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Robinson A, Versteeg B, Abdurahman OS, Clatworthy I, Shuka G, Debela D, Hordofa G, Reis de Oliveira Gomes L, Abraham Aga M, Dumessa G, Sarah V, Macleod D, Last A, Burton MJ, Logan JG. Field- and laboratory-based studies on correlates of Chlamydia trachomatis transmission by Musca sorbens: Determinants of fly-eye contact and investigations into fly carriage of elementary bodies. PLoS Negl Trop Dis 2024; 18:e0012280. [PMID: 38954734 PMCID: PMC11249242 DOI: 10.1371/journal.pntd.0012280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 07/15/2024] [Accepted: 06/07/2024] [Indexed: 07/04/2024] Open
Abstract
Musca sorbens (Diptera: Muscidae) flies are thought to be vectors of the blinding eye disease trachoma, carrying the bacterium Chlamydia trachomatis (Ct) between the eyes of individuals. While their role as vectors has been convincingly demonstrated via randomised controlled trials in The Gambia, studies of fly-borne trachoma transmission remain scant and as such our understanding of their ability to transmit Ct remains poor. We examined fly-eye contact and caught eye-seeking flies from 494 individuals (79% aged ≤9 years) in Oromia, Ethiopia. Ct-carrying flies (harbouring Ct DNA) were found to cluster spatially in and nearby to households in which at least one resident had Ct infection. Fly-eye contact was positively associated with the presence of trachoma (disease), lower human body weight and increased human body temperature. Studies of laboratory-reared M. sorbens indicated that Ct is found both externally and internally following feeds on Ct culture, with scanning electron microscopy revealing how Ct bodies can cling to fly hairs (setae). Testing for Ct on field-caught M. sorbens found fly 'bodies' (thorax, wings and abdomen) to consistently test positive for Ct while legs and heads were infrequently Ct-positive. These studies strongly support the role of M. sorbens as vectors of trachoma and highlight the need for improved understanding of fly-borne trachoma transmission dynamics and vector competence.
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Affiliation(s)
- Ailie Robinson
- Department of Disease Control, LSHTM, London, United Kingdom
| | - Bart Versteeg
- International Centre for Eye Health, Clinical Research Department, London School of Hygiene & Tropical Medicine (LSHTM), London, United Kingdom
- Knowledge Institute of the Dutch Association of Medical Specialists, Utrecht, The Netherlands
| | - Oumer Shafi Abdurahman
- International Centre for Eye Health, Clinical Research Department, London School of Hygiene & Tropical Medicine (LSHTM), London, United Kingdom
- The Fred Hollows Foundation Ethiopia, Addis Ababa, Ethiopia
| | | | - Gemeda Shuka
- The Fred Hollows Foundation Ethiopia, Addis Ababa, Ethiopia
| | - Dereje Debela
- The Fred Hollows Foundation Ethiopia, Addis Ababa, Ethiopia
| | | | | | | | | | | | - David Macleod
- International Centre for Eye Health, Clinical Research Department, London School of Hygiene & Tropical Medicine (LSHTM), London, United Kingdom
- MRC International Statistics and Epidemiology Group, LSHTM, London, United Kingdom
| | - Anna Last
- International Centre for Eye Health, Clinical Research Department, London School of Hygiene & Tropical Medicine (LSHTM), London, United Kingdom
| | - Matthew J Burton
- International Centre for Eye Health, Clinical Research Department, London School of Hygiene & Tropical Medicine (LSHTM), London, United Kingdom
- National Institute for Health Research Biomedical Research Centre for Ophthalmology at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
| | - James G Logan
- Department of Disease Control, LSHTM, London, United Kingdom
- Arctech Innovation Ltd, Dagenham, United Kingdom
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Kreis AJ, Gower EW, Kropp M, Kello AB, Nouhoum G, Resnikoff S, Talero SL, Solomon AW. The prevention and management of postoperative trachomatous trichiasis: A systematic review. Surv Ophthalmol 2024; 69:93-102. [PMID: 36878359 DOI: 10.1016/j.survophthal.2023.02.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 02/24/2023] [Accepted: 02/27/2023] [Indexed: 03/07/2023]
Abstract
Among ocular infections, trachoma is the main cause of blindness. Repeated conjunctival Chlamydia trachomatis infections lead to trichiasis, corneal opacification, and visual impairment. Surgery is often needed to relieve discomfort and preserve vision; however, a high postoperative trachomatous trichiasis (PTT) rate has been observed in various settings. We wanted to know why, whether PTT rates could be reduced, and how to manage the PTT that occurs. We performed a search of the literature. Of 217 papers screened, 59 studies were identified for inclusion as potentially relevant, the majority having been excluded for not directly concerning PTT in humans. Preventing PTT is a major challenge. Only one published trial, the STAR trial in Ethiopia, has reported a cumulative PTT rate <10% one year after surgery. The literature on the management of PTT is sparse. Though no PTT management guidelines are available, high-quality surgery with a low rate of unfavorable outcomes for PTT patients is likely to require enhanced training of a smaller group of highly-skilled surgeons. Based on the surgical complexity and the authors' own experience, the pathway for patients suffering from PTT should be studied further for improvement.
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Affiliation(s)
- Andreas J Kreis
- Experimental Ophthalmology, University of Geneva, Geneva, Switzerland; Department of Ophthalmology, University Hospitals of Geneva, Geneva, Switzerland.
| | - Emily W Gower
- Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Martina Kropp
- Experimental Ophthalmology, University of Geneva, Geneva, Switzerland; Department of Ophthalmology, University Hospitals of Geneva, Geneva, Switzerland
| | - Amir B Kello
- World Health Organization Regional Office for Africa, Brazzaville, Congo
| | - Guirou Nouhoum
- Techniques and Technologies of Bamako, Institut d'Ophtalmologie Tropicale d'Afrique, University of the Sciences, Bamako, Mali
| | - Serge Resnikoff
- Organisation pour la Prévention de la Cécité, Paris, France; School of Optometry & Vision Science (SOVS), University of New South Wales, Sydney, Australia
| | - Sandra L Talero
- Research Department of Development and Innovation, Superior School of Ophthalmology, Barraquer Institute of America, Bogotá, Colombia
| | - Anthony W Solomon
- Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
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Kebede F, Jamal M. Prevalence of active trachoma infection and associated factors post-war resettled population in raya kobo districts, North East Ethiopia: A community-based cross-sectional study in 2022. Health Sci Rep 2023; 6:e1486. [PMID: 37554953 PMCID: PMC10404653 DOI: 10.1002/hsr2.1486] [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] [Received: 04/04/2023] [Revised: 07/25/2023] [Accepted: 07/26/2023] [Indexed: 08/10/2023] Open
Abstract
Background Active trachoma infection poses a serious threat to public health, particularly for those who live in an unprivileged area and has practiced open-field defecation. This study aimed to estimate the prevalence of active trachoma infection and associated factors in the post-war resettled population in Raya Kobo district, North East Ethiopia: a community-based cross-sectional study in 2022. Methods A community-based cross-sectional study was conducted among 602 participants randomly selected in 14 slum villages in Raya Kobo from February 16th to March 30th, 2023. After the data was collected using a semi-structured questionnaire and entered into Epi-data version 3.2. The study participants were chosen using a two-stage sampling process. Binary logistic regression was used to identify factors for active trachoma infection. Adjusted odds ratios (AORs) with 95% confidence intervals (CIs) were claimed for the strength of association at p < 0.05. Results Overall, 602 (99.9%) study participants were included in the final analysis. At the end of the study period, 126 (20.9) participants developed active trachoma infection. On multivariable analysis, were aged ≥45 years (AOR = 7.9, 95% CI = 2.4-25.3), history of eye infection (AOR = 3.7, 95% CI = 2.4-10.4, p = 0.001), were poor wealth index (AOR = 9.2, 95% CI = 2.7-23.7), having separated kitchen (AOR = 4.05, 95% CI = 1.86-8.86), living with animals (AOR = 5.92, 95% CI = 2.31-14.7) and having got administration of mass-drug (AOR = 8.9, 95% CI = 2.36-33.6) were significant risk factors for active trachoma infection. Whereas, face washing practice regularly (AOR = 0.23, 95% CI = 0.127-0.43), and toilet availability (AOR = 0.35, 95% CI = 0.20-0.97) were preventive factors for active trachoma infection. Conclusion A significant prevalence of active trachoma infection was reported in the area as compared with previous findings and urgent clinical intervention, and the WHO critical SAFE strategies (surgery, antibiotics, facial cleanliness, and environmental improvement) implementation is highly needed in the area. In addition, healthcare providers should focus on information dissemination on proper latrine utilization, and washing the face regularly to prevent active trachoma infection is highly recommended.
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Affiliation(s)
- Fassikaw Kebede
- Department of Epidemiology and BiostaticsCollege of Health ScienceWoldia UniversityWoldiaEthiopia
| | - Muhammad Jamal
- Mersa Health CentreHabru Woreda North WolloNorth WolloEthiopia
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Abstract
Trachoma is a neglected tropical disease caused by infection with conjunctival strains of Chlamydia trachomatis. It can result in blindness. Pathophysiologically, trachoma is a disease complex composed of two linked chronic processes: a recurrent, generally subclinical infectious-inflammatory disease that mostly affects children, and a non-communicable, cicatricial and, owing to trichiasis, eventually blinding disease that supervenes in some individuals later in life. At least 150 infection episodes over an individual's lifetime are needed to precipitate trichiasis; thus, opportunity exists for a just global health system to intervene to prevent trachomatous blindness. Trachoma is found at highest prevalence in the poorest communities of low-income countries, particularly in sub-Saharan Africa; in June 2021, 1.8 million people worldwide were going blind from the disease. Blindness attributable to trachoma can appear in communities many years after conjunctival C. trachomatis transmission has waned or ceased; therefore, the two linked disease processes require distinct clinical and public health responses. Surgery is offered to individuals with trichiasis and antibiotic mass drug administration and interventions to stimulate facial cleanliness and environmental improvement are designed to reduce infection prevalence and transmission. Together, these interventions comprise the SAFE strategy, which is achieving considerable success. Although much work remains, a continuing public health problem from trachoma in the year 2030 will be difficult for the world to excuse.
