negl Trop Dis 2009; 3:e462. [PMID: 19529762 PMCID: PMC2691478 DOI: 10.1371/journal.pntd.0000462] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Accepted: 05/19/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Trachoma, the worldwide leading infectious cause of blindness, is due to repeated conjunctival infection with Chlamydia trachomatis. The effects of control interventions on population levels of infection and active disease can be promptly measured, but the effects on severe ocular sequelae require long-term monitoring. We present an age-structured mathematical model of trachoma transmission and disease to predict the impact of interventions on the prevalence of blinding trachoma. METHODOLOGY/PRINCIPAL FINDINGS The model is based on the concept of multiple reinfections leading to progressive conjunctival scarring, trichiasis, corneal opacity and blindness. It also includes aspects of trachoma natural history, such as an increasing rate of recovery from infection and a decreasing chlamydial load with subsequent infections that depend upon a (presumed) acquired immunity that clears infection with age more rapidly. Parameters were estimated using maximum likelihood by fitting the model to pre-control infection prevalence data from hypo-, meso- and hyperendemic communities from The Gambia and Tanzania. The model reproduces key features of trachoma epidemiology: 1) the age-profile of infection prevalence, which increases to a peak at very young ages and declines at older ages; 2) a shift in this prevalence peak, toward younger ages in higher force of infection environments; 3) a raised overall profile of infection prevalence with higher force of infection; and 4) a rising profile, with age, of the prevalence of the ensuing severe sequelae (trachomatous scarring, trichiasis), as well as estimates of the number of infections that need to occur before these sequelae appear. CONCLUSIONS/SIGNIFICANCE We present a framework that is sufficiently comprehensive to examine the outcomes of the A (antibiotic) component of the SAFE strategy on disease. The suitability of the model for representing population-level patterns of infection and disease sequelae is discussed in view of the individual processes leading to these patterns.
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Park N, Yamanaka K, Tran D, Chandrangsu P, Akers JC, de Leon JC, Morrissette NS, Selsted ME, Tan M. The cell-penetrating peptide, Pep-1, has activity against intracellular chlamydial growth but not extracellular forms of Chlamydia trachomatis. J Antimicrob Chemother 2009; 63:115-23. [PMID: 18957395 PMCID: PMC2721699 DOI: 10.1093/jac/dkn436] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Revised: 09/12/2008] [Accepted: 09/24/2008] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES In the course of studies to identify novel treatment strategies against the pathogenic bacterium, Chlamydia, we tested the carrier peptide, Pep-1, for activity against an intracellular infection. METHODS Using a cell culture model of Chlamydia trachomatis infection, the effect of Pep-1 was measured by incubating the peptide with extracellular chlamydiae prior to infection, or by adding Pep-1 to the medium at varying times after infection, and assaying for inhibition of inclusion formation. RESULTS Pep-1 had a concentration-dependent effect on chlamydial growth with 100% inhibition of inclusion formation at 8 mg/L peptide. There was a window of susceptibility during the chlamydial developmental cycle with a maximal effect when treatment was begun within 12 h of infection. Pep-1 treatment caused a severe reduction in the production of infectious progeny even when started later, when the effect on inclusion formation was minimal. Furthermore, electron micrographs showed a paucity of progeny elementary bodies (EBs) in the inclusion. In contrast, pre-incubation of EBs with Pep-1 prior to infection did not affect inclusion formation. Taken together, these findings indicate that the antichlamydial effect was specific for the intracellular stage of chlamydial infection. By comparison, Pep-1 had no antimicrobial activity against Escherichia coli and Staphylococcus aureus or the obligate intracellular parasite, Toxoplasma gondii. CONCLUSIONS Pep-1 has antichlamydial activity by preventing intracellular chlamydial growth and replication but has no effect on extracellular chlamydiae.
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Affiliation(s)
- Narae Park
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA
| | - Kinrin Yamanaka
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA
| | - Dat Tran
- Department of Pathology and Laboratory Medicine, University of California, Irvine, CA 92697-4025, USA
| | - Pete Chandrangsu
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA
| | - Johnny C. Akers
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA
| | - Jessica C. de Leon
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-4025, USA
| | - Naomi S. Morrissette
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-4025, USA
| | - Michael E. Selsted
- Department of Pathology and Laboratory Medicine, University of California, Irvine, CA 92697-4025, USA
| | - Ming Tan
- Department of Microbiology and Molecular Genetics, University of California, Irvine, CA 92697-4025, USA
- Department of Medicine, University of California, Irvine, CA 92697-4025, USA
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Polkinghorne A, Ziegler U, González-Hernández Y, Pospischil A, Timms P, Vaughan L. Chlamydophila pneumoniae HflX belongs to an uncharacterized family of conserved GTPases and associates with the Escherichia coli 50S large ribosomal subunit. MICROBIOLOGY-SGM 2008; 154:3537-3546. [PMID: 18957606 DOI: 10.1099/mic.0.2008/022137-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Predicted members of the HflX subfamily of phosphate-binding-loop guanosine triphosphatases (GTPases) are widely distributed in the bacterial kingdom but remain virtually uncharacterized. In an attempt to understand mechanisms used for regulation of growth and development in the chlamydiae, obligate intracellular and developmentally complex bacteria, we have begun investigations into chlamydial GTPases; we report here what appears to be the first analysis of a HflX family GTPase using a predicted homologue from Chlamydophila pneumoniae. In agreement with phylogenetic predictions for members of this GTPase family, purified recombinant Cp. pneumoniae HflX was specific for guanine nucleotides and exhibited a slow intrinsic GTPase activity when incubated with [gamma-(32)P]GTP. Using HflX-specific monoclonal antibodies, HflX could be detected by Western blotting and high-resolution confocal microscopy throughout the vegetative growth cycle of Cp. pneumoniae and, at early time points, appeared to partly localize to the membrane. Ectopic expression of Cp. pneumoniae HflX in Escherichia coli revealed co-sedimentation of HflX with the E. coli 50S large ribosomal subunit. The results of this work open up some intriguing possibilities for the role of GTPases belonging to this previously uncharacterized family of bacterial GTPases. Ribosome association is a feature shared by other important conserved GTPase families and more detailed investigations will be required to delineate the role of HflX in bacterial ribosome function.
