Global Elimination of Trachoma by 2020: A Work in Progress

When this special trachoma issue of Ophthalmic Epidemiology goes to print, there will be only 67 months remaining before 31 December 2020, the deadline set by the World Health Assembly for the global elimination of trachoma as a public health problem. Within the trachoma community, there is considerable optimism about our prospects for achieving the elimination objective on time. Such optimism is based on the premise that we know, or are close to knowing, where and how best to intervene against trachoma, and have, or will garner, the resources and political will to undertake the interventions. Contributions to this special issue underscore the impression that the Alliance for the Global Elimination of Trachoma by 2020 is on track for success, as well as highlighting a few areas where further focused, thoughtful research is required. A pre-requisite for undertaking an efficient disease elimination campaign is a complete understanding of where the disease is endemic. In 2006, the World Health Organization (WHO) published guidelines for population-based surveys to estimate the prevalence of trachoma at the district level; these guidelines were a codification of current practice that was already being widely, if sporadically, applied to map trachoma, producing data on all scales from individual districts to surveys covering entire countries. Several problems remained, however. First, a great deal of effort and energy was needed from individual programs to attract funding for these surveys, so coverage was patchy. Second, the WHO guidelines were generic and only went so far, with the result that they were interpreted differently in different contexts, and some considerations, such as those surrounding data ownership and data handling, were not covered at all. Three good surveys undertaken in that context are published in this issue: although each work is a good example of ophthalmic epidemiology in its own right and has proven valuable for local programming, readers attempting to compare the results may note the variation in sample sizes, size of underlying evaluation units, grader training, field team supervision, age and sex of individuals selected for examination, and types of data collected, all of which reflect WHO’s failure to make its guidelines sufficiently prescriptive or make centralized epidemiological expertise available to support survey planning. Third, although inter-grader agreement exercises against ‘‘gold standard’’ graders were recommended as part of the grader training pathway, there was no process in place for ensuring consistency between ‘‘gold standard’’ graders. The extent to which trained, experienced observers agree on the presence or absence of signs of trachoma is imperfect, probably for multiple reasons that may include the necessity for each observer to interpret the evidence they see against rather incomplete definitions of signs, plus the difficulties inherent in examining the eyelids of small children in remote communities, a process that both examiner and examinee may at times find uncomfortable. Fourth, most protocols were silent on the epidemiological consequences of incomplete enrolment of the intended sample, which probably led to overestimation of the prevalence of trichiasis. The Global Trachoma Mapping Project (GTMP) has tried to address each of these problems, by developing a complete set of systems and processes to fund baseline surveys, facilitate ministries of health to select and train field teams and verify the adequacy of training, decide where mapping is and is not