Biology subjects

Hubbard, A. E.

Publications and source records attributed to Hubbard, A. E..

5 recordsLinked to original sources

bioRxiv2025

Associations between floor material and E. coli contamination in rural Bangladeshi households

Soil floors are common in low-income countries and can harbor contamination from unsafely managed human and animal fecal waste. Soil/dust ingestion directly from floors or indirectly via hands, drinking water and food can significantly contribute to childrens ingestion of fecal organisms. We assessed if finished (e.g., concrete) floors are associated with lower E. coli contamination in the domestic environment in rural Bangladesh. We collected samples from 1864 households over 3.5 years, including stored drinking water, child and caregiver hand rinses, courtyard soil, food, and flies (n=24,118 samples), and enumerated E. coli using IDEXX Quanti-Tray/2000. Controlling for potential confounders (socio-demographics, water/sanitation status, animal ownership), households with finished floors had slightly lower log10-transformed E. coli counts ({Delta}log10= -0.10 (-0.20, 0.00)) and prevalence (prevalence ratio=0.90 (0.83, 0.98)) on child hands than households with soil floors; floor material was not associated with contamination levels in other sample types. Finished floors were associated with lower E. coli contamination of child hands, food and stored drinking water following periods of higher rainfall and temperature, and lower E. coli contamination of child hands in households with more domestic animals. Measures to control enteric infections in low-income countries should test flooring improvements to reduce exposure to fecal contamination.

microbiology↗

bioRxiv2019

Comparison of multi-parallel qPCR and Kato-Katz for detection of soil-transmitted helminth infection among children in rural Bangladesh

An active area of research investigates whether soil-transmitted helminths (STH) can be locally eliminated in endemic settings. In such settings, highly sensitive diagnostics are needed to detect STH infection. We compared double-slide Kato-Katz, the most commonly used copromicroscopic detection method, to multi-parallel quantitative polymerase chain reaction (qPCR) in 2,800 stool samples from children 2-12 years in rural Bangladesh. We estimated the sensitivity and specificity of each diagnostic using Bayesian latent class analysis. Compared to Kato-Katz, STH prevalence using qPCR was almost 3-fold higher for hookworm species and nearly 2-fold higher for Trichuris trichiura. Ascaris lumbricoides prevalence was lower using qPCR, and 26% of samples classified as A. lumbricoides positive by Kato-Katz were negative by qPCR. Amplicon sequencing of the 18S rDNA from 10 samples confirmed that A. lumbricoides was absent in samples classified as positive by Kato-Katz and negative by qPCR. The sensitivity of Kato-Katz was 49% for A. lumbricoides, 32% for hookworm, and 52% for T. trichiura; the sensitivity of qPCR was 79% for A. lumbricoides, 93% for hookworm, and 90% for T. trichiura. Specificity was [≥] 97% for both tests for all STH except for Kato-Katz for A. lumbricoides (specificity = 68%). There were moderate negative, monotonic correlations between qPCR cycle quantification values and eggs per gram quantified by Kato-Katz. While it is widely assumed that Kato-Katz has few false positives, our results indicate otherwise. Our findings suggest that qPCR is more appropriate than Kato-Katz in low intensity infection settings because of its higher sensitivity and specificity.\n\nAuthor summarySoil-transmitted helminth infections (STH) (e.g., Ascaris, hookworm, Trichuris) contribute to a large burden of disease among children in low- and middle-income countries. There is increasing interest in implementing large-scale deworming programs to eliminate STH in certain settings. Efforts to monitor whether local elimination has occurred require sensitive diagnostic tests that will not miss positive cases. Kato-Katz, a microscopy-based diagnostic test, has commonly been used to identify STH eggs in stool, but in settings where infection intensity is low, this method frequently misses positive samples because it requires visual identification of small numbers of eggs, and eggs may degrade prior to visualization. Quantitative polymerase chain reaction (qPCR) is a molecular diagnostic method that may miss fewer infections because it identifies STH DNA in stool, which can be detected in very small quantities and is less likely to degrade. This study compared the performance of Kato-Katz and qPCR using 2,800 stool samples from children aged 2-12 years in rural Bangladesh. qPCR detected substantially more hookworm and Trichuris infections than Kato-Katz. 26% of samples were classified as Ascaris positive by Kato-Katz and negative by qPCR. We conclude that qPCR is a more appropriate diagnostic method than Kato-Katz in low infection intensity settings.

epidemiology↗

bioRxiv2019

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

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.

clinical trials↗

bioRxiv2017

Spillover effects of a combined water, sanitation, and handwashing intervention in rural Bangladesh: a randomized controlled trial

