Children Without Worms receives funding from Johnson & Johnson and GlaxoSmithKline for its programs to control soil-transmitted helminthiasis.
Conceived and designed the experiments: SO DA DH MCF. Performed the experiments: MS CM. Analyzed the data: MS SO MCF. Wrote the first draft of the manuscript: MS SO MCF. Contributed to the writing of the manuscript: MS SO MCF DA DH.
Matthew Freeman and colleagues identified 86 individual studies that reported a measure of the effect of water, sanitation, and hygiene on trachoma and conducted 15 meta-analyses for specific exposure-outcome pairs.
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.
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
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.
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 disease—“surgery” 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).
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.
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.
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.
Please access these Web sites via the online version of this summary at
WHO provides information on
The US Centers for Disease Control and Prevention provide
International Trachoma Initiative is dedicated to the goal of elimination of
The Carter Center: Trachoma Control Program has a
WASHNTD has an
Trachoma is the world's leading cause of infectious blindness, responsible for visual impairment of an estimated 2.2 million people, of whom 1.2 million are irreversibly blind
Intensive effort since the founding of the Global Alliance for Elimination of Blinding Trachoma by 2020 (GET 2020) has led to considerable reduction in the global burden of trachoma from 84 million cases of active trachoma in 2003 to 21.4 million in 2012
The World Health Assembly (WHA) in resolution 51.11 has called for the elimination of blinding trachoma by 2020
There is a need for increased intersectoral collaboration between neglected tropical disease (NTD) and water, sanitation, and hygiene (WASH) sectors, as well as for increased financial resources for WASH interventions in the context of trachoma control
We conducted a systematic review and meta-analysis to quantify the relationship between WASH exposures and
We performed a systematic review and meta-analysis of the literature to address the effects of WASH exposures on infection and clinical signs of trachoma. We systematically searched PubMed, Embase, ISI Web of Knowledge, MedCarib, Lilacs, REPIDISCA, DESASTRES, and African Index Medicus databases with no restrictions on language or year of publication. Our search was performed through October 27, 2013 with no restriction of start date. We employed a broad set of search terms, pairing the term [trachom*] with the following WASH-related keywords: [clean* fac*], [environment*], [excre*], [face washing], [facewashing], [faec*], [fec*], [hand washing], [handwashing], [hygiene], [latrine*], [sanitation], [toilet*], [towel*], [wash cloth*], [waste], and [water]. In addition, we examined seven previous reviews pertaining to trachoma and some aspect of WASH
Studies were included in the systematic review only if they measured WASH exposure, trachoma infection, and attempted to quantify the association between a WASH exposure, condition, or risk factor on trachoma. All study types were eligible if they met these inclusion criteria, and we employed no additional exclusion criteria in our approach. If an article was considered relevant, but data were not available in the format needed for our meta-analysis, the corresponding authors were contacted by e-mail and asked to supply the relevant data. We conducted meta-analyses for specific exposure-outcome relationships based on available data. Meta-analyses were conducted in adherence to the PRISMA statement (
Articles were selected for inclusion using a two-step review process. First, the titles and abstracts of all identified studies were examined, and studies that failed to meet the inclusion criteria after this step were excluded. Second, two reviewers (MES and CM) independently examined the full text of potentially relevant articles using a standard protocol developed by MES and MCF. In the event of disagreement regarding the eligibility of a study during this phase, the opinion of a third reviewer (MCF) was sought, and the parameters of the study's inclusion were discussed until consensus was reached.
Once a set of eligible studies was agreed upon, relevant data were extracted from each study by MES using a standard protocol. To ensure extraction reliability, CM also extracted data from a subset of 10% of identified studies, and no discrepancies were found. Data extracted included a brief description of the study (e.g., study design, setting, year, and sample size), details of the study population, and measures of trachoma. Measures of trachoma included
WASH Exposure | Article Count |
Distance to water |
36 |
Type of water source | 19 |
Access to water | 7 |
Quantity used for washing | 6 |
Total quantity of water | 5 |
Sanitation access |
38 |
Sanitation use |
8 |
Sanitation type | 6 |
Sanitation maintenance | 3 |
Sanitation education | 3 |
Facial cleanliness |
33 |
Face-washing frequency |
19 |
Ocular discharge |
14 |
Nasal discharge |
13 |
Soap use |
7 |
Hygiene education | 6 |
Towel use |
6 |
Bathing frequency |
5 |
Nose wiping practices | 5 |
Towel sharing | 3 |
Exposures with sufficient number of comparable measures of effect to warrant a meta-analysis.