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Rysava K, Mancero T, Caldas E, de Carvalho MF, Castro APB, Gutiérrez V, Haydon DT, Johnson PCD, Mancy R, Montebello LR, Rocha SM, Gonzalez Roldan JF, Vigilato MAN, Vilas VDR, Hampson K. Towards the elimination of dog-mediated rabies: development and application of an evidence-based management tool. BMC Infect Dis 2020; 20:778. [PMID: 33081712 PMCID: PMC7574347 DOI: 10.1186/s12879-020-05457-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Accepted: 09/27/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND International organizations advocate for the elimination of dog-mediated rabies, but there is only limited guidance on interpreting surveillance data for managing elimination programmes. With the regional programme in Latin America approaching elimination of dog-mediated rabies, we aimed to develop a tool to evaluate the programme's performance and generate locally-tailored rabies control programme management guidance to overcome remaining obstacles. METHODS We developed and validated a robust algorithm to classify progress towards rabies elimination within sub-national administrative units, which we applied to surveillance data from Brazil and Mexico. The method combines criteria that are easy to understand, including logistic regression analysis of case detection time series, assessment of rabies virus variants, and of incursion risk. Subjecting the algorithm to robustness testing, we further employed simulated data sub-sampled at differing levels of case detection to assess the algorithm's performance and sensitivity to surveillance quality. RESULTS Our tool demonstrated clear epidemiological transitions in Mexico and Brazil: most states progressed rapidly towards elimination, but a few regressed due to incursions and control lapses. In 2015, dog-mediated rabies continued to circulate in the poorest states, with foci remaining in only 1 of 32 states in Mexico, and 2 of 27 in Brazil, posing incursion risks to the wider region. The classification tool was robust in determining epidemiological status irrespective of most levels of surveillance quality. In endemic settings, surveillance would need to detect less than 2.5% of all circulating cases to result in misclassification, whereas in settings where incursions become the main source of cases the threshold detection level for correct classification should not be less than 5%. CONCLUSION Our tool provides guidance on how to progress effectively towards elimination targets and tailor strategies to local epidemiological situations, while revealing insights into rabies dynamics. Post-campaign assessments of dog vaccination coverage in endemic states, and enhanced surveillance to verify and maintain freedom in states threatened by incursions were identified as priorities to catalyze progress towards elimination. Our finding suggests genomic surveillance should become increasingly valuable during the endgame for discriminating circulating variants and pinpointing sources of incursions.
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Affiliation(s)
- Kristyna Rysava
- University of Warwick, School of Life Sciences, Gibbet Hill Road, Coventry, UK
- University of Glasgow, Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr building, MVLS, Glasgow, G12 8QQ UK
| | - Tamara Mancero
- Pan American Health Organization (PAHO), Duque de Caxias, Rio de Janeiro, Brazil
| | - Eduardo Caldas
- Virology, Central Laboratory, State Center for Health Surveillance, State Department of Health, São Paulo, Rio Grande do Sul Brazil
| | | | | | | | - Daniel T. Haydon
- University of Glasgow, Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr building, MVLS, Glasgow, G12 8QQ UK
| | - Paul C. D. Johnson
- University of Glasgow, Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr building, MVLS, Glasgow, G12 8QQ UK
| | - Rebecca Mancy
- University of Glasgow, Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr building, MVLS, Glasgow, G12 8QQ UK
| | | | | | | | | | - Victor Del Rio Vilas
- Pan American Health Organization (PAHO), Duque de Caxias, Rio de Janeiro, Brazil
- University of Surrey, School of Veterinary Medicine, VSM Building, Guildford, UK
| | - Katie Hampson
- University of Glasgow, Institute of Biodiversity, Animal Health and Comparative Medicine, Graham Kerr building, MVLS, Glasgow, G12 8QQ UK
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Solomon AW, Kello AB, Bangert M, West SK, Taylor HR, Tekeraoi R, Foster A. The simplified trachoma grading system, amended. Bull World Health Organ 2020; 98:698-705. [PMID: 33177759 PMCID: PMC7652564 DOI: 10.2471/blt.19.248708] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Revised: 07/06/2020] [Accepted: 07/07/2020] [Indexed: 11/27/2022] Open
Abstract
A simplified grading system for trachoma was published by the World Health Organization (WHO) in 1987. Intended for use by non-specialist personnel working at community level, the system includes five signs, each of which can be present or absent in any eye: (i) trachomatous trichiasis; (ii) corneal opacity; (iii) trachomatous inflammation—follicular; (iv) trachomatous inflammation—intense; and (v) trachomatous scarring. Though neither perfectly sensitive nor perfectly specific for trachoma, these signs have been essential tools for identifying populations that need interventions to eliminate trachoma as a public health problem. In 2018, at WHO’s 4th global scientific meeting on trachoma, the definition of one of the signs, trachomatous trichiasis, was amended to exclude trichiasis that affects only the lower eyelid. This paper presents the amended system, updates its presentation, offers notes on its use and identifies areas of ongoing debate.
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Affiliation(s)
- Anthony W Solomon
- Department of Control of Neglected Tropical Diseases, World Health Organization, Avenue Appia 20, 1211 Geneva 27, Switzerland
| | - Amir B Kello
- World Health Organization Regional Office for Africa, Brazzaville, Congo
| | - Mathieu Bangert
- Department of Control of Neglected Tropical Diseases, World Health Organization, Avenue Appia 20, 1211 Geneva 27, Switzerland
| | - Sheila K West
- Wilmer Eye Institute, Johns Hopkins University, Baltimore, United States of America
| | - Hugh R Taylor
- Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Australia
| | - Rabebe Tekeraoi
- Eye Department, Ministry of Health and Medical Services, South Tarawa, Kiribati
| | - Allen Foster
- International Centre for Eye Health, London School of Hygiene & Tropical Medicine, London, England
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de Brito CMG, Barbosa CC, de Andrade SMC, de Oliveira ALS, Montarroyos UR, Ferraz C, Vieira MDT, Lopes MDFC, Gouveia GC, de Medeiros ZM. Household Survey of Trachoma among Children Living in Pernambuco, Brazil. Pathogens 2019; 8:pathogens8040263. [PMID: 31775360 PMCID: PMC6963545 DOI: 10.3390/pathogens8040263] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Revised: 09/28/2019] [Accepted: 10/10/2019] [Indexed: 11/18/2022] Open
Abstract
This study analyzed the association between individual and household factors and the incidence of trachoma among a population aged between 1 and 9 years in the state of Pernambuco. This was a population-based household study conducted using a population-based sample of residents from 96 census sectors of the 1778 sectors considered to be at social risk in the state. The estimated odds ratio of the univariate analysis presented a confidence interval of 95%. Weights and clusters were adjusted through the Generalized Linear and Latent Mixed Model (GLLAM) method. Trachoma cases were the dependent variable in the multivariate analysis. The independent variables were selected through the stepwise forward method, with an input criterion of 20% (p < 0.20) and an output criterion of 10% (p < 0.10). The prevalence was 6.65%. Trachoma was associated with a female sex, age of 5–9 years, either the absence of use or infrequent use of soap to wash the hands and face, the presence of nasal secretion, a lack of piped water from a public supply system, a greater number of rooms used for sleeping, a greater number of people living in the same household, and a family income of up to one minimum monthly wage. The prevalence of follicular trachoma in Pernambuco was higher than what is recommended by the World Health Organization (WHO).
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Affiliation(s)
- Cintia Michele Gondim de Brito
- University of Pernambuco, Recife 50100130, Pernambuco, Brazil; (U.R.M.)
- Department of Epidemiological Surveillance, First Healthcare Region of the Health Department of the State of Pernambuco, Recife 50050911, Pernambuco, Brazil;
- Correspondence: ; Tel.: +55-(81)-991388298
| | - Celivane Cavalcanti Barbosa
- Department of Epidemiological Surveillance, First Healthcare Region of the Health Department of the State of Pernambuco, Recife 50050911, Pernambuco, Brazil;
- Aggeu Magalhães Institute (IAM), Oswaldo Cruz Foundation (FIOCRUZ), Recife 50740465, Pernambuco, Brazil; (S.M.C.d.A.); (A.L.S.d.O.); (G.C.G.)
| | - Sérgio Murilo Coelho de Andrade
- Aggeu Magalhães Institute (IAM), Oswaldo Cruz Foundation (FIOCRUZ), Recife 50740465, Pernambuco, Brazil; (S.M.C.d.A.); (A.L.S.d.O.); (G.C.G.)
| | - André Luiz Sá de Oliveira
- Aggeu Magalhães Institute (IAM), Oswaldo Cruz Foundation (FIOCRUZ), Recife 50740465, Pernambuco, Brazil; (S.M.C.d.A.); (A.L.S.d.O.); (G.C.G.)
| | | | - Cristiano Ferraz
- Federal University of Pernambuco, Recife 50670901 Pernambuco, Brazil;
| | | | | | - Giselle Campozana Gouveia
- Aggeu Magalhães Institute (IAM), Oswaldo Cruz Foundation (FIOCRUZ), Recife 50740465, Pernambuco, Brazil; (S.M.C.d.A.); (A.L.S.d.O.); (G.C.G.)
| | - Zulma Maria de Medeiros
- University of Pernambuco, Recife 50100130, Pernambuco, Brazil; (U.R.M.)
- Aggeu Magalhães Institute (IAM), Oswaldo Cruz Foundation (FIOCRUZ), Recife 50740465, Pernambuco, Brazil; (S.M.C.d.A.); (A.L.S.d.O.); (G.C.G.)
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Lietman TM, Pinsent A, Liu F, Deiner M, Hollingsworth TD, Porco TC. Models of Trachoma Transmission and Their Policy Implications: From Control to Elimination. Clin Infect Dis 2019; 66:S275-S280. [PMID: 29860288 PMCID: PMC5982784 DOI: 10.1093/cid/ciy004] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Despite great progress in eliminating trachoma from the majority of worldwide districts, trachoma control seems to have stalled in some endemic districts. Can mathematical models help suggest the way forward? We review specific achievements of models in trachoma control in the past. Models showed that, even with incomplete coverage, mass drug administration could eliminate disease through a spillover effect, somewhat analogous to how incomplete vaccine campaigns can eliminate disease through herd protection. Models also suggest that elimination can always be achieved if enough people are treated often enough with an effective enough drug. Other models supported the idea that targeting ages at highest risk or continued improvements in hygiene and sanitation can contribute meaningfully to trachoma control. Models of intensive targeting of a core group may point the way to final eradication even in areas with substantial transmission and within-community heterogeneity.
