Clinic on Meaningful Modeling of Epidemiological Data

The thirteenth MMED clinic ~ June 17-29, 2024 ~ Muizenberg, Cape Town, South Africa

  1. Projects
  2. Potential Project

Enhancing Trachoma Elimination

Overview

Trachoma is a bacterial infection that causes blindness after repeated infection. Fortunately, the SAFE strategy (surgery, antibiotics, facial cleanliness and environmental hygiene) has shown success in reducing the burden of disease. In particular, the annual distribution of azithromycin to children between 1 and 9 years of age has been shown to be effective in cluster randomized trials.

Given the success of SAFE, the WHO has declared a goal to eliminate trachoma as a public health problem (EGHP) by 2030. The strategy for doing this is based on the measured TF prevalence at the district level. TF is a clinical marker of recent disease caused by inflammation of the eye. TF persists for months even after active infection is cleared - thus it acts as a serological marker of sorts.

For each district where TF is greater than 5%, the WHO recommends annual MDA. The duration depends on the specific value of TF. If TF is < 5% in two prevalence measurements separated by more than 2 years, then the district is declared EGHP.

There are several challenges with the WHO plan. These include:

  • Unknown accuracy of TF prevalence measurements
  • Lack of direct relationship between the effective reproduction number and TF thresholds (and thus lack of clarity on whether the TF < 5% is a robust marker of disease elimination)

Together these challenges promote a concern that 1) districts declared as achieving EGHP may not have R < 1, 2) some districts with TF > 5% may have missed EGHP simply because of surveillance error, and 3) some districts may not achieve control with annual MDA and would benefit from bi-annual MDA instead

The goal of this project will be to evaluate how the age distribution of MDA coverage and clinical markers of disease can be used to address the aforementioned challenges.

Things to consider

  • This group is recommended for:
    • Those interested in neglected tropical diseases
    • Those interested in models that are related to WHO guidelines
  • This group will have the opportunity to engage in any of the following:
    • Simulations of disease surveillance
    • Construction and simulation of simple models of trachoma transmission and natural - history of trachoma
    • Review of relevant literature

Data

  • Line listing data on antibiotic coverage and age prevalence
  • Published data on age-prevalence of clinical markers of trachoma infection (PCR, TF, serology)

Resources

  • https://www.who.int/news-room/fact-sheets/detail/trachoma
  • https://www.trachomaatlas.org/

References

  • https://www.nature.com/articles/s41572-022-00359-5
  • https://www.nature.com/articles/nm0599_572
  • https://doi.org/10.1093/cid/ciab189
  • https://doi.org/10.1093/trstmh/traa170
  • https://www.nature.com/articles/s41467-023-38940-5