In order to determine the quality of identified studies, we developed a set of criteria derived from the GRADE methodology
We conducted meta-analyses for all WASH-related exposures for which three or more studies reported comparable odds ratios (ORs) for the same WASH–trachoma association (i.e., ORs describing the effect of similarly defined exposures on the same measure of trachoma). All ORs used in meta-analyses reflected the results of cross-sectional risk factor analyses. WASH conditions included sanitation access, sanitation use, distance to water of less than 1 km, clean face, lack of ocular discharge, lack of nasal discharge, washing face at least once daily, washing face at least twice daily, bathing at least once daily, towel use, and soap use. Data were stratified by clinically relevant trachoma measures:
We used Microsoft Excel (Microsoft Corporation) to conduct meta-analyses and to develop forest plots
Our initial search yielded 5,425 publications (
Circles indicate ORs, while the size of circles represents the number of studies included in the meta-analysis (
Reference | Study Design and Setting | Year | Study Population | WASH Components | Type of Trachoma Measure | Diagnostic Approach | Data Obtained | Assessment Method | ||
W | S | H | ||||||||
Alemu et al. |
Intervention study in Dalocha District, Central Ethiopia | 1998–2002 | 644 children between aged 1–9 years | Access to water | TF/TI | Clinical exam | Change in prevalence | Q | — | — |
Assaad et al. |
Descriptive study on Island of Taiwan | 1960–1961 | Pre-WWII Chinese immigrants in sample units of approximately 125 people | Distance to water, type of water source | TF/TI | Clinical exam | Age-standardized trachoma rate | Q, O | — | — |
Cairncross et al. |
Descriptive study in two villages in the Mueda Plateau in Northern Mozambique | 1983 | 100 households in each village | Water access | Any trachoma sign | Clinical exam | X2 | O | — | — |
Caligaris et al. |
Descriptive study in nine day care centers of Bela Vista district in Sao Paulo, Brazil | 1995 | All preschool students attending day care centers, aged 0–7 years | Water access | TF/TI, |
DFA | OR | Q | — | — |
Chumbley et al. |
Descriptive study in West Bank and Gaza Strip | 1982– 1983 | 9,058 Palestinian Arabs | Water access | Any trachoma sign | Clinical exam | 2×2 (from bar chart) | O | — | — |
Hoeschmann et al. |
Descriptive study in Malawi | 1999 | 1,363 adults >50 years, 2,251 children aged 1–6 years | Distance to water | TF, TI, TF/TI | Clinical exam | OR | Q | — | — |
Marshall et al. |
Descriptive study in Naha, Japan | 1962 | 58,480 primary and junior high students | Type of water source | TF/TI | Clinical exam | Change in prevalence | O | — | — |
Polack et al. |
Descriptive study in sub-village of Kahe Mpya in Rombo District, northern Tanzania | 2000 | All consenting residents ( |
Distance to water | TF/TI, |
Clinical exam, PCR | OR | Q, O | — | — |
West et al. |
Descriptive study in 20 villages in Kongwa sub-district, Dodoma region, Tanzania | n.s. | All preschool-age children and caretakers in randomly selected sub-districts | Water access | TF/TI | Clinical exam | Prevalence ratio | O | — | — |
H, hygiene; O, observed directly; Q, questionnaire; S, sanitation; W, water.
Reference | Study Design and Setting | Year | Study Population | WASH Components | Type of Trachoma Measure | Diagnostic Approach | Data Obtained | Assessment Method | ||
W | S | H | ||||||||
Courtright et al. |
Descriptive study in the hamlet of Kafr in the Egyptian Nile Delta | 1987 | 225 children aged 1–5 years from 96 households | Sanitation presence | TI | Clinical exam | OR | — | Q, O | — |
Emerson et al. |
Intervention study in rural communities in the North Bank and Central River divisions of The Gambia | 1999–2001 | All residents over 4 months of age ( |
Sanitation presence | TF/TI | Clinical exam | Change in prevalence | — | O | — |
Haile et al. |
Descriptive study following an antibiotic and sanitation promotion intervention in twelve communities in Amhara region of Ethiopia. | 2006–2008 | 50 randomly selected sentinel children aged 0–9 years from each of the 12 communities. | Sanitation use | TF/TI, |
Clinical exam, PCR | Difference in prevalence | — | O | — |
Montgomery et al. |
Descriptive study in seven rural Tanzanian communities | 2007 | 594 households (92 cases, 502 controls) | Sanitation type, sanitation use | TF/TI | Clinical exam | OR | — | Q O | — |
Reilly et al. |
Descriptive study in Marajo Island in Para State, Brazil | 2004 | 180 adults (>15 years) and 187 children (0–15 years) | Sanitation presence | Any trachoma sign | Clinical exam | Regression coefficient | — | Q, O | — |
Stoller et al. |
Intervention study in 24 communities in Amhara state, Ethiopia | 2006–2008 | 60 randomly selected children aged 0–9 years from each sentinel site | Sanitation presence | TF/TI, |
Clinical exam, PCR | Change in prevalence | — | O | — |
H, hygiene; O, observed directly; Q, questionnaire; S, sanitation; W, water.
