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Nikolakis ZL, Adams RH, Wade KJ, Lund AJ, Carlton EJ, Castoe TA, Pollock DD. Prospects for genomic surveillance for selection in schistosome parasites. FRONTIERS IN EPIDEMIOLOGY 2022; 2:932021. [PMID: 38455290 PMCID: PMC10910990 DOI: 10.3389/fepid.2022.932021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 09/12/2022] [Indexed: 03/09/2024]
Abstract
Schistosomiasis is a neglected tropical disease caused by multiple parasitic Schistosoma species, and which impacts over 200 million people globally, mainly in low- and middle-income countries. Genomic surveillance to detect evidence for natural selection in schistosome populations represents an emerging and promising approach to identify and interpret schistosome responses to ongoing control efforts or other environmental factors. Here we review how genomic variation is used to detect selection, how these approaches have been applied to schistosomes, and how future studies to detect selection may be improved. We discuss the theory of genomic analyses to detect selection, identify experimental designs for such analyses, and review studies that have applied these approaches to schistosomes. We then consider the biological characteristics of schistosomes that are expected to respond to selection, particularly those that may be impacted by control programs. Examples include drug resistance, host specificity, and life history traits, and we review our current understanding of specific genes that underlie them in schistosomes. We also discuss how inherent features of schistosome reproduction and demography pose substantial challenges for effective identification of these traits and their genomic bases. We conclude by discussing how genomic surveillance for selection should be designed to improve understanding of schistosome biology, and how the parasite changes in response to selection.
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Affiliation(s)
- Zachary L. Nikolakis
- Department of Biology, University of Texas at Arlington, Arlington, TX, United States
| | - Richard H. Adams
- Department of Biological and Environmental Sciences, Georgia College and State University, Milledgeville, GA, United States
| | - Kristen J. Wade
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, United States
| | - Andrea J. Lund
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado, Anschutz, Aurora, CO, United States
| | - Elizabeth J. Carlton
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado, Anschutz, Aurora, CO, United States
| | - Todd A. Castoe
- Department of Biology, University of Texas at Arlington, Arlington, TX, United States
| | - David D. Pollock
- Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, United States
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Lund AJ, Wade KJ, Nikolakis ZL, Ivey KN, Perry BW, Pike HNC, Paull SH, Liu Y, Castoe TA, Pollock DD, Carlton EJ. Integrating genomic and epidemiologic data to accelerate progress toward schistosomiasis elimination. eLife 2022; 11:79320. [PMID: 36040013 PMCID: PMC9427098 DOI: 10.7554/elife.79320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/11/2022] [Indexed: 11/13/2022] Open
Abstract
The global community has adopted ambitious goals to eliminate schistosomiasis as a public health problem, and new tools are needed to achieve them. Mass drug administration programs, for example, have reduced the burden of schistosomiasis, but the identification of hotspots of persistent and reemergent transmission threaten progress toward elimination and underscore the need to couple treatment with interventions that reduce transmission. Recent advances in DNA sequencing technologies make whole-genome sequencing a valuable and increasingly feasible option for population-based studies of complex parasites such as schistosomes. Here, we focus on leveraging genomic data to tailor interventions to distinct social and ecological circumstances. We consider two priority questions that can be addressed by integrating epidemiological, ecological, and genomic information: (1) how often do non-human host species contribute to human schistosome infection? and (2) what is the importance of locally acquired versus imported infections in driving transmission at different stages of elimination? These questions address processes that can undermine control programs, especially those that rely heavily on treatment with praziquantel. Until recently, these questions were difficult to answer with sufficient precision to inform public health decision-making. We review the literature related to these questions and discuss how whole-genome approaches can identify the geographic and taxonomic sources of infection, and how such information can inform context-specific efforts that advance schistosomiasis control efforts and minimize the risk of reemergence.
