The results of a randomized clinical trial in Ethiopia suggest mass azithromycin distribution to wide, contiguous areas may reduce the likelihood of the infection that causes trachoma, researchers reported today in Clinical Infectious Diseases.
In the cluster-randomized trial, 60 Ethiopian communities were randomized to receive mass azithromycin distributions (either annually, biannually, or quarterly) over 12 months and 12 to receive no treatments until after the first year. Mass distribution of a single dose of azithromycin has been shown to reduce the prevalence of ocular chlamydia infection—which causes trachoma—in entire communities but has not resulted in complete elimination because of reinfection.
The aim of the trial was to test the theory that reinfection from nearby untreated communities may be a contributing factor. Most infections occur in children under 10 years old.
After assessing a random sample of children ages 0 to 9 years from treated and untreated communities at baseline and at 12 months, the investigators found that the prevalence of ocular chlamydia in the 60 treated communities fell from 43% (95% confidence interval [CI], 39% to 47%) to 11% (95% CI, 9% to 14%). In the 12 untreated communities, prevalence of ocular chlamydia was 46% (95% CI, 38% to 54%) after 12 months.
Untreated areas as reservoirs
In addition, the post-treatment prevalence of ocular chlamydia was significantly higher in communities that were closer to untreated communities after adjusting for baseline prevalence and the number of mass treatments during the year (odds ratio, 1.12; 95% CI, 1.03 to 1.22 for each 1 kilometer closer to an untreated community).
The study authors speculate that routine travel to untreated areas may present opportunities for infections to be reintroduced to treated communities.
"The study supports the World Health Organization recommendation to use districts as the unit of trachoma treatment because administering mass azithromycin distributions over wide contiguous areas should reduce the impact of untreated areas as reservoirs for ocular chlamydia infections," they concluded.