Reference | Study Design and Setting | Year | Study Population | WASH Components | Type of Trachoma Measure | Diagnostic Approach | Data Obtained | Assessment Method | ||
W | S | H | ||||||||
Alene et al. |
Descriptive study in Jangua Mariam, North Western Ethiopia | 1998 | 1,718 individuals of all age groups in 414 households | Face-washing frequency | Any trachoma sign | Clinical exam | OR | — | — | Q |
De Sole et al. |
Intervention study in a primary school in Metahara, Ethiopia | 1984–1985 | 239 children aged <10 years at primary school | Hygiene education | TF/TI | Clinical exam | Change in prevalence | — | — | O |
Gower et al. |
Descriptive study in Maindi and Kahe Mpya, Tanzania and a cluster of 14 small villages in Jareng, Upper Saloum District, The Gambia | n.s. | 1,128 children aged <9 years | Nasal discharge | TF, TF/TI | Clinical exam | 2×2 | — | — | O |
Guraksin et al. |
Descriptive study in Koprukoy and Pasinler districts in Turkey | 1993–1994 | 6,386 individuals aged <30 years, 2,220 individuals aged >30 years | Face-washing frequency, soap use, towel sharing | TF/TI | Clinical exam | X2 | — | — | Q |
Hagi et al. |
Descriptive study in 203 villages in Mali | 1996–1997 | 14,627 children aged <10 years in 2,269 randomly selected households | Facial cleanliness, flies on face, towel use | TF/TI | Clinical exam | OR | — | — | Q, O |
Hall et al. |
Descriptive study in Ethiopia | n.s. | 7,572 school-children aged 7–17 years | Face-washing frequency | Any trachoma sign | Clinical exam | OR | — | — | Q |
Khanduja et al. |
Descriptive study in10 rural villages in Haryana, India | 2006 | 1,000 children aged 1–9 years | Facial cleanliness | TF/TI, |
Clinical exam, PCR | OR | — | — | O |
King et al. |
Descriptive study in one Malian and two Tanzanian villages | 2006 | All 424 children aged 1–5 years | Ocular discharge | TF/TI | Clinical exam | OR | — | — | O |
Koizumi et al. |
Descriptive study in 10 Regional Health Administration Areas (RHAA) in Sao Paulo, Brazil | 1999 | 27,091 public preschool and school children aged 4–14 years | Facial cleanliness | Any trachoma sign | Clinical exam | 2×2 | — | — | O |
Roba et al. |
Descriptive study in Enemor and Ener District of Curage Zone, Ethiopia | 2006 | 848 children aged 1–9 years | Facial cleanliness | TF/TI | Clinical exam | OR | — | — | O |
West et al. |
Descriptive study in 2 villages in Kongwa, Tanzania | n.s. | 500 children aged 1–7 years | Facial cleanliness, ocular discharge, nasal discharge, flies on face | TF/TI | Clinical exam | OR | — | — | O |
West et al. |
Intervention study in 3 pairs of villages in the Kongwa subdistrict of central Tanzania | 1989–1990 | 1,417 children aged 1–7 years enrolled, 1,168 participated in all four examinations. | Facial cleanliness, hygiene education | Any trachoma sign, TI | Clinical exam | OR | — | — | O |
Wilson et al. |
Descriptive study in 5 villages in Chiapas, Mexico | n.s. | 475 children in villages aged 2–10 years, primarily from farming families of Mayan descent | Nose wiping practices | TI | Clinical exam | OR | — | — | Q |
H, hygiene; O, observed directly; Q, questionnaire; S, sanitation; W, water.
Reference | Study Design and Setting | Year | Study Population | WASH Components | Type of Trachoma Measure | Diagnostic Approach | Data Obtained | Assessment Method | ||
W | S | H | ||||||||
Ezz al Arab et al. |
Descriptive study in Menofiya governate in Nile Delta, Egypt | n.s. | 3,272 children aged 2–6 years and 3,322 adults aged >50 years | Type of water source, sanitation type | TF/TI | Clinical exam | X2 | Q | Q | — |
Katz et al. |
Descriptive study in Sarlahi district, Nepal | 1990–1991 | 836 children aged 24–76 months | Type of water source, water access, sanitation access | TF/TI | Clinical exam | OR | Q | — | — |
Luna et al. |
Descriptive study in Bebedouro municipality in Sao Paulo | 1986 | 1,959 children aged 1–10 years in 1,416 households. | Type of water source, total quantity of water, sanitation presence, sanitation type | TF/TI | Clinical exam | OR, 2×2 | O | n.s. | — |
Montgomery et al. |
Descriptive case-control study in eight villages in Kongwa district, Tanzania | 2006–2008 | 678 households (95 cases, 583 controls) with a sentinel child aged 1–5 years | Distance to water, sanitation use, sanitation maintenance | TF/TI | Clinical exam | OR, 2×2 | Q | Q, O | — |
Ngondi et al. |
Descriptive study in 11 districts in Southern Sudan | 2001–2006 | 11,155 children aged 1–14 years from 3,950 households | Distance to water, type of water source, sanitation presence | TT | Clinical exam | OR | Q | Q, O | — |
Sallam et al. |
Descriptive study in Yemen | 2001 | 787 randomly selected school children under age 20 | Type of water source, sanitation presence | PCR | OR | Q | Q | — | |
Zerihun et al. |
Descriptive study in 14 villages and 1 town in Dedo, Manna, Sekka, and Kossa districts of Jimma Zone, Ethiopia | 1994–1995 | 7,423 residents of 100 randomly selected households in each village | Distance to water, presence of sanitation | TF/TI, TS | Clinical exam | OR | Q | Q | — |
H, hygiene; O, observed directly; Q, questionnaire; S, sanitation; W, water.
Reference | Study Design and Setting | Year | Study Population | WASH Components | Type of Trachoma Measure | Diagnostic Approach | Data Obtained | Assessment Method | ||
W | S | H | ||||||||
Baggaley et al. |
Descriptive study in randomly selected households in 64 villages in Rombo district, Tanzania | 2002 | 12,415 children aged 1–9 years | Distance to water, flies on face | TF/TI | Clinical exam | OR | Q, O | — | O |
D'Amaral et al. |
Descriptive case-control study in Greater Metropolitan Sao Paulo, Brazil | 1999 | 121 pairs of cases/controls matched by age and school | Water access, face-washing frequency | TF/TI | Clinical exam | OR | Q | — | Q |
Hsieh et al. |
Descriptive study in Kongwa, Tanzania | 1989–1995 | 176 children who were 1–2 years old in 1989 survey and available for follow-up in 1995 | Distance to water, facial cleanliness | TF/TI | Clinical exam | OR | Q | — | O |
Schemann et al. |
Descriptive study in 210 villages in Mali | n.s. | All children aged <10 years and women aged >14 years in randomly chosen households | Distance to water, facial cleanliness, flies on face | TF/TI, TS, TT, CO | Clinical exam | OR | Q | — | O |
Taylor et al. |
Descriptive study in 2 communities in Chiapas, Mexico | n.s. | Entire population of both communities ( |
Face-washing frequency, nose wiping practices | Any trachoma sign | Clinical exam | Relative risk, X2 | — | — | Q |
West et al. |
Descriptive study in 20 villages in the Kongwa, Tanzania | 1986 | 3,800 children aged 1–7 years | Distance to water, total quantity of water, facial cleanliness | TF/TI | Clinical exam | OR | Q | — | O |
West et al. |
Descriptive study in 9 villages in Tanzania | n.s. | 1,085 children aged 1–7 years | Distance to water, facial cleanliness, nose wiping practices | TF/TI, |
Clinical exam, PCR | OR | Q | — | O |
West et al. |
Intervention study in 3 pairs of villages in the Kongwa subdistrict of central Tanzania | 1989–1990 | 1,417 children aged 1–7 years enrolled, 1,168 participated in all four examinations | Distance to water, hygiene education, facial cleanliness | TI | Clinical exam | OR, 2×2 | Q | — | O |
H, hygiene; O, observed directly; Q, questionnaire; S, sanitation; W, water.
