Community-level Association between Clinical Trachoma and Ocular Chlamydia Infection after MASS Azithromycin Distribution in a Mesoendemic Region of Niger

Abstract

Purpose: The clinical sign trachomatous inflammation - follicular (TF) is used to monitor indication for and response to mass azithromycin distribution in trachoma-endemic communities. Here, we assess the relationship between TF, trachomatous inflammation - intense (TI), and infection with ocular Chlamydia trachomatis over time during annual mass azithromycin distribution. Methods: We used data from a cluster-randomized trial of mass azithromycin distribution for trachoma control in a mesoendemic region of Niger. This study includes 24 communities that received 3 years of annual mass azithromycin distribution. TF, TI, and ocular chlamydia infection were monitored among children aged 0-5 years. We assessed the correlation between the prevalence of ocular chlamydia infection and 1) TF and 2) TI prevalence over time. Results: At baseline, ocular chlamydia prevalence was 21.2% (95% CI 14.3-28.1%), TF prevalence was 27.7% (95% CI 21.2-34.2%), and TI prevalence was 8.3% (95% CI 5.2-11.5%). The prevalence of all three measures decreased significantly over time (P < 0.001). At baseline, ocular chlamydia infection prevalence was strongly correlated with both TF (rho = 0.78, P < 0.0001) and TI (rho = 0.76, P < 0.0001). The correlation between ocular chlamydia infection and both TF and TI was weak at months 12 and 24. At 36 months, when TF prevalence had dropped below 10%, ocular chlamydia infection and TF were moderately correlated (rho = 0.70, P= 0.0002). Conclusions: Both TF and TI are good indicators of infection prevalence prior to mass azithromycin distribution. However, this relationship may be affected by repeated rounds of mass azithromycin distribution.

Keywords: Trachoma; azithromycin; mass drug administration.

Figure 1.

Longitudinal prevalence of trachomatous inflammation-follicular, trachomatous inflammation-intense, and ocular chlamydia infection in 24 trachoma mesoendemic communities in Niger.

Figure 2.

Relationship between trachomatous inflammation-follicular (TF) and ocular chlamydia infection at Months 0 (a), 12 (b), 24 (c), and 36 (d). Blue lines indicate loess curves for relationship between TF and ocular chlamydia, and grey shading indicates 95% confidence intervals.

Figure 3.

Relationship between trachomatous inflammation-intense (TI) and ocular chlamydia infection at Months 0 (a), 12 (b), 24 (c), and 36 (d). Blue lines indicate loess curves for relationship between TI and ocular chlamydia, and grey shading indicates 95% confidence intervals.