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Geographical analysis of the role of water supply and sanitation in the risk of helminth infections of children in West Africa.

ABSTRACT: Globally, inadequate water supply, sanitation, and hygiene (WASH) are major contributors to mortality and burden of disease. We aimed to quantify the role of WASH in the risk of Schistosoma hematobium, Schistosoma mansoni, and hookworm infection in school-aged children; to estimate the population attributable fraction (PAF) of helminth infection due to WASH; and to spatially predict the risk of infection. We generated predictive maps of areas in West Africa without piped water, toilet facilities, and improved household floor types, using spatial risk models. Our maps identified areas in West Africa where the millennium development goal for water and sanitation is lagging behind. There was a generally better geographical coverage for toilets and improved household floor types compared with water supply. These predictions, and their uncertainty, were then used as covariates in Bayesian geostatistical models for the three helminth species. We estimated a smaller attributable fraction for water supply in S. mansoni (PAF 47%) compared with S. hematobium (PAF 71%). The attributable fraction of S. hematobium infection due to natural floor type (PAF 21%) was comparable to that of S. mansoni (PAF 16%), but was significantly higher for hookworm infection (PAF 86%). Five percent of hookworm cases could have been prevented if improved toilet facilities had been available. Mapping the distribution of infection risk adjusted for WASH allowed the identification of communities in West Africa where preventive chemotherapy integrated with interventions to improve WASH will yield the greatest health benefits.

SUBMITTER: Soares Magalhaes RJ

PROVIDER: S-EPMC3250163 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Geographical analysis of the role of water supply and sanitation in the risk of helminth infections of children in West Africa.

Soares Magalhães Ricardo J RJ Barnett Adrian G AG Clements Archie C A AC

Proceedings of the National Academy of Sciences of the United States of America 20111128 50

Globally, inadequate water supply, sanitation, and hygiene (WASH) are major contributors to mortality and burden of disease. We aimed to quantify the role of WASH in the risk of Schistosoma hematobium, Schistosoma mansoni, and hookworm infection in school-aged children; to estimate the population attributable fraction (PAF) of helminth infection due to WASH; and to spatially predict the risk of infection. We generated predictive maps of areas in West Africa without piped water, toilet facilities ...[more]

PMID: 22123948

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Project description:BackgroundUnderstanding geographic inequalities in coverage of drinking-water supply and sanitation (WSS) will help track progress towards universal coverage of water and sanitation by identifying marginalized populations, thus helping to control a large number of infectious diseases. This paper uses household survey data to develop comprehensive maps of WSS coverage at high spatial resolution for sub-Saharan Africa (SSA). Analysis is extended to investigate geographic heterogeneity and relative geographic inequality within countries.Methods and findingsCluster-level data on household reported use of improved drinking-water supply, sanitation, and open defecation were abstracted from 138 national surveys undertaken from 1991-2012 in 41 countries. Spatially explicit logistic regression models were developed and fitted within a Bayesian framework, and used to predict coverage at the second administrative level (admin2, e.g., district) across SSA for 2012. Results reveal substantial geographical inequalities in predicted use of water and sanitation that exceed urban-rural disparities. The average range in coverage seen between admin2 within countries was 55% for improved drinking water, 54% for use of improved sanitation, and 59% for dependence upon open defecation. There was also some evidence that countries with higher levels of inequality relative to coverage in use of an improved drinking-water source also experienced higher levels of inequality in use of improved sanitation (rural populations r = 0.47, p = 0.002; urban populations r = 0.39, p = 0.01). Results are limited by the quantity of WSS data available, which varies considerably by country, and by the reliability and utility of available indicators.ConclusionsThis study identifies important geographic inequalities in use of WSS previously hidden within national statistics, confirming the necessity for targeted policies and metrics that reach the most marginalized populations. The presented maps and analysis approach can provide a mechanism for monitoring future reductions in inequality within countries, reflecting priorities of the post-2015 development agenda. Please see later in the article for the Editors' Summary.