Reference | Study Design and Setting | Year | Study Population | WASH Components | Type of Trachoma Measure | Diagnostic Approach | Data Obtained | Assessment Method | ||
W | S | H | ||||||||
Abdou et al. |
Intervention study in 10 randomly selected communities in Maradi, Niger | 2005–2008 | 557 randomly selected sentinel children aged 1–5 years from each village | Hygiene education, sanitation education | TF/TI, |
Clinical exam, PCR | OR | — | O | O |
Burton et al. |
Descriptive study in Upper Saloum District, The Gambia | n.s. | All available residents ( |
Sanitation presence, ocular discharge, nasal discharge, flies on face | PCR | OR | — | Q | O | |
Burton et al. |
Descriptive study in 14 villages in rural Gambia | 2001–2003 | All consenting residents living in the area for more than 6 months ( |
Sanitation presence, ocular discharge, nasal discharge, flies on face | PCR | OR | — | Q | O | |
Hassan et al. |
Descriptive study in 88 districts in 12 northern states of Sudan | 2006– 2010 | Children aged 1–9 years | Sanitation access, face-washing frequency | TF/TI | Clinical exam | OR | — | O | Q |
Khandekar et al. |
Intervention study in villages My Thon and Xom Ngoai, Vietnam | 2002–2005 | All households and residents of all ages comprised target population | Sanitation education, hygiene education | TF/TI | Clinical exam | Additional decline in prevalence due to FE | — | O | O |
Resnikoff et al. |
Intervention study in four villages in Oulessebougou, Mali | 1994 | 347 subjects with TF/TI | Sanitation education, hygiene education | TF/TI | Clinical exam | OR | — | O | O |
Rubinstein et al. |
Intervention study in four villages in the Egyptian delta | 1991–1992 | Children aged <10 years | Sanitation use, sanitation education, nasal discharge, flies on face, hygiene education, soap use | Any trachoma sign | Clinical exam | Relative risk | — | Q, O | Q, O |
Schemann et al. |
Descriptive study in Burkina Faso | 1997 | All children aged <10 years in randomly selected villages ( |
Sanitation presence, face-washing frequency, bathing frequency, facial cleanliness, flies on face | TF/TI, TI | Clinical exam | OR | — | O | Q, O |
Vinke et al. |
Descriptive study in Kembata Tembaro Zone in Ethiopia | n.s. | 1,513 children aged 1–9 years from 306 households | Distance to sanitation, facial cleanliness | TF/TI | Clinical exam | OR | — | Q, O | O |
H, hygiene; O, observed directly; Q, questionnaire; S, sanitation; W, water.
Reference | Study Design and Setting | Year | Study Population | WASH Components | Type of Trachoma Measure | Diagnostic Approach | Data Obtained | Assessment Method | ||
W | S | H | ||||||||
Abdou et al. |
Descriptive study in 12 randomly selected villages in Niger | n.s. | 641 children aged 1–5 years | Distance to water, sanitation presence, facial cleanliness, flies on face | TF/TI, |
Clinical exam, PCR | OR | Q | O | O |
Amza et al. |
Descriptive study in 48 randomly selected Nigerian communities | 2010 | 24,536 participants in study, including 4,484 sentinel children aged 0–5 years | Distance to water, sanitation presence, ocular discharge, nasal discharge, flies on face | TF/TI, |
Clinical exam, PCR | Regression coefficient | Q | Q | O |
Ayele et al. |
Descriptive study in 12 communities in Goncha Siso Enese woreda, Amhara Region, Ethiopia | 2009 | 50 children aged 0–9 years from each of 12 communities ( |
Distance to water, sanitation presence, ocular discharge, nasal discharge, flies on face | TF/TI, |
Clinical exam, PCR (DNA and RNA) | OR | Q | Q | O |
Bailey et al. |
Descriptive case-control study in village of Keneba in the Kiang West district of The Gambia | 1987 | Cases: 18 mothers whose children had one or more cases of active trachoma ( |
Quantity of water used for washing, sanitation presence, facial cleanliness, face-washing frequency, bathing frequency, soap use, towel sharing | Any trachoma sign | Clinical exam | OR | O | O | Q, O |
Cajas-Monson et al. |
Descriptive study in 4 villages in Kongwa district, Tanzania | 2009 | 1,991 children aged <9 years | Time to water, sanitation presence, facial cleanliness | TF/TI, |
Clinical exam, PCR | 2×2 | Q | O | O |
Cruz et al. |
Descriptive study in San Gabriel da Cachoeira, Brazil | n.s. | 440 children aged <9 years, 1,069 adults aged >15 years | Type of water source, sanitation type, sanitation use, facial cleanliness, ocular discharge, towel use | Any trachoma sign | Clinical exam | Prevalence ratio | Q, O | Q, O | Q, O |
Cumberland et al. |
Descriptive study in Gurage, Oromia, and South Welo zones of Ethiopia | 2002 | 1,960 children aged 3–9 years in selected households | Type of water source, distance to water, sanitation use, bathing frequency, ocular discharge, nasal discharge, flies on face | TF/TI | Clinical exam | OR | Q, O | Q, O | Q, O |
Edwards et al. |
