Does persistent active trachoma mandate antibiotic mass drug administration? A comparison of prevalence of trachomatous inflammation–follicular with that of conjunctival infection and anti-chlamydial antibodies, Western Province, Zambia

The evaluation unit comprising Kaoma, Luampa, and Nkeyema districts, Western Province, Zambia, has persistent active trachoma. In 2023, we sought to compare the evaluation unit-level prevalence of the active trachoma sign, trachomatous inflammation-follicular (TF), to that of conjunctival Chlamydia trachomatis (Ct) infection and anti-Chlamydia trachomatis (Ct) seropositivity. We conducted a cluster-sampled cross-sectional survey. In selected households, we examined all consenting residents ≥1 y of age for trachoma. We collected dried blood spots (DBSs) by finger-prick from children ages 1-9-y and conjunctival swabs from the left eyes of children ages 1-5-y. DBSs were tested for antibodies to the C. trachomatis antigen Pgp3 by lateral flow assay. We tested conjunctival swabs for C. trachomatis DNA by GeneXpert polymerase chain reaction (PCR). The TF prevalence in children ages 1-9-y was 9.2%. In children ages 1-5-y, anti-Pgp3 seroprevalence was 1.7% and the seroconversion rate was 0.6 per 100 person-years. The prevalence of conjunctival C. trachomatis DNA in children ages 1-5-y was 0%. Based on TF prevalence, this population qualified for additional antibiotic mass drug administration rounds, but PCR and serology-more specific indicators of current or recent C. trachomatis infection than TF-confirmed an absence of significant current community C. trachomatis transmission, allowing a transition to surveillance. Adding these indicators is helpful in persistent active trachoma.