Trachoma MDA threshold — DTM&H MCQ
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Correct answer: D — Trachomatous inflammation-follicular (TF) prevalence ≥10% in 1-9 year olds
The correct answer is D, trachomatous inflammation-follicular (TF) prevalence of 10% or more in children aged 1-9 years. This is the WHO-defined district-level threshold that triggers mass drug administration (MDA) with azithromycin under the A (antibiotics) component of the SAFE strategy. TF is chosen as the operational indicator because it is a simple, highly reproducible clinical sign assessed on community-based surveys, avoiding reliance on laboratory diagnosis of Chlamydia trachomatis, which is impractical in most endemic districts. Children 1-9 years are surveyed because this age group carries the highest burden of active, transmissible infection and drives ongoing transmission within the community. Why the other options are wrong: C. Trachomatous trichiasis (TT) prevalence ≥1%: this is a surgical (S component) elimination threshold applied to adults aged 15 years and above, not the antibiotic trigger, and the actual district elimination target for unknown-to-the-health-system TT is ≥0.2%, not the MDA decision point. E. Corneal opacity prevalence ≥5%: corneal opacity reflects irreversible blinding sequelae used in broader burden-of-disease assessment, not a treatment-triggering indicator for MDA. A. Any case of active trachoma: a single case does not meet the population-level threshold required; WHO policy bases MDA decisions on district prevalence, not individual case detection, to avoid unnecessary mass treatment. B. Trachomatous scarring (TS) prevalence ≥20%: TS indicates cumulative past inflammation and scarring, useful for monitoring disease history, but it is not used to decide on antibiotic distribution. Key point: District-level TF prevalence of 10% or more in children aged 1-9 years is the WHO threshold that mandates mass azithromycin distribution under the SAFE strategy.
Reference: WHO, Trachoma control: the SAFE strategy; district-level TF prevalence ≥10% in children 1-9 years triggers mass antibiotic treatment, with the elimination target being TF <5% (PMC6288535).