Descriptive study in 40 randomly selected villages in Unity State, South Sudan | 2002–2005 | 1,722 children aged 3–9 years | Distance to water, type of water source, sanitation presence, sanitation use, face-washing frequency, ocular discharge, flies on face, towel sharing | TF/TI | Clinical exam | OR | Q | Q, O | Q, O |
Edwards et al. |
Descriptive study in 37 Ethiopian communities | 2010 | All consenting residents ( |
Distance to water, type of water source, sanitation presence, ocular discharge, nasal discharge | TF, TT | Clinical exam | OR | Q | Q | O |
Ejigu et al. |
Descriptive study in Kersa District, Southwest Ethiopia | 2011 | 305 children aged 1–9 years | Distance to water, sanitation presence, facial cleanliness | TF/TI | Clinical exam | OR | Q | O | O |
Faye et al. |
Descriptive study in Nioro department, Kaolack Region, Senegal | 2003 | 1,648 randomly selected children aged 2–5 years | Distance to water, quantity of water used for washing, sanitation presence, sanitation use, facial cleanliness, flies on face, face-washing frequency, soap use | TF/TI | Clinical exam | OR | Q | Q | Q, O |
Golovaty et al. |
Descriptive cross-sectional study in one community in Ankober, Ethiopia | 2007 | 507 children aged 1–9 years | Type of water source, sanitation presence, facial cleanliness, flies on eyes | TF/TI | Clinical exam | OR | Q | Q | O |
Harding-Esch et al. |
Descriptive study in the Gambia's Lower River Region and North Bank Region | n.s. | Children aged <10 years | Distance to water, type of water source, sanitation presence, sanitation type, facial cleanliness, ocular discharge, nasal discharge | TF/TI | Clinical exam | OR | Q | Q | O |
Harding-Esch et al. |
Descriptive study in 48 Gambian and 36 Tanzanian communities | n.s. | 5,036 randomly selected children aged 0–5 years | Distance to water, sanitation presence, ocular discharge, nasal discharge, flies on face, hygiene education | PCR | OR | Q | Q | O | |
Jip et al. |
Descriptive study in 10 local government areas in Katsina State, Nigeria | n.s. | 11,407 children and 8,901 adults from 2,244 households | Distance to water, water access, sanitation presence, facial cleanliness, face-washing frequency, ocular discharge, nasal discharge, flies on face, | TF/TI | Clinical exam | OR | Q | Q | Q, O |
Kalua et al. |
Descriptive study in Chikwawa and Mchinji districts, Malawi | n.s. | Children aged 1–9 years ( |
Water access, type of water source, sanitation presence, sanitation type, facial cleanliness | TF | Clinical exam | OR | Q | O | O |
Ketema et al. |
Descriptive study in 5 randomly selected villages in Baso Liben District, East Gojjam, Amhara Regional state, Ethiopia | 2012 | 792 children aged 1–9 years | Distance to water, total quantity of water, sanitation use, facial cleanliness, soap use | TF/TI | Clinical exam | OR | Q | Q | Q, O |
Khandekar et al. |
Descriptive study in Nizwa, Oman | 2002 | 229 children aged 0–15 years | Water source type, sanitation maintenance, facial cleanliness | TF/TI | Clinical exam | 2×2 | Q | O | O |
Lucena et al. |
Descriptive study in Brazil | 2007 | 412 individuals aged 1–86 years | Type of water source, sanitation presence, facial cleanliness | Any trachoma sign | Clinical exam | 2×2 | Q | Q | Q, O |
Mahande et al. |
Descriptive study in Maasai village, Hai district, Tanzania | 2005 | Households with two or more children aged 1–9 years | Distance to water, quantity of water used for washing, total quantity of water, sanitation presence, face-washing frequency, sharing water for washing, towel sharing, soap use | TF/TI | Clinical exam | OR | Q | Q | Q |
Mesfin et al. |
Descriptive study in 48 villages in Tigray, Ethiopia | n.s. | 3,900 randomly selected people from 1200 households | Distance to water, sanitation presence, face-washing frequency, soap use | TF/TI | Clinical exam | OR | Q, O | Q, O | Q |
Mpyet et al. |
Descriptive study in 27 villages in Yobe state, Nigeria | n.s. | 639 children aged 1–5 years | Distance to water, quantity of water used for washing, sanitation presence, facial cleanliness, flies on face | TF/TI | Clinical exam | OR | Q | O | O |
Mpyet et al. |
Descriptive population-based cross-sectional survey using multistage cluster random sampling in Kano state, Nigeria | 2008 | 4,491 people, including 1,572 aged <10 years | Quantity of water used for washing, sanitation presence, facial cleanliness, flies on face | TF/TI | Clinical exam | OR | Q | Q | O |
Ngondi et al. |
Descriptive study in 10 sites in southern Sudan | 2001– 2005 | 7,418 children aged 1–9 years | Distance to water, sanitation presence, facial cleanliness, face-washing frequency | TF/TI | Clinical exam | OR | Q | Q, O | Q, O |
Ngondi et al. |
Descriptive study in Amhara Regional State, Ethiopia | 2006–2007 | 5,427 children aged 1–9 years from 2,845 households and 9,098 adults aged 15 and up from 4,039 households | Distance to water, type of water source, sanitation presence, ocular discharge, nasal discharge | TF/TI | Clinical exam | OR | Q | Q, O | O |