Project description:BackgroundChildhood anaemia is considered a severe public health problem in most countries of sub-Saharan Africa. We investigated the geographical distribution of prevalence of anaemia and mean haemoglobin concentration (Hb) in children aged 1-4 y (preschool children) in West Africa. The aim was to estimate the geographical risk profile of anaemia accounting for malnutrition, malaria, and helminth infections, the risk of anaemia attributable to these factors, and the number of anaemia cases in preschool children for 2011.Methods and findingsNational cross-sectional household-based demographic health surveys were conducted in 7,147 children aged 1-4 y in Burkina Faso, Ghana, and Mali in 2003-2006. Bayesian geostatistical models were developed to predict the geographical distribution of mean Hb and anaemia risk, adjusting for the nutritional status of preschool children, the location of their residence, predicted Plasmodium falciparum parasite rate in the 2- to 10-y age group (Pf PR(2-10)), and predicted prevalence of Schistosoma haematobium and hookworm infections. In the four countries, prevalence of mild, moderate, and severe anaemia was 21%, 66%, and 13% in Burkina Faso; 28%, 65%, and 7% in Ghana, and 26%, 62%, and 12% in Mali. The mean Hb was lowest in Burkina Faso (89 g/l), in males (93 g/l), and for children 1-2 y (88 g/l). In West Africa, severe malnutrition, Pf PR(2-10), and biological synergisms between S. haematobium and hookworm infections were significantly associated with anaemia risk; an estimated 36.8%, 14.9%, 3.7%, 4.2%, and 0.9% of anaemia cases could be averted by treating malnutrition, malaria, S. haematobium infections, hookworm infections, and S. haematobium/hookworm coinfections, respectively. A large spatial cluster of low mean Hb (<80 g/l) and maximal risk of anaemia (>95%) was predicted for an area shared by Burkina Faso and Mali. We estimate that in 2011, approximately 6.7 million children aged 1-4 y are anaemic in the three study countries.ConclusionsBy mapping the distribution of anaemia risk in preschool children adjusted for malnutrition and parasitic infections, we provide a means to identify the geographical limits of anaemia burden and the contribution that malnutrition and parasites make to anaemia. Spatial targeting of ancillary micronutrient supplementation and control of other anaemia causes, such as malaria and helminth infection, can contribute to efficiently reducing the burden of anaemia in preschool children in Africa.

Project description:BackgroundSoil 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 findingsIn 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/significanceIn 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 registrationNCT01590095.

Project description:BackgroundThe Geshiyaro project is a 5-year intervention to assess the impact of community- and school-based water, sanitation, and hygiene (WaSH) interventions on reducing infection with soil-transmitted helminths (STH) and schistosome parasites in combination with deworming in Wolayita zone, Ethiopia.MethodsA population-based, cross-sectional census and parasitological mapping activity was conducted between 2018 and 2019. Individuals in the census were identified using either a registered study ID card or biometric fingerprint to enable linkage of their household WaSH data with baseline STH and schistosome prevalence for risk analysis.ResultsPrevalence of STH was 15.5% for any STH species, 9.47% for Ascaris lumbricoides, 1.78% for Trichuris trichiura, and 7.24% for hookworm. Intestinal schistosomiasis (Schistosoma mansoni) infection prevalence was 0.85% by Kato Katz, 21.6% by POC-CCA trace positive (Tr +), and 13.3% trace negative (Tr-). Microhaematuria was 2.77%, with 0.13% of people examined with S. haematobium eggs detected by urine filtration. At the household level, increased (> 30 min) time taken to collect drinking water, sharing a latrine, and lack of handwashing facilities were all associated with a greater risk of A. lumbricoides, hookworm, and S. mansoni infection. Not disposing of infant stool at the household and clothes washing/recreational freshwater contact were significantly associated with higher risk of schistosomiasis infection. Aggregating WaSH data at the community level showed odds of A. lumbricoides, hookworm, and T. trichiura infection were significantly lower as both community sanitation coverage and access to improved drinking water improved.ConclusionsThe principal finding of this study is that lack of access to WaSH, such as improved drinking water and shared toilet and hand-washing facilities, were linked to an increased risk of infection with STH and schistosome parasites. These associations are difficult to establish at an individual household level because of wide variability in access between houses but are detectable when coverage is aggregated at the community level. Maintenance of WaSH facilities as well as increased access within the whole community is important in influencing the community-wide prevalence of infection with STH and schistosome parasites.

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Geographical analysis of the role of water supply and sanitation in the risk of helminth infections of children in West Africa.

Publications

Geographical analysis of the role of water supply and sanitation in the risk of helminth infections of children in West Africa.

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