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Affiliation(s)
- Andrea J Lund
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado AnschutzAuroraUnited States
| | - Kristen J Wade
- Department of Biochemistry & Molecular Genetics, University of Colorado School of MedicineAuroraUnited States
| | - Zachary L Nikolakis
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - Kathleen N Ivey
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - Blair W Perry
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - Hamish NC Pike
- Department of Biochemistry & Molecular Genetics, University of Colorado School of MedicineAuroraUnited States
| | - Sara H Paull
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado AnschutzAuroraUnited States
| | - Yang Liu
- Sichuan Centers for Disease Control and PreventionChengduChina
| | - Todd A Castoe
- Department of Biology, University of Texas at ArlingtonArlingtonUnited States
| | - David D Pollock
- Department of Biochemistry & Molecular Genetics, University of Colorado School of MedicineAuroraUnited States
| | - Elizabeth J Carlton
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado AnschutzAuroraUnited States
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Rogers MJ, McManus DP, Muhi S, Gordon CA. Membrane Technology for Rapid Point-of-Care Diagnostics for Parasitic Neglected Tropical Diseases. Clin Microbiol Rev 2021; 34:e0032920. [PMID: 34378956 PMCID: PMC8404699 DOI: 10.1128/cmr.00329-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Parasitic neglected tropical diseases (NTDs) affect over one billion people worldwide, with individuals from communities in low-socioeconomic areas being most at risk and suffering the most. Disease management programs are hindered by the lack of infrastructure and resources for clinical sample collection, storage, and transport and a dearth of sensitive diagnostic methods that are inexpensive as well as accurate. Many diagnostic tests and tools have been developed for the parasitic NTDs, but the collection and storage of clinical samples for molecular and immunological diagnosis can be expensive due to storage, transport, and reagent costs, making these procedures untenable in most areas of endemicity. The application of membrane technology, which involves the use of specific membranes for either sample collection and storage or diagnostic procedures, can streamline this process, allowing for long-term sample storage at room temperature. Membrane technology can be used in serology-based diagnostic assays and for nucleic acid purification prior to molecular analysis. This facilitates the development of relatively simple and rapid procedures, although some of these methods, mainly due to costs, lack accessibility in low-socioeconomic regions of endemicity. New immunological procedures and nucleic acid storage, purification, and diagnostics protocols that are simple, rapid, accurate, and cost-effective must be developed as countries progress control efforts toward the elimination of the parasitic NTDs.
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Affiliation(s)
- Madeleine J. Rogers
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland, Australia
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Donald P. McManus
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
| | - Stephen Muhi
- Victorian Infectious Diseases Service, The Royal Melbourne Hospital, Parkville, Victoria, Australia
| | - Catherine A. Gordon
- Molecular Parasitology Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia
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Nikolakis ZL, Hales NR, Perry BW, Schield DR, Timm LE, Liu Y, Zhong B, Kechris KJ, Carlton EJ, Pollock DD, Castoe TA. Patterns of relatedness and genetic diversity inferred from whole genome sequencing of archival blood fluke miracidia (Schistosoma japonicum). PLoS Negl Trop Dis 2021; 15:e0009020. [PMID: 33406094 PMCID: PMC7815185 DOI: 10.1371/journal.pntd.0009020] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 01/19/2021] [Accepted: 11/30/2020] [Indexed: 02/05/2023] Open
Abstract
Genomic approaches hold great promise for resolving unanswered questions about transmission patterns and responses to control efforts for schistosomiasis and other neglected tropical diseases. However, the cost of generating genomic data and the challenges associated with obtaining sufficient DNA from individual schistosome larvae (miracidia) from mammalian hosts have limited the application of genomic data for studying schistosomes and other complex macroparasites. Here, we demonstrate the feasibility of utilizing whole genome amplification and sequencing (WGS) to analyze individual archival miracidia. As an example, we sequenced whole genomes of 22 miracidia from 11 human hosts representing two villages in rural Sichuan, China, and used these data to evaluate patterns of relatedness and genetic diversity. We also down-sampled our dataset to test how lower coverage sequencing could increase the cost effectiveness of WGS while maintaining power to accurately infer relatedness. Collectively, our results illustrate that population-level WGS datasets are attainable for individual miracidia and represent a powerful tool for ultimately providing insight into overall genetic diversity, parasite relatedness, and transmission patterns for better design and evaluation of disease control efforts.
