Effect of Water, Sanitation, and Hygiene on the Prevention of Trachoma: A Systematic Review and MetaAnalysis

Background Trachoma is the world's leading cause of infectious blindness. The World Health Organization (WHO) has endorsed the SAFE strategy in order to eliminate blindness due to trachoma by 2020 through surgery, antibiotics, facial cleanliness, and environmental improvement. While the S and A components have been widely implemented, evidence and specific targets are lacking for the F and E components, of which water, sanitation, and hygiene (WASH) are critical elements. Data on the impact of WASH on trachoma are needed to support policy and program recommendations. Our objective was to systematically review the literature and conduct meta-analyses where possible to report the effects of WASH conditions on trachoma and identify research gaps. Methods and Findings We systematically searched PubMed, Embase, ISI Web of Knowledge, MedCarib, Lilacs, REPIDISCA, DESASTRES, and African Index Medicus databases through October 27, 2013 with no restrictions on language or year of publication. Studies were eligible for inclusion if they reported a measure of the effect of WASH on trachoma, either active disease indicated by observed signs of trachomatous inflammation or Chlamydia trachomatis infection diagnosed using PCR. We identified 86 studies that reported a measure of the effect of WASH on trachoma. To evaluate study quality, we developed a set of criteria derived from the GRADE methodology. Publication bias was assessed using funnel plots. If three or more studies reported measures of effect for a comparable WASH exposure and trachoma outcome, we conducted a random-effects meta-analysis. We conducted 15 meta-analyses for specific exposure-outcome pairs. Access to sanitation was associated with lower trachoma as measured by the presence of trachomatous inflammation-follicular or trachomatous inflammation-intense (TF/TI) (odds ratio [OR] 0.85, 95% CI 0.75-0.95) and C. trachomatis infection (OR 0.67, 95% CI 0.55-0.78). Having a clean face was significantly associated with reduced odds of TF/TI (OR 0.42, 95% CI 0.32-0.52), as were facial cleanliness indicators lack of ocular discharge (OR 0.42, 95% CI 0.23-0.61) and lack of nasal discharge (OR 0.62, 95% CI 0.52-0.72). Facial cleanliness indicators were also associated with reduced odds of C. trachomatis infection: lack of ocular discharge (OR 0.40, 95% CI 0.31-0.49) and lack of nasal discharge (OR 0.56, 95% CI 0.37-0.76). Other hygiene factors found to be significantly associated with reduced TF/TI included face washing at least once daily (OR 0.76, 95% CI 0.57-0.96), face washing at least twice daily (OR 0.85, 95% CI 0.80-0.90), soap use (OR 0.76, 95% CI 0.59-0.93), towel use (OR 0.65, 95% CI 0.53-0.78), and daily bathing practices (OR 0.76, 95% CI 0.53-0.99). Living within 1 km of a water source was not found to be significantly associated with TF/TI or C. trachomatis infection, and the use of sanitation facilities was not found to be significantly associated with TF/TI. Conclusions We found strong evidence to support F and E components of the SAFE strategy. Though limitations included moderate to high heterogenity, low study quality, and the lack of standard definitions, these findings support the importance of WASH in trachoma elimination strategies and the need for the development of standardized approaches to measuring WASH in trachoma control programs.Please see later in the article for the Editors' Summary Editors' Summary Background Trachoma is a bacterial eye infection, which if left untreated may lead to irreversible blindness. Repeated infections over many years cause scarring on the eyelid, making the eyelashes turn inward. This causes pain and damage to the cornea at the front of the eye, which eventually leads to loss of vision. The disease is most common in rural areas in low-income countries, specifically sub-Saharan Africa. It spreads easily through contact with the discharge from an infected eye or nose, by hands, or by flies landing on the face. Women and children are more often affected than men. Trachoma is the world's leading cause of preventable blindness. A global alliance, led by The World Health Organization, is aiming to eliminate trachoma by 2020 by adopting the SAFE strategy. There are four components of this strategy. Two relate to treating the diseasesurgery and antibiotics. The other two components relate to long-term prevention by promoting facial cleanliness and environmental changes (for example improving access to water and sanitation or reducing the breeding grounds for flies). Why Was This Study Done? The SAFE approach has been very successful in reducing the number of people with trachoma from 84 million in 2003 to 21.4 million in 2012. However, it is widely recognized that efforts need to be scaled up to reach the 