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Hemmings A, Sharpe H, Allen K, Bartel H, Campbell IC, Desrivières S, Dobson RJ, Folarin AA, French T, Kelly J, Micali N, Raman S, Treasure J, Abbas R, Heslop B, Street T, Schmidt U. EDIFY (Eating Disorders: Delineating Illness and Recovery Trajectories to Inform Personalised Prevention and Early Intervention in Young People): project outline. BJPsych Bull 2023; 47:328-336. [PMID: 36545688 PMCID: PMC10694679 DOI: 10.1192/bjb.2022.83] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 11/01/2022] [Accepted: 11/04/2022] [Indexed: 12/24/2022] Open
Abstract
EDIFY (Eating Disorders: Delineating Illness and Recovery Trajectories to Inform Personalised Prevention and Early Intervention in Young People) is an ambitious research project aiming to revolutionise how eating disorders are perceived, prevented and treated. Six integrated workstreams will address key questions, including: What are young people's experiences of eating disorders and recovery? What are the unique and shared risk factors in different groups? What helps or hinders recovery? How do the brain and behaviour change from early- to later-stage illness? How can we intervene earlier, quicker and in a more personalised way? This 4-year project, involving over 1000 participants, integrates arts, design and humanities with advanced neurobiological, psychosocial and bioinformatics approaches. Young people with lived experience of eating disorders are at the heart of EDIFY, serving as advisors and co-producers throughout. Ultimately, this work will expand public and professional perceptions of eating disorders, uplift under-represented voices and stimulate much-needed advances in policy and practice.
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Affiliation(s)
- Amelia Hemmings
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | | | - Karina Allen
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
| | | | - Iain C. Campbell
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Sylvane Desrivières
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Richard J.B. Dobson
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- Institute of Health Informatics, University College London, London, UK
- Health Data Research UK London, University College London, London, UK
- National Institute for Health and Care Research Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London, London, UK
- National Institute for Health and Care Research Biomedical Research Centre at University College London NHS Foundation Trust, London, UK
| | - Amos A. Folarin
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- Institute of Health Informatics, University College London, London, UK
- National Institute for Health and Care Research Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London, London, UK
| | | | | | - Nadia Micali
- University College London, London, UK
- Psychiatric Research Centre Ballerup, Ballerup, Denmark
| | | | - Janet Treasure
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
| | | | | | | | - Ulrike Schmidt
- Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
- South London and Maudsley NHS Foundation Trust, London, UK
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2
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Kabiljo R, Bowles H, Marriott H, Jones AR, Bouton CR, Dobson RJ, Quinn JP, Al Khleifat A, Swanson CM, Al-Chalabi A, Iacoangeli A. RetroSnake: A modular pipeline to detect human endogenous retroviruses in genome sequencing data. iScience 2022; 25:105289. [PMID: 36339261 PMCID: PMC9626663 DOI: 10.1016/j.isci.2022.105289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 08/08/2022] [Accepted: 10/04/2022] [Indexed: 12/02/2022] Open
Abstract
Human endogenous retroviruses (HERVs) integrated into the human genome as a result of ancient exogenous infections and currently comprise ∼8% of our genome. The members of the most recently acquired HERV family, HERV-Ks, still retain the potential to produce viral molecules and have been linked to a wide range of diseases including cancer and neurodegeneration. Although a range of tools for HERV detection in NGS data exist, most of them lack wet lab validation and they do not cover all steps of the analysis. Here, we describe RetroSnake, an end-to-end, modular, computationally efficient, and customizable pipeline for the discovery of HERVs in short-read NGS data. RetroSnake is based on an extensively wet-lab validated protocol, it covers all steps of the analysis from raw data to the generation of annotated results presented as an interactive html file, and it is easy to use by life scientists without substantial computational training. Availability and implementation: The Pipeline and an extensive documentation are available on GitHub.