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Affiliation(s)
- Zachary L. Nikolakis
- Department of Biology, University of Texas at Arlington, Arlington, Texas, United States of America
| | - Nicole R. Hales
- Department of Biology, University of Texas at Arlington, Arlington, Texas, United States of America
| | - Blair W. Perry
- Department of Biology, University of Texas at Arlington, Arlington, Texas, United States of America
| | - Drew R. Schield
- Department of Biology, University of Texas at Arlington, Arlington, Texas, United States of America
| | - Laura E. Timm
- Department of Biochemistry & Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Yang Liu
- Institute of Parasitic Disease, Sichuan Center for Disease Control and Prevention, Chengdu, The People’s Republic of China
| | - Bo Zhong
- Institute of Parasitic Disease, Sichuan Center for Disease Control and Prevention, Chengdu, The People’s Republic of China
| | - Katerina J. Kechris
- Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado, Anschutz, Aurora, Colorado, United States of America
| | - Elizabeth J. Carlton
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado, Anschutz, Aurora, Colorado, United States of America
| | - David D. Pollock
- Department of Biochemistry & Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado, United States of America
| | - Todd A. Castoe
- Department of Biology, University of Texas at Arlington, Arlington, Texas, United States of America
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Doyle SR, Sankaranarayanan G, Allan F, Berger D, Jimenez Castro PD, Collins JB, Crellen T, Duque-Correa MA, Ellis P, Jaleta TG, Laing R, Maitland K, McCarthy C, Moundai T, Softley B, Thiele E, Ouakou PT, Tushabe JV, Webster JP, Weiss AJ, Lok J, Devaney E, Kaplan RM, Cotton JA, Berriman M, Holroyd N. Evaluation of DNA Extraction Methods on Individual Helminth Egg and Larval Stages for Whole-Genome Sequencing. Front Genet 2019; 10:826. [PMID: 31616465 PMCID: PMC6764475 DOI: 10.3389/fgene.2019.00826] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 08/12/2019] [Indexed: 01/19/2023] Open
Abstract
Whole-genome sequencing is being rapidly applied to the study of helminth genomes, including de novo genome assembly, population genetics, and diagnostic applications. Although late-stage juvenile and adult parasites typically produce sufficient DNA for molecular analyses, these parasitic stages are almost always inaccessible in the live host; immature life stages found in the environment for which samples can be collected non-invasively offer a potential alternative; however, these samples typically yield very low quantities of DNA, can be environmentally resistant, and are susceptible to contamination, often from bacterial or host DNA. Here, we have tested five low-input DNA extraction protocols together with a low-input sequencing library protocol to assess the feasibility of whole-genome sequencing of individual immature helminth samples. These approaches do not use whole-genome amplification, a common but costly approach to increase the yield of low-input samples. We first tested individual parasites from two species spotted onto FTA cards-egg and L1 stages of Haemonchus contortus and miracidia of Schistosoma mansoni-before further testing on an additional five species-Ancylostoma caninum, Ascaridia dissimilis, Dirofilaria immitis, Strongyloides stercoralis, and Trichuris muris-with an optimal protocol. A sixth species-Dracunculus medinensis-was included for comparison. Whole-genome sequencing followed by analyses to determine the proportion of on- and off-target mapping revealed successful sample preparations for six of the eight species tested with variation both between species and between different life stages from some species described. These results demonstrate the feasibility of whole-genome sequencing of individual parasites, and highlight a new avenue toward generating sensitive, specific, and information-rich data for the diagnosis and surveillance of helminths.
