The utility of serology for elimination surveillance of trachoma

Abstract

Robust surveillance methods are needed for trachoma control and recrudescence monitoring, but existing methods have limitations. Here, we analyse data from nine trachoma-endemic populations and provide operational thresholds for interpretation of serological data in low-transmission and post-elimination settings. Analyses with sero-catalytic and antibody acquisition models provide insights into transmission history within each population. To accurately estimate sero-conversion rates (SCR) for trachoma in populations with high-seroprevalence in adults, the model accounts for secondary exposure to Chlamydia trachomatis due to urogenital infection. We estimate the population half-life of sero-reversion for anti-Pgp3 antibodies to be 26 (95% credible interval (CrI): 21–34) years. We show SCRs below 0.015 (95% confidence interval (CI): 0.0–0.049) per year correspond to a prevalence of trachomatous inflammation—follicular below 5%, the current threshold for elimination of active trachoma as a public health problem. As global trachoma prevalence declines, we may need cross-sectional serological survey data to inform programmatic decisions.

Ocular Chlamydia trachomatis infection, anti-Pgp3 antibodies and conjunctival scarring in Vanuatu and Tarawa, Kiribati before antibiotic treatment for trachoma

“…Seroconversion rates (SCRs) in children aged 1-9 years were estimated from age-specific seroprevalence curves using a simple reversible catalytic model (RCM) as described elsewhere, using parameters as recommended by those authors. 31 Based on the epidemiological context, we used a RCM in which the SCR was assumed to be constant for all individuals aged between 1 and 9 (20) and Kiribati (21). TF estimates were adjusted for age and gender in one-year age bands and TT estimates were adjusted for age and gender in five-year age bands.CI, confidence interval; EU, evaluation unit; TF, trachomatous inflammation-follicular; TI, trachomatous inflammation-intense; TT, trachomatous trichiasis.…”

“…Because of the low seroprevalence, the seroreversion rate (SRR) was assumed to be 0 events per person per year, as demonstrated for seroepidemiological studies of malaria. 32 The model deployed corresponded to scenario 1 version 2 of the scenarios tested by Pinsent et al 31 Proportions were compared using Fisher's Exact Test. For small, non-parametric group comparisons (such as comparing the load of infection in those with or without TF in Vanuatu), Mann Whitney U tests were used.…”

Seroprevalence of antibodies against Chlamydia trachomatis and enteropathogens and distance to the nearest water source among young children in the Amhara Region of Ethiopia

“…Antibody responses may be an informative and efficient approach to simultaneously measure enteropathogen and C. trachomatis exposure [11][12][13]. Unlike pathogen detection from stool samples or conjunctival swabs, antibody response integrates information over time, offering a longer window to identify exposed individuals.…”

Fine-scale heterogeneity in Schistosoma mansoni force of infection measured through antibody response

“…enteric pathogens. [11][12][13] Serological testing is growing in use to monitor progress of many neglected tropical disease control programs such as trachoma, 14 lymphatic filariasis, 15 and onchocerciasis. 16 The near-term potential for integrated, population-based serologic surveillance with multiplex assays creates an opportunity for more frequent, broader monitoring of diseases with well-validated serological assays and methods to translate antibody response into measures of transmission.…”