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Affiliation(s)
- Renata Kabiljo
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London SE5 8AF, UK
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 9NU, UK
| | - Harry Bowles
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London SE5 8AF, UK
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 9NU, UK
| | - Heather Marriott
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London SE5 8AF, UK
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 9NU, UK
| | - Ashley R. Jones
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 9NU, UK
| | - Clement R. Bouton
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, London, UK
| | - Richard J.B. Dobson
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London SE5 8AF, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London, London, UK
- Institute of Health Informatics, University College London, London, UK
- NIHR Biomedical Research Centre at University College London Hospitals NHS Foundation Trust, London, UK
| | - John P. Quinn
- Department of Pharmacology and Therapeutics, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 3BX, UK
| | - Ahmad Al Khleifat
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 9NU, UK
| | - Chad M. Swanson
- Department of Infectious Diseases, School of Immunology and Microbial Sciences, King’s College London, London, UK
| | - Ammar Al-Chalabi
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 9NU, UK
| | - Alfredo Iacoangeli
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London SE5 8AF, UK
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London SE5 9NU, UK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London, London, UK
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3
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Bean DM, Kraljevic Z, Searle T, Bendayan R, Kevin O, Pickles A, Folarin A, Roguski L, Noor K, Shek A, Zakeri R, Shah AM, Teo JT, Dobson RJ. Angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers are not associated with severe COVID-19 infection in a multi-site UK acute hospital trust. Eur J Heart Fail 2020; 22:967-974. [PMID: 32485082 PMCID: PMC7301045 DOI: 10.1002/ejhf.1924] [Citation(s) in RCA: 138] [Impact Index Per Article: 34.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 05/22/2020] [Accepted: 05/27/2020] [Indexed: 01/08/2023] Open
Abstract
AIMS The SARS-CoV-2 virus binds to the angiotensin-converting enzyme 2 (ACE2) receptor for cell entry. It has been suggested that angiotensin-converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARB), which are commonly used in patients with hypertension or diabetes and may raise tissue ACE2 levels, could increase the risk of severe COVID-19 infection. METHODS AND RESULTS We evaluated this hypothesis in a consecutive cohort of 1200 acute inpatients with COVID-19 at two hospitals with a multi-ethnic catchment population in London (UK). The mean age was 68 ± 17 years (57% male) and 74% of patients had at least one comorbidity. Overall, 415 patients (34.6%) reached the primary endpoint of death or transfer to a critical care unit for organ support within 21 days of symptom onset. A total of 399 patients (33.3%) were taking ACEi or ARB. Patients on ACEi/ARB were significantly older and had more comorbidities. The odds ratio for the primary endpoint in patients on ACEi and ARB, after adjustment for age, sex and co-morbidities, was 0.63 (95% confidence interval 0.47-0.84, P < 0.01). CONCLUSIONS There was no evidence for increased severity of COVID-19 in hospitalised patients on chronic treatment with ACEi or ARB. A trend towards a beneficial effect of ACEi/ARB requires further evaluation in larger meta-analyses and randomised clinical trials.
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Affiliation(s)
- Daniel M. Bean
- Department of Biostatistics and Health InformaticsInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
- Health Data Research UK LondonUniversity College LondonLondonUK
| | - Zeljko Kraljevic
- Department of Biostatistics and Health InformaticsInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
| | - Thomas Searle
- Department of Biostatistics and Health InformaticsInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
| | - Rebecca Bendayan
- Department of Biostatistics and Health InformaticsInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College LondonLondonUK
| | - O'Gallagher Kevin
- King's College Hospital NHS Foundation TrustLondonUK
- School of Cardiovascular Medicine & SciencesKing's College London British Heart Foundation Centre of ExcellenceLondonUK
| | - Andrew Pickles
- Department of Biostatistics and Health InformaticsInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
| | - Amos Folarin
- Department of Biostatistics and Health InformaticsInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
- Health Data Research UK LondonUniversity College LondonLondonUK
- Institute of Health InformaticsUniversity College LondonLondonUK
- NIHR Biomedical Research CentreUniversity College London Hospitals NHS Foundation TrustLondonUK
| | - Lukasz Roguski
- Health Data Research UK LondonUniversity College LondonLondonUK
- Institute of Health InformaticsUniversity College LondonLondonUK