Ngondi et al. |
Descriptive study in 25 villages in Southern Sudan | 2005 | 1,712 children aged 1–9 years | Distance to water, sanitation presence, facial cleanliness, face-washing frequency, hygiene education | TF/TI | Clinical exam | OR | Q | Q, O | Q, O |
Ngondi et al. |
Descriptive study in five trachoma hyperendemic districts of Amhara region | n.s. | 1,813 randomly selected children aged 1–9 years from 912 households | Distance to water, sanitation presence, facial cleanliness, face-washing frequency | TF/TI | Clinical exam | OR | Q | Q, O | Q, O |
Polack et al. |
Descriptive study in Shimbi Mashiriki village in northern Tanzania | 2003 | 914 children aged 1–9 years for larger study, 233 children for sub-study of water allocation and trachoma | Distance to water, total quantity of water, quantity of water used for washing, sanitation maintenance, sanitation use, facial cleanliness, face-washing frequency, hand washing frequency | TF/TI, |
Clinical exam, PCR | OR | Q | Q | Q, O |
Quicke et al. |
Descriptive study in the urban area of Brikama in The Gambia. | 2012 | 652 children aged 1–9 years | Distance to water, type of water source, total quantity of water, sanitation presence, facial cleanliness, ocular discharge, nasal discharge, bathing frequency | TF | Clinical exam | OR | Q | Q | Q,O |
Regassa et al. |
Descriptive study in Damot Gale District of South Ethiopia | 2002 | 855 adults aged >15 years in randomly selected households | Distance to water, sanitation presence, face-washing frequency | TF/TI | Clinical exam | OR | Q | Q | Q |
Schemann et al. |
Descriptive study in 30 villages in each of Mali's seven regions | 1996–1997 | Sample of 30 villages randomly selected in each of Mali's seven regions | Type of water source, sanitation presence, bathing frequency, face-washing frequency, facial cleanliness, flies on face, soap use, towel use | TF/TI, TI | Clinical exam | OR | O | O | Q, O |
Schemann et al. |
Descriptive study in 9 villages in Segou and Mopti regions of Mali | 2000–2002 | Children aged <11 years | Distance to water, type of water source, sanitation presence, facial cleanliness, face-washing frequency, bathing frequency | TF/TI | Clinical exam | OR | Q | Q | Q, O |
Taylor et al. |
Descriptive study in 20 villages in Kongwa district in central Tanzania | n.s. | Approximately 200 children aged 1–7 years from each of 20 villages | Distance to water, sanitation presence, facial cleanliness, towel use, nose wiping practices | TF/TI, TI | Clinical exam | OR | Q | Q, O | Q, O |
Tielsch et al. |
Descriptive study in Lower Shire River Valley in Malawi | 1983 | 5,436 children aged <6 years and 1,664 persons aged ≥6 years | Distance to water, sanitation presence, nose wiping practices, face-washing frequency | TI | Clinical exam | OR, 2×2 | Q | Q | Q |
H, hygiene; O, observed directly; Q, questionnaire; S, sanitation; W, water.
WASH Exposure | Active Trachoma (TF/TI) | |||||
Random Effects Pooled OR (95% CI) | Random Effects Pooled OR (95% CI) | |||||
12 | 0.97 (0.83–1.11) | 77 (60–87) | 4 | 1.08 (0.86–1.30) | 0 (0–85) | |
26 | 0.85 (0.75–0.95) | 75 (70–86) | 7 | 0.67 (0.55–0.78) | 0 (0–71) | |
6 | 0.86 (0.57–1.15) | 64 (12–85) | — | — | — | |
25 | 0.42 (0.32–0.52) | 78 (69–85) | — | — | — | |
10 | 0.42 (0.23–0.61) | 68 (37–83) | 4 | 0.40 (0.31–0.49) | 0 (0–85) | |
9 | 0.62 (0.52–0.72) | 30 (0–68) | 4 | 0.56 (0.37–0.76) | 8 (0–86) | |
6 | 0.76 (0.57–0.96) | 70 (31–87) | — | — | — | |
8 | 0.85 (0.80–0.90) | 0 (0–68) | — | — | — | |
4 | 0.76 (0.53–0.99) | 60 (0–87) | — | — | — | |
4 | 0.65 (0.53–0.78) | 40 (0–80) | — | — | — | |
6 | 0.76 (0.59–0.93) | 48 (0–79) | — | — | — |
Seventy-six of the included publications were descriptive cross-sectional surveys, assessing at least one WASH-related condition or risk factor for
“Sanitation access” was generally assessed through interviews or questionnaires given to household head or child caretaker, sometimes verified through direct observation of the presence of a sanitation facility, which typically meant presence of a household-level, onsite, toilet or latrine facility. Access does not necessarily take into account use of the facility, which was generally assessed independently using questionnaires given to the head-of-household or a child's caregiver and, in some cases, verified through observation of indirect sanitation usage indicators (e.g., the presence of a beaten path to the door of the sanitation facility or the presence of feces). “Sanitation type” mainly referred to shared status or the location of a toilet or latrine (within house versus within compound). Each study assessing “facility maintenance” defined a different method of assessing and grading maintenance. All “sanitation education” was part of larger programs that also included a hygiene education component.
