A Longitudinal Analysis of Chlamydial Infection and Trachomatous Inflammation Following Mass Azithromycin Distribution.

BACKGROUND: Mass azithromycin distributions are effective for clearing ocular strains of Chlamydia trachomatis, yet infection frequently returns in areas with hyperendemic trachoma. A better understanding of the factors associated with chlamydial reinfection could be helpful to plan trachoma elimination strategies. METHODS: This was a prospective cohort study conducted in a trachoma-hyperendemic region of Ethiopia in 2003. As part of a larger cluster-randomized trial, 21 villages were treated with a single mass azithromycin distribution and all children 5 years and younger were monitored for ocular chlamydia and clinically active trachoma at baseline and at 2 and 6 months following the treatment. RESULTS: In 20 villages with available data, azithromycin treatment coverage was 88.7% (95% confidence interval [CI] 85.7-91.8%). In total, 1005 children tested negative for ocular chlamydia at the 2-month visit, of whom 41 became infected by 6 months (1.0 incident chlamydia infections per 100 person-months, 95%CI 0.7-1.4). The presence of intense trachomatous inflammation (TI) at baseline was associated with incident infection at 6 months (incidence rate ratio 1.91, 95%CI 1.03-3.55). Ocular chlamydia infections clustered more within households than communities: (intraclass correlation coefficient 0.01 for communities and 0.29 for households six months posttreatment). Younger children were more likely to have persistent clinically active trachoma (P = 0.03). CONCLUSIONS: More intensive antibiotic distributions may be warranted for younger children, for children with TI, and for households containing children with ocular chlamydia infections.

Diversity of Chlamydia trachomatis in Trachoma-Hyperendemic Communities Treated With Azithromycin.

Prior studies have theorized that low chlamydial genetic diversity following mass azithromycin treatments for trachoma may create a population bottleneck that prevents the return of infection, but little empirical evidence exists to support this hypothesis. In this study, a single mass azithromycin distribution was administered to 21 communities in the Gurage Zone of Ethiopia in 2003. All children aged 1-5 years had conjunctival swabs performed before treatment and 2 and 6 months after treatment. All swabs positive for Chlamydia trachomatis at 2 months underwent typing of the gene encoding the major outer membrane protein (ompA) of C. trachomatis, as did the same number of swabs per community from the pretreatment and 6-month visits. Diversity of ompA types, expressed as the reciprocal of Simpson's index, was calculated for each community. In total, 15 ompA types belonging to the A and B genovars were identified. The mean diversity was 2.11 (95% confidence interval: 1.79, 2.43) before treatment and 2.16 (95% confidence interval: 1.76, 2.55) 2 months after treatment (P = 0.78, paired t test). Diversity of ompA was not associated with the prevalence of ocular chlamydia (P = 0.76) and did not predict subsequent changes in the prevalence of ocular chlamydia (P = 0.32). This study found no evidence to support the theory that ompA diversity is associated with transmission of ocular chlamydia.