Clinical activity and polymerase chain reaction evidence of chlamydial infection after repeated mass antibiotic treatments for trachoma

Abstract

It is unclear how the prevalence of clinically active trachoma correlates with the prevalence of ocular chlamydial infection at the community level. In 24 villages from a cluster-randomized clinical trial of mass azithromycin distributions in Ethiopia, the correlation between the prevalence of clinical activity (on examination) and chlamydial infection (by polymerase chain reaction) was moderately strong before mass antibiotic treatments (Pearson's correlation coefficient r = 0.75, 95% confidence interval [CI] = 0.52-0.87), but decreased at each time point during four biannual treatments (at 24 months, r = 0.15, 95% CI = -0.14-0.41). One year after the final treatment, the correlation coefficient had increased, but not to the pre-treatment level (r = 0.55, 95% CI = 0.30-0.73). In a region with hyperendemic trachoma, conjunctival examination was a useful indicator of the prevalence of chlamydial infection before treatments, less useful during mass treatments, but regained utility by one year after treatments had stopped.

Figure 1.

Chlamydial infection and clinical activity in villages in Ethiopia treated with four biannual treatments of azithromycin. Mean prevalence of chlamydial infection and clinically active trachoma are depicted over time for 16 villages that received four biannual mass treatments. Error bars show bootstrapped 95% confidence intervals.

Figure 2.

Chlamydial infection and clinical activity in villages in Ethiopia treated with six biannual treatments of azithromycin. Mean prevalence of chlamydial infection and clinically active trachoma are depicted over time for 8 villages that received six biannual mass treatments. Error bars show bootstrapped 95% confidence intervals.

Figure 3.

Correlation between prevalence of chlamydial infection and prevalence of clinical activity in villages in Ethiopia treated with repeated mass antibiotic distributions. A, Pearson correlation coefficient before and during mass antibiotic treatments for 24 villages that received biannual treatments at months 0, 6, 12, and 18 (shaded region). Eight of these villages received two additional biannual mass antibiotic treatments at months 24 and 30. B, Pearson correlation coefficient at the final mass treatment and during one year of follow-up for all 24 villages. Error bars show bootstrapped 95% confidence intervals.