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Single dose of azithromycin effective against trachoma
Researchers in Tanzania have been working closely with a small village to determine the magnitude of azithromycin’s efficacy.
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One round of high-coverage mass treatment with azithromycin can interrupt the transmission of the infection that causes trachoma, researchers working in East Africa found. The findings were based on a 2-year study of residents of Kahe Mpya sub village in the Rombo district of Tanzania conducted by Anthony W. Solomon, MB, BS, PhD, and colleagues at the London School of Hygiene & Tropical Medicine and other institutions.
The study, designed to determine the degree of azithromycin’s effectiveness when used for mass population treatment, was funded by the Wellcome Trust/Burroughs Wellcome Fund, the Edna McConnell Clark Foundation, the International Trachoma Initiative and the Medical Research Council. The study was published in the New England Journal of Medicine.
“The efficacy of azithromycin for trachoma, in terms of proving that it is the best drug for the job, has been proven previously with trials comparing azithromycin to treatment with topical tetracycline. What we didn’t know about azithromycin was quite how powerful it was, and that is what we set out to do,” Dr. Solomon said in an interview with Ocular Surgery News.
In the study, prior to azithromycin treatment, swabs of the tarsal conjunctiva of each of the 978 village residents were collected to determine the prevalence and intensity of Chlamydia trachomatis infection in the community. After swabbing, 956 residents (97.8%) received either one oral dose of azithromycin or, if azithromycin was contraindicated, a course of tetracycline eye ointment. Swabs were then collected again at 2, 6, 12, 18 and 24 months after mass treatment.
According to the results, the prevalence of infection fell from 9.5% before mass treatment to 2.1% at 2 months and 0.1% at 24 months. The quantitative burden of ocular C. trachomatis infection in the community was 13.9% of its pretreatment level at 2 months and 0.8% at 24 months.
“These large, progressive decreases in the prevalence and intensity of infection suggest that transmission was stopped,” the researchers said in their published report.
At each time point after baseline, over 90% of the total community burden of the infection was found among subjects who had tested positive the previous time they were tested, according to the report.
| Image: Solomon AW |
Children as indicators
Children play a large role as carriers of ocular chlamydial infection. According to the study, children younger than 10 years accounted for at least 90% of the total burden of infection at each follow-up point except the 12-month follow-up, when one 13-year-old post-treatment immigrant accounted for a large fraction of the total community burden.
However, according to Dr. Solomon and colleagues, the study results imply that signs of active disease are not indicative of the effect of azithromycin treatment on infection levels.
“The prevalence of follicular trachomatous inflammation among children 1 to 9 years of age was 36% at baseline, 13.2% at 2 months and 16.3% at 2 years, yet the community load of ocular C. trachomatis infection fell by more than 99% during this interval,” the authors said.
Currently, the World Health Organization recommends that the percentage of children having follicular trachomatous inflammation should be used to determine which communities need antibiotics and when annual treatment should be stopped. Given these results, this recommendation may need to be reconsidered, Dr. Solomon said.
Cultural factors
| Image: Solomon AW |
The study further concluded that the magnitude of the observed decrease in prevalence and intensity of infection could be attributed to the high baseline treatment coverage of the community, a coverage rate that might prove difficult on a larger scale.
“It could be quite difficult to achieve the same very high level of coverage if you were treating everyone in a district of 250,000 or a million people,” Dr. Solomon said.
According to the report, further research is needed to assess the reasons for incomplete acceptance of antibiotics in national trachoma control programs, but Dr. Solomon suggested that with a smaller community comes more interaction and therefore more trust.
“We were in the village a lot before the study started. We were in the village on a daily basis for several months, and that means that people were very familiar with us. We talked to people about trachoma, and we enrolled them in a study that gave them certain tangible benefits. For example, every time we saw them, they could if necessary get treatment for other conditions like malaria, respiratory tract infections or intestinal worms. So people were quite keen to be involved,” Dr. Solomon said.
For Your Information:
- Anthony W. Solomon, MB, BS, PhD, can be reached at London School of Hygeine & Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom; e-mail: anthony.solomon@lshtm.ac.uk.
- Jared Schultz is an OSN Staff Writer who covers all aspects of ophthalmology. He focuses geographically on Europe and the Asia-Pacific region.