7-year trial discovers ocular chlamydia infection rebounds after azithromycin cessation

Continuous mass-drug administration (MDA) with oral azithromycin in northern Ethiopia, where trachoma is a major cause of blindness, is effective for trachoma prevention but doesn’t eliminate the disease entirely, according to new research.

The WHO recommends annual MDA with azithromycin in communities with a >5% prevalence of trachomatous inflammation-follicular in children, followed by reassessment and possibly further treatment after either 1, 3, or 5 years depending on the baseline severity seen in clinical exams. However, to-date the effect of stopping mass azithromycin distribution after multiple rounds of treatment, but before the stopping threshold of <5% TF in children ages 1–9 years, hasn’t been well understood.

This study, recently published in PLoS Medicine, investigated 48 communities including 3938 children aged 0–9 years in northern Ethiopia. The communities had previously participated in the TANA trial; receiving MDA with azithromycin for two years as part of the TANA study.

In this trial, termed TANA II, the researchers randomized the communities to receive either a continuation or discontinuation of treatment and measured the prevalence of ocular chlamydial infection in a random sample of children 36 months after baseline.

The team discovered that ocular chlamydia prevalence in communities where mass azithromycin distribution was continued was 7.2% at baseline and 6.6% at 36 months, demonstrating that despite 7 years of treatments, infections had not been eliminated in these communities. However, the prevalence of ocular chlamydia was significantly lower when compared with the communities who had discontinued azithromycin, which rose from 8.3% at baseline to 14.7% at 36 months. Neither the communities in the stopping arm nor the continuation arm reached the stopping threshold of <5% TF in children ages 1-9 years.

Although continued azithromycin distribution didn’t eliminate infection or meet WHO control goals, it did prevent resurgence. However, the authors caution that the results may not apply outside of trachoma hyperendemic regions.

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Sources: Keenan JD, Tadesse Z, Gebresillasie S et al. Mass azithromycin distribution for hyperendemic trachoma following a cluster-randomized trial: A continuation study of randomly reassigned subclusters (TANA II). PLoS Med. doi:10.1371/journal.pmed.1002633 (2018); www.eurekalert.org/pub_releases/2018-08/p-e7t080718.php


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