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Affiliation(s)
- Thomas M Lietman
- Francis I. Proctor Foundation, San Francisco.,Department of Ophthalmology, San Francisco.,Department of Epidemiology and Biostatistics, San Francisco.,Global Health Sciences, University of California, San Francisco
| | - Amy Pinsent
- School of Public Health and Preventative Medicine, Monash University, Melbourne, Australia
| | | | - Michael Deiner
- Francis I. Proctor Foundation, San Francisco.,Department of Ophthalmology, San Francisco
| | - T Deirdre Hollingsworth
- Big Data Institute, Li Ka Shing Centre for Health Information and Discovery, University of Oxford, United Kingdom
| | - Travis C Porco
- Francis I. Proctor Foundation, San Francisco.,Department of Ophthalmology, San Francisco.,Department of Epidemiology and Biostatistics, San Francisco
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Macleod CK, Binnawi KH, Elshafie BE, Sadig HE, Hassan A, Cocks N, Willis R, Chu B, Solomon AW. Unimproved water sources and open defecation are associated with active trachoma in children in internally displaced persons camps in the Darfur States of Sudan. Trans R Soc Trop Med Hyg 2019; 113:599-609. [PMID: 31612959 PMCID: PMC6792159 DOI: 10.1093/trstmh/trz042] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 04/01/2019] [Accepted: 05/30/2019] [Indexed: 11/13/2022] Open
Abstract
PURPOSE To estimate the proportion of children with trachomatous inflammation-follicular (TF) and adults with trachomatous trichiasis (TT) in internally displaced persons (IDP) camps in the Darfur States of Sudan and to evaluate associated risk factors. METHODS IDP camps were identified from government census data. We conducted a subanalysis of data collected in these camps during 2014-2015 as part of surveys covering 37 districts of the Darfur States within the Global Trachoma Mapping Project. A random-effects hierarchical model was used to evaluate factors associated with TF in children or TT in adults. RESULTS Thirty-six IDP camps were represented in the survey data, in which 1926 children aged 1-9 y were examined, of whom 38 (8%) had TF. Poor sanitation, younger age and living in a household that purchased water from a vendor were associated with TF in children aged 1-9 y. Of 2139 individuals examined aged ≥15 y, 16 (0.7%) had TT. TT was strongly independently associated with being older and living alone. CONCLUSION Trachoma is found at low levels in these camps, but still at levels where intervention is needed. Disease elimination in conflict-related settings presents a unique challenge for the trachoma community, and may require an innovative approach. Understanding how best to undertake trachoma elimination interventions in these areas should be prioritized.
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Affiliation(s)
- Colin K Macleod
- Clinical Research Department, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK
| | - Kamal Hashim Binnawi
- National Program for Prevention of Blindness, Federal Ministry of Health, PO Box 303 Khartoum, Sudan
- Department of Ophthalmology, Al Neelain University, Khartoum, Sudan
| | - Balgesa Elkheir Elshafie
- National Program for Prevention of Blindness, Federal Ministry of Health, PO Box 303 Khartoum, Sudan
| | - Husam Eldin Sadig
- Faculty of Mathematical Sciences and Statistics, Al-Neelain University, Sudan
| | | | - Naomi Cocks
- Clinical Research Department, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK
| | - Rebecca Willis
- Task Force for Global Health, 330 W Ponce de Leon Ave, Decatur, GA, USA
| | - Brian Chu
- Task Force for Global Health, 330 W Ponce de Leon Ave, Decatur, GA, USA
| | - Anthony W Solomon
- Clinical Research Department, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK
- Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
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10
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Mwale C, Mumbi W, Funjika M, Sokesi T, Silumesii A, Mulenga M, Mutati G, Kwendakwema D, Chelu C, Adamu Y, Alemayehu W, Al-Khatib T, Bakhtiari A, Dejene M, Massae PA, Mpyet C, Nwosu C, Willis R, Courtright P, Solomon AW. Prevalence of Trachoma in 47 Administrative Districts of Zambia: Results of 32 Population-Based Prevalence Surveys. Ophthalmic Epidemiol 2019; 25:171-180. [PMID: 30806543 PMCID: PMC6444202 DOI: 10.1080/09286586.2018.1546880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Purpose: A number of previous administrative-district-level baseline trachoma prevalence estimates in Zambia required verification. We used methodologies and systems for trachoma surveys considered to represent international best practice in order to generate reliable estimates of the prevalence of trachoma. Methods: Between March 2016 and July 2017, we undertook 32 population-based prevalence surveys covering 47 administrative districts. In each of the 32 evaluation units (EUs), we selected 31 households in each of 24 clusters. In selected households, trained, certified graders examined all residents aged 1 year and above for evidence of trachomatous inflammation—follicular (TF) and trichiasis. In eyes that had trichiasis, the presence or absence of trachomatous scarring (TS) was recorded, and the subject was asked about previous trichiasis management recommendations from health workers. Results: Five EUs (encompassing seven administrative districts) had prevalence estimates of trichiasis+TS unknown to the health system in ≥15-year-olds of ≥0.2%, and require public-health-level implementation of trichiasis surgery services. Eleven EUs (encompassing 16 administrative districts) had TF prevalence estimates in 1–9-year-olds of ≥5%. Intervention with the A, F and E components of the SAFE strategy for trachoma elimination is required for nearly 1.5 million people. Conclusion: Trachoma is a public health problem in some parts of Zambia. The Ministry of Health will continue to partner with other stakeholders to implement the multi-sectoral SAFE strategy. Consideration should be given to re-surveying other suspected-endemic administrative districts in which surveys using older methodologies returned TF prevalence estimates ≥5%.
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Affiliation(s)
- Consity Mwale
- a Lusaka Provincial Health Office , Lusaka , Zambia.,b University Teaching Eye Hospital , Lusaka , Zambia
| | - Willard Mumbi
- c Ophthalmology Unit , Kabwe General Hospital , Kabwe , Zambia
| | - Misa Funjika
- d Ophthalmology Unit , Ndola Teaching Hospital , Ndola , Zambia
| | - Teddy Sokesi
- d Ophthalmology Unit , Ndola Teaching Hospital , Ndola , Zambia
| | | | - Muma Mulenga
- b University Teaching Eye Hospital , Lusaka , Zambia
| | - Grace Mutati
- b University Teaching Eye Hospital , Lusaka , Zambia
| | | | | | - Yilikal Adamu
- g Department of Ophthalmology, Faculty of Medicine , Addis Ababa University , Addis Ababa , Ethiopia
| | - Wondu Alemayehu
- h The Fred Hollows Foundation , Addis Ababa , Ethiopia.,i Berhan Public Health and Eye Care Consultancy , Addis Ababa , Ethiopia
| | - Tawfik Al-Khatib
- j Prevention of Blindness Program , Ministry of Public Health & Population , Sana'a , Yemen.,k Department of Ophthalmology, College of Medicine , University of Sana'a , Sana'a , Yemen.,l Eye Unit , Al-Thawra Hospital , Sana'a , Yemen
| | | | - Michael Dejene
- n Michael Dejene Public Health Consultancy Services , Addis Ababa , Ethiopia
| | | | - Caleb Mpyet
- p Department of Ophthalmology , University of Jos , Jos , Nigeria.,q Sightsavers , Kaduna , Nigeria.,r Kilimanjaro Centre for Community Ophthalmology International, Division of Ophthalmology , University of Cape Town , Cape Town , South Africa
| | | | | | - Paul Courtright
- r Kilimanjaro Centre for Community Ophthalmology International, Division of Ophthalmology , University of Cape Town , Cape Town , South Africa
| | - Anthony W Solomon
- s Clinical Research Department , London School of Hygiene & Tropical Medicine , London , UK.,t Department of Control of Neglected Tropical Diseases , World Health Organization , Geneva , Switzerland
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Solomon AW, Bella ALF, Negussu N, Willis R, Taylor HR. How much trachomatous trichiasis is there? A guide to calculating district-level estimates. COMMUNITY EYE HEALTH 2019; 31:S5-S8. [PMID: 31086446 PMCID: PMC6390516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Anthony W Solomon
- Medical Officer for Trachoma: Department of Control of Neglected Tropical Diseases, World Health Organization, Geneva, Switzerland
| | | | - Nebiyu Negussu
- Neglected Tropical Diseases Team Leader: Federal Ministry of Health, Addis Ababa, Ethiopia
| | - Rebecca Willis
- Data and Analytics Team Manager: International Trachoma Initiative, Task Force for Global Health, Decatur GA, USA
| | - Hugh R Taylor
- Harold Mitchell Professor of Indigenous Eye Health: University of Melbourne, Melbourne, Australia
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Tilahun Z, Fenta TG. Coverage of azithromycin mass treatment for trachoma elimination in Northwestern Ethiopia: a community based cross-sectional study. BMC Ophthalmol 2018; 18:193. [PMID: 30081851 PMCID: PMC6091195 DOI: 10.1186/s12886-018-0868-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 07/25/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mass drug administration with antibiotics predominantly with azithromycin is one of the four arms of the SAFE strategy. The elimination of ocular chlamydial infection is only achieved as long as the azithromycin mass treatments (AMT) are given frequently enough and at a high enough coverage. This study was conducted to assess the coverage of azithromycin mass treatment and its determinants in Awi Zone, Northwestern Ethiopia. METHODS House to house survey using a structured questionnaire was done between July 7 to July 25, 2013. Coverage is defined as the proportion of individuals in the eligible population who actually ingested the Azithromycin during the Campaign. RESULTS A total of 1267 households were enrolled in the survey in which 5826 eligible members were living in these households. Almost half (54.6%) of the community members who were eligible for all six campaigns had participated in more than three campaigns of azithromycin mass treatment. The overall average self-reported coverage of the azithromycin mass treatment (AMT) in all six campaigns was 62.8% (64% in rural vs. 61.6% urban). On average, each eligible person had taken the drug 3.77 times. The rural residents were significantly more likely to have received treatment during the last round of AMT in 2012 {AOR = 2.35; 95% CI [1.80-3.06]}. Azithromycin uptake status of female household heads was less than the corresponding male household heads {AOR = 0.41; 95% CI [0.24-0.72]}. Household heads' awareness about trachoma (AOR = 2.55; 95% CI [1.19-5.44]) and AMT {AOR = 7.19; 95% CI [3.27-15.82]} had positive association with acceptability. CONCLUSION The overall average AMT coverage was found to be low. There was low coverage of the treatment in the urban community as compared to the rural residents. Misconceptions of household heads about trachoma and azithromycin have negatively affected the coverage. Further work on why female household heads are associated with higher risk of non-participation in AMT is warranted. Strengthening awareness creation and consideration of additional campaigns is essential.
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Affiliation(s)
- Zelalem Tilahun
- Social and Adminstrative Pharmacy Working Group, Departement of Pharmaceutics and Social Pharmacy, College of Health Sciences, Addis Ababa University, P.O.Box 1176, Addis Ababa, Ethiopia
| | - Teferi Gedif Fenta
- Social and Adminstrative Pharmacy Working Group, Departement of Pharmaceutics and Social Pharmacy, College of Health Sciences, Addis Ababa University, P.O.Box 1176, Addis Ababa, Ethiopia.
