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Background: Trachoma recrudescence after elimination as a public health problem has been reached is a concern for control programs globally. Programs typically conduct district-level trachoma surveillance surveys (TSS) ≥ 2 years after the elimination threshold is achieved to determine whether the prevalence of trachomatous inflammation-follicular (TF) among children ages 1 to 9 years remains <5%. Many TSS are resulting in a TF prevalence ≥5%. Once a district returns to TF ≥5%, a program typically restarts costly mass drug administration (MDA) campaigns and surveys at least twice, for impact and another TSS. In Amhara, Ethiopia, most TSS which result in a TF ≥5% have a prevalence close to 5%, making it difficult to determine whether the result is due to true recrudescence or to statistical variability. This study's aim was to monitor recrudescence within Amhara by waiting to restart MDA within 2 districts with a TF prevalence ≥5% at TSS, Metema = 5.2% and Woreta Town = 5.1%. The districts were resurveyed 1 year later using traditional and alternative indicators, such as measures of infection and serology, a "wait and watch" approach. Methods/Principal findings: These post-surveillance surveys, conducted in 2021, were multi-stage cluster surveys whereby certified graders assessed trachoma signs. Children ages 1 to 9 years provided a dried blood spot and children ages 1 to 5 years provided a conjunctival swab. TF prevalence in Metema and Woreta Town were 3.6% (95% Confidence Interval [CI]:1.4–6.4) and 2.5% (95% CI:0.8–4.5) respectively. Infection prevalence was 1.2% in Woreta Town and 0% in Metema. Seroconversion rates to Pgp3 in Metema and Woreta Town were 0.4 (95% CI:0.2–0.7) seroconversions per 100 child-years and 0.9 (95% CI:0.6–1.5) respectively. Conclusions/Significance: Both study districts had a TF prevalence <5% with low levels of Chlamydia trachomatis infection and transmission, and thus MDA interventions are no longer warranted. The wait and watch approach represents a surveillance strategy which could lead to fewer MDA campaigns and surveys and thus cost savings with reduced antibiotic usage. Author summary: The return of trachoma transmission after elimination as a public health problem has been reached is a concern for control programs globally. Currently, many district-level trachoma surveillance surveys (conducted ≥2 years since elimination threshold has been reached) are resulting in a prevalence above the established threshold. Once a district returns above threshold, a program typically restarts costly mass drug administration campaigns and conducts more surveys. This study's aim was to monitor recrudescence through a "wait and watch" approach within Amhara, Ethiopia. This entailed waiting to restart mass drug administration within 2 districts with trachoma prevalence above but close to the threshold at surveillance survey, then surveying the districts 1 year later using traditional and alternative indicators. These post-surveillance surveys assessed traditional trachoma signs, and additionally, children provided a dried blood spot for serology outcomes and a conjunctival swab for infection. The results of the study demonstrated that both districts had a prevalence below threshold with low levels of infection and serological evidence of transmission, and thus mass drug administration interventions are no longer warranted. The wait and watch approach represents a surveillance strategy that could lead to fewer surveys and mass drug administration campaigns and thus savings in programmatic costs with reduced usage of antibiotics. [ABSTRACT FROM AUTHOR]

Sudan is endemic for multiple neglected tropical diseases, including trachoma, onchocerciasis (OV), lymphatic filariasis (LF), and schistosomiasis (SCH). In 2019, dried blood spot samples were collected for a baseline trachoma serosurvey in three localities (El Seraif, Kotom, and Saraf Omrah) in North Darfur State. None were classified previously as OV- or LF-endemic, although low levels of SCH had been identified in all three. Approximately 30 households from 25 communities in each locality were selected by multistage cluster random sampling. Collections of DBSs were analyzed by multiplex bead assay for antibodies to multiple pathogens. This paper presents data on OV (Ov16), LF (Wb123, Bm14, Bm33), and SCH (soluble egg antigen [SEA], Sm25) antibodies among 8,322 individuals from 2,119 households. The survey-adjusted seroprevalence estimates for Ov16 were <0.3% in all localities. Lymphatic filariasis-antigen seroprevalences were discordant. Seroprevalence estimates ranged from 4.6-6.0% (Wb123), 0.99-1.4% (Bm14), and 29.2-33.3% (Bm33). Schistosomiasis seroprevalence estimates among school-aged children ranged from 2.7-8.0% (SEA) and 10.9-15.6% (Sm25). Ov16 seropositivity was low and supported the localities' classification as nonendemic. The results suggested LF exposure, but discordance between antigens, challenges defining seropositivity thresholds, and the absence of programmatic guidance based on antibody serology alone for Wuchereria bancrofti indicate a need for remapping surveys to confirm transmission. Schistosomiasis antibody levels were high enough to warrant further mapping to guide treatment decisions. The lack of gold standards limited interpretation of results, particularly for LF, but in resource-challenged areas, integrated serological surveillance offers the possibility of efficient monitoring of exposure to multiple diseases.

After years of programmatic inaccessibility, in 2019-2020 the Sudan Federal Ministry of Health Trachoma Control Program conducted population-based trachoma surveys in three localities (districts) in North Darfur state, Sudan. These baseline surveys were to determine the prevalence of trachomatous inflammation-follicular (TF) among children aged 1-9 years and to further use serological markers to understand the historical trachoma burden within this mass drug administration (MDA)-naive area. Trained and certified graders collected trachoma clinical data, and trained nurses collected dried blood spot (DBS) samples. The DBSs were assayed on a multiplex bead array for antibody responses to the Chlamydia trachomatis antigens Pgp3 and CT694. Across the three localities, 3,613 individuals aged 1-9 years and 3,542 individuals aged ≥15 years were examined for clinical signs, and 8,322 DBSs were collected. The prevalence of TF among children aged 1-9 years was endemic (≥5%) in two localities (El Seraif, 15.6%, and Saraf Omrah, 11.0%) and below the TF elimination threshold (<5%) in the third (Kotom, 1.4%). The Pgp3 seroprevalence among children aged 1-9 years was 34.1% in El Seraif, 35.0% in Saraf Omrah, and 11.0% in Kotom. Locality prevalence results were similar for Pgp3 and CT694. Seroprevalence increased with age in all three localities. Serological data collected within these surveys demonstrate that all three localities have had a long history of exposure to Chlamydia trachomatis and that two of the three localities require MDA to reach elimination as a public health problem threshold.