Serological Measures of Trachoma Transmission Intensity

Abstract

Ocular infection with Chlamydia trachomatis can lead to trachoma, a leading infectious cause of blindness. Trachoma is targeted for elimination by 2020. Clinical grading for ocular disease is currently used for evaluating trachoma elimination programs, but serological surveillance can be a sensitive measure of disease transmission and provide a more objective testing strategy than clinical grading. We calculated the basic reproduction number from serological data in settings with high, medium, and low disease transmission based on clinical disease. The data showed a striking relationship between age seroprevalence and clinical data, demonstrating the proof-of-principle that age seroprevalence predicts transmission rates and therefore could be used as an indicator of decreased transmission of ocular trachoma.

Figure 1. Seroprevalence percentages by age broken down by antigen (pgp3 and CT694) and village prevalence (below 5% TF, 10-30% TF, and above 30% TF).

Seroprevalences are represented with circles scaled by the sample size and shaded regions denote 95% confidence intervals. For antigen-specific seroprevalences by age, confidence intervals use the incomplete beta function to account for village-level clustering (except when the seroprevalence was zero and Clopper-Pearson (1934) limit were used).