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Dyson L, Marks M, Crook OM, Sokana O, Solomon AW, Bishop A, Mabey DCW, Hollingsworth TD. Targeted Treatment of Yaws With Household Contact Tracing: How Much Do We Miss? Am J Epidemiol 2018; 187:837-844. [PMID: 29140407 PMCID: PMC5888927 DOI: 10.1093/aje/kwx305] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 08/22/2017] [Indexed: 11/13/2022] Open
Abstract
Yaws is a disabling bacterial infection found primarily in warm and humid tropical areas. The World Health Organization strategy mandates an initial round of total community treatment (TCT) with single-dose azithromycin followed either by further TCT or active case-finding and treatment of cases and their contacts (the Morges strategy). We sought to investigate the effectiveness of the Morges strategy. We employed a stochastic household model to study the transmission of infection using data collected from a pre-TCT survey conducted in the Solomon Islands. We used this model to assess the proportion of asymptomatic infections that occurred in households without active cases. This analysis indicated that targeted treatment of cases and their household contacts would miss a large fraction of asymptomatic infections (65%–100%). This fraction was actually higher at lower prevalences. Even assuming that all active cases and their households were successfully treated, our analysis demonstrated that at all prevalences present in the data set, up to 90% of (active and asymptomatic) infections would not be treated under household-based contact tracing. Mapping was undertaken as part of the study “Epidemiology of Yaws in the Solomon Islands and the Impact of a Trachoma Control Programme,” in September–October 2013.
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Affiliation(s)
- Louise Dyson
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Michael Marks
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Hospital for Tropical Diseases, University College London Hospitals NHS Trust, London, United Kingdom
| | - Oliver M Crook
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - Oliver Sokana
- Ministry of Health and Medical Services, Honiara, Solomon Islands
| | - Anthony W Solomon
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Hospital for Tropical Diseases, University College London Hospitals NHS Trust, London, United Kingdom
| | - Alex Bishop
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
| | - David C W Mabey
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Hospital for Tropical Diseases, University College London Hospitals NHS Trust, London, United Kingdom
| | - T Déirdre Hollingsworth
- Mathematics Institute, University of Warwick, Coventry, United Kingdom
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
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14
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Last A, Burr S, Alexander N, Harding-Esch E, Roberts CH, Nabicassa M, Cassama ETDS, Mabey D, Holland M, Bailey R. Spatial clustering of high load ocular Chlamydia trachomatis infection in trachoma: a cross-sectional population-based study. Pathog Dis 2018; 75:3791466. [PMID: 28472466 PMCID: PMC5808645 DOI: 10.1093/femspd/ftx050] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 05/02/2017] [Indexed: 11/12/2022] Open
Abstract
Chlamydia trachomatis (Ct) is the most common cause of bacterial sexually transmitted infection and infectious cause of blindness (trachoma) worldwide. Understanding the spatial distribution of Ct infection may enable us to identify populations at risk and improve our understanding of Ct transmission. In this study, we sought to investigate the spatial distribution of Ct infection and the clinical features associated with high Ct load in trachoma-endemic communities on the Bijagós Archipelago (Guinea Bissau). We collected 1507 conjunctival samples and corresponding detailed clinical data during a cross-sectional population-based geospatially representative trachoma survey. We used droplet digital PCR to estimate Ct load on conjunctival swabs. Geostatistical tools were used to investigate clustering of ocular Ct infections. Spatial clusters (independent of age and gender) of individuals with high Ct loads were identified using local indicators of spatial association. We did not detect clustering of individuals with low load infections. These data suggest that infections with high bacterial load may be important in Ct transmission. These geospatial tools may be useful in the study of ocular Ct transmission dynamics and as part of trachoma surveillance post-treatment, to identify clusters of infection and thresholds of Ct load that may be important foci of re-emergent infection in communities.
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Affiliation(s)
- Anna Last
- Clinical Research Department, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Sarah Burr
- Disease Control and Elimination Theme, Medical Research Council Unit The Gambia, PO Box 273 Banjul, Atlantic Boulevard, Fajara, The Gambia
| | - Neal Alexander
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Emma Harding-Esch
- Clinical Research Department, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Chrissy H Roberts
- Clinical Research Department, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Meno Nabicassa
- Programa Nacional de Saúde de Visão, Ministério de Saúde Publica, PO Box 50, Avenida de Unidade Africana, Bisssau, Guiné Bissau
| | | | - David Mabey
- Clinical Research Department, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Martin Holland
- Clinical Research Department, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Robin Bailey
- Clinical Research Department, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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15
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Pinsent A, Liu F, Deiner M, Emerson P, Bhaktiari A, Porco TC, Lietman T, Gambhir M. Probabilistic forecasts of trachoma transmission at the district level: A statistical model comparison. Epidemics 2017; 18:48-55. [PMID: 28279456 PMCID: PMC5340843 DOI: 10.1016/j.epidem.2017.01.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 01/20/2017] [Accepted: 01/31/2017] [Indexed: 11/09/2022] Open
Abstract
The World Health Organization and its partners are aiming to eliminate trachoma as a public health problem by 2020. In this study, we compare forecasts of TF prevalence in 2011 for 7 different statistical and mechanistic models across 9 de-identified trachoma endemic districts, representing 4 unique trachoma endemic countries. We forecast TF prevalence between 1-6 years ahead in time and compare the 7 different models to the observed 2011 data using a log-likelihood score. An SIS model, including a district-specific random effect for the district-specific transmission coefficient, had the highest log-likelihood score across all 9 districts and was therefore the best performing model. While overall the deterministic transmission model was the least well performing model, although it did comparably well to the other models for 8 of 9 districts. We perform a statistically rigorous comparison of the forecasting ability of a range of mathematical and statistical models across multiple endemic districts between 1 and 6 years ahead of the last collected TF prevalence data point in 2011, assessing results against surveillance data. This study is a step towards making statements about likelihood and time to elimination with regard to the WHO GET2020 goals.
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Affiliation(s)
- Amy Pinsent
- Department of Public Health and Preventative Medicine, Monash University, Melbourne, Australia.
| | - Fengchen Liu
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, CA, USA
| | - Michael Deiner
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, CA, USA; Department of Ophthalmology, University of California San Francisco, San Francisco, CA, USA
| | - Paul Emerson
- International Trachoma Initiative, Atlanta, GA, USA; School of Public Health, Emory University, Atlanta, GA, USA
| | | | - Travis C Porco
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, CA, 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
| | - Thomas Lietman
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, CA, 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; Global Health Sciences, University of California San Francisco, San Francisco, CA, USA
| | - Manoj Gambhir
- Department of Public Health and Preventative Medicine, Monash University, Melbourne, Australia
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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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17
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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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Antibiotic Resistance in Streptococcus pneumoniae after Azithromycin Distribution for Trachoma. J Trop Med 2015; 2015:917370. [PMID: 26557143 PMCID: PMC4628654 DOI: 10.1155/2015/917370] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 09/27/2015] [Indexed: 12/14/2022] Open
Abstract
Trachoma is caused by Chlamydia trachomatis and is a leading cause of blindness worldwide. Mass distribution of azithromycin (AZM) is part of the strategy for the global elimination of blinding trachoma by 2020. Although resistance to AZM in C. trachomatis has not been reported, there have been concerns about resistance in other organisms when AZM is administered in community settings. We identified studies that measured pneumococcal prevalence and resistance to AZM following mass AZM provision reported up to 2013 in Medline and Web of Science databases. Potential sources of bias were assessed using the Cochrane Risk of Bias Tool. A total of 45 records were screened, of which 8 met the inclusion criteria. We identified two distinct trends of resistance prevalence, which are dependent on frequency of AZM provision and baseline prevalence of resistance. We also demonstrated strong correlation between the prevalence of resistance at baseline and at 2-3 months (r = 0.759). Although resistance to AZM in C. trachomatis has not been reported, resistance to this commonly used macrolide antibiotic in other diseases could compromise treatment. This should be considered when planning long-term trachoma control strategies.
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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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Shattock AJ, Gambhir M, Taylor HR, Cowling CS, Kaldor JM, Wilson DP. Control of trachoma in Australia: a model based evaluation of current interventions. PLoS Negl Trop Dis 2015; 9:e0003474. [PMID: 25860143 PMCID: PMC4393231 DOI: 10.1371/journal.pntd.0003474] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 12/15/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Australia is the only high-income country in which endemic trachoma persists. In response, the Australian Government has recently invested heavily towards the nationwide control of the disease. METHODOLOGY/PRINCIPAL FINDINGS A novel simulation model was developed to reflect the trachoma epidemic in Australian Aboriginal communities. The model, which incorporates demographic, migration, mixing, and biological heterogeneities, was used to evaluate recent intervention measures against counterfactual past scenarios, and also to assess the potential impact of a series of hypothesized future intervention measures relative to the current national strategy and intensity. The model simulations indicate that, under the current intervention strategy and intensity, the likelihood of controlling trachoma to less than 5% prevalence among 5-9 year-old children in hyperendemic communities by 2020 is 31% (19%-43%). By shifting intervention priorities such that large increases in the facial cleanliness of children are observed, this likelihood of controlling trachoma in hyperendemic communities is increased to 64% (53%-76%). The most effective intervention strategy incorporated large-scale antibiotic distribution programs whilst attaining ambitious yet feasible screening, treatment, facial cleanliness and housing construction targets. Accordingly, the estimated likelihood of controlling trachoma in these communities is increased to 86% (76%-95%). CONCLUSIONS/SIGNIFICANCE Maintaining the current intervention strategy and intensity is unlikely to be sufficient to control trachoma across Australia by 2020. However, by shifting the intervention strategy and increasing intensity, the likelihood of controlling trachoma nationwide can be significantly increased.