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Affiliation(s)
- Stephen R. Doyle
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
| | | | - Fiona Allan
- Department of Life Sciences, Natural History Museum, London, United Kingdom
| | - Duncan Berger
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
| | - Pablo D. Jimenez Castro
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
- Grupo de Parasitologia Veterinaria, Universidad Nacional de Colombia, Bogotá, Colombia
| | - James Bryant Collins
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - Thomas Crellen
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
- Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | | | - Peter Ellis
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
| | - Tegegn G. Jaleta
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Roz Laing
- Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Kirsty Maitland
- Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Catherine McCarthy
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
| | | | - Ben Softley
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
| | - Elizabeth Thiele
- Department of Biology, Vassar College, Poughkeepsie, NY, United States
| | | | - John Vianney Tushabe
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
- Medical Research Council/Uganda Virus Research Institute and London School of Hygiene & Tropical Medicine Uganda Research Unit, Entebbe, Uganda
| | - Joanne P. Webster
- Centre for Emerging, Endemic and Exotic Diseases, Department of Pathology and Population Sciences, Royal Veterinary College, University of London, Herts, United Kingdom
| | - Adam J. Weiss
- Guinea Worm Eradication Program, The Carter Center, Atlanta, GA, United States
| | - James Lok
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Eileen Devaney
- Institute of Biodiversity Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Ray M. Kaplan
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA, United States
| | - James A. Cotton
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
| | - Matthew Berriman
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
| | - Nancy Holroyd
- Parasites and Microbes, Wellcome Sanger Institute, Hinxton, United Kingdom
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Shortt JA, Card DC, Schield DR, Liu Y, Zhong B, Castoe TA, Carlton EJ, Pollock DD. Whole Genome Amplification and Reduced-Representation Genome Sequencing of Schistosoma japonicum Miracidia. PLoS Negl Trop Dis 2017; 11:e0005292. [PMID: 28107347 PMCID: PMC5287463 DOI: 10.1371/journal.pntd.0005292] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 02/01/2017] [Accepted: 12/29/2016] [Indexed: 11/18/2022] Open
Abstract
Background In areas where schistosomiasis control programs have been implemented, morbidity and prevalence have been greatly reduced. However, to sustain these reductions and move towards interruption of transmission, new tools for disease surveillance are needed. Genomic methods have the potential to help trace the sources of new infections, and allow us to monitor drug resistance. Large-scale genotyping efforts for schistosome species have been hindered by cost, limited numbers of established target loci, and the small amount of DNA obtained from miracidia, the life stage most readily acquired from humans. Here, we present a method using next generation sequencing to provide high-resolution genomic data from S. japonicum for population-based studies. Methodology/Principal Findings We applied whole genome amplification followed by double digest restriction site associated DNA sequencing (ddRADseq) to individual S. japonicum miracidia preserved on Whatman FTA cards. We found that we could effectively and consistently survey hundreds of thousands of variants from 10,000 to 30,000 loci from archived miracidia as old as six years. An analysis of variation from eight miracidia obtained from three hosts in two villages in Sichuan showed clear population structuring by village and host even within this limited sample. Conclusions/Significance This high-resolution sequencing approach yields three orders of magnitude more information than microsatellite genotyping methods that have been employed over the last decade, creating the potential to answer detailed questions about the sources of human infections and to monitor drug resistance. Costs per sample range from $50-$200, depending on the amount of sequence information desired, and we expect these costs can be reduced further given continued reductions in sequencing costs, improvement of protocols, and parallelization. This approach provides new promise for using modern genome-scale sampling to S. japonicum surveillance, and could be applied to other schistosome species and other parasitic helminthes. Schistosomiasis is a devastating tropical disease that affects more than 200 million people worldwide. Over the past several decades, transmission control strategies implemented in China have reduced the prevalence and morbidity of Schistosoma japonicum in many areas. Infections still persist, however, and it is therefore of great interest to determine the sources of recurring infections. Genetic analysis is a promising means to achieve this. Towards this aim, we conducted a pilot study to assess the feasibility of using high-throughput sequencing to assess the geographic distribution of schistosome genetic variants. Because DNA yields from miracidia, the most easily accessible life stage, are insufficient for high throughput sequencing, we first employed whole genome amplification to obtain sufficient quantities of DNA. We then employed a technique that reproducibly sequences the same fraction of a genome across numerous samples. We successfully sequenced 6-year old S. japonicum samples from Sichuan Province, China, easily and economically identifying tens of thousands of variable loci, a sufficient number to discriminate fine-scale population structure. Further population sampling will help answer important questions concerning the persistence of infections, the sources of new infections, and whether parasite populations have undergone incipient evolution of drug resistance.