- NIHR Biomedical Research CentreUniversity College London Hospitals NHS Foundation TrustLondonUK
| | - Kawsar Noor
- Health Data Research UK LondonUniversity College LondonLondonUK
- Institute of Health InformaticsUniversity College LondonLondonUK
- NIHR Biomedical Research CentreUniversity College London Hospitals NHS Foundation TrustLondonUK
| | - Anthony Shek
- Department of Clinical NeuroscienceInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
| | - Rosita Zakeri
- King's College Hospital NHS Foundation TrustLondonUK
- School of Cardiovascular Medicine & SciencesKing's College London British Heart Foundation Centre of ExcellenceLondonUK
| | - Ajay M. Shah
- King's College Hospital NHS Foundation TrustLondonUK
- School of Cardiovascular Medicine & SciencesKing's College London British Heart Foundation Centre of ExcellenceLondonUK
| | - James T.H. Teo
- King's College Hospital NHS Foundation TrustLondonUK
- Department of Clinical NeuroscienceInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
| | - Richard J.B. Dobson
- Department of Biostatistics and Health InformaticsInstitute of Psychiatry, Psychology and Neuroscience, King's College LondonLondonUK
- Health Data Research UK LondonUniversity College LondonLondonUK
- NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King's College LondonLondonUK
- Institute of Health InformaticsUniversity College LondonLondonUK
- NIHR Biomedical Research CentreUniversity College London Hospitals NHS Foundation TrustLondonUK
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4
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Leirer DJ, Iyegbe CO, Di Forti M, Patel H, Carra E, Fraietta S, Colizzi M, Mondelli V, Quattrone D, Lally J, Ajnakina O, Lee SH, Curtis CJ, Breen G, Pariante C, Aitchison K, Dazzan P, Murray RM, Dobson RJ, Newhouse SJ. Differential gene expression analysis in blood of first episode psychosis patients. Schizophr Res 2019; 209:88-97. [PMID: 31113746 PMCID: PMC6677921 DOI: 10.1016/j.schres.2019.05.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 02/22/2019] [Accepted: 05/05/2019] [Indexed: 12/26/2022]
Abstract
BACKGROUND Psychosis is a condition influenced by an interaction of environmental and genetic factors. Gene expression studies can capture these interactions; however, studies are usually performed in patients who are in remission. This study uses blood of first episode psychosis patients, in order to characterise deregulated pathways associated with psychosis symptom dimensions. METHODS Peripheral blood from 149 healthy controls and 131 first episode psychosis patients was profiled using Illumina HT-12 microarrays. A case/control differential expression analysis was performed, followed by correlation of gene expression with positive and negative syndrome scale (PANSS) scores. Enrichment analyses were performed on the associated gene lists. We test for pathway differences between first episode psychosis patients who qualify for a Schizophrenia diagnosis against those who do not. RESULTS A total of 978 genes were differentially expressed and enriched for pathways associated to immune function and the mitochondria. Using PANSS scores we found that positive symptom severity was correlated with immune function, while negative symptoms correlated with mitochondrial pathways. CONCLUSIONS Our results identified gene expression changes correlated with symptom severity and showed that key pathways are modulated by positive and negative symptom dimensions.
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Affiliation(s)
- Daniel J. Leirer
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK,Corresponding author.
| | - Conrad O. Iyegbe
- Department of Psychosis Studies, Institute of Psychiatry, Kings College London, Box P092, De Crespigny Park, SE5 8AF London, UK
| | - Marta Di Forti
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK
| | - Hamel Patel
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK,Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK
| | - Elena Carra
- Department of Psychosis Studies, Institute of Psychiatry, Kings College London, Box P092, De Crespigny Park, SE5 8AF London, UK
| | - Sara Fraietta
- Department of Psychosis Studies, Institute of Psychiatry, Kings College London, Box P092, De Crespigny Park, SE5 8AF London, UK
| | - Marco Colizzi
- Department of Psychosis Studies, Institute of Psychiatry, Kings College London, Box P092, De Crespigny Park, SE5 8AF London, UK
| | - Valeria Mondelli
- Department of Psychological Medicine, Institute of Psychiatry, Kings College London, De Crespigny Park, SE5 8AF London, UK
| | - Diego Quattrone
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK
| | - John Lally
- Department of Psychosis Studies, Institute of Psychiatry, Kings College London, Box P092, De Crespigny Park, SE5 8AF London, UK
| | - Olesya Ajnakina
- Department of Psychosis Studies, Institute of Psychiatry, Kings College London, Box P092, De Crespigny Park, SE5 8AF London, UK
| | - Sang Hyuck Lee
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK,NIHR BioResource Centre Maudsley, NIHR Maudsley Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust (SLaM) & Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London
| | - Charles J. Curtis
