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

BackgroundSoil transmitted helminths (STH) infect >1.5 billion people. Mass drug administration (MDA) reduces infection; however, drug resistance is emerging and reinfection occurs rapidly. 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 FindingsWe randomized clusters of pregnant women into water treatment, sanitation, handwashing, combined water+sanitation+handwashing (WSH), nutrition, nutrition+WSH (N+WSH) or control arms. After 2.5 years of intervention, we enumerated STH infections in children aged 2-12 years 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. In 2012-2013, we randomized 5551 women in 720 clusters. In 2015-2016, we enrolled 7795 children of 4102 available women for STH follow-up and collected stool from 7187. 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 (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 (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% (2-3 percentage points) and marginally reduced A. lumbricoides. Effects on infection intensity were similar. Conclusions/SignificanceIn a low-intensity infection setting with MDA, we found modest but sustained hookworm reduction from water treatment, sanitation and combined WSH interventions. Interventions more effectively reduced STH species with no persistent environmental reservoirs. Our findings highlight waterborne transmission for hookworm and suggest that water treatment and sanitation improvements can augment MDA programs to interrupt STH transmission. Author summarySoil-transmitted helminths (STH) infect >1.5 billion people worldwide. Mass-administration of deworming drugs is the cornerstone of global strategy for STH control but treated individuals often rapidly get reinfected and there is also concern about emerging drug resistance. Interventions to treat drinking water, wash hands at critical times and isolate human feces from the environment through improved sanitation could reduce STH transmission by reducing the spread of ova from the feces of infected individuals into the environment and subsequently to new hosts, while nutrition improvements could reduce host susceptibility to infection. Existing evidence on the effect of these interventions on STH is scarce. In a setting with ongoing mass-drug administration, we assessed the effect of individual and combined water, sanitation, handwashing and nutrition interventions on STH infection in children. Approximately 2.5 years after delivering interventions, we found reductions in STH infection from water treatment and sanitation interventions; there was no reduction from the handwashing and nutrition interventions. While the reductions were modest in magnitude compared to cure rates achieved by deworming drugs, they indicated sustained reduction in environmental transmission. The reductions were more pronounced for STH species that do not have persistent environmental reservoirs. These findings suggest that water treatment and sanitation interventions can augment mass-drug administration programs in striving toward elimination of STH.