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Affiliation(s)
| | - Manoj Gambhir
- Department of Epidemiology and Preventive Medicine, Monash University, Melbourne, Australia
| | - Hugh R. Taylor
- Melbourne School of Population Health, The University of Melbourne, Melbourne, Australia
| | | | - John M. Kaldor
- The Kirby Institute, University of New South Wales, Sydney, Australia
| | - David P. Wilson
- The Kirby Institute, University of New South Wales, Sydney, Australia
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Ssemanda EN, Mkocha H, Levens J, Munoz B, West SK. Community mass treatment with azithromycin for trachoma: Factors associated with change in participation of children from the first to the second round. CLINICAL EPIDEMIOLOGY AND GLOBAL HEALTH 2015; 3:37-43. [PMID: 26462290 DOI: 10.1016/j.cegh.2013.06.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
BACKGROUND Mass drug administration (MDA) with azithromycin is an important part of trachoma control programs. Maintaining high participation among children is challenging. AIM We assessed factors identifying households with a child who changed participation from the first MDA to the second MDA compared to households where all children participated at both MDAs. METHODS Two case-control comparisons were conducted in 11 Tanzanian communities, which underwent MDA in 2008 and 2009. The first case group (n=165) was a random sample of households with a child who changed from a 2008 non-participant to a 2009 participant (delayed participant). The second case group (n=165) was a random sample of households with a child who went from a 2008 participant to a 2009 non-participant (change to non-participant). Controls (n=330) were a random sample of households where all children participated in both rounds. Risk factors were assessed using questionnaires asked of children's guardians. Logistic models with a random-intercept were used to estimate odds ratios and 95% confidence intervals. RESULTS Households with delayed participation were more likely to be in communities with fewer treatment days (OR=2.98, 95% CI=1.80-4.92) and assigned to Community Treatment Assistants (CTA) with a wide area to cover (OR=1.88, 95% CI=1.09-3.23). Households with change to non-participation were more likely to live further from the distribution site (OR=3.17, 95% CI=1.19-8.46), have the guardian born outside the village with short-term residency (OR=2.64, 95% CI=1.32-5.31), and be assigned to a male CTA (OR=1.75, 95% CI=1.08-2.83). CONCLUSIONS Factors related to program accessibility were associated with delayed participation and maintaining participation.
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Affiliation(s)
- Elizabeth N Ssemanda
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | | | - Joshua Levens
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Beatriz Munoz
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
| | - Sheila K West
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA
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Rahman SA, West SK, Mkocha H, Munoz B, Porco TC, Keenan JD, Lietman TM. The distribution of ocular Chlamydia prevalence across Tanzanian communities where trachoma is declining. PLoS Negl Trop Dis 2015; 9:e0003682. [PMID: 25815466 PMCID: PMC4376383 DOI: 10.1371/journal.pntd.0003682] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 03/06/2015] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND Mathematical models predict an exponential distribution of infection prevalence across communities where a disease is disappearing. Trachoma control programs offer an opportunity to test this hypothesis, as the World Health Organization has targeted trachoma for elimination as a public health concern by the year 2020. Local programs may benefit if a single survey could reveal whether infection was headed towards elimination. Using data from a previously-published 2009 survey, we test the hypothesis that Chlamydia trachomatis prevalence across 75 Tanzanian communities where trachoma had been documented to be disappearing is exponentially distributed. METHODS/FINDINGS We fit multiple continuous distributions to the Tanzanian data and found the exponential gave the best approximation. Model selection by Akaike Information Criteria (AICc) suggested the exponential distribution had the most parsimonious fit to the data. Those distributions which do not include the exponential as a special or limiting case had much lower likelihoods of fitting the observed data. 95% confidence intervals for shape parameter estimates of those distributions which do include the exponential as a special or limiting case were consistent with the exponential. Lastly, goodness-of-fit testing was unable to reject the hypothesis that the prevalence data came from an exponential distribution. CONCLUSIONS Models correctly predict that infection prevalence across communities where a disease is disappearing is best described by an exponential distribution. In Tanzanian communities where local control efforts had reduced the clinical signs of trachoma by 80% over 10 years, an exponential distribution gave the best fit to prevalence data. An exponential distribution has a relatively heavy tail, thus occasional high-prevalence communities are to be expected even when infection is disappearing. A single cross-sectional survey may be able to reveal whether elimination efforts are on-track.
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Affiliation(s)
- Salman A. Rahman
- F.I. Proctor Foundation, San Francisco, California, United States of America
| | - Sheila K. West
- Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Harran Mkocha
- Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Beatriz Munoz
- Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Travis C. Porco
- F.I. Proctor Foundation, 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
| | - Jeremy D. Keenan
- F.I. Proctor Foundation, San Francisco, California, United States of America
- Department of Ophthalmology, University of California, San Francisco, San Francisco, California, United States of America
| | - Thomas M. Lietman
- F.I. Proctor Foundation, 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
- * E-mail:
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Lietman TM, Gebre T, Abdou A, Alemayehu W, Emerson P, Blumberg S, Keenan JD, Porco TC. The distribution of the prevalence of ocular chlamydial infection in communities where trachoma is disappearing. Epidemics 2015; 11:85-91. [PMID: 25979286 PMCID: PMC4986606 DOI: 10.1016/j.epidem.2015.03.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 03/10/2015] [Accepted: 03/13/2015] [Indexed: 11/16/2022] Open
Abstract
Mathematical models predict that the prevalence of infection in different
communities where an infectious disease is disappearing should approach a
geometric distribution. Trachoma programs offer an opportunity to test this
hypothesis, as the World Health Organization (WHO) has targeted trachoma to be
eliminated as a public health concern by the year 2020. We assess the
distribution of the community prevalence of childhood ocular chlamydia infection
from periodic, cross-sectional surveys in two areas of Ethiopia. These surveys
were taken in a controlled setting, where infection was documented to be
disappearing over time. For both sets of surveys, the geometric distribution had
the most parsimonious fit of the distributions tested, and goodness-of-fit
testing was consistent with the prevalence of each community being drawn from a
geometric distribution. When infection is disappearing, the single sufficient
parameter describing a geometric distribution captures much of the
distributional information found from examining every community. The relatively
heavy tail of the geometric suggests that the presence of an occasional
high-prevalence community is to be expected, and does not necessarily reflect a
transmission hot spot or program failure. A single cross-sectional survey can
reveal which direction a program is heading. A geometric distribution of the
prevalence of infection across communities may be an encouraging sign,
consistent with a disease on its way to eradication.
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Affiliation(s)
- Thomas M Lietman
- F.I Proctor Foundation, San Francisco, CA, USA; Department of Ophthalmology, San Francisco, CA, USA; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA.
| | | | - Amza Abdou
- Programme National de Lutte Contre la Cecité, Niamey, Niger
| | - Wondu Alemayehu
- F.I Proctor Foundation, San Francisco, CA, USA; Department of Ophthalmology, San Francisco, CA, USA; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA; The Carter Center, Atlanta, GA, USA; Programme National de Lutte Contre la Cecité, Niamey, Niger; NIH Fogarty International Center, Bethesda, MD, USA; Berhan Health, Addis Ababa, Ethiopia
| | | | - Seth Blumberg
- F.I Proctor Foundation, San Francisco, CA, USA; NIH Fogarty International Center, Bethesda, MD, USA
| | - Jeremy D Keenan
- F.I Proctor Foundation, San Francisco, CA, USA; Department of Ophthalmology, San Francisco, CA, USA
| | - Travis C Porco
- F.I Proctor Foundation, San Francisco, CA, USA; Department of Ophthalmology, San Francisco, CA, USA; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA
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Modelling the effects of mass drug administration on the molecular epidemiology of schistosomes. ADVANCES IN PARASITOLOGY 2015; 87:293-327. [PMID: 25765198 DOI: 10.1016/bs.apar.2014.12.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
As national governments scale up mass drug administration (MDA) programs aimed to combat neglected tropical diseases (NTDs), novel selection pressures on these parasites increase. To understand how parasite populations are affected by MDA and how to maximize the success of control programmes, it is imperative for epidemiological, molecular and mathematical modelling approaches to be combined. Modelling of parasite population genetic and genomic structure, particularly of the NTDs, has been limited through the availability of only a few molecular markers to date. The landscape of infectious disease research is being dramatically reshaped by next-generation sequencing technologies and our understanding of how repeated selective pressures are shaping parasite populations is radically altering. Genomics can provide high-resolution data on parasite population structure, and identify how loci may contribute to key phenotypes such as virulence and/or drug resistance. We discuss the incorporation of genetic and genomic data, focussing on the recently sequenced Schistosoma spp., into novel mathematical transmission models to inform our understanding of the impact of MDA and other control methods. We summarize what is known to date, the models that exist and how population genetics has given us an understanding of the effects of MDA on the parasites. We consider how genetic and genomic data have the potential to shape future research, highlighting key areas where data are lacking, and how future molecular epidemiology knowledge can aid understanding of transmission dynamics and the effects of MDA, ultimately informing public health policy makers of the best interventions for NTDs.
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Abstract
Trachoma is the most common infectious cause of blindness. Repeated episodes of infection with Chlamydia trachomatis in childhood lead to severe conjunctival inflammation, scarring, and potentially blinding inturned eyelashes (trichiasis or entropion) in later life. Trachoma occurs in resource-poor areas with inadequate hygiene, where children with unclean faces share infected ocular secretions. Much has been learnt about the epidemiology and pathophysiology of trachoma. Integrated control programmes are implementing the SAFE Strategy: surgery for trichiasis, mass distribution of antibiotics, promotion of facial cleanliness, and environmental improvement. This strategy has successfully eliminated trachoma in several countries and global efforts are underway to eliminate blinding trachoma worldwide by 2020.
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Affiliation(s)
- Hugh R Taylor
- Melbourne School of Population and Global Health, University of Melbourne, Carlton, VIC, Australia.
| | - Matthew J Burton
- International Centre for Eye Health, Department of Clinical Research, London School of Hygiene & Tropical Medicine, London, UK
| | - Danny Haddad
- Global Vision Initiative, Emory Eye Center, Emory University School of Medicine, Atlanta, GA, USA
| | - Sheila West
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Heathcote Wright
- Centre for Eye Research Australia, University of Melbourne, East Melbourne, VIC, Australia
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26
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Edwards T, Allen E, Harding-Esch EM, Hart J, Burr SE, Holland MJ, Sillah A, West SK, Mabey D, Bailey R. Non-participation during azithromycin mass treatment for trachoma in The Gambia: heterogeneity and risk factors. PLoS Negl Trop Dis 2014; 8:e3098. [PMID: 25165994 PMCID: PMC4148234 DOI: 10.1371/journal.pntd.0003098] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 06/20/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND There is concern that untreated individuals in mass drug administration (MDA) programs for neglected tropical diseases can reduce the impact of elimination efforts by maintaining a source of transmission and re-infection. METHODOLOGY/PRINCIPAL FINDINGS Treatment receipt was recorded against the community census during three MDAs with azithromycin for trachoma in The Gambia, a hypo-endemic setting. Predictors of non-participation were investigated in 1-9 year olds using random effects logistic regression of cross-sectional data for each MDA. Two types of non-participators were identified: present during MDA but not treated (PNT) and eligible for treatment but absent during MDA (EBA). PNT and EBA children were compared to treated children separately. Multivariable models were developed using baseline data and validated using year one and two data, with a priori adjustment for previous treatment status. Analyses included approximately 10000 children at baseline and 5000 children subsequently. There was strong evidence of spatial heterogeneity, and persistent non-participation within households and individuals. By year two, non-participation increased significantly to 10.4% overall from 6.2% at baseline, with more, smaller geographical clusters of non-participating households. Multivariable models suggested household level predictors of non-participation (increased time to water and household head non-participation for both PNT and EBA; increased household size for PNT status only; non-inclusion in a previous trachoma examination survey and younger age for EBA only). Enhanced coverage efforts did not decrease non-participation. Few infected children were detected at year three and only one infected child was EBA previously. Infected children were in communities close to untreated endemic areas with higher rates of EBA non-participation during MDA. CONCLUSIONS/SIGNIFICANCE In hypo-endemic settings, with good coverage and no association between non-participation and infection, efforts to improve participation during MDA may not be required. Further research could investigate spatial hotspots of infection and non-participation in other low and medium prevalence settings before allocating resources to increase participation.