BackgroundWater, sanitation, and handwashing (WSH) interventions may confer indirect benefits (\"spillovers\") on neighbors of recipients by interrupting pathogen transmission. We measured geographically local spillovers in WASH Benefits, a cluster-randomized trial in rural Bangladesh, by comparing outcomes among neighbors of intervention vs. control participants.\n\nMethodsWASH Benefits had randomly allocated geographically-defined clusters to a compound-level intervention (chlorinated drinking water, upgraded sanitation, and handwashing promotion) or control and followed children for two years. We enrolled neighboring children age-matched to trial participants that would have been eligible for WASH Benefits had they been conceived slightly earlier or later. After 28 months of intervention, we quantified fecal indicator bacteria in toy rinse and drinking water samples, measured soil-transmitted helminth infections, and recorded caregiver-reported diarrhea and respiratory illness. Neither fieldworkers nor participants were masked. Analysis was intention-to-treat.\n\nResultsWe enrolled neighbors of WASH Benefits participants in 90 control (N=900) and 90 intervention clusters (N=899). Neighbors characteristics were balanced across arms. The prevalence of any detectable E. coli in tubewell samples was lower for neighbors of intervention vs. control (prevalence ratio=0.83; 0.73, 0.95). There was no difference in E. coli and coliform prevalence between arms for other environmental samples. Disease prevalence was similar in neighbors of intervention vs. control participants: Ascaris (prevalence difference [PD]=0.00; -0.07, 0.08), hookworm (PD=0.01; -0.01, 0.04), Trichuris (PD=0.02; -0.02, 0.05), diarrhea (PD=0.00; -0.02,0.03), respiratory illness (PD=-0.01; -0.04, 0.03).\n\nConclusionsWe found spillover effects of a compound-level combined WSH intervention for tubewell water contamination but not for child health outcomes.\n\nKey MessagesO_LIWater, sanitation, and handwashing (WSH) interventions may confer indirect benefits (\"spillovers\") on neighbors of recipients by interrupting pathogen transmission, reducing environmental contamination, or spurring the adoption of health behaviors.\nC_LIO_LIWe conducted a randomized trial in rural Bangladesh to measure whether neighbors of a compound-level WSH intervention improved hygiene behaviors and had lower prevalence environmental contamination, soil-transmitted helminth infection, diarrhea, and respiratory illness among children under 5 years after two years of intervention.\nC_LIO_LIWe did not find evidence of intervention adoption or improved hygiene behavior among neighbors of a WSH intervention delivered for 2 years.\nC_LIO_LIThe WSH intervention reduced fecal contamination of neighbors tubewell water but did not lead to spillovers for other proximal measures of contamination in the domestic environment or for child health outcomes. For proximal spillover effects to translate to distal spillover effects, improvements in neighbors health behaviors may have been necessary.\nC_LI

epidemiology↗

bioRxiv2017

Measuring changes in transmission of neglected tropical diseases, malaria, and enteric pathogens from quantitative antibody levels

BackgroundSerologicalantibody levels are a sensitive marker of pathogen exposure, and advances in multiplex assays have created enormous potential for large-scale, integrated infectious disease surveillance. Most methods to analyze antibody measurements reduce quantitative antibody levels to seropositive and seronegative groups, but this can be difficult for many pathogens and may provide lower resolution information than quantitative levels in low transmission settings. Analysis methods have predominantly maintained a single disease focus, yet integrated surveillance platforms would benefit from methodologies that work across diverse pathogens included in multiplex assays.\n\nMethods/Principal FindingsWe developed an approach to measure changes in transmission from quantitative antibody levels that can be applied to diverse pathogens of global importance. We compared age-dependent immunoglobulin G curves in repeated cross-sectional surveys between populations with differences in transmission for multiple pathogens, including: lymphatic filariasis (Wuchereria bancrofti) measured before and after mass drug administration on Mauke, Cook Islands, malaria (Plasmodium falciparum) before and after a combined insecticide and mass drug administration intervention in the Garki project, Nigeria, and enteric protozoans (Cryptosporidium parvum, Giardia intestinalis, Entamoeba histolytica), bacteria (enterotoxigenic Escherichia coli, Salmonella spp.), and viruses (norovirus groups I and II) in children living in Haiti and the USA. Age-dependent antibody curves fit with ensemble machine learning followed a characteristic shape across pathogens that aligned with predictions from basic mechanisms of humoral immunity. Differences in pathogen transmission led to shifts in fitted antibody curves that were remarkably consistent across pathogens, assays, and populations. Mean antibody levels correlated strongly with traditional measures of transmission intensity, such as the entomological inoculation rate for P. falciparum (Spearmans rho=0.75). Seroprevalence estimates recapitulated patterns observed in quantitative antibody levels, albeit with lower resolution.\n\nConclusions/SignificanceAge-dependent antibody curves and summary means provided a robust and sensitive measure of changes in transmission, with greatest sensitivity among young children. The method generalizes to pathogens that can be measured in high-throughput, multiplex serological assays, and scales to surveillance activities that require high spatiotemporal resolution. The approach represents a new opportunity to conduct integrated serological surveillance for neglected tropical diseases, malaria, and other infectious diseases with well-defined antigen targets.\n\nAuthor SummaryGlobal elimination strategies for infectious diseases like neglected tropical diseases and malaria rely on accurate estimates of pathogen transmission to target and evaluate control programs. Circulating antibody levels can be a sensitive measure of recent pathogen exposure, but no broadly applicable method exists to measure changes in transmission directly from quantitative antibody levels. We developed a novel method that applies recent advances in machine learning and data science to flexibly fit age-dependent antibody curves. Shifts in age-dependent antibody curves provided remarkably consistent, sensitive measures of transmission changes when evaluated across many globally important pathogens (filarial worms, malaria, enteric infections). The methods generality and performance in diverse applications demonstrate its broad potential for integrated serological surveillance of infectious diseases.

epidemiology↗