Abstract
Abstract: :
Purpose: Many countries are defining treatment strategies for trachoma control. Data on C. trachomatis load and transmission within the community is necessary for determining what strategies are most effective for adequate trachoma control. This study was conducted to 1) characterize the load of C. trachomatis in a hyperendemic community, determining the characteristics of those with high chlamydial loads and 2) to evaluate the effect of treatment on chlamydial load within this community, to determine whether single dose of azithromycin eliminates infection. Methods: A longitudinal study was conducted in Maindi, Tanzania. A census was carried out of all households, followed by a baseline survey to evaluate clinical trachoma status, collect ocular swabs to test for C. trachomatis, and treat with azithromycin. A follow up survey was conducted at two months post–treatment. Quantitative PCR was used to determine chlamydial load for each specimen at baseline and two months. Hight loads of infection were defined as having more than the median number of omp1 copies among those positive. Results: 86% of the village participated in the baseline survey and were treated. The greatest concentration of chlamydial load was found in young children, but people in all age groups carried high infection loads. Although the proportion of individuals with clinical signs of trachoma increased with increasing infection load, 22% of those with a high load had no clinical signs. Treatment was very effective, except in a subgroup of children age 2 and under; 50% of whom had high loads at both baseline and follow up. Age, gender and contact with other highly infected individuals were predictors of high loads at baseline. Conclusions: Our data confirm that a significant portion of the infectious load of C. trachomatis resides in children. However, adults and those with no clinical signs of trachoma who also carry heavy loads could be another source of transmission in the community. Such data support the mass treatment approach to trachoma control in hyperendemic villages. While treatment was effective in decreasing the community pool of infection, it appeared to be least effective in the very young children with heavy loads, half of whom still had heavy loads two months later. The causes of persistence or re–emergence in very young children should be further investigated to ensure dosing is adequate. The data also suggest that treatment of very young children should be encouraged.
Keywords: trachoma • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials • clinical (human) or epidemiologic studies: risk factor assessment