Effects of water, sanitation, handwashing and nutritional interventions on soil-transmitted helminth infections in young children: A cluster-randomized controlled trial in rural Bangladesh

Abstract

Background: Soil transmitted helminths (STH) infect >1.5 billion people. Mass drug administration (MDA) effectively reduces infection; however, there is evidence for rapid reinfection and risk of potential drug resistance. We conducted a randomized controlled trial in Bangladesh (WASH Benefits, NCT01590095) to assess whether water, sanitation, hygiene and nutrition interventions, alone and combined, reduce STH in a setting with ongoing MDA.

Methodology/principal findings: In 2012-2013, we randomized 720 clusters of 5551 pregnant women into water treatment, sanitation, handwashing, combined water+sanitation+handwashing (WSH), nutrition, nutrition+WSH (N+WSH) or control arms. In 2015-2016, we enrolled 7795 children, aged 2-12 years, of 4102 available women for STH follow-up and collected stool from 7187. We enumerated STH infections with Kato-Katz. We estimated intention-to-treat intervention effects on infection prevalence and intensity. Participants and field staff were not blinded; laboratory technicians and data analysts were blinded. Prevalence among controls was 36.8% for A. lumbricoides, 9.2% for hookworm and 7.5% for T. trichiura. Most infections were low-intensity. Compared to controls, the water intervention reduced hookworm by 31% (prevalence ratio [PR] = 0.69 (0.50,0.95), prevalence difference [PD] = -2.83 (-5.16,-0.50)) but did not affect other STH. Sanitation improvements reduced T. trichiura by 29% (PR = 0.71 (0.52,0.98), PD = -2.17 (-4.03,-0.38)), had a similar borderline effect on hookworm and no effect on A. lumbricoides. Handwashing and nutrition interventions did not reduce any STH. WSH and N+WSH reduced hookworm prevalence by 29-33% (WSH: PR = 0.71 (0.52,0.99), PD = -2.63 (-4.95,-0.31); N+WSH: PR = 0.67 (0.50,0.91), PD = -3.00 (-5.14,-0.85)) and marginally reduced A. lumbricoides. Effects on infection intensity were similar.

Conclusions/significance: In a low-intensity infection setting with MDA, we found modest but sustained hookworm reduction from water treatment and combined WSH interventions. Impacts were more pronounced on STH species with short vs. long-term environmental survival. Our findings suggest possible waterborne transmission for hookworm. Water treatment and sanitation improvements can augment MDA to interrupt STH transmission.

Trial registration: NCT01590095.

Fig 1. Flowchart of study participation.

The STH assessment enrolled (1) the birth cohort born to the enrolled women (referred to as “index child”), (2) children living in the same household as the index child (referred to as “index HH child”) and (3) children living in the same multi-household compound as the index child (referred to as “other HH child”).

Fig 2. Interventions implemented at index child, index household, and compound levels.

Index child refers to the birth cohort born to enrolled pregnant women. Index household refers to the household where the index child lived. Each enrolled compound contained a single index household and an average of 2.5 households total. Index children were the primary intervention recipients of the nutrition intervention delivered in the nutrition and N+WSH arms. Index households were the primary recipients of the water treatment and handwashing interventions; in the water, WSH and N+WSH arms they received water treatment products, and in the handwashing, WSH and N+WSH arms they received handwashing stations. The sanitation intervention was delivered to the entire compound; all households in compounds enrolled in the sanitation, WSH and N+WSH arms received latrine upgrades, child potties and scoops.

Fig 3. Prevalence and prevalence ratio (PR) for A. lumbricoides, hookworm, and T. trichiura infection in children aged 2–12 years measured with double-slide Kato-Katz 2.5 years after intervention initiation. Vertical bars indicate 95% confidence intervals.

Fig 4. Geometric mean eggs per gram for A. lumbricoides, hookworm and T. trichiura in children aged 2–12 years measured with double-slide Kato-Katz 2.5 years after intervention initiation.