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. 2018 Jan 22;12(1):e0006110.
doi: 10.1371/journal.pntd.0006110. eCollection 2018 Jan.

Sanitation and water supply coverage thresholds associated with active trachoma: Modeling cross-sectional data from 13 countries

Joshua V Garn  1 , Sophie Boisson  2 , Rebecca Willis  3 , Ana Bakhtiari  3 , Tawfik Al-Khatib  4 , Khaled Amer  5 , Wilfrid Batcho  6 , Paul Courtright  7 , Michael Dejene  8 , Andre Goepogui  9 , Khumbo Kalua  10 , Biruck Kebede  11 , Colin K Macleod  12 , Kouakou IIunga Marie Madeleine  13 , Mariamo Saide Abdala Mbofana  14 , Caleb Mpyet  7   15   16 , Jean Ndjemba  17 , Nicholas Olobio  18 , Alexandre L Pavluck  3 , Oliver Sokana  19 , Khamphoua Southisombath  20 , Fasihah Taleo  21 , Anthony W Solomon  22   23 , Matthew C Freeman  1
Affiliations

Sanitation and water supply coverage thresholds associated with active trachoma: Modeling cross-sectional data from 13 countries

Joshua V Garn et al. PLoS Negl Trop Dis. .

Abstract

Background: Facial cleanliness and sanitation are postulated to reduce trachoma transmission, but there are no previous data on community-level herd protection thresholds. We characterize associations between active trachoma, access to improved sanitation facilities, and access to improved water sources for the purpose of face washing, with the aim of estimating community-level or herd protection thresholds.

Methods and findings: We used cluster-sampled Global Trachoma Mapping Project data on 884,850 children aged 1-9 years from 354,990 households in 13 countries. We employed multivariable mixed-effects modified Poisson regression models to assess the relationships between water and sanitation coverage and trachomatous inflammation-follicular (TF). We observed lower TF prevalence among those with household-level access to improved sanitation (prevalence ratio, PR = 0.87; 95%CI: 0.83-0.91), and household-level access to an improved washing water source in the residence/yard (PR = 0.81; 95%CI: 0.75-0.88). Controlling for household-level water and latrine access, we found evidence of community-level protection against TF for children living in communities with high sanitation coverage (PR80-90% = 0.87; 95%CI: 0.73-1.02; PR90-100% = 0.76; 95%CI: 0.67-0.85). Community sanitation coverage levels greater than 80% were associated with herd protection against TF (PR = 0.77; 95%CI: 0.62-0.97)-that is, lower TF in individuals whose households lacked individual sanitation but who lived in communities with high sanitation coverage. For community-level water coverage, there was no apparent threshold, although we observed lower TF among several of the higher deciles of community-level water coverage.

Conclusions: Our study provides insights into the community water and sanitation coverage levels that might be required to best control trachoma. Our results suggest access to adequate water and sanitation can be important components in working towards the 2020 target of eliminating trachoma as a public health problem.

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Conflict of interest statement

MCF has received funding as a consultant for WHO as part of separate assessments of sanitation on health. The authors alone are responsible for the views expressed in this article and they do not necessarily represent the views, decisions or policies of the institutions with which they are affiliated. The authors declare no other competing interests exist.

Figures

Fig 1
Fig 1. Study flow diagram.
Fig 2
Fig 2
Unadjusted relationship between sanitation coverage (a) or water coverage (b) and prevalence of trachomatous inflammation—follicular (TF) among children aged 1–9 years.
Fig 3
Fig 3. Results from multivariable model showing the association between community-level sanitation and water coverage on trachomatous inflammation—Follicular prevalence among children aged 1–9 years.
Fig 4
Fig 4. Association between trachomatous inflammation—Follicular in children aged 1–9 years and both household and community associations combined together (i.e. the “total effect”).
The reference group is participants without household washing water/sanitation living in the lowest coverage decile.
Fig 5
Fig 5. Results from multivariable interaction model showing the association between community-level sanitation coverage and water coverage on trachomatous inflammation—Follicular prevalence, stratified by household access to sanitation or water among children aged 1–9 years.
See this image and copyright information in PMC

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