Use of complementary indicators in trachoma surveys in Nigeria: results of impact surveys in two local government areas.

OBJECTIVES

Trachoma elimination progress is hampered in some districts by persistent or recrudescent trachomatous inflammation-follicular (TF). In Sokoto State, Nigeria, two local government areas (LGAs) have been classified as having persistent TF. We aimed to determine whether there was ongoing, programmatically significant conjunctival Chlamydia trachomatis (Ct) community transmission in these LGAs.

METHODS

In addition to examination for trachoma clinical signs, we took conjunctival swabs (for Ct nucleic acid amplification testing) from children aged 1-5 years, and dried blood spots [for estimation of anti-chlamydial plasmid gene protein 3 seroconversion rates (SCRs)] from children aged 1-9 years.

RESULTS

In Binji LGA, TF prevalence (4.1%) was below the elimination threshold, SCR was 1.1 per 100 child years in 1-5-year-olds, and Ct infection prevalence was 0.1%. In Silame LGA, TF prevalence (5.6%) was above the elimination threshold, but SCR was 1.6, and Ct infection prevalence was 0.2%.

CONCLUSION

Binji has attained the active trachoma elimination threshold, thus transitioning to surveillance. In Silame, despite the TF prevalence remaining slightly above threshold, the low Ct infection prevalence and low SCR suggest Ct transmission is minimal, and mass drug administration will not be conducted. Silame can therefore also transition to the surveillance phase. Complementary trachoma survey indicators help ensure appropriate and cost-efficient programmatic decisions.