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Sheila K. West, Beatriz E. Munoz, Harran Mkocha, Charlotte Gaydos, Thomas Quinn; After Multiple Rounds of Mass Drug Administration for Trachoma, are there only "Trachoma families" left?. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6936.
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Mass drug administration (MDA) with azithromycin in areas with endemic trachoma is part of the World Health Organization (WHO) SAFE strategy, and at least 3 rounds of MDA are recommended. We hypothesized that after each successive round of MDA as infection declined, trachoma and infection would be increasingly clustered in a few high risk families in the communities, and the proportion of families with an isolated child with infection would decline.
In four villages in Kongwa Tanzania, a longitudinal cohort of children ages under ten years at baseline was followed up to 30 months post 3 rounds of MDA. MDA was carried out at baseline, 12, and 24 months, with coverage with azithromycin over 90% in each round. Surveys for infection with C. trachomatis and clinical trachoma were carried out at baseline, 6, 12, 18, 24, and 30 months. A trained grader used the WHO simplified grading system determined the presence of active trachoma. Ocular swabs were collected and shipped to the International Chlamydia laboratory at JHU for determination of infection using Amplicor polymerase chain reaction. We studied the sub set of households with at least 2 children/ household in order to allow more than one child to be infected. We determined the percentage of households with infection after each round of MDA, and the percentage of children infected in each household.
At baseline, 2210 children under age ten years resided in 963 households. The overall prevalence of trachoma was 27% and infection was 22%. There were 261 households with at least one infection and who contained more than one child, and 50.6% of them had more than one child infected. By 30 months, infection declined to 3% and trachoma to 9%. There were only 53 households with more than one child and at least one infection, reflecting the overall decline in prevalence. Only 35.8% of them had more than one child infected.
This prospective study did not find evidence of increased clustering of infections within a few households after multiple rounds of MDA. In fact, proportionately more households after 3 rounds of MDA had a single child infection than was the case at baseline. It appears that although infection declines with each successive round of MDA in these communities, the pattern of clustering does not change.
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