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Affiliation(s)
- Jonathan A. Shortt
- Department of Biochemistry & Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, United States of America
| | - Daren C. Card
- Department of Biology, University of Texas Arlington, Arlington, TX, United States of America
| | - Drew R. Schield
- Department of Biology, University of Texas Arlington, Arlington, TX, United States of America
| | - Yang Liu
- Institute of Parasitic Disease, Sichuan Center for Disease Control and Prevention, Chengdu, The People’s Republic of China
| | - Bo Zhong
- Institute of Parasitic Disease, Sichuan Center for Disease Control and Prevention, Chengdu, The People’s Republic of China
| | - Todd A. Castoe
- Department of Biology, University of Texas Arlington, Arlington, TX, United States of America
| | - Elizabeth J. Carlton
- Department of Environmental and Occupational Health, University of Colorado, Colorado School of Public Health, Aurora, CO, United States of America
| | - David D. Pollock
- Department of Biochemistry & Molecular Genetics, University of Colorado School of Medicine, Aurora, CO, United States of America
- * E-mail:
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Gao YM, Lu DB, Ding H, Lamberton PHL. Detecting genotyping errors at Schistosoma japonicum microsatellites with pedigree information. Parasit Vectors 2015; 8:452. [PMID: 26350750 PMCID: PMC4563838 DOI: 10.1186/s13071-015-1074-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 09/04/2015] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND Schistosomiasis japonica remains a major public health problem in China. Integrating molecular analyses, such as population genetic analyses, of the parasite into the on-going surveillance programs is helpful in exploring the factors causing the persistence and/or spread of Schistosoma japonicum. However, genotyping errors can seriously affect the results of such studies, unless accounted for in the analyses. METHODS We assessed the genotyping errors (missing alleles or false alleles) of seven S. japonicum microsatellites, using a pedigree data approach for schistosome miracidia, which were stored on Whatman FTA cards. RESULTS Among 107 schistosome miracidia successfully genotyped, resulting in a total of 715 loci calls, a total of 31 genotyping errors were observed with 25.2% of the miracidia having at least one error. The error rate per locus differed among loci, which ranged from 0 to 9.8%, with the mean error rate 4.3% over loci. With the parentage analysis software Cervus, the assignment power with these seven markers was estimated to be 89.5% for one parent and 99.9% for a parent pair. One locus was inferred to have a high number of null alleles and a second with a high mistyping rate. CONCLUSION To the authors' knowledge, this is the first time that S. japonicum pedigrees have been used in an assessment of genotyping errors of microsatellite markers. The observed locus-specific error rate will benefit downstream epidemiological or ecological analyses of S. japonicum with the markers.
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Affiliation(s)
- Yu-Meng Gao
- Department of Epidemiology and Statistics, School of Public Health, Soochow University, Suzhou, 215123, China.
- Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, School of Public Health, Soochow University, Suzhou, 215123, PR China.
| | - Da-Bing Lu
- Department of Epidemiology and Statistics, School of Public Health, Soochow University, Suzhou, 215123, China.
- Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, School of Public Health, Soochow University, Suzhou, 215123, PR China.
| | - Huan Ding
- Department of Epidemiology and Statistics, School of Public Health, Soochow University, Suzhou, 215123, China.
