Mass Treatment With Azithromycin Reduces Prevalence of Trachoma
Laurie Barclay, MD
Nov. 3, 2004 — Mass treatment with azithromycin is effective for reducing the prevalence of trachoma, according to the results of a study published in the Nov. 4 issue of the New England Journal of Medicine.
"Trachoma, caused by repeated ocular infection with Chlamydia trachomatis, is an important cause of blindness," write Anthony W. Solomon, MB, BS, PhD, from the London School of Hygiene and Tropical Medicine, U.K., and colleagues. "Current recommended dosing intervals for mass azithromycin treatment for trachoma are based on a mathematical model."
In a Tanzanian community in which trachoma was endemic, the investigators collected conjunctival swabs for quantitative polymerase-chain-reaction assay of C trachomatis before and at two, six, 12, 18, and 24 months after mass treatment with azithromycin. Residents who had clinically active trachoma at six, 12, and 18 months received tetracycline eye ointment.
At baseline, 956 (97.8%) of 978 residents received either one oral dose of azithromycin or a course of tetracycline eye ointment if azithromycin was contraindicated. Infection prevalence was 9.5% before mass treatment, 2.1% at two months, and 0.1% at 24 months.
Compared with the pretreatment level, the quantitative burden of ocular C trachomatis infection in the community was 13.9% at two months and 0.8% at 24 months. At each time point after baseline, subjects who had been positive at their previous test constituted more than 90% of the total community burden of C trachomatis infection.
"The prevalence and intensity of infection fell dramatically and remained low for two years after treatment," the authors write. "One round of very-high-coverage mass treatment with azithromycin, perhaps aided by subsequent periodic use of tetracycline eye ointment for persons with active disease, can interrupt the transmission of ocular C. trachomatis infection."
Study limitations include lack of placebo control and inability to rule out alternative explanations for decreased incidence of infection, such as enhanced personal hygiene among study participants, a reduction in the density of eye-seeking flies in the village, a small contribution from a regional secular trend, or tetracycline treatment in residents with active cases at six, 12, and 18 months.
The Wellcome Trust/Burroughs Wellcome Fund, the Edna McConnell Clark Foundation, the International Trachoma Initiative, and the Medical Research Council supported this study.
In an accompanying editorial, Silvio P. Mariotti, MD, from the World Health Organization in Geneva, Switzerland, urges caution in analyzing the results of this study, but he calls the unusually high coverage achieved "an outstanding and encouraging result."
"Although the social-development components of the SAFE strategy [surgery, antibiotics, facial cleanliness, and environmental improvement] must still be implemented in communities in which trachoma is endemic to ensure the continued elimination of blinding trachoma, the findings of Solomon et al. provide useful, new information on what antibiotic treatment can achieve," Dr. Mariotti writes. "Increased knowledge of the effect of different components of the SAFE strategy can be of great help to poor communities that have already paid too high a toll in the form of preventable blindness."
N Engl J Med. 2004;351:1962-1971, 2004-2007
Reviewed by Gary D. Vogin, MD
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