2020 goal. Furthermore, if current improvements are to be sustained, then more attention needs to be given to the F and E elements and effective prevention. This study aimed to identify the most effective ways to improve hygiene, sanitation, and access to water for better trachoma control, and to find better ways of monitoring progress. The overall goal was to summarize the evidence in order to devise strategic and cost-effective approaches to trachoma prevention. What Did the Researchers Do and Find? The researchers conducted a systematic review, which involved first identifying and then assessing the quality of all of the research published on this topic. They then carried out a statistical analysis of the combined data from these studies, with the aim of drawing more robust conclusions (a meta-analysis). The analysis involved 15 different water, sanitation, and hygiene exposures (either hardware or practices, as determined by what was available in the literature) to determine which had the biggest impact on reducing the levels of trachoma. Most of the data came from studies carried out in Africa. The findings suggested that 11 of these exposures made a significant difference to the risk of infection or clinical symptoms of the disease. Improving personal hygiene had the greatest impact. Effective measures included face washing once or twice a day, using soap, using a towel, and daily bathing. Similarly, access to a sanitation facility, rather than open ground, also had a positive impact. The researchers also analyzed the data relating to water access. However, the studies so far have not yet measured this in a way that addresses the issues relevant to trachoma infection. Most studies have looked at whether the distance from a water source has an impact (and it seems it does not), whereas it may be more important to assess whether people have access to clean water or to enough water to wash. Many of these analyses require additional research to further clarify the impact of individual water, sanitation, and hygiene exposure on disease. What Do These Findings Mean? Overall, the results support that notion that water, sanitation, and hygiene are important components of an integrated strategy to control trachoma. Based on the research available to date, the two most effective ways are face washing and having access to a household-level sanitation facility, typically a simple pit latrine. The findings also point to ways in which current policy could be improved. Firstly, public health guidance should be placing greater emphasis on keeping the face clean. Current advice tends to focus on washing with clean water, but use of soap appears more effective. There are also opportunities for organizations to collaborate in this area. For example, organizations focusing on the prevention of diarrhea in children, which promote handwashing, could at the same time campaign for face washing to reduce transmission of trachoma. The second policy area to target is access to good quality sanitation. Such policy initiatives need to be better resourced in countries where trachoma is a problem. For example, although sub-Saharan Africa has the world's highest burden of trachoma, more than 50% of households there still do not have access to any sanitation facility. There were a number of limitations to this study, which may affect the strength of the conclusions. The researchers found that many studies on this topic were observational, meaning that they did not assess an intervention and employ a control group, thus they are of limited rigor for assessing the impact of a water, sanitation, and hygiene intervention on trachoma. There was also a lot of variation in the way that different studies had defined and measured improvements to water, sanitation, and hygiene access. This made it difficult to make comparisons. Standard methods and indicators need to be developed for this purpose. The study also highlighted gaps in the research. More work is required to determine precisely what is needed in terms of access to water to reduce the incidence of trachoma. Similarly, in terms of improving sanitation, it is still unclear whether ensuring every household has a simple, onsite facility would be more effective than providing clean communal facilities. The potential role of schools in promoting relevant public health measures also needs investigation. Additional Information Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001605. WHO provides information on trachoma (in several languages) The US Centers for Disease Control and Prevention provide information on trachoma International Trachoma Initiative is dedicated to the goal of elimination of blinding trachoma The Carter Center: Trachoma Control Program has a Trachoma Health Education Materials Library WASHNTD has an online manual resource for NTDs for WASH policy and programming