Measuring trachomatous inflammation-intense (TI) when prevalence is low provides data on infection with Chlamydia trachomatis

Purpose: Clinical trachoma is the current measure of effectiveness of antibiotic and environmental improvements in trachoma endemic communities. Impact assessments measure only trachomatous inflammation-follicular (TF). Trachomatous inflammation-intense (TI) is not used for decisions on stopping mass drug administration (MDA) or achieving intervention goals. We tested the supposition that TI was not associated with Chlamydia trachomatis when disease prevalence is low. Methods: In 35 communities undergoing MDA as part of a larger project, 110 children ages 1 to 9 years were randomly selected in each community for surveys at baseline, 6, and 12 months. Both eyelids were graded for TF and TI, and a swab for detection of C. trachomatis infection was taken. Results: Overall TF prevalence was 5% at baseline. Cases of TI alone constituted 15% of trachoma; 37% of TI cases had infection. At 6 and 12 months, the proportion of trachoma cases that had TI only was 13% and 20%; infection rates were similar to the rates in cases with TF alone. Conclusions: Despite low prevalence of trachoma, infection rates for TF alone and TI alone were similar at each time point. The exclusion of cases of TI alone when reporting trachoma prevalence discards additional information on infection. Trachomatous inflammation-intense could be considered as part of impact surveys.