When the Neighboring Village is Not Treated: Role of Geographic Proximity to Communities Not Receiving Mass Antibiotics for Trachoma

Abstract Background Mass administration of azithromycin is an established strategy for decreasing the prevalence of trachoma in endemic areas. However, nearby untreated communities could serve as a reservoir that may increase the chances of chlamydia reinfection in treated communities. Methods As part of a cluster-randomized trial in Ethiopia, 60 communities were randomized to receive mass azithromycin distributions and 12 communities were randomized to no treatments until after the first year. Ocular chlamydia was assessed from a random sample of children per community at baseline and month 12. Distances between treated and untreated communities were assessed from global positioning system coordinates collected for the study. Results The pretreatment prevalence of ocular chlamydia among 0 to 9 year olds was 43% (95% confidence interval [CI], 39%-47%), which decreased to 11% (95% CI, 9%-14%) at the 12-month visit. The posttreatment prevalence of chlamydia was significantly higher in communities that were closer to an untreated community after adjusting for baseline prevalence and the number of mass treatments during the year (odds ratio, 1.12 [95% CI, 1.03-1.22] for each 1 km closer to an untreated community). Conclusions Mass azithromycin distributions to wide, contiguous geographic areas may reduce the likelihood of continued ocular chlamydia infection in the setting of mass antibiotic treatments. Ethiopian communities were randomized to mass azithromycin distributions for trachoma or to delayed treatment. In adjusted analyses, the prevalence of ocular chlamydia at 12 months was significantly higher in communities that were closer to an untreated community.