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21-02-2013 | Internal medicine | Article

Three rounds of azithromycin needed for trachoma elimination


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medwireNews: Results from a randomized trial suggest that at least three annual mass drug administrations (MDAs) of azithromycin are needed to eliminate trachoma, even in regions with a relatively low initial prevalence of the infection.

Trachoma is the leading global cause of blindness and disproportionately affects the poorest parts of the world. To tackle the disease, the World Health Organization has developed a four-pronged approach that encompasses surgery, mass administration of antibiotics, facial cleanliness, and environmental improvements.

The Partnership for the Rapid Elimination of Trachoma (PRET)-Ziada Trial was designed to see whether WHO's current recommendation regarding MDAs - namely, to give at least three annual rounds of azithromycin - is always necessary, or whether MDAs could cease if the infection rate fell.

The trial was conducted in 16 communities in Tanzania in which the trachoma prevalence was low, at between 10% and 20%. One hundred children aged 5 years or younger were randomly selected from each community.

The communities were then randomly assigned to usual care (ie, three annual rounds of azithromycin) or to a stopping rule whereby MDAs with azithromycin could cease if the prevalence of Chlamydia trachomatis declined to less than 5%.

Writing in JAMA Ophthalmology, Sheila West (Wilmer Eye Institute, Baltimore, Maryland, USA) and co-authors report that none of the communities was free of C. trachomatis at 6 or 18 months. Therefore all communities underwent all three rounds of azithromycin MDA.

The prevalence of C. trachomatis infection was similar in usual care and intervention communities at 18 months, at 2.9% and 4.7%, respectively.

Neither baseline infection nor trachoma predicted infection or trachoma prevalence in these communities at 18 months, the authors add. Thus, even communities with a low prevalence of trachoma require at least three rounds of MDA.

"None could be stopped early based on a stopping rule of infection of less than 5%," West et al write.

They conclude: "The fact that these communities were at the low end of baseline prevalence in a district with overall higher rates of trachoma suggests the wisdom of treating a wide geographic area for at least three rounds before impact surveys, and not presuming that subdistricts on their own can be stopped if the wider district-level prevalence supports mass treatment."

By Joanna Lyford, Senior medwireNews Reporter