The time and distance increments used in examining the effect of “distance to water” varied from study to study, although the baseline for comparison was most commonly <30 min, or within 1 km to source. Because households often estimate distance to source in terms of travel time, WASH household surveys commonly equate a 30 min round trip from household to source (15 min each way) to a distance of 1 km (average walking speed of 4 km/hr)
The definition of “facial cleanliness” varied slightly from study to study, but generally was defined as the lack of ocular discharge, nasal discharge, and/or flies on face at the time of clinical examination. “Ocular discharge” included any discharge in or surrounding the eye, including “sleep” in eyes, and “nasal discharge” included any discharge present from the nose. “Face washing frequency” and “bathing frequency” were assessed using questionnaires and were most commonly reported as at least once daily (versus not daily) and at least twice daily (versus only daily or not daily) for face-washing frequency, and at least once daily (versus not daily) for bathing frequency. “Soap use” and “towel use” were also assessed using questionnaires and were reported as either use or no use. “Towel sharing” was defined as self-reported towel sharing or the availability of less than one towel per person. “Nose wiping practices” were also self-reported and compared children who wipe or blow nose using clothing or handkerchief and those who used neither. “Hygiene education” included both cross-sectional assessments of exposure or uptake of hygiene education and interventions involving hygiene education and promotion, including combined programs that also included sanitation education.
Studies often examined more than one WASH exposure or condition and sometimes reported multiple effect measures (e.g., incremental measures of distance or face-washing frequency).
Created using eulerAPE software.
Fifty-eight of the studies identified in our systematic review reported at least one measure of effect for a water-related exposure or risk factor on trachoma, with a total 151 reported effect measures overall. Two intervention studies that improved access to water by installing water sources were identified; the remaining studies were observational. Study participants were chosen at random, either at individual or at household level in 69% of the relevant studies. In 14 studies, all individuals of a particular community, village, or special population group were enrolled, whereas no selection criteria for study participation were specified in four studies.
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.
†OR was calculated using data sent from author.
Meta-analyses were not performed for other water-related conditions or risk factors owing to the lack of sufficient number of studies with comparable ORs and the variation in how exposures were measured and defined across studies (e.g., the type of water source reported in a study varied depending on context, and there were no common increments in measuring quantity of water collected or used for washing). The components for which meta-analyses were not conducted included: type of water source (20 articles, 37 effect measures), access to water (seven articles, seven effect measures), total quantity of water used for washing (six articles, 16 effect measures), and total quantity of water used daily within a household (six articles, nine effect measures). Despite the high number of water source-related studies identified, no meta-analyses were conducted because water source types tended to be poorly defined, and individual studies generally examined the relative effects of site-specific water sources, making comparison of across studies difficult. No clear significant effect of water source type was found across the articles, but, in general, those that showed a significant association between water source and trachoma found that “safer” water sources (those defined as “safe or protected” or piped water versus various types of wells versus an unprotected source) were protective against trachoma. “Access to water” was defined as either the presence of an improved water source or self-reported access to water year-round versus sporadically; most effect measures assessing access to water were not statistically significant (four effect measures), but those did find a significant effect suggest improved access is protective (three effect measures). Additionally, neither intervention that included the component improving water access led to a significant reduction in trachoma. Seven reported ORs suggest that using more water for washing is associated with significantly lower odds of trachoma, but the remaining nine reported ORs did not show a statistically significant relationship. Four of six studies reported a significant association between increased total quantity of water and lowered odds of trachoma. One study determined that, regardless of total water collection, using a higher proportion of the total household water for hygiene is protective
Fifty-six of the studies identified in our systematic review reported at least one measure of effect for a sanitation-related risk factor on trachoma, with a total of 96 reported effect measures overall. Four of these studies involved interventions to improve sanitation or sanitation/hygiene promotion; the remaining studies were observational. Study participants were chosen at random, either at individual or at household level in 68% of relevant studies. In 17 studies, all individuals of a particular community, village, or special population group were enrolled, whereas no selection criteria for study participation were specified in one study.
*OR was adjusted for possible confounders. †OR was calculated using data sent from author.
Results reported separately for aThe Gambia population, bTanzania population. *OR was adjusted for possible confounders. †OR was calculated using data sent from author.
*OR was adjusted for possible confounders. †OR was calculated using data sent from author.
Meta-analyses were not performed for other sanitation-related conditions or risk factors owing to a lack of sufficient number of studies with comparable ORs and the variation in how exposures were measured and defined across studies (e.g., there was no standard definition of either “facility maintenance” or “sanitation type”). These exposures included sanitation type (six articles, 11 effect measures), sanitation education (three articles, six effect measures), and facility maintenance (three articles, five effect measures). One study found the presence of a sanitation facility within the house to be significantly protective against TF/TI compared to facilities located outside of the house
Sixty-four studies identified in our systematic review reported some association between a hygiene-related exposure and trachoma, with a total of 213 reported measures of effect. Six studies assessed the effect of a hygiene education intervention on trachoma; all other studies were observational. Study participants were chosen at random, either at individual or at household level in 61% of relevant studies. In 23 studies, all individuals of a particular community, village, or special population group were enrolled, whereas no selection criteria for study participation were specified in two studies.
Facial cleanliness status was reported in 35 publications, with a total reported 49 measures of effect. We found that having a clean face was protective against TF/TI (OR 0.42, 95% CI 0.32–0.52) (
*OR was adjusted for possible confounders.
*OR was adjusted for possible confounders. †OR was calculated using data sent from author.
*OR was adjusted for possible confounders. †OR was calculated using data sent from author.
*OR was adjusted for possible confounders. †OR was calculated using data sent from author.
*OR was adjusted for possible confounders. †OR was calculated using data sent from author.
*OR was adjusted for possible confounders.
*OR was adjusted for possible confounders.
*OR was adjusted for possible confounders.
*OR was adjusted for possible confounders.
*OR was adjusted for possible confounders.
