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. 2023 Feb 13;17(2):e0011103.
doi: 10.1371/journal.pntd.0011103. eCollection 2023 Feb.

Exploring water, sanitation, and hygiene coverage targets for reaching and sustaining trachoma elimination: G-computation analysis

Kristin M Sullivan  1 , Emma M Harding-Esch  2 , Alexander P Keil  1 , Matthew C Freeman  3 , Wilfrid E Batcho  4 , Amadou A Bio Issifou  5 , Victor Bucumi  6 , Assumpta L Bella  7 , Emilienne Epee  8 , Segni Bobo Barkesa  9 , Fikre Seife Gebretsadik  9 , Salimato Sanha  10 , Khumbo M Kalua  11 , Michael P Masika  12 , Abdallahi O Minnih  13 , Mariamo Abdala  14 , Marília E Massangaie  14 , Abdou Amza  15 , Boubacar Kadri  15 , Beido Nassirou  15 , Caleb D Mpyet  16 , Nicholas Olobio  17 , Mouctar D Badiane  18 , Balgesa E Elshafie  19 , Gilbert Baayenda  20 , George E Kabona  21 , Oscar Kaitaba  21 , Alistidia Simon  21 , Tawfik Q Al-Khateeb  22 , Consity Mwale  23 , Ana Bakhtiari  24 , Daniel Westreich  1 , Anthony W Solomon  25 , Emily W Gower  1
Affiliations

Exploring water, sanitation, and hygiene coverage targets for reaching and sustaining trachoma elimination: G-computation analysis

Kristin M Sullivan et al. PLoS Negl Trop Dis. .

Abstract

Background: Trachoma is the leading infectious cause of blindness. To reduce transmission, water, sanitation, and hygiene (WaSH) improvements are promoted through a comprehensive public health strategy. Evidence supporting the role of WaSH in trachoma elimination is mixed and it remains unknown what WaSH coverages are needed to effectively reduce transmission.

Methods/findings: We used g-computation to estimate the impact on the prevalence of trachomatous inflammation-follicular among children aged 1-9 years (TF1-9) when hypothetical WaSH interventions raised the minimum coverages from 5% to 100% for "nearby" face-washing water (<30 minutes roundtrip collection time) and adult latrine use in an evaluation unit (EU). For each scenario, we estimated the generalized prevalence difference as the TF1-9 prevalence under the intervention scenarios minus the observed prevalence. Data from 574 cross-sectional surveys conducted in 16 African and Eastern Mediterranean countries were included. Surveys were conducted from 2015-2019 with support from the Global Trachoma Mapping Project and Tropical Data. When modeling interventions among EUs that had not yet met the TF1-9 elimination target, increasing nearby face-washing water and latrine use coverages above 30% was generally associated with consistent decreases in TF1-9. For nearby face-washing water, we estimated a ≥25% decrease in TF1-9 at 65% coverage, with a plateau upon reaching 85% coverage. For latrine use, the estimated decrease in TF1-9 accelerated from 80% coverage upward, with a ≥25% decrease in TF1-9 by 85% coverage. Among EUs that had previously met the elimination target, results were inconclusive.

Conclusions: Our results support Sustainable Development Goal 6 and provide insight into potential WaSH-related coverage targets for trachoma elimination. Targets can be tested in future trials to improve evidence-based WaSH guidance for trachoma.

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Conflict of interest statement

I have read the journal’s policy and the authors of this manuscript have the following competing interests: AB is employed by the International Trachoma Initiative at The Task Force for Global Health, which receives an operating budget and research funds from Pfizer Inc., the manufacturers of Zithromax (azithromycin); EMHE is funded by the International Trachoma Initiative, a program of The Task Force for Global Health, which receives funding from Pfizer Inc., the manufacturers of Zithromax (azithromycin). All other authors have no completing interests to declare.

Figures

Fig 1
Fig 1. EU and participant inclusion by elimination group.
Observations from the most recent surveys (denoted with a t) were the basis for the study populations, while observations from the prior surveys (denoted with a t-1) were used to calculate EU-level measures used for confounding adjustments. 69 EUs (n = 253,017 individuals) had a survey sequence of baseline-impact-surveillance and were therefore included in both the reaching elimination target EUs and in the adjustment EUs for the maintaining elimination target EUs.
Fig 2
Fig 2. Prevalence difference and number and percentage of EUs modified after implementing hypothetical interventions on nearby face-washing water and latrine coverages among reaching elimination target EUs.
These figures show the results presented in Table 2 graphically for (a) nearby face-washing water interventions, (b) latrine interventions, and (c) simultaneous interventions on both nearby face-washing water and latrines for the reaching elimination target EUs. When present, the vertical bar indicates the minimum coverage target at which the relative prevalence decrease was at least 25%.
Fig 3
Fig 3. Prevalence difference and number and percentage of EUs modified after implementing hypothetical interventions on nearby face-washing water and latrine coverages among maintaining elimination target EUs.
These figures show the results presented in Table 2 graphically for (a) nearby face-washing water interventions, (b) latrine interventions, and (c) simultaneous interventions on both nearby face-washing water and latrines for the maintaining elimination target EUs. When present, the vertical bar indicates the minimum coverage target at which the relative prevalence decrease was at least 25%. Shaded areas indicate values the prevalence difference cannot reach.
See this image and copyright information in PMC

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