Effect of water, sanitation, and hygiene on the prevention of trachoma: a systematic review and meta-analysis

Abstract

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.

Figure 1. Flow chart of publications identified and excluded for this review.

Figure 2. Summary of meta-analyses examining association of WASH exposures with active trachoma (TF/TI) and C. trachomatis infection.

Circles indicate ORs, while the size of circles represents the number of studies included in the meta-analysis (n). Horizontal lines represent 95% CIs.

Figure 3. Publications reporting on the association between trachoma and water, sanitation, and hygiene exposures.

Created using eulerAPE software.

Figure 4. Meta-analysis examining the association of distance to water (≤1 km) with TF/TI.

Circles indicate ORs, while the size of circles represents the sample size. Horizontal lines represent 95% confidence intervals. The diamond and corresponding line represent the random effects pooled OR and 95% confidence interval. *OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 5. Meta-analysis examining the association of distance to water (≤1 km) with C. trachomatis infection.

†OR was calculated using data sent from author.

Figure 6. Meta-analysis examining the association of sanitation access with TF/TI.

*OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 7. Meta-analysis examining the association of sanitation access with C. trachomatis infection.

Results reported separately for ^aThe Gambia population, ^bTanzania population. *OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 8. Meta-analysis examining the association of sanitation use with TF/TI.

*OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 9. Meta-analysis examining the association of clean face with TF/TI.

*OR was adjusted for possible confounders.

Figure 10. Meta-analysis examining the association of no ocular discharge with TF/TI.

*OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 11. Meta-analysis examining the association of no ocular discharge with C. trachomatis infection.

*OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 12. Meta-analysis examining the association of no nasal discharge with TF/TI.

*OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 13. Meta-analysis examining the association of no nasal discharge with C. trachomatis infection.

*OR was adjusted for possible confounders. †OR was calculated using data sent from author.

Figure 14. Meta-analysis examining the association of washing face ≥1 time per day (versus <1 time per day) with TF/TI.

*OR was adjusted for possible confounders.

Figure 15. Meta-analysis examining the association of washing face ≥2 times per day (versus <2× per day) with TF/TI.

*OR was adjusted for possible confounders.

Figure 16. Meta-analysis examining the association of towel use with TF/TI.

*OR was adjusted for possible confounders.

Figure 17. Meta-analysis examining the association of soap use with TF/TI.

*OR was adjusted for possible confounders.

Figure 18. Meta-analysis examining the association of bathing at least once daily with TF/TI.

*OR was adjusted for possible confounders.