Trachoma Control: 14 Years Later

Trachoma, a chronic conjunctivitis caused by repeated episodes of Chlamydia trachomatis, is still the leading infectious cause of blindness in the world. However, it has dropped from being the second or third leading cause of blindness overall to now fifth.1 The target for elimination of blinding trachoma is the year 2020. In 2001, Ophthalmic Epidemiology published a special issue on trachoma, one of the most cited issues in its publication history. We were fortunate enough to be asked to write a joint editorial for that issue. In 2015 this second special issue is being published; it will provide evidence from groundbreaking work to inform the global initiative for trachoma elimination. The comparison of articles indicating where we were in 2001 and what we have learned in the ensuing 14 years shows how far the field of trachoma, and trachoma research, has come.

Two of the original articles in 2001 described experiences using trachoma rapid assessment (TRA) methodology.2^,3 This methodology was developed by the World Health Organization (WHO) to provide trachoma endemic countries a way to prioritize districts where trachoma programs might start. Unfortunately, the methodology has been misused to generate prevalence data for an area, which was inappropriate because the design of TRA was to target suspected “worse areas” of a district and do surveys there, thus providing some basis for prioritizing scarce (at that time) resources. Understandably, since TRA was not representative of a district, it provided no baseline on which to gauge progress from program implementation. The TRA approach was replaced by proper population-based prevalence surveys, which became the gold standard for mapping and impact assessment. In this issue, the Global Trachoma Mapping Project is described,4, 5 the largest mapping project of its kind in the world, which uses population-based surveys to provide data to assist countries in the decision to embark on trachoma control for a district, and serves as the baseline data against which to measure progress. The challenge of deciding where to map and where not to map remains, however; furthermore, some countries ask “do we need to map every district in my country?” This is a particularly acute issue for some countries, as one article from Guatemala in this issue6 highlights. Trachoma foci in countries like Guatemala have raised the issue of potentially having to map surrounding districts in the absence of any data. Is the TRA the best tool for this purpose? Fourteen years later the answer is not clear and using a targeted approach to indicate where mapping may be needed is appealing.

In the 1980s and 1990s, large cross-sectional prevalence surveys demonstrated the rise in the percentage of persons, largely women, with scarring with increasing age. The increase was felt to be related to increasing numbers of episodes of infection. In 2001, two studies provided strong evidence that scarring could be the result of persistent infection and trachoma. One study in women provided genotype data for the persistence of infection in women, many of whom had no obvious household source of infection.7 The other provided the first evidence for progression of trachoma to scarring in a cohort of children with the finding that children who seem unable to clear trachoma, about 10% of this cohort, had rapid progression to scarring.8 Numerous papers have since explored the contribution of genetic variation to risk of scarring trachoma, and protective and pathogenic immune responses to infection. To date, we have learned much about the personal factors that contribute to risk of scarring, but we are unable to intervene specifically in the scarring pathways to decrease the risk of trichiasis. The best way to ensure that scarring does not develop into trichiasis is to prevent scarring itself through the prevention of active trachoma in children.

Trichiasis, the in-turning of eyelashes that rub on the globe due to scarring, is the vision-threatening sequelae of multiple bouts of trachoma. As part of the achievement of elimination of blinding trachoma, a country must show that it has reduced trachomatous trichiasis to less than 1/1000 population at district level, these remaining cases being “unknown to the health care system,” meaning they have not been offered surgery before, or have refused surgery, or be recurrent cases following surgery. Three papers in the 2001 issue dealt with issues around trichiasis; the first, in Oman, evaluated the significant problem of recurrent trichiasis after surgery,9 the second reported the barriers of uptake to lid surgery in a community in Nigeria,10 and the third outlined the value of trichiasis surgery in the Gambia.11 In many ways, these articles from different locales are linked. For the patient, trichiasis that recurs post-surgery means a risk that can be devastating and can undermine community confidence in the trachoma program as a whole. The slow scale up in trichiasis surgical services between 2001 and 2012 can partly be blamed on poor quality of service. In the 14 years since these articles appeared, much has been learned about trichiasis surgical services, summarized during the Global Trichiasis Scientific Meeting in Moshi, Tanzania in 2012.12 First and foremost, the trachoma community has a better appreciation of the necessity for adequate training and certification of trichiasis surgeons. The recent publication of the second edition of the WHO Manual for Trichiasis Surgery,13 and publications from the International Coalition for Trachoma Control (www.trachomacoalition.org), now include alternative surgical methods, cover the use of clamps designed to improve surgical experience, outline the process for certification, as well as how to organize trichiasis surgical outreach programs, training of trichiasis case finders, and training the trainers of trichiasis surgeons. Improving quality of care improves patient perspectives of their outcome, as noted by a study in this issue.14 Linking improved quality with improved productivity of trichiasis surgeons seems self-evident but is difficult to measure. Nevertheless, as one paper15 in this issue notes, current trichiasis manpower-related activities are unlikely to enable countries to achieve their elimination targets, further evidence for the need to re-think how effective and efficient trichiasis services are to be provided. As programs near their elimination targets the challenges of case detection and efficient use of human resources will emerge and further research that focuses on ways to identify and refer cases within communities while maintaining high quality of care will be needed.

Trachoma research continues to provide insights into disease pathogenesis, the magnitude and extent of the global burden, the factors that increase the risk of trachoma within communities and families, interventions that can reduce that risk, and the most efficient and effective ways of implementing trachoma elimination. We have only 5 more years in which to reach our goal of elimination by 2020, and even fewer years to publish results that can impact that timeline. Prioritizing our research to be certain it has the potential for high impact is ever more urgent.

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.