Mass treatment with single-dose azithromycin for trachoma

Abstract

Background: Trachoma, caused by repeated ocular infection with Chlamydia trachomatis, is an important cause of blindness. Current recommended dosing intervals for mass azithromycin treatment for trachoma are based on a mathematical model.

Methods: We collected conjunctival swabs for quantitative polymerase-chain-reaction assay of C. trachomatis before and 2, 6, 12, 18, and 24 months after mass treatment with azithromycin in a Tanzanian community in which trachoma was endemic. For ethical reasons, at 6, 12, and 18 months, we gave tetracycline eye ointment to residents who had clinically active trachoma.

Results: At baseline, 956 of 978 residents (97.8 percent) received either one oral dose of azithromycin or (if azithromycin was contraindicated) a course of tetracycline eye ointment. The prevalence of infection fell from 9.5 percent before mass treatment to 2.1 percent at 2 months and 0.1 percent at 24 months. The quantitative burden of ocular C. trachomatis infection in the community was 13.9 percent of the pretreatment level at 2 months and 0.8 percent at 24 months. At each time point after baseline, over 90 percent of the total community burden of C. trachomatis infection was found among subjects who had been positive the previous time they were tested.

Conclusions: The prevalence and intensity of infection fell dramatically and remained low for two years after treatment. One round of very-high-coverage mass treatment with azithromycin, perhaps aided by subsequent periodic use of tetracycline eye ointment for persons with active disease, can interrupt the transmission of ocular C. trachomatis infection.

Figure 1. Number of Copies of omp1 per Swab According to Age and Sex at Baseline (Panel A), 2 Months (Panel B), 6 Months (Panel C), 12 Months (Panel D), 18 Months (Panel E), and 24 Months (Panel F).

Swabs that were negative on a highly sensitive PCR assay are not shown.

Figure 2. Overall (Panel A) and Age-Specific (Panel B) Community Ocular Chlamydia trachomatis Load at Each Time Point.

Vertical bars in Panel A are 95 percent confidence intervals.

Figure 3. Prevalence of Active Disease over Time among the Various Age Groups.

Active disease was defined according to the World Health Organization simplified grading system, by the presence of trachomatous inflammation–follicular, trachomatous inflammation–intense, or both in either eye.