Ocular Chlamydia Trachomatis Infection, anti-Pgp3 Antibodies and Conjunctival Scarring in Vanuatu and Tarawa, Kiribati Before Antibiotic Treatment for Trachoma

03 Apr 2020
Robert Butcher, Becca Handley, Mackline Garae, Raebwebwe Taoaba, Harry Pickering, Annie Bong, Oliver Sokana, Matthew J Burton, Nuno Sepúlveda, Ana Cama, Richard Le Mesurier, Anthony W Solomon, David Mabey, Fasihah Taleo, Rabebe Tekeraoi, Chrissy H Roberts

Introduction: In the peri-elimination setting, the positive predictive value of trachomatous inflammation-follicular (TF), the primary marker used to determine need for antibiotics for trachoma, is suboptimal. Here, three non-TF measures are used to compare two regions where TF prevalence exceeds the threshold for intervention, but where the Chlamydia trachomatis (Ct) prevalence is different.

Methods: Population prevalence of trachoma was measured in Vanuatu (n = 3470) and Kiribati (n = 2922). Dried blood spots (DBS) and conjunctival photographs were collected from every survey participant, and conjunctival swabs were collected from those aged 1-9 years. Individuals were tested for blood anti-Pgp3 antibodies, Ct DNA at the conjunctiva and severity of conjunctival scarring.

Results: The prevalence of TF in 1-9-year-olds was 16.5% in Vanuatu and 38.2% in Tarawa. 7% of people aged ≥1 year in Vanuatu had conjunctival scarring compared to 27% in Tarawa. The prevalence of ocular Ct infection in 1-9-year-olds was 1.5% in Vanuatu and 27.4% in Tarawa. The seroconversion rate amongst 1-9-year-old children in Vanuatu and Tarawa was 0.018 and 0.197 events per child per year, respectively.

Conclusions: Comparing Vanuatu to Tarawa demonstrates several markers that could be used to differentiate the trachoma status of populations in these (and other) locations.