Abstract
BackgroundTrachoma, caused by ocular Chlamydia trachomatis infection, is the leading infectious cause of blindess, but its prevalence is now falling in many countries. As the prevalence falls, an increasing proportion of individuals with clinical signs of follicular trachoma (TF) is not infected with C. trachomatis. A recent study in Tanzania suggested that other bacteria may play a role in the persistence of these clinical signs.Methodology/Principal FindingsWe examined associations between clinical signs of TF and ocular colonization with four pathogens commonly found in the nasopharnyx, three years after the initiation of mass azithromycin distribution. Children aged 0 to 5 years were randomly selected from 16 Gambian communitites. Both eyes of each child were examined and graded for trachoma according to the World Health Organization (WHO) simplified system. Two swabs were taken from the right eye: one swab was processed for polymerase chain reaction (PCR) using the Amplicor test for detection of C. trachomatis DNA and the second swab was processed by routine bacteriology to assay for the presence of viable Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus and Moraxella catarrhalis. Prevalence of TF was 6.2% (96/1538) while prevalence of ocular C. trachomatis infection was 1.0% (16/1538). After adjustment, increased odds of TF were observed in the presence of C. trachomatis (OR = 10.4, 95%CI 1.32–81.2, p = 0.03), S. pneumoniae (OR = 2.14, 95%CI 1.03–4.44, p = 0.04) and H. influenzae (OR = 4.72, 95% CI 1.53–14.5, p = 0.01).Conclusions/SignificanceClinical signs of TF can persist in communities even when ocular C. trachomatis infection has been controlled through mass azithromycin distribution. In these settings, TF may be associated with ocular colonization with bacteria commonly carried in the nasopharnyx. This may affect the interpretation of impact surveys and the determinations of thresholds for discontinuing mass drug administration.
Highlights
Trachoma, caused by ocular infection with the intracellular bacterium Chlamydia trachomatis, remains the leading infectious cause of blindness world-wide
We carried out this study to investigate associations between ocular carriage of nonchlamydial pathogens and a clinical diagnosis of TF following a mass treatment campaign in The Gambia
We found that children who carried Streptococcus pneumoniae or Haemophilus influenza in their eyes were more likely to have been diagnosed with TF than children who did not carry these pathogens
Summary
Trachoma, caused by ocular infection with the intracellular bacterium Chlamydia trachomatis, remains the leading infectious cause of blindness world-wide. In 1986, The Gambia’s first national blindness survey indicated that trachoma was a significant cause of blindness in the country with active trachoma affecting 17% of children aged 0–14 years and very high rates of trichiasis in those 15 years and older [1,2]. In response to these findings, the National Eye Health Programme (formerly the National Eye Care Programme), supported by SightSavers International, established a network of Community Ophthalmic Nurses (CONs) trained and equipped to screen communities for active trachoma and to conduct trichiasis surgery. A recent study in Tanzania suggested that other bacteria may play a role in the persistence of these clinical signs
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