Antibiotic not sufficient for treating trachoma in populations with high disease prevalence

Treating trachoma, an eye infection that can lead to blindness, with a single mass antibiotic distribution in Ethiopian communities with high prevalence of infection is not effective in eliminating the disease, according to a study in the March 8 issue of JAMA: The Journal of the American Medical Association.

At present, trachoma remains the most important infectious cause of blindness in the world, according to background information in the article. To reduce this infection (due to Chlamydia trachomatis), the World Health Organization (WHO) has recommended communitywide antibiotic distributions as part of its strategy to eliminate this infection as a public health concern by the year 2020. Current WHO guidelines recommend 3 annual mass distributions. It has been suggested that infection might not return after a single mass treatment with high coverage.

Jaya D. Chidambaram, M.B.B.S., of the University of California, San Francisco, and colleagues investigated whether ocular chlamydial infection returns to the community in the long term after a single mass antibiotic treatment in a high-prevalence setting. Eight villages in Ethiopia were followed up for 24 months from March 2003 to March 2005 after receipt of a single mass treatment of single dose oral azithromycin was offered to all residents who were aged 1 year or older. Fifteen untreated villages were randomly chosen and enrolled 12 months into the program. Children aged 1 to 5 years were monitored because this age group is known to have the highest prevalence of ocular chlamydial infection in the community and may form a core group for transmission.

Five hundred fifteen children were examined for ocular chlamydial infection at baseline. For the follow-up examinations, the average participation rate was 83 percent. Prior to treatment, the average prevalence of infection in children aged 1 to 5 years by village was 43.5 percent. By 2 months after treatment, the average prevalence of infection had decreased to 5.1 percent, which was significantly lower than baseline. By 24 months after treatment, the average prevalence of infection had risen to 11.3 percent.

The prevalence of infection varied considerably by village; 7 of the 8 villages had more infection in children at 24 months than at 2 months. In the remaining village, infection in children was reduced from 36 percent at baseline to 0 at all 5 subsequent visits. Villages enrolled at 12 months had significantly fewer infections than those enrolled 12 months earlier.

"Our results suggest that if infection is not eliminated by a single mass antibiotic treatment, then it predictably returns into the community, at least in this hyperendemic [area of high prevalence] area in 1- to 5-year-old children. However, infection comes back slowly and does not approach baseline prevalence even by 2 years," the authors write. " repeated treatments or other measures will be necessary for elimination of infection, as recommended by WHO. A single treatment will not suffice."