Reduction and Return of Infectious Trachoma in Severely Affected Communities in Ethiopia

Background: Antibiotics are a major tool in the WHO's trachoma control program. Even a single mass distribution reduces the prevalence of the ocular chlamydia that causes trachoma. Unfortunately, infection returns after a single treatment, at least in severely affected areas. Here, we test whether additional scheduled treatments further reduce infection, and whether infection returns after distributions are discontinued. Methods: Sixteen communities in Ethiopia were randomly selected. Ocular chlamydial infection in 1- to 5- year-old children was monitored over four biannual azithromycin distributions and for 24 months after the last treatment. Findings: The average prevalence of infection in 1- to 5- year-old children was reduced from 63.5% pre-treatment to 11.5% six months after the first distribution (P<0.0001). It further decreased to 2.6% six months after the fourth and final treatment (P=0.0004). In the next 18 months, infection returned to 25.2%, a significant increase from six months after the last treatment (P=0.008), but still far lower than baseline (P<0.0001). Although the prevalence of infection in any particular village fluctuated, the mean prevalence of the 16 villages steadily decreased with each treatment and steadily returned after treatments were discontinued. Conclusion: In some of the most severely affected communities ever studied, we demonstrate that repeated mass oral azithromycin distributions progressively reduce ocular chlamydial infection in a community, as long as these distributions are given frequently enough and at a high enough coverage. However, infection returns into the communities after the last treatment. Sustainable changes or complete local elimination of infection will be necessary.