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Affiliation(s)
- Tansy Edwards
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom
- * E-mail:
| | - Elizabeth Allen
- Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Emma M. Harding-Esch
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - John Hart
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Sarah E. Burr
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Disease Control and Elimination Theme, Medical Research Council Unit (MRC), Fajara, Banjul, The Gambia
| | - Martin J. Holland
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
- Disease Control and Elimination Theme, Medical Research Council Unit (MRC), Fajara, Banjul, The Gambia
| | - Ansumana Sillah
- National Eye Health Programme, Ministry of Health and Social Welfare, Kanifing, The Gambia
| | - Sheila K. West
- Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - David Mabey
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Robin Bailey
- Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Last AR, Burr SE, Weiss HA, Harding-Esch EM, Cassama E, Nabicassa M, Mabey DC, Holland MJ, Bailey RL. Risk factors for active trachoma and ocular Chlamydia trachomatis infection in treatment-naïve trachoma-hyperendemic communities of the Bijagós Archipelago, Guinea Bissau. PLoS Negl Trop Dis 2014; 8:e2900. [PMID: 24967629 PMCID: PMC4072588 DOI: 10.1371/journal.pntd.0002900] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Accepted: 04/11/2014] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Trachoma, caused by ocular infection with Chlamydia trachomatis, is hyperendemic on the Bijagós Archipelago of Guinea Bissau. An understanding of the risk factors associated with active trachoma and infection on these remote and isolated islands, which are atypical of trachoma-endemic environments described elsewhere, is crucial to the implementation of trachoma elimination strategies. METHODOLOGY/PRINCIPAL FINDINGS A cross-sectional population-based trachoma prevalence survey was conducted on four islands. We conducted a questionnaire-based risk factor survey, examined participants for trachoma using the World Health Organization (WHO) simplified grading system and collected conjunctival swab samples for 1507 participants from 293 randomly selected households. DNA extracted from conjunctival swabs was tested using the Roche Amplicor CT/NG PCR assay. The prevalence of active (follicular and/or inflammatory) trachoma was 11% (167/1508) overall and 22% (136/618) in 1-9 year olds. The prevalence of C. trachomatis infection was 18% overall and 25% in 1-9 year olds. There were strong independent associations of active trachoma with ocular and nasal discharge, C. trachomatis infection, young age, male gender and type of household water source. C. trachomatis infection was independently associated with young age, ocular discharge, type of household water source and the presence of flies around a latrine. CONCLUSIONS/SIGNIFICANCE In this remote island environment, household-level risk factors relating to fly populations, hygiene behaviours and water usage are likely to be important in the transmission of ocular C. trachomatis infection and the prevalence of active trachoma. This may be important in the implementation of environmental measures in trachoma control.
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Affiliation(s)
- Anna R. Last
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- * E-mail:
| | - Sarah E. Burr
- Disease Control and Elimination Theme, Medical Research Council Unit, The Gambia, Fajara, The Gambia
| | - Helen A. Weiss
- MRC Tropical Epidemiology Group, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Emma M. Harding-Esch
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Eunice Cassama
- Programa Nacional de Saúde de Visão, Ministério de Saúde Publica, Bisssau, Guiné Bissau
| | - Meno Nabicassa
- Programa Nacional de Saúde de Visão, Ministério de Saúde Publica, Bisssau, Guiné Bissau
| | - David C. Mabey
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Martin J. Holland
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Robin L. Bailey
- Clinical Research Department, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Liu F, Porco TC, Mkocha HA, Muñoz B, Ray KJ, Bailey RL, Lietman TM, West SK. The efficacy of oral azithromycin in clearing ocular chlamydia: mathematical modeling from a community-randomized trachoma trial. Epidemics 2014; 6:10-7. [PMID: 24593917 PMCID: PMC4420489 DOI: 10.1016/j.epidem.2013.12.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 12/05/2013] [Accepted: 12/11/2013] [Indexed: 11/29/2022] Open
Abstract
Mass oral azithromycin distributions have dramatically reduced the prevalence of the ocular strains of chlamydia that cause trachoma. Assessing efficacy of the antibiotic in an individual is important in planning trachoma elimination. However, the efficacy is difficult to estimate, because post-treatment laboratory testing may be complicated by nonviable organisms or reinfection. Here, we monitored ocular chlamydial infection twice a year in pre-school children in 32 communities as part of a cluster-randomized clinical trial in Tanzania (prevalence in children was lowered from 22.0% to 4.7% after 3-year of annual treatment). We used a mathematical transmission model to estimate the prevalence of infection immediately after treatment, and found the effective field efficacy of antibiotic in an individual to be 67.6% (95% CI: 56.5–75.1%) in this setting. Sensitivity analyses suggested that these results were not dependent on specific assumptions about the duration of infection. We found no evidence of decreased efficacy during the course of the trial. We estimated an 89% chance of elimination after 10 years of annual treatment with 95% coverage.
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Affiliation(s)
- Fengchen Liu
- F.I. Proctor Foundation, University of California, San Francisco, CA, USA
| | - Travis C Porco
- F.I. Proctor Foundation, University of California, San Francisco, CA, USA; Department of Ophthalmology, University of California, San Francisco, CA, USA; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA.
| | | | - Beatriz Muñoz
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD, USA
| | - Kathryn J Ray
- F.I. Proctor Foundation, University of California, San Francisco, CA, USA
| | - Robin L Bailey
- Faculty of Infectious and Tropical Diseases, Clinical Research Department, London School of Hygiene & Tropical and Medicine, London, UK
| | - Thomas M Lietman
- F.I. Proctor Foundation, University of California, San Francisco, CA, USA; Department of Ophthalmology, University of California, San Francisco, CA, USA; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA; Institute for Global Health, University of California, San Francisco, CA, USA
| | - Sheila K West
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD, USA
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Liu F, Porco TC, Ray KJ, Bailey RL, Mkocha H, Muñoz B, Quinn TC, Lietman TM, West SK. Assessment of transmission in trachoma programs over time suggests no short-term loss of immunity. PLoS Negl Trop Dis 2013; 7:e2303. [PMID: 23875038 PMCID: PMC3708821 DOI: 10.1371/journal.pntd.0002303] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 05/18/2013] [Indexed: 11/18/2022] Open
Abstract
Trachoma programs have dramatically reduced the prevalence of the ocular chlamydia that cause the disease. Some have hypothesized that immunity to the infection may be reduced because of program success in reducing the incidence of infection, and transmission may then increase. Longitudinal studies of multiple communities would be necessary to test this hypothesis. Here, we quantify transmission using an estimated basic reproduction number based on 32 communities during the first, second, and third years of an antibiotic treatment program. We found that there is little to no increase in the basic reproduction number over time. The estimated linear trend in the basic reproduction number, , was found to be −0.025 per year, 95% CI −0.167 to 0.117 per year. We are unable to find evidence supporting any loss of immunity over the course of a 3-year program. This is encouraging, as it allows the possibility that repeated mass antibiotic distributions may eliminate infection from even the most severely affected areas. Trachoma, caused by repeated infections by the ocular strains of Chlamydia trachomatis, is the most common infectious cause of blindness in the world. Treatment for trachoma includes mass azithromycin treatments to the entire community. To reduce the prevalence of infection, the World Health Organization (WHO) advocates at least three annual community-wide distributions of oral antibiotics in affected areas, with further mass treatments based on the prevalence of trachoma. Trachoma programs have dramatically reduced the community prevalence of infection, and some have argued that lowered prevalence of infection may lead to reductions in immunity, and that less immunity may in turn lead to increased transmission from what infection remains. Here, we used a stochastic transmission model to analyze data collected from a 3-year antibiotic treatment program (a 32-community, cluster-randomized clinical trial in Tanzania) to assess whether or not transmission actually increases during elimination campaigns. We found no evidence supporting any increase in transmission over the course of the program. The absence of a short term increase in transmission as the prevalence decreases is good news for trachoma programs.
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Affiliation(s)
- Fengchen Liu
- F.I. Proctor Foundation, University of California, San Francisco, California, United States of America
| | - Travis C. Porco
- F.I. Proctor Foundation, University of California, San Francisco, California, United States of America
- Department of Ophthalmology, University of California, San Francisco, California, United States of America
- Department of Epidemiology and Biostatistics, University of California, San Francisco, California, United States of America
- * E-mail:
| | - Kathryn J. Ray
- F.I. Proctor Foundation, University of California, San Francisco, California, United States of America
| | - Robin L. Bailey
- Faculty of Infectious and Tropical Diseases, Clinical Research Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | - Beatriz Muñoz
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
| | - Thomas C. Quinn
- Johns Hopkins Center for Global Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Thomas M. Lietman
- F.I. Proctor Foundation, University of California, San Francisco, California, United States of America
- Department of Ophthalmology, University of California, San Francisco, California, United States of America
- Department of Epidemiology and Biostatistics, University of California, San Francisco, California, United States of America
| | - Sheila K. West
- Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, Maryland, United States of America
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Koukounari A, Moustaki I, Grassly NC, Blake IM, Basáñez MG, Gambhir M, Mabey DCW, Bailey RL, Burton MJ, Solomon AW, Donnelly CA. Using a nonparametric multilevel latent Markov model to evaluate diagnostics for trachoma. Am J Epidemiol 2013; 177:913-22. [PMID: 23548755 PMCID: PMC3639724 DOI: 10.1093/aje/kws345] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In disease control or elimination programs, diagnostics are essential for assessing the impact of interventions, refining treatment strategies, and minimizing the waste of scarce resources. Although high-performance tests are desirable, increased accuracy is frequently accompanied by a requirement for more elaborate infrastructure, which is often not feasible in the developing world. These challenges are pertinent to mapping, impact monitoring, and surveillance in trachoma elimination programs. To help inform rational design of diagnostics for trachoma elimination, we outline a nonparametric multilevel latent Markov modeling approach and apply it to 2 longitudinal cohort studies of trachoma-endemic communities in Tanzania (2000–2002) and The Gambia (2001–2002) to provide simultaneous inferences about the true population prevalence of Chlamydia trachomatis infection and disease and the sensitivity, specificity, and predictive values of 3 diagnostic tests for C. trachomatis infection. Estimates were obtained by using data collected before and after mass azithromycin administration. Such estimates are particularly important for trachoma because of the absence of a true “gold standard” diagnostic test for C. trachomatis. Estimated transition probabilities provide useful insights into key epidemiologic questions about the persistence of disease and the clearance of infection as well as the required frequency of surveillance in the postelimination setting.
