preprint · medRxiv
This study evaluated modified mass drug administration strategies for trachoma in four districts in northern Tanzania between 2022 and 2023. Researchers monitored sentinel sites in districts receiving either more frequent than annual administration or standard annual rounds. Children aged one to nine years were assessed for clinical signs of active trachoma, alongside testing of conjunctival swabs and dried blood spots for molecular infection and serological markers. Although ocular Chlamydia trachomatis infection prevalence declined over time, clinical inflammation prevalence and antibody measures showed no change during the follow-up period. Infection was more common among younger children, girls, and households facing longer water collection times, while greater distance to health facilities was linked to rising community infection rates. The evidence supports tailored drug distribution schedules and enhanced monitoring across the target districts.
Trachoma remains a persistent public health problem in several regions despite long-term control efforts. By demonstrating that molecular testing reveals infection declines before clinical signs change, this research offers public health programmes a clearer framework for adjusting drug administration schedules. It also highlights the vital role of local infrastructure, such as water access and proximity to clinics, in controlling infectious eye disease.
The abstract outlines an applied public health monitoring strategy rather than a commercial product. The findings could inform public sector health agencies, non-governmental organisations, and diagnostic service providers integrating molecular and serological assays into disease surveillance programmes. This represents field-tested operational research intended for policy decision-making and post-elimination validation, rather than a direct commercialisation pathway.
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Abstract Background Since the first azithromycin mass drug administration (MDA) in 1999, Tanzania has made remarkable progress towards trachoma elimination. Yet several districts have seen prevalence of trachomatous inflammation—follicular (TF) in children aged 1–9 years remain or rebound ≥5%. From 2022, Tanzania modified MDA implementation in these districts to either more frequent than annual (MFTA) or two additional annual MDA. Conducted in four districts receiving MFTA MDA (Longido and Ngorongoro) or annual MDA (Monduli and Simanjiro), our sentinel site monitoring study aimed to: 1) estimate TF prevalence, anti-Pgp3 serology measures, and ocular Chlamydia trachomatis (Ct) infection prevalence among children aged 1– 9 years; 2) characterize ocular Ct infection prevalence over time; and, 3) identify factors associated with ocular Ct infection and increasing community Ct infection prevalence. Methods Ten sentinel sites, with the highest prevalence of active trachoma, were selected per district. At each site, during three monitoring rounds just before MDA in June 2022, January 2023, and October 2023, 50 children aged 1–9 years were examined for trachoma clinical signs and had conjunctival swab and dried blood spot samples taken. Results Though ocular Ct infection prevalence declined, there was no change in TF prevalence, Pgp3 seroprevalence, or Pgp3 seroconversion during follow-up. Younger age, female gender, and more time required to collect water were associated with higher infection prevalence, and greater distance to a health facility was associated with increasing community infection prevalence. Discussion Findings support shift from annual to MFTA MDA in Monduli, continued MFTA MDA in Longido and Ngorongoro, and “Wait and Watch” in Simanjiro. Annual monitoring and environmental improvement will be valuable alongside further investigation of relationships between water and sanitation conditions and ocular Ct infection in this setting. Prevalence surveys with additional molecular and serological testing are recommended in the four districts at the end of the MDA cycle. What is already known on this topic Persistent and recrudescent active trachoma is recognized as a late-stage challenge that prevents several countries from attaining elimination of trachoma as a public health problem. Evidence is lacking on how to optimally modify and monitor implementation of the surgery, antibiotics, facial cleanliness, and environmental change (SAFE) strategy in settings with persistent and recrudescent active trachoma. What this study adds We selected sentinel sites with greatest likelihood of trachoma transmission in districts with persistent and recrudescent active trachoma to monitor changes over time of clinical, serological, and molecular measures of trachoma during modified mass drug administration (MDA). We found fewer ocular Chlamydia trachomatis infections following MDA, though TF and serological measures were slow to respond to intervention. We observed an association between water availability and individual infection and distance to a health facility with increasing community infection prevalence. How this study might affect research, practice, or policy Our study shows that enhanced monitoring using molecular and serological measures is useful for tailoring implementation of control interventions, like MDA. Sentinel site monitoring could be undertaken to help disease control programs decide whether to undertake substantive trachoma prevalence surveys and used for sero-surveillance for trachoma, once elimination has been validated.
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DOI: 10.1101/2025.06.03.25328347
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