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S.K. West, B. Munoz, H. Mkocha, A.W. Solomon, A. Aguirre, A. Foster, D.C. Mabey; C Trachomatis Infection Following Mass Treatment of a Trachoma Hyperendemic Community in Tanzania: Predictors of Re–Emergence and Implications for Treatment Strategies . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1167.
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Background: Re–emergent trachoma, and infection with ocular C. trachomatis, can follow mass treatment. This longitudinal study of a hyperendemic community before and after mass treatment charts the pattern of re–emergence and examines risk factors for infection post treatment. Methods: Maindi village, Tanzania was enumerated in a census. Baseline, 2, 6, 12, and 18 month surveys for trachoma status were done and ocular swabs taken to determine the presence, and quantity, of C. trachomatis. Mass treatment with azithromycin was provided after the baseline survey. Census updates were carried out every two weeks to determine the influx of visitors, and to chart travel outside the village. Infection load greater than median at baseline was defined as "heavy infection". Results: Infection was high at baseline in this village, 69% in children ages <8 years. Mass treatment reduced the prevalence of infection, which stayed around 20% for the remaining 18 months. In children age <8 years, intense trachoma (TI) was highly associated with infection, with about 50% of TI cases infected at all time points. TF was less associated with infection following treatment. Evidence for resurgence of infection, heavy infection, and disease appeared by 18 months. Incident infection at 6 months was 3.5 times more likely if a household member had heavy infection at 2 months. Travel outside the village, and visitors to the community, did not increase the risk of infection. Conclusions: Unlike findings in trachoma low endemic communities, these data suggest infection does not disappear following mass treatment, at least by 18 months, in hyper–endemic communities. Infection also did not return to pre–treatment levels, nor was there evidence of steady increase over time since treatment. Household transmission of infection was important by six months post–treatment, but only in households where one member had a heavy load. The effect of surveillance for such households, using the clinical sign of TI, should be studied.
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