Abstract
BackgroundTrachoma, a neglected tropical disease, is caused by ocular infection with Chlamydia trachomatis (Ct). The World Health Organization (WHO) recommends three annual rounds of community mass drug treatment with azithromycin (MDA) if the prevalence of follicular trachoma in 1–9 year olds (TF1–9) exceeds 10% at district level to achieve an elimination target of district-level TF1–9 below 5% after. To evaluate this strategy in treatment-naïve trachoma-endemic island communities in Guinea Bissau, we conducted a cross-sectional population-based trachoma survey on four islands. The upper tarsal conjunctivae of each participant were clinically assessed for trachoma and conjunctival swabs were obtained (n = 1507). We used a droplet digital PCR assay to detect Ct infection and estimate bacterial load. We visited the same households during a second cross-sectional survey and repeated the ocular examination and obtained conjunctival swabs from these households one year after MDA (n = 1029).ResultsPre-MDA TF1–9 was 22.0% (136/618). Overall Ct infection prevalence (CtI) was 18.6% (25.4% in 1–9 year olds). Post-MDA (estimated coverage 70%), TF1–9 and CtI were significantly reduced (7.4% (29/394, P < 0.001) and 3.3% (34/1029, P < 0.001) (6.6% in 1–9 year olds, P < 0.001), respectively. Median ocular Ct load was reduced from 2038 to 384 copies/swab (P < 0.001). Following MDA cases of Ct infection were highly clustered (Moran’s I 0.27, P < 0.001), with fewer clusters of Ct infection overall, fewer clusters of cases with high load infections and less severe disease.ConclusionsDespite a significant reduction in the number of clusters of Ct infection, mean Ct load, disease severity and presence of clusters of cases of high load Ct infection suggesting the beginning of trachoma control in isolated island communities, following a single round of MDA we demonstrate that transmission is still ongoing. These detailed data are useful in understanding the epidemiology of ocular Ct infection in the context of MDA and the tools employed may have utility in determining trachoma elimination and surveillance activities in similar settings.
Highlights
Trachoma, a neglected tropical disease, is caused by ocular infection with Chlamydia trachomatis (Ct)
mass drug treatment with azithromycin (MDA) was conducted following the baseline survey and coverage was estimated at 70% across the study islands
13% (37/ 293) households were lost to follow-up, and of those almost half (18/37) were households where C. trachomatis infection was detected in 1–9 year olds at baseline
Summary
A neglected tropical disease, is caused by ocular infection with Chlamydia trachomatis (Ct). The World Health Organization (WHO) recommends three annual rounds of community mass drug treatment with azithromycin (MDA) if the prevalence of follicular trachoma in 1–9 year olds (TF1–9) exceeds 10% at district level to achieve an elimination target of district-level TF1–9 below 5% after. To evaluate this strategy in treatment-naïve trachomaendemic island communities in Guinea Bissau, we conducted a cross-sectional population-based trachoma survey on four islands. Trachoma is caused by infection with ocular strains of C. trachomatis and manifests as distinct clinical syndromes, beginning with an acute self-limiting kerato-conjunctivitis which may progress to chronic inflammatory disease with subsequent conjunctival scarring and blinding sequelae. Community-wide MDA, as part of the SAFE strategy, aims to interrupt transmission, reducing the number of infections that each individual is exposed to and eliminate blinding trachoma as a public health concern [2, 5]
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