- Jiangsu Key Laboratory of Preventive and Translational Medicine for Geriatric Diseases, School of Public Health, Soochow University, Suzhou, 215123, PR China.
| | - Poppy H L Lamberton
- Department of Infectious Disease Epidemiology, Imperial College London, London, W2 1PG, UK.
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Bian CR, Gao YM, Lamberton PHL, Lu DB. Comparison of genetic diversity and population structure between two Schistosoma japonicum isolates—the field and the laboratory. Parasitol Res 2015; 114:2357-62. [DOI: 10.1007/s00436-015-4433-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 03/11/2015] [Indexed: 12/01/2022]
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Carlton EJ, Liu Y, Zhong B, Hubbard A, Spear RC. Associations between schistosomiasis and the use of human waste as an agricultural fertilizer in China. PLoS Negl Trop Dis 2015; 9:e0003444. [PMID: 25590142 PMCID: PMC4295866 DOI: 10.1371/journal.pntd.0003444] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/26/2014] [Indexed: 12/12/2022] Open
Abstract
Background Human waste is used as an agricultural fertilizer in China and elsewhere. Because the eggs of many helminth species can survive in environmental media, reuse of untreated or partially treated human waste, commonly called night soil, may promote transmission of human helminthiases. Methodology/Principal Findings We conducted an open cohort study in 36 villages to evaluate the association between night soil use and schistosomiasis in a region of China where schistosomiasis has reemerged and persisted despite control activities. We tested 2,005 residents for Schistosoma japonicum infection in 2007 and 1,365 residents in 2010 and interviewed heads of household about agricultural practices each study year. We used an intervention attributable ratio framework to estimate the association between night soil use and S. japonicum infection. Night soil use was reported by half of households (56% in 2007 and 46% in 2010). Village night soil use was strongly associated with human S. japonicum infection in 2007. We estimate cessation of night soil use would lead to a 49% reduction in infection prevalence in 2007 (95% CI: 12%, 71%). However, no association between night soil and schistosomiasis was observed in 2010. These inconsistent findings may be due to unmeasured confounding or temporal shifts in the importance of different sources of S. japonicum eggs on the margins of disease elimination. Conclusions/Significance The use of untreated or partially treated human waste as an agricultural fertilizer may be a barrier to permanent reductions in human helminthiases. This practice warrants further attention by the public health community. Many people use human waste as an agricultural fertilizer, often called “night soil.” If the waste is not properly treated, the use of night soil may promote the spread of infectious diseases. We suspected that night soil use may facilitate the spread of the water-borne disease, schistosomiasis, as some schistosomiasis eggs can survive in the environment for weeks. We conducted a study in 36 villages in rural China in order to see if the amount of night soil used in a village was associated with schistosomiasis. The study was conducted in an area where schistosomiasis reemerged and persisted despite an aggressive disease control program. We found half of households reported using night soil—it was used on all major crops and by people across the socio-economic spectrum. We also found that night soil use was strongly associated with schistosomiasis infection in 2007, but not in 2010. Our findings show the use of human waste as an agricultural fertilizer is common in our study region and may increase schistosomiasis infections. The extent to which night soil is used and risks of this practice should be evaluated as part of disease control programs targeting schistosomiasis and other human helminthiases.
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Affiliation(s)
- Elizabeth J Carlton
- Department of Environmental and Occupational Health, Colorado School of Public Health, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Yang Liu
- Institute of Parasitic Diseases, Sichuan Center for Disease Control and Prevention, Chengdu, China
| | - Bo Zhong
- Institute of Parasitic Diseases, Sichuan Center for Disease Control and Prevention, Chengdu, China
| | - Alan Hubbard
- Division of Biostatistics, School of Public Health, University of California, Berkeley, California, United States of America
| | - Robert C Spear
- Center for Occupational and Environmental Health, School of Public Health, University of California, Berkeley, California, United States of America
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