부산대학교 도서관

Background: To eliminate trachoma as a public health problem, countries must achieve a district-level prevalence of trachomatous inflammation—follicular (TF) <5% in children ages 1–9 years. Re-emergence of TF could trigger additional rounds of mass drug/antibiotic administration (MDA), so accurate tools for use in surveys assessing trachoma prevalence are essential. Methodology & principal findings: We surveyed 2401 children ages 1–9 years from 50 villages in Kongwa, Tanzania, 2 years post-MDA and 1.5 years after an impact survey found TF <5% in the same villages. Our survey included multiple tools: clinical determination of TF, Cepheid testing for Chlamydia trachomatis infection, and testing for anti-pgp3 antibodies via multiplex bead array. Photographs of the upper tarsal conjunctiva were taken in a subset of children to corroborate the field grades. Overall TF prevalence in 1–9 year olds was 7.1% (95% CI: 5.6%-8.9%), which decreased with age (p = <0.0001). TF prevalence by village was heterogeneous, with 19 villages having TF <5% and 16 villages having TF >10%. There was a strong correlation between field and photo grading of TF (kappa = 0.69; 95% CI: 0.60–0.78) and between TF and infection, with 21.5% of TF-positive children also testing positive for infection, as compared to only 1.6% of TF-negative children (p = 0.0010). Overall seroprevalence was 18.2% (95% CI: 14.8%-22.1%), which increased with age (p = <0.0001). Notably, 1–2 year olds, who were born after the cessation of MDA and theoretically should not have had exposure to C. trachomatis in the absence of transmission, had an average seroprevalence of 6.7%. Conclusions & significance: Field TF prevalence, supported by photographic review and infection data, suggested re-emergence of trachoma in Kongwa. Moreover, seropositivity in the children born after cessation of MDA indicated exposure to C. trachomatis despite a previous survey finding of TF <5%. Examining seropositivity in specific age groups expected to have limited exposure to C. trachomatis can be used to detect re-emergence. Author summary: Trachoma, a chronic conjunctivitis caused by the bacterium Chlamydia trachomatis, is the leading infectious cause of blindness worldwide. To eliminate trachoma as a public health problem, countries must achieve trachomatous inflammation—follicular (TF) prevalence <5% in children ages 1–9 years in each endemic district, as measured by two surveys conducted after cessation of mass drug/antibiotic administration (MDA). An impact survey in Kongwa District 6 months post-MDA found TF <5%. We conducted another survey 2 years post-MDA in the same villages as the impact survey using multiple tools: assessment of TF (including via photographs of the upper tarsal conjunctiva), infection with C. trachomatis, and seropositivity to chlamydial antigen pgp3. We found a TF prevalence of 7.1%, and 21.5% of TF-positive children tested positive for infection (p = <0.0001). Review of photographic images showed good agreement with field grading. Seropositivity was 18.2% and increased with age (p = <0.0001). The youngest children—who were born after the last round of MDA and in theory should not have had much exposure to infection—had a seropositivity of 6.7%, indicating community transmission during the 2 years post-MDA. All tools pointed to re-emergence of trachoma and supported the feasibility of using targeted serologic markers as a robust surveillance tool. [ABSTRACT FROM AUTHOR]