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Affiliation(s)
- Artemis Koukounari
- Correspondence to Dr. Artemis Koukounari, Medical Research Council Centre for Outbreak Analysis and Modelling, Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, United Kingdom (e-mail: )
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31
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Abstract
Trachoma, a chronic conjunctivitis caused by Chlamydia trachomatis, is the leading infectious cause of blindness worldwide. In recognition of this public health problem, the World Health Assembly has targeted the year 2020 to eliminate blinding trachoma, and a multifaceted strategy (SAFE) is recommended, including antibiotics for treatment of infection. Trachoma is a disease of entire communities, and the pool of infection resides largely in preschool age children. Thus, for endemic communities, mass treatment with antibiotics annually for at least 3-5 years is carried out. The antibiotics used, the effectiveness of this approach, and the challenges of antibiotic treatment of communities are discussed, concluding with a view towards the elimination of trachoma in the future.
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Affiliation(s)
- Sheila West
- Wilmer RM 129, Johns Hopkins University, 600 N Wolfe Street, Baltimore, MD 21205, USA.
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Amza A, Kadri B, Nassirou B, Stoller NE, Yu SN, Zhou Z, Chin S, West SK, Bailey RL, Mabey DCW, Keenan JD, Porco TC, Lietman TM, Gaynor BD. Community risk factors for ocular Chlamydia infection in Niger: pre-treatment results from a cluster-randomized trachoma trial. PLoS Negl Trop Dis 2012; 6:e1586. [PMID: 22545165 PMCID: PMC3335874 DOI: 10.1371/journal.pntd.0001586] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Accepted: 02/11/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Trachoma control programs utilize mass azithromycin distributions to treat ocular Chlamydia trachomatis as part of an effort to eliminate this disease world-wide. But it remains unclear what the community-level risk factors are for infection. METHODS This cluster-randomized, controlled trial entered 48 randomly selected communities in a 2×2 factorial design evaluating the effect of different treatment frequencies and treatment coverage levels. A pretreatment census and examination established the prevalence of risk factors for clinical trachoma and ocular chlamydia infection including years of education of household head, distance to primary water source, presence of household latrine, and facial cleanliness (ocular discharge, nasal discharge, and presence of facial flies). Univariate and multivariate associations were tested using linear regression and Bayes model averaging. FINDINGS There were a total of 24,536 participants (4,484 children aged 0-5 years) in 6,235 households in the study. Before treatment in May to July 2010, the community-level prevalence of active trachoma (TF or TI utilizing the World Health Organization [WHO] grading system) was 26.0% (95% CI: 21.9% to 30.0%) and the mean community-level prevalence of chlamydia infection by Amplicor PCR was 20.7% (95% CI: 16.5% to 24.9%) in children aged 0-5 years. Univariate analysis showed that nasal discharge (0.29, 95% CI: 0.04 to 0.54; P = 0.03), presence of flies on the face (0.40, 95% CI: 0.17 to 0.64; P = 0.001), and years of formal education completed by the head of household (0.07, 95% CI: 0.07 to 0.13; P = 0.03) were independent risk factors for chlamydia infection. In multivariate analysis, facial flies (0.26, 95% CI: 0.02 to 0.49; P = 0.03) and years of formal education completed by the head of household (0.06, 95% CI: 0.008 to 0.11; P = 0.02) were associated risk factors for ocular chlamydial infection. INTERPRETATION We have found that the presence of facial flies and years of education of the head of the household are risk factors for chlamydia infection when the analysis is done at the community level. TRIAL REGISTRATION ClinicalTrials.gov NCT00792922.
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Affiliation(s)
- Abdou Amza
- Programme National de Lutte Contre la Cecité, Niamey, Niger
| | - Boubacar Kadri
- Programme National de Lutte Contre la Cecité, Niamey, Niger
| | - Baido Nassirou
- Programme National de Lutte Contre la Cecité, Niamey, Niger
| | - Nicole E. Stoller
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America
| | - Sun N. Yu
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America
| | - Zhaoxia Zhou
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America
| | - Stephanie Chin
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America
| | - 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 and Tropical Medicine, London, United Kingdom
| | - David C. W. Mabey
- Clinical Research Unit, Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Jeremy D. Keenan
- F.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
| | - Travis C. Porco
- F.I. Proctor Foundation, University of California San Francisco, San Francisco, California, United States of America
- Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, California, United States of America
- Institute for Global Health, University of California San Francisco, San Francisco, California, United States of America
- Center for Infectious Disease and Emergency Readiness, University of California, Berkeley, California, United States of America
| | - Thomas M. Lietman
- F.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 and Biostatistics, University of California San Francisco, San Francisco, California, United States of America
- Institute for Global Health, University of California San Francisco, San Francisco, California, United States of America
| | - Bruce D. Gaynor
- F.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
- * E-mail:
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Ssemanda EN, Levens J, Mkocha H, Munoz B, West SK. Azithromycin mass treatment for trachoma control: risk factors for non-participation of children in two treatment rounds. PLoS Negl Trop Dis 2012; 6:e1576. [PMID: 22448296 PMCID: PMC3308937 DOI: 10.1371/journal.pntd.0001576] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2010] [Accepted: 02/07/2012] [Indexed: 11/18/2022] Open
Abstract
Background Persistent non-participation of children in mass drug administration (MDAs) for trachoma may reduce program impact. Risk factors that identify families where participation is a problem or program characteristics that foster non-participation are poorly understood. We examined risk factors for households with at least one child who did not participate in two MDAs compared to households where all children participated in both MDAs. Methods/Principal Findings We conducted a case control study in 28 Tanzanian communities. Cases included all 152 households with at least one child who did not participate in the 2008 and 2009 MDAs with azithromycin. Controls consisted of a random sample of 460 households where all children participated in both MDAs. A questionnaire was asked of all families. Random-intercept logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs), control for clustering, and adjust for community size. In total, 140 case households and 452 control households were included in the analyses. Compared to controls, guardians in case households had higher odds of reporting excellent health (OR 4.12 (CI 95% 1.57–10.86)), reporting a burden due to family health (OR 3.15 (95% CI 1.35–7.35)), reduced ability to rely on others for assistance (OR 1.66 (95% CI 1.01–2.75)), being in a two (versus five) days distribution program (OR 3.31 (95% CI 1.68–6.50)) and living in a community with <2 community treatment assistants (CTAs)/1000 residents (OR 2.07 (95% CI 1.04–4.12). Furthermore, case households were more likely to have more children, younger guardians, unfamiliarity with CTAs, and CTAs with more travel time to their assigned households (p-values<0.05). Conclusions/Significance Compared to full participation households, households with persistent non-participation had a higher burden of familial responsibility and seemed less connected in the community. Additional distribution days and lessening CTAs' travel time to their furthest assigned households may prevent non-participation. The World Health Organization advocates at least three mass drug administrations (MDAs) with antibiotics when the prevalence of follicular trachoma (TF) is greater than 10% in children under age ten. Full child participation is necessary for maximizing the impact of trachoma control programs. The present paper identifies guardian, household, and program risk factors for households with a child who never participated in two annual rounds of MDAs with azithromycin. In comparison to households with full child participation, guardians with at least one child who never participated had a higher burden of familial responsibility, as represented by reporting ill family members, more children, and were younger in age. In addition, guardians of persistent non-participants seemed less well connected in the community, in terms of reliance on others and not knowing who their assigned community treatment assistants (CTAs) were. These guardians were assigned to CTAs who had a wide geographic dispersion of their assigned households. By developing programs with local groups to find and encourage participation in at-risk households, program managers may have the greatest impact on preventing persistent child non-participation. Increasing the number of distribution days and reducing CTAs' travel time may further prevent non-participation.
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Affiliation(s)
- Elizabeth N. Ssemanda
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Joshua Levens
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | | | - Beatriz Munoz
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Sheila K. West
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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Brooks-Pollock E, Becerra MC, Goldstein E, Cohen T, Murray MB. Epidemiologic inference from the distribution of tuberculosis cases in households in Lima, Peru. J Infect Dis 2011; 203:1582-9. [PMID: 21592987 DOI: 10.1093/infdis/jir162] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Tuberculosis (TB) often occurs among household contacts of people with active TB. It is unclear whether clustering of cases represents household transmission or shared household risk factors for TB. METHODS We used cross-sectional data from 764 households in Lima, Peru, to estimate the relative contributions of household and community transmission, the average time between cases, and the immunity afforded by a previous TB infection. RESULTS The distribution of cases per household suggests that almost 7 of 10 nonindex household cases were infected in the community rather than in the household. The average interval between household cases was 3.5 years. We observed a saturation effect in the number of cases per household and estimated that protective immunity conferred up to 35% reduction in the risk of disease. CONCLUSIONS Cross-sectional household data can elucidate the natural history and transmission dynamics of TB. In this high-incidence setting, we found that the majority of cases were attributable to community transmission and that household contacts of case patients derive some immunity from household exposures. Screening of household contacts may be an effective method of detecting new TB cases if carried out over several years.
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Affiliation(s)
- Ellen Brooks-Pollock
- Department of Epidemiology, Harvard School of Public Health, Brigham and Women's Hospital, Massachusetts General Hospital, Boston, USA.
