A recent article in The Journal of the American Medical Association reports that when preschool children in villages in Ethiopia took the antibiotic azithromycin twice per year instead of once per year, the number of children with eye infections caused by the contagious eye disease trachoma was significantly reduced. The study was conducted by Muluken Melese of Orbis International, Addis Ababa, Ethiopia and colleagues.
Trachoma is the an infectious eye disease that is the leading cause of the world’s preventable blindness. It is caused by the a chlamydia bacterium.
Trachoma is common in poor, dry areas like rural sub-Saharan Africa, but it has been eradicated from Western Europe and the United States. “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,” according to the authors of the study..
The elimination of trachoma is possible, according to some mathematical models. However, it may require recurrent treatment in areas where people are at a greater risk of becoming infected. It is regarded that elimination is a particularly important goal – if antibotics are discontinued and communities lose some their immunity, there is a concern that infection may return.
The researchers focused on the Gurage Zone in Ethiopia – 16 rural villages with a high prevalence of trachoma. They analyzed the results of azithromycin given once and twice per year to all residents age 1 year or older from March 2003 to April 2005. About 91% of the 16,403 eligible individuals received their scheduled treatment.
One major result of the study showed a 6-fold decrease in infections of preschool children from eight villages who received two annual treatments compared to one, from 42.6% to 6.8% by 24 months. When the treatment was administered four times in the other eight villages, infections were reduced in preschool children by a factor of 35, from 31.6% to 0.9% by 24 months.
The researchers report that at 24 months, 0.9 percent of children were infected in the biannually treated villages compared to 6.8 percent of children in the annually treated villages – a significant difference. At 24 months, 75% of preschool children did not show any infection after receiving biannual treatment compared to 12.5% of the residents receiving annual treatments. There was also an association between having no infection identified at 24 months and 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,” conclude the researchers.
An editorial by David Mabey and Anthony W. Solomon of the London School of Hygiene & Tropical Medicine, London maintains that the research performed by Melese and colleagues is valuable for the treatment of trachoma.
They write:
“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.”
Comparison of Annual and Biannual Mass Antibiotic Administration for Elimination of Infectious Trachoma
Muluken Melese, Wondu Alemayehu, Takele Lakew, Elizabeth Yi, Jenafir House, Jaya D. Chidambaram, Zhaoxia Zhou, Vicky Cevallos, Kathryn Ray, Kevin Cyrus Hong, Travis C. Porco, Isabella Phan, Ali Zaidi, Bruce D. Gaynor, John P. Whitcher, Thomas M. Lietman
JAMA. (2008). Vol. 299 No. 7: pp. 778-784
Mass Antibiotic Administration for Eradication of Ocular Chlamydia trachomatis
David Mabey and Anthony W. Solomon
JAMA. (2008). Vol. 299 No. 7: pp. 819-820
Written by: Peter M Crosta