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      The impact of a single round of community mass treatment with azithromycin on disease severity and ocular Chlamydia trachomatis load in treatment-naïve trachoma-endemic island communities in West Africa

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          Abstract

          Background

          Trachoma, a neglected tropical disease, is caused by ocular infection with Chlamydia trachomatis ( Ct). The World Health Organization (WHO) recommends three annual rounds of community mass drug treatment with azithromycin (MDA) if the prevalence of follicular trachoma in 1–9 year olds (TF 1–9) exceeds 10% at district level to achieve an elimination target of district-level TF 1–9 below 5% after. To evaluate this strategy in treatment-naïve trachoma-endemic island communities in Guinea Bissau, we conducted a cross-sectional population-based trachoma survey on four islands. The upper tarsal conjunctivae of each participant were clinically assessed for trachoma and conjunctival swabs were obtained ( n = 1507). We used a droplet digital PCR assay to detect Ct infection and estimate bacterial load. We visited the same households during a second cross-sectional survey and repeated the ocular examination and obtained conjunctival swabs from these households one year after MDA ( n = 1029).

          Results

          Pre-MDA TF 1–9 was 22.0% (136/618). Overall Ct infection prevalence ( CtI) was 18.6% (25.4% in 1–9 year olds). Post-MDA (estimated coverage 70%), TF 1–9 and CtI were significantly reduced (7.4% (29/394, P < 0.001) and 3.3% (34/1029, P < 0.001) (6.6% in 1–9 year olds, P < 0.001), respectively. Median ocular Ct load was reduced from 2038 to 384 copies/swab ( P < 0.001). Following MDA cases of Ct infection were highly clustered (Moran’s I 0.27, P < 0.001), with fewer clusters of Ct infection overall, fewer clusters of cases with high load infections and less severe disease.

          Conclusions

          Despite a significant reduction in the number of clusters of Ct infection, mean Ct load, disease severity and presence of clusters of cases of high load Ct infection suggesting the beginning of trachoma control in isolated island communities, following a single round of MDA we demonstrate that transmission is still ongoing. These detailed data are useful in understanding the epidemiology of ocular Ct infection in the context of MDA and the tools employed may have utility in determining trachoma elimination and surveillance activities in similar settings.

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          Most cited references34

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          Global data on visual impairment in the year 2002.

          This paper presents estimates of the prevalence of visual impairment and its causes in 2002, based on the best available evidence derived from recent studies. Estimates were determined from data on low vision and blindness as defined in the International statistical classification of diseases, injuries and causes of death, 10th revision. The number of people with visual impairment worldwide in 2002 was in excess of 161 million, of whom about 37 million were blind. The burden of visual impairment is not distributed uniformly throughout the world: the least developed regions carry the largest share. Visual impairment is also unequally distributed across age groups, being largely confined to adults 50 years of age and older. A distribution imbalance is also found with regard to gender throughout the world: females have a significantly higher risk of having visual impairment than males. Notwithstanding the progress in surgical intervention that has been made in many countries over the last few decades, cataract remains the leading cause of visual impairment in all regions of the world, except in the most developed countries. Other major causes of visual impairment are, in order of importance, glaucoma, age-related macular degeneration, diabetic retinopathy and trachoma.
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            A simple system for the assessment of trachoma and its complications.

            A simple grading system for trachoma, based on the presence or absence of five selected "key" signs, has been developed. The method was tested in the field and showed good observer agreement, the most critical point being the identification of severe cases of the disease. It is expected that the system will facilitate the assessment of trachoma and its complications by non-specialist health personnel working at the community level.
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              Trachoma.

              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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                Author and article information

                Contributors
                anna.last@lshtm.ac.uk
                sarah.burr@lshtm.ac.uk
                emma.hardingesch@googlemail.com
                eunitxsil@gmail.com
                pnlcegueira@yahoo.com.br
                chrissyhroberts@yahoo.co.uk
                david.mabey@lshtm.ac.uk
                martin.holland@lshtm.ac.uk
                robin.bailey@lshtm.ac.uk
                Journal
                Parasit Vectors
                Parasit Vectors
                Parasites & Vectors
                BioMed Central (London )
                1756-3305
                28 December 2017
                28 December 2017
                2017
                : 10
                : 624
                Affiliations
                [1 ]ISNI 0000 0004 0425 469X, GRID grid.8991.9, Clinical Research Department, , London School of Hygiene and Tropical Medicine, ; Keppel Street, London, WC1E 7HT UK
                [2 ]ISNI 0000 0004 0606 294X, GRID grid.415063.5, Disease Control and Elimination Theme, Medical Research Council Unit The Gambia, ; P.OBox 273, Banjul, Atlantic Boulevard, Fajara, The, Gambia
                [3 ]Programa Nacional de Saúde de Visão, Ministério de Saúde Publica, P.O. Box 50, Avenida de Unidade Africana, Bisssau, Guinea-Bissau
                Article
                2566
                10.1186/s13071-017-2566-x
                5745817
                29282126
                cb0db094-4e91-4771-865c-bc5bb1edd347
                © The Author(s). 2017

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 12 December 2016
                : 3 December 2017
                Funding
                Funded by: FundRef http://dx.doi.org/10.13039/100004440, Wellcome Trust;
                Award ID: 097330/Z/11/Z
                Award Recipient :
                Categories
                Research
                Custom metadata
                © The Author(s) 2017

                Parasitology
                chlamydia trachomatis,bacterial load,spatial clustering,trachoma,disease severity,community mass treatment

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