TUESDAY, Feb. 19 (HealthDay News) -- Increasing the administration of antibiotics from annually to twice a year in rural African villages could help reduce serious eye infections that can lead to blindness, a new study suggests.

An ocular strain of the sexual transmitted disease chlamydia causes the contagious eye disease trachoma, the leading infectious cause of blindness worldwide. Although it has been eliminated from Western Europe and the United States, it is still common in poor, arid areas such as rural sub-Saharan Africa.

The study, published in the Feb. 20 issue of the Journal of the American Medical Association, showed that giving azithromycin to all residents in eight Ethiopian villages twice a year for two years reduced infection in preschool children 35-fold, from 31.6 percent to 0.9 percent. In eight other villages where only annual doses of the antibiotic were given, researchers found the infection rate in preschool children dropped only sixfold, from 42.6 percent to 6.8 percent at the end of two years.

The prevalence of infection 24 months after the first dose of antibiotics was significantly lower in children in the biannually treated villages (0.9 percent) than in the annually treated villages (6.8 percent). At 24 months, no infection could be identified in preschool children in six of eight of the residents receiving biannual treatment but only in one of eight of the residents receiving annual treatments.

The World Health Organization has launched a program to control trachoma, relying in large part on annual repeated mass azithromycin administrations. Elimination of ocular chlamydia has become a particularly important goal because of a growing concern that infection may return into communities that have lost some of their immunity to chlamydia after antibiotics are discontinued.

Mathematical models have suggested that elimination is possible but may require relatively frequent treatments in regions with high incidence, according to background information in the article.

Biannual coverage of a large portion of the community may be necessary to eliminate infection from a severely affected community or at least to do so in a timely manner. Although programs may be reluctant to devote their scarce resources to more frequent treatment, this may be more cost-effective in the long term. Local elimination of the ocular strains of chlamydia from villages is a feasible goal but may require biannual distributions in hyperendemic areas. The results of this study confirm models that suggest treatments will need to be given for more than the two years to predictably achieve elimination in more than 95 percent of villages. Whether elimination from a larger area is possible will depend on the frequency of community-to-community transmission, the authors concluded.

More information

The U.S. Centers for Disease Control and Prevention has more about chlamydia.