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.

Background: 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.

Methods: 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).

Results: 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%.

Conclusions: 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.