Surveillance Surveys for Reemergent Trachoma in Formerly Endemic Districts in Nepal From 2 to 10 Years After Mass Drug Administration Cessation

Abstract

IMPORTANCETo verify districts for elimination of blinding trachoma, the World Health Organization requires a population-based surveillance survey for follicular trachoma (TF) and trachomatous trichiasis (TT) 2 years after mass drug administration (MDA) activities have ceased. However, it is unknown if 2 years provides enough time to discover reemergence.OBJECTIVE To determine the prevalence of trachoma from surveys among 4 districts in Nepal (Dailekh, Dang, Surkhet, and Kanchanpur) that had surveillance intervals of 2, 4, 8, and 10 years, respectively, after cessation of MDA. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional surveys were carried out in 2015 and 2016. Data analyses were done from March to September 2016. Among 20 clusters randomly selected from each district, 15 were randomly selected for infection and antibody testing: TF and TT were assessed, conjunctival swabs were tested for chlamydial infection, and blood spots were collected on filter paper to test for antibodies to Chlamydia trachomatis pgp3 using a multiplex bead assay. The study setting was 4 districts previously endemic for trachoma in Nepal. Participants were randomly selected and included 50 children aged 1 to 9 years and 100 adolescents and adults 15 years and older from each of the 20 clusters; this investigation reports on the children. MAIN OUTCOMES AND MEASURESLength of time since the last round of MDA and the prevalence of TF among children aged 1 to 9 years and the prevalence of TT among adolescents and adults 15 years and older. RESULTSOf 3024 children surveyed in the clusters, 48.0% (n = 1452) were female. The mean (SD) age of the children was 5.4 (2.6) years. Eleven cases of TF were found, with a TF prevalence less than 1% in all 4 districts. Three cases of infection were found. Seropositivity for pgp3 antibody varied from 1.4% (95% CI, 0.7-2.6) in the district with a 10-year surveillance interval to 2.5% (95% CI, 1.3-4.5) in the district with a 4-year surveillance interval. Seropositivity increased slightly with age in only one district. The TT prevalence was less than 1 case per 1000 among the total population in all 4 districts after accounting for cases known to the health system and cases with no scarred conjunctiva. CONCLUSIONS AND RELEVANCEThis study found no evidence of reemergence of trachoma up to 10 years after cessation of MDA in 4 districts in children in Nepal. The recommendation for a surveillance survey at 2 years, as proposed by the World Health Organization, is supported by these data. Determining if individuals with TT had scarring or are known to the health system was critical for meeting elimination criteria of blinding trachoma.

Population-Based Prevalence of Chlamydia trachomatis Infection and Antibodies in Four Districts with Varying Levels of Trachoma Endemicity in Amhara, Ethiopia

“…33 These data align with survey-based trachoma antibody data from other lowprevalence or post-endemic settings. 5,6,30,[34][35][36][37] For example, a recent report of surveillance surveys, conducted in six Ghanaian districts with low TF, demonstrated a district range of Pgp3 prevalence between 2.5% and 8.2% and 1.3 seroconversions per 100 children per year. 37 In addition, Pgp3 and CT694 seroprevalence did not increase with age in Woreta town, nor did CT694 seroprevalence increase with age in Alefa, a finding which has been observed in other post-endemic settings.…”

“…37 In addition, Pgp3 and CT694 seroprevalence did not increase with age in Woreta town, nor did CT694 seroprevalence increase with age in Alefa, a finding which has been observed in other post-endemic settings. 35,36 This low seroprevalence in Woreta town and Alefa was most likely due to the lack of C. trachomatis exposure. Serological markers may be particularly well suited to detecting the recrudescence of trachoma transmission.…”

Trachoma prevalence remains below threshold in five districts after stopping mass drug administration: results of five surveillance surveys within a hyperendemic setting in Amhara, Ethiopia

“…Other markers of active trachoma in that district, such as TI (0.9%) and C. trachomatis infection (1.4%), were detectable, suggesting that in areas with low TF, it is still possible for limited chlamydial infection to occur, a finding similar to that demonstrated in earlier surveillance surveys. 7 – 9 Given that the prevalence of TF was close to the 5% threshold in Finot Selam, that the prevalence of latrines appeared to be decreasing and that it is surrounded by a district highly prevalent for trachoma, further surveillance may be warranted to ensure that trachoma control has been sustained.…”

Milestones in the fight to eliminate trachoma

“…The cycle of surveys for impact, stopping the programme and waiting to survey for re‐emergence, then having to re‐start the programme if necessary takes years. Fortunately, many districts that have reached the TF threshold of < 5% have sufficiently reduced transmission to the point where disease does not appear to return …”