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Affiliation(s)
- Adam Polkinghorne
- Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 268, Zurich 8057, Switzerland
| | - Urs Ziegler
- Institute of Anatomy and Center for Microscopy and Image Analysis, University of Zurich, Winterthurerstrasse 190, Zurich 8057, Switzerland
| | | | - Andreas Pospischil
- Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 268, Zurich 8057, Switzerland
| | - Peter Timms
- Institute of Health and Biomedical Innovation and School of Life Sciences, Faculty of Science, Queensland University of Technology, Brisbane, Australia
| | - Lloyd Vaughan
- Institute of Veterinary Pathology, University of Zurich, Winterthurerstrasse 268, Zurich 8057, Switzerland
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Grassly NC, Ward ME, Ferris S, Mabey DC, Bailey RL. The natural history of trachoma infection and disease in a Gambian cohort with frequent follow-up. PLoS Negl Trop Dis 2008; 2:e341. [PMID: 19048024 PMCID: PMC2584235 DOI: 10.1371/journal.pntd.0000341] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Accepted: 11/06/2008] [Indexed: 11/03/2022] Open
Abstract
Background The natural history of ocular Chlamydia trachomatis infections in endemic communities has not been well characterised and is an important determinant of the effectiveness of different mass treatment strategies to prevent blindness due to trachoma. Methodology/Principal Findings A multistate hidden Markov model was fitted to data on infection and active disease from 256 untreated villagers in The Gambia who were examined every 2 weeks over a 6-month period. Parameters defining the natural history of trachoma were estimated, and associations between these parameters, demographic and baseline immune measurements examined. The median incubation period following infection was estimated at 17 days (95% confidence interval: 11–28). Disease persisted for longer than infection (median 21 (15–32) weeks) versus 17 (12–24) weeks), with an estimated median duration of post-infection inflammation of 5 (3–8) weeks. The duration of active disease showed a significant decline with age even after accounting for lower rates of re-infection and disease at older ages (p = 0.004). Measurements of levels of baseline IgA to epitopes in the major outer membrane protein of Chlamydia trachomatis were not significantly correlated with protection or more rapid clearance of infection. Conclusions The average duration of infection with Chlamydia trachomatis especially at younger ages is long. This contributes to the persistence and gradual return of trachoma after community-wide treatment with antibiotics. Trachoma is an infectious disease of the eye that causes blindness in many of the poorest parts of the world. In this paper, we use a novel statistical approach to estimate the characteristics of this disease among people living in The Gambia who were examined every 2 weeks over a 6-month period. We found that the typical duration of infection with Chlamydia trachomatis and of clinically active disease were significantly longer than previously estimated. We tested different hypotheses about the natural history of trachoma that explain the relationship between infection and disease observed in the field. We also confirmed that disease lasts significantly longer among young children under 5 years old compared with older children and adults, even after accounting for high rates of re-infection in this age group, consistent with the development of immunity with age. The long duration of infection, especially among younger children, contributes to the persistence and gradual return of trachoma after community-wide treatment with azithromycin. This implies the need for high treatment coverage if infection is to be eliminated from a community, even where the return of infection after treatment is seen to be slow.
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Affiliation(s)
- Nicholas C Grassly
- Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom.
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Vidal SM, Malo D, Marquis JF, Gros P. Forward genetic dissection of immunity to infection in the mouse. Annu Rev Immunol 2008; 26:81-132. [PMID: 17953509 DOI: 10.1146/annurev.immunol.26.021607.090304] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Forward genetics is an experimental approach in which gene mapping and positional cloning are used to elucidate the molecular mechanisms underlying phenotypic differences between two individuals for a given trait. This strategy has been highly successful for the study of inbred mouse strains that show differences in innate susceptibility to bacterial, parasitic, fungal, and viral infections. Over the past 20 years, these studies have led to the identification of a number of cell populations and critical biochemical pathways and proteins that are essential for the early detection of and response to invading pathogens. Strikingly, the macrophage is the point of convergence for many of these genetic studies. This has led to the identification of diverse pathways involved in extracellular and intracellular pathogen recognition, modification of the properties and content of phagosomes, transcriptional response, and signal transduction for activation of adaptive immune mechanisms. In models of viral infections, elegant genetic studies highlighted the pivotal role of natural killer cells in the detection and destruction of infected cells.
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Affiliation(s)
- S M Vidal
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada H3G 1Y6
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Dunn MF, Niks D, Ngo H, Barends TR, Schlichting I. Tryptophan synthase: the workings of a channeling nanomachine. Trends Biochem Sci 2008; 33:254-64. [DOI: 10.1016/j.tibs.2008.04.008] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2008] [Revised: 04/07/2008] [Accepted: 04/08/2008] [Indexed: 01/25/2023]
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