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Lietman TM, Gebre T, Ayele B, Ray KJ, Maher MC, See CW, Emerson PM, Porco TC. The epidemiological dynamics of infectious trachoma may facilitate elimination. Epidemics 2011; 3:119-24. [PMID: 21624783 DOI: 10.1016/j.epidem.2011.03.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Revised: 03/29/2011] [Accepted: 03/30/2011] [Indexed: 10/18/2022] Open
Abstract
INTRODUCTION Trachoma programs use mass distributions of oral azithromycin to treat the ocular strains of Chlamydia trachomatis that cause the disease. There is debate whether infection can be eradicated or only controlled. Mass antibiotic administrations clearly reduce the prevalence of chlamydia in endemic communities. However, perfect coverage is unattainable, and the World Health Organization's goal is to control infection to a level where resulting blindness is not a public health concern. Here, we use mathematical models to assess whether more ambitious goals such as local elimination or even global eradication are possible. METHODS We fit a class of non-linear, stochastic, susceptible-infectious-susceptible (SIS) models which allow positive or negative feedback, to data from a recent community-randomized trial in Ethiopia, and make predictions using model averaging. RESULTS The models predict that reintroduced infection may not repopulate the community, or may do so sufficiently slowly that surveillance might be effective. The preferred model exhibits positive feedback, allowing a form of stochastic hysteresis in which infection returns slowly after mass treatment, if it returns at all. Results for regions of different endemicity suggest that elimination may be more feasible than earlier models had predicted. DISCUSSION If trachoma can be eradicated with repeated mass antibiotic distributions, it would encourage similar strategies against other bacterial diseases whose only host is humans and for which effective vaccines are not available.
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Affiliation(s)
- Thomas M Lietman
- F.I. Proctor Foundation, University of California, San Francisco, CA, 94143-0412, USA
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Cajas-Monson LC, Mkocha H, Muñoz B, Quinn TC, Gaydos CA, West SK. Risk factors for ocular infection with Chlamydia trachomatis in children 6 months following mass treatment in Tanzania. PLoS Negl Trop Dis 2011; 5:e978. [PMID: 21423645 PMCID: PMC3057946 DOI: 10.1371/journal.pntd.0000978] [Citation(s) in RCA: 17] [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: 06/17/2010] [Accepted: 02/04/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Trachoma is the leading infectious cause of blindness in the world, and for endemic communities, mass treatment with azithromycin reduces the pool of infection. High coverage is essential, especially in children as they are the infectious reservoir. However, infection remains post-mass treatment. We sought to determine risk factors for infection in children post-mass treatment. METHODOLOGY All children under 9 years in 4 villages in Tanzania were followed from baseline pre-mass treatment to six months post treatment. 1,991 children under nine years were enrolled in the longitudinal study and data on individual and household characteristics was collected at baseline. Clinical trachoma was determined by an ocular exam and infection detected by PCR of an eyelid swab. Azithromycin was offered and infection was reassessed at 6 months. A multilevel logistic regression model was used, accounting for household clustering of children for analysis. PRINCIPAL FINDINGS Baseline infection was 23.7% and at 6 months was 10.4%, despite 95% coverage. Infection at baseline was positively associated with infection at 6 months (OR = 3.31, 95%CI 2.40-4.56) and treatment had a protective effect (OR = 0.45, 95%CI 0.25-0.80). The age group 2-4 years had an increased risk of infection at 6 months. The household characteristics predictive of infection at 6 months were increasing number of children infected in the household at baseline and increasing number of untreated children in the household. CONCLUSIONS While one round of mass treatment with high coverage did decrease infection by over 50%, it appears that it is not sufficient to eliminate infection. Findings that young children (ages 2-4 years) and households with increasing numbers of infected and untreated children have a positive association with infection at 6 months suggest that such households could be targeted for more intensive follow up.
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Affiliation(s)
- Luis Carlos Cajas-Monson
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | | | - Beatriz Muñoz
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Thomas C. Quinn
- International Chlamydia Laboratory, Department of Infectious Diseases, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Charlotte A. Gaydos
- International Chlamydia Laboratory, Department of Infectious Diseases, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Sheila K. West
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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Blake IM, Burton MJ, Solomon AW, West SK, Basáñez MG, Gambhir M, Bailey RL, Mabey DCW, Grassly NC. Targeting antibiotics to households for trachoma control. PLoS Negl Trop Dis 2010; 4:e862. [PMID: 21072225 PMCID: PMC2970531 DOI: 10.1371/journal.pntd.0000862] [Citation(s) in RCA: 18] [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: 04/29/2010] [Accepted: 09/29/2010] [Indexed: 11/30/2022] Open
Abstract
Background Mass drug administration (MDA) is part of the current trachoma control strategy, but it can be costly and results in many uninfected individuals receiving treatment. Here we explore whether alternative, targeted approaches are effective antibiotic-sparing strategies. Methodology/Principal Findings We analysed data on the prevalence of ocular infection with Chlamydia trachomatis and of active trachoma disease among 4,436 individuals from two communities in The Gambia (West Africa) and two communities in Tanzania (East Africa). An age- and household-structured mathematical model of transmission was fitted to these data using maximum likelihood. The presence of active inflammatory disease as a marker of infection in a household was, in general, significantly more sensitive (between 79% [95%CI: 60%–92%] and 86% [71%–95%] across the four communities) than as a marker of infection in an individual (24% [16%–33%]–66% [56%–76%]). Model simulations, under the best fit models for each community, showed that targeting treatment to households has the potential to be as effective as and significantly more cost-effective than mass treatment when antibiotics are not donated. The cost (2007US$) per incident infection averted ranged from 1.5 to 3.1 for MDA, from 1.0 to 1.7 for household-targeted treatment assuming equivalent coverage, and from 0.4 to 1.7 if household visits increased treatment coverage to 100% in selected households. Assuming antibiotics were donated, MDA was predicted to be more cost-effective unless opportunity costs incurred by individuals collecting antibiotics were included or household visits improved treatment uptake. Limiting MDA to children was not as effective in reducing infection as the other aforementioned distribution strategies. Conclusions/Significance Our model suggests that targeting antibiotics to households with active trachoma has the potential to be a cost-effective trachoma control measure, but further work is required to assess if costs can be reduced and to what extent the approach can increase the treatment coverage of infected individuals compared to MDA in different settings. Repeated ocular infection with the bacterium Chlamydia trachomatis leads to the development of trachoma, a major cause of infectious blindness worldwide. Mass distribution of antibiotics, a component of the current trachoma control strategy, has had success in reducing infection in some areas, but results in a large number of uninfected people receiving antibiotics. We have previously shown that transmission of the bacteria between people in the same household is very efficient. Here, we investigated the effectiveness and cost-effectiveness of targeting antibiotics to households with active trachoma (inflammatory disease) compared to mass distribution, using data from four trachoma-endemic populations and a mathematical model of transmission. We found a high correspondence between households with active trachoma and infected households. In all populations the household targeted approach was predicted to be as effective as mass distribution, but it reduced the number of uninfected individuals receiving antibiotics, making the targeted strategy more cost-effective when antibiotics are not donated. Assuming antibiotics are donated, we predicted the targeted strategy to be more cost effective if it increases the proportion of infected individuals receiving treatment. Further work to address the feasibility and the cost variability in implementing the targeted approach in different settings is now required.
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Affiliation(s)
- Isobel M Blake
- Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom.
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Ssemanda EN, Munoz B, Harding-Esch EM, Edwards T, Mkocha H, Bailey RL, Sillah A, Stare D, Mabey DCW, West SK. Mass treatment with azithromycin for trachoma control: participation clusters in households. PLoS Negl Trop Dis 2010; 4:e838. [PMID: 20957196 PMCID: PMC2950137 DOI: 10.1371/journal.pntd.0000838] [Citation(s) in RCA: 18] [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: 05/13/2010] [Accepted: 09/03/2010] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Mass treatment to trachoma endemic communities is a critical part of the World Health Organization SAFE strategy. However, non-participation may not be at random, affecting coverage surveys and effectiveness if infection is differential. METHODOLOGY/PRINCIPAL FINDINGS As part of the Partnership for Rapid Elimination of Trachoma (PRET), 32 communities in Tanzania, and 48 in The Gambia had a detailed census taken followed by mass treatment with azithromycin. The target coverage in each community was >80% of children ages <10 years. Community treatment assistants observed treatment and recorded compliance, thus coverage at the community, household, and individual level could be determined. Within each community, we determined the actual proportions of households where all, some, or none of the children were treated. Assuming the coverage in children <10 years of the community was as observed and non-participation was at random, we did 500 simulations to derive expected proportions of households where all, some, or none of the children were treated. Clustering of household treatment was detected comparing greater-than-expected proportions of households where none or all of children were treated, and the intraclass correlation (ICC) was calculated. Tanzanian and Gambian mass treatment coverages for children <10 years of age ranged from 82-100% and 62-99%, respectively. Clustering of households where all children were treated or no children were treated was greater than expected. Compared to model simulations, all Tanzanian communities and 44 of 48 (91.7%) Gambian communities had significantly higher proportions of households where all children were treated. Furthermore, 30 of 32 (93.8%) Tanzanian communities and 34 of 48 (70.8%) Gambian communities had a significantly elevated proportion of households compared to the expected proportion where no children were treated. The ICC for Tanzania was 0.77 (95% CI 0.74-0.81) and for The Gambia was 0.55 (95% CI 0.51-0.59). CONCLUSIONS/SIGNIFICANCE In programs aiming for high coverage, complete compliance or non-compliance with mass treatment clusters within households. Non-compliance cannot be assumed to be at random.
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Affiliation(s)
- Elizabeth N Ssemanda
- Dana Center for Preventive Ophthalmology, Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland, United States of America.
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Hu VH, Harding-Esch EM, Burton MJ, Bailey RL, Kadimpeul J, Mabey DCW. Epidemiology and control of trachoma: systematic review. Trop Med Int Health 2010; 15:673-91. [PMID: 20374566 PMCID: PMC3770928 DOI: 10.1111/j.1365-3156.2010.02521.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Trachoma is the commonest infectious cause of blindness. Recurrent episodes of infection with serovars A-C of Chlamydia trachomatis cause conjunctival inflammation in children who go on to develop scarring and blindness as adults. It was estimated that in 2002 at least 1.3 million people were blind from trachoma, and currently 40 million people are thought to have active disease and 8.2 million to have trichiasis. The disease is largely found in poor, rural communities in developing countries, particularly in sub-Saharan Africa. The WHO promotes trachoma control through a multifaceted approach involving surgery, mass antibiotic distribution, encouraging facial cleanliness and environmental improvements. This has been associated with significant reductions in the prevalence of active disease over the past 20 years, but there remain a large number of people with trichiasis who are at risk of blindness.
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Affiliation(s)
- Victor H Hu
- London School of Hygiene and Tropical Medicine, UK.
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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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