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B.E. Munoz, S.K. West, P.M. Emerson, W. Mchiwa, D. Mabey; Effect of Fly Control Following Mass Treatment for Trachoma in Hyper–endemic Setting: A Randomized Trial in Tanzania . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5022.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine whether an intensive insecticide spray intervention to control the fly population following mass treatment with azithromicin will reduce trachoma in hyperendemic neighborhoods Methods: A single blind, randomized, neighborhood–based clinical trial conducted in 16 geo–political neighborhood units in Kongwa, Tanzania. All children ages 1–7 years living in the selected neighborhoods were enrolled, resulting in 119 children in the intervention arm and 183 children in the control arm. Photographs and of the eye lid and ocular swabs to test for the presence of ocular chlamydia infection were taken at baseline, six months, and one year post treatment. Analyses were carried out at the neighborhood level, and at the child level, adjusting for clustering. Azithromycin (20mg/kg) was offered to all residents over age 1 following the baseline survey. Households and surrounding areas in neighborhoods randomized to the intervention were sprayed on a regular schedule. Sticky traps were placed in each neighborhood at a fix location to monitor fly density. The main outcome was the prevalence of active trachoma at six months and one year Results: The children in intervention neighborhoods were similar to the children randomized to control in terms of age gender and baseline trachoma. In both groups, more than 80% of children were treated. Over the study period, the average fly density in the intervention group was significantly lower than in the control group. The average prevalence of trachoma in the intervention neighborhoods was lower at 6 months post treatment, 20%, compared to the control neighborhoods, 33%, (p=0.07). There was no difference in active trachoma at one year, 43% versus 44%. The risk of trachoma, adjusted for age, gender, and baseline trachoma, was significantly lower at 6 months in children in the intervention arm compared to the control arm (OR(95%CI)) (0.38(0.24–0.60), but not at one year (1.16(0.70–0.90)). Conclusions: Insecticide spraying significantly reduced the number of flies in the intervention neighborhoods, but had only a modest effect on trachoma at 6 months and no effect out to one year. In this hyper–endemic setting, flies are likely to be only one of several routes of transmission. The results do not support the long term added value of fly reduction following mass treatment for trachoma control, although reducing flies may have other public health benefits.
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