Risk factors for active trachoma and ocular Chlamydia trachomatis infection in treatment-naïve trachoma-hyperendemic communities of the Bijagós Archipelago, Guinea Bissau.

Anna R Last,Martin J Holland,Meno Nabicassa,Robin L Bailey,David C Mabey,Emma M Harding-Esch,Helen A Weiss,Sarah E Burr,Eunice Cassama,Julius Schachter

doi:10.1371/journal.pntd.0002900

Abstract

BackgroundTrachoma, 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 FindingsA 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/SignificanceIn 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.

Highlights

Trachoma is caused by ocular infection with Chlamydia trachomatis and is the leading infectious cause of blindness worldwide
We examined household and individual-level risk factor associations with ocular C. trachomatis infection and active trachoma in this unique environment, where trachoma is a significant public health problem
We found C. trachomatis infection to be more strongly clustered at the household level than active trachoma, which has been reported in Tanzanian communities [18]

Summary

Introduction

Trachoma is caused by ocular infection with Chlamydia trachomatis and is the leading infectious cause of blindness worldwide. It manifests as distinct clinical syndromes beginning with an acute self-limiting keratoconjunctivitis, which following repeated episodes may progress to a more chronic inflammatory and immunofibrogenic process leading to conjunctival scarring and blinding sequelae. Trachoma is endemic in 50 countries, with 325 million people at risk of blinding disease [1]. Trachoma, caused by ocular infection with Chlamydia trachomatis, is hyperendemic on the Bijagos 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

Methods

Results

Conclusion