Meta-analyses were not performed for other hygiene-related conditions or risk factors due to a lack of sufficient number of studies with comparable ORs, often resulting from variation in how exposures were measured and defined across studies (e.g., the nose-wiping practices of interest varied from study to study, hygiene education interventions may or may not have included a sanitation component). These exposures included towel sharing (three articles, four measures of effect), hygiene education (six articles and 12 measures of effect), and nose-wiping practices (five articles, seven measures of effect). Towel sharing among family members was not found to be significantly associated with trachoma in any study. One of two interventions focused solely on face-washing education reported a significant reduction in severe trachoma (TI) compared to control villages
Our analysis revealed evidence of an association between improved WASH conditions and exposures and reduced trachoma in 11 of the 15 meta-analyses conducted with the available literature. Pooled estimates of effect for the relationship between a WASH exposure and clinical trachoma (TF/TI) ranged from strong effects associated with a clean face (OR 0.42) to little evidence of an association for distance to water source <1 km (OR 0.97). Three of the four meta-analyses assessing trachoma through PCR found associations between WASH conditions and lower infection with
We found the strongest evidence of the association between hygiene factors and trachoma. Our analyses suggest that the presence of a clean face, the lack of ocular and nasal discharge, increased frequency of face washing, towel use, the use of soap, and daily bathing were all associated with lower odds of trachoma. The relationship between a clean face and reduced odds of trachoma was one of the strongest associations. The shared use of towels, which has long been thought to be a key risk factor in the transmission of trachoma
Our analysis did not reveal any evidence of an assocation between the distance to drinking water source and
Our review identified relationships between WASH conditions and trachoma that require additional research. While we found several studies assessing the association of household sanitation access and facial cleanliness on signs of trachoma, there are comparatively fewer exploring the relationship between water use and trachoma, as well as other characteristics of sanitation, such as maintenance of sanitation facilities and use of facilities shared by more than one household. As a result, the association of these variables with trachoma and the potential role of these variables in trachoma control remains unknown.
We searched three widely used databases—EMBASE, Web of Science, and PubMed—as well as MedCarib, Lilacs, REPIDISCA, DESASTRES, and African Index Medicus using a pre-specified, systematic search protocol. In addition, we hand-searched the bibliographies of available reviews. We adhered to the MOOSE guidelines for reporting meta-analysis of observational studies. The lack of standard definitions and methods of measuring WASH components in the available studies made meta-analysis for certain exposures infeasible. In addition, variations in the definitions and methods could have introduced error in our meta-analyses. Study design and setting varied, and heterogeneity was moderate to high in some meta-analyses, particularly those examining the relationship between WASH and TF/TI (refer to
All studies included in meta-analyses had relatively low quality scores. These low-quality grades were due in part to the fact that only observational studies were included in the meta-analyses, and all ORs reflected cross-sectional data. WASH exposures were often assessed as secondary risk factors of interest (e.g., sanitation access could be included in a model focused on assessing an antibiotic intervention), meaning that there is a potential for publication bias if non-significant associations were not included in final published manuscripts.
We found many different measures of WASH exposures and many of these parameters were poorly described in the methods. This lack of specificity and standardization of measures limits the harmonization of findings into a meta-analysis; this creates challenges to amassing a consistent and useable body of evidence, and effectively demonstrating impact across the WASH and disease control sectors. In addition, we only reported measures of TF/TI together. Since TI has been dropped from some surveys in recent years, our measures of effect may represent small differences in the definition of the outcome.
While there has been considerable progress in global access to improved drinking water supply, specifically in East and South Asia, there is evidence that these gains have systematically ignored the poorest and most marginalized populations
Face washing has long been an elemental component of the SAFE strategy. Among NGOs not specifically targeting trachoma control, however, improving WASH access is typically promoted to reduce diarrheal diseases, and as such few promote face washing alongside handwashing with soap. Our data support the importance, found by others, of daily face washing to reduce trachoma. Increasing attention to and investment in improved hygiene practices that include daily face washing will support the achievement of trachoma control and elimination targets.
Access to household sanitary facility is an important factor in trachoma, and continued use of program indicators that record progress toward improving household access to sanitation is recommended. Though sanitation use, in addition to access, is theoretically important to control trachoma, our review found no significant association between measures of sanitation use and trachoma. This may suggest that current measures of sanitation use, which vary between observation of sanitation characteristics and direct household surveys related to defecation practices, are not sufficiently accurate or consistent on the whole. Additionally, despite a scarcity of literature examining the role of sanitation facility quality or maintenance, interventions to improve the usability and acceptability of existing sanitation facilities may be effective. Further research is needed to understand whether sanitation access at a household level, or whether reaching high sanitation coverage within the community as a whole is more important to achieving trachoma reduction. None of these studies focused on schools, revealing a gap in the literature of the importance of school-based WASH promotion.
Our review finds that the F and E components of the SAFE strategy—specifically face washing, facial cleanliness, and sanitation access—but also general hygiene behaviors for trachoma control are well supported by evidence. Facial cleanliness and environmental improvement are, in general, highly associated with trachoma infection and disease. Lack of evidence of the association between water access and trachoma may be due to the low number of studies available or a parameterization of water access (<1 km distance to source) in a majority of studies that does not best capture the impact of increased access to water for hygiene and cleanliness. These data support the need for a more harmonized approach to monitoring WASH exposures as they relate to trachoma, better monitoring and reporting of these associations, and increased attention to and funds for the use of WASH to meet trachoma elimination targets as part of the full SAFE strategy. Further studies should employ WASH definitions compatible with those used in the WASH sector, such as the Joint Monitoring Program definitions for improved and unimproved water sources and infrastructure
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odds ratio
trachomatous inflammation-follicular
trachomatous inflammation-intense
water, sanitation, and hygiene