Feb. 19, 2008 Changing the administration of the antibiotic azithromycin from once to twice a year in villages in Ethiopia substantially reduced eye infections in preschool children caused by chlamydia, which causes the serious, contagious eye disease trachoma, according to a new study.
Trachoma is 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 World Health Organization has launched a program to control trachoma, relying in large part on annual repeated mass azithromycin administrations. Program administrators anticipate that the treatments will reduce the prevalence of the ocular strains of chlamydia that cause trachoma to a level low enough that resulting blindness will be no longer be a major public health concern. However, local elimination of ocular chlamydia may be obtainable," the authors write.
Elimination 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.
Muluken Melese, M.D., M.P.H., of Orbis International, Addis Ababa, Ethiopia, and colleagues compared the outcomes of azithromycin given annually and biannually to all residents (age 1 year or older) of 16 rural villages in the Gurage Zone, Ethiopia, an area with a high prevalence of trachoma, from March 2003 to April 2005. Overall, 14,897 of 16,403 eligible individuals (90.8 percent) received their scheduled treatment.
The researchers found that two annual treatments (at the beginning of the study and 12 months) reduced infection in preschool children in eight villages 6-fold, from 42.6 percent to 6.8 percent by 24 months. Four biannual treatments (baseline, 6, 12, and 18 months) reduced infection in preschool children in the other eight villages 35-fold, from 31.6 percent to 0.9 percent by 24 months. The prevalence of infection at 24 months 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 6 of 8 of the residents receiving biannual treatment and 1 of 8 of the residents receiving annual treatments. Having no infection identified at 24 months was associated with being in the biannual treatment group.
"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 2 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 conclude.
Journal reference: JAMA. 2008;299:778-784.
Editorial: Mass Antibiotic Administration for Eradication of Ocular Chlamydia Trachomatis
In an accompanying editorial, David Mabey, D.M., F.R.C.P., and Anthony W. Solomon, M.R.C.P., Ph.D., of the London School of Hygiene & Tropical Medicine, London, write that the findings by Melese and colleagues add important information regarding treating trachoma.
"Treating entire regions twice yearly could help ensure that gains made from frequent antibiotic use are not eroded by reintroduction of infection from outside the treated area but will significantly increase the cost of antibiotics and of their distribution. Finally, studies to examine whether more frequent azithromycin use will result in the emergence of macrolide-resistant strains of C trachomatis or other important pathogens are urgently required, for such an outcome would more than offset any gain derived from biannual treatment. In the meantime, the findings of Melese et al represent an important contribution to understanding how blinding trachoma can be reduced and hopefully eliminated."
Editorial reference: JAMA. 2008;299:819-820.
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