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK,NIHR BioResource Centre Maudsley, NIHR Maudsley Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust (SLaM) & Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London
| | - Gerome Breen
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK,NIHR BioResource Centre Maudsley, NIHR Maudsley Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust (SLaM) & Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London
| | - Carmine Pariante
- Department of Psychological Medicine, Institute of Psychiatry, Kings College London, De Crespigny Park, SE5 8AF London, UK
| | - Katherine Aitchison
- Departments of Psychiatry and Medical Genetics, University of Alberta, 11361-87 Avenue, AB T6G 2E1, Edmonton, Canada
| | - Paola Dazzan
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK,Department of Psychological Medicine, Institute of Psychiatry, Kings College London, De Crespigny Park, SE5 8AF London, UK
| | - Robin M. Murray
- Department of Psychosis Studies, Institute of Psychiatry, Kings College London, Box P092, De Crespigny Park, SE5 8AF London, UK
| | - Richard J.B. Dobson
- NIHR BioResource Centre Maudsley, NIHR Maudsley Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust (SLaM) & Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London,Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK
| | - Stephen J. Newhouse
- MRC Social, Genetic and Developmental Psychiatry (SGDP) Centre, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK,Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology and Neuroscience, Box P080, De Crespigny Park, SE5 8AF London, UK
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Shi L, Nevado-Holgado AJ, Liu BY, Killick R, Ribe EM, Dixit A, Kiddle SJ, Sattlecker M, Dobson RJ, Cuadrado A, Lovestone S. P3-245: DKK1 OVEREXPRESSION IN VITRO NOMINATES PROTEINS PREDICTING ALZHEIMER'S PATHOLOGY IN BLOOD. Alzheimers Dement 2019. [DOI: 10.1016/j.jalz.2019.06.3275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Liu Shi
- Department of Psychiatry; University of Oxford; Oxford United Kingdom
| | | | | | - Richard Killick
- Institute of Psychiatry, Psychology and Neuroscience; King's College London; London United Kingdom
| | - Elena M. Ribe
- Department of Psychiatry; University of Oxford; Oxford United Kingdom
| | - Abhishek Dixit
- Institute of Psychiatry, Psychology and Neuroscience; King's College London; London United Kingdom
| | - Steven John Kiddle
- Institute of Psychiatry, Psychology and Neuroscience; King's College London; London United Kingdom
- MRC Social, Genetic and Developmental Psychiatry Centre; King's College London; London United Kingdom
| | - Martina Sattlecker
- Institute of Psychiatry, Psychology and Neuroscience; King's College London; London United Kingdom
- MRC Social, Genetic and Developmental Psychiatry Centre; King's College London; London United Kingdom
| | - Richard J.B. Dobson
- Institute of Psychiatry, Psychology and Neuroscience; King's College London; London United Kingdom
- MRC Social, Genetic and Developmental Psychiatry Centre; King's College London; London United Kingdom
- NIHR Biomedical Research Centre for Mental Health and Biomedical Research Unit for Dementia at South London and Maudsley NHS Foundation; London United Kingdom
| | - Antonio Cuadrado
- Department of Biochemistry, Faculty of Medicine; Autonomous University of Madrid; Madrid Spain
| | - Simon Lovestone
- Department of Psychiatry; University of Oxford; Oxford United Kingdom
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Iacoangeli A, Al Khleifat A, Sproviero W, Shatunov A, Jones AR, Morgan SL, Pittman A, Dobson RJ, Newhouse SJ, Al-Chalabi A. DNAscan: personal computer compatible NGS analysis, annotation and visualisation. BMC Bioinformatics 2019; 20:213. [PMID: 31029080 PMCID: PMC6487045 DOI: 10.1186/s12859-019-2791-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 04/02/2019] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND Next Generation Sequencing (NGS) is a commonly used technology for studying the genetic basis of biological processes and it underpins the aspirations of precision medicine. However, there are significant challenges when dealing with NGS data. Firstly, a huge number of bioinformatics tools for a wide range of uses exist, therefore it is challenging to design an analysis pipeline. Secondly, NGS analysis is computationally intensive, requiring expensive infrastructure, and many medical and research centres do not have adequate high performance computing facilities and cloud computing is not always an option due to privacy and ownership issues. Finally, the interpretation of the results is not trivial and most available pipelines lack the utilities to favour this crucial step. RESULTS We have therefore developed a fast and efficient bioinformatics pipeline that allows for the analysis of DNA sequencing data, while requiring little computational effort and memory usage. DNAscan can analyse a whole exome sequencing sample in 1 h and a 40x whole genome sequencing sample in 13 h, on a midrange computer. The pipeline can look for single nucleotide variants, small indels, structural variants, repeat expansions and viral genetic material (or any other organism). Its results are annotated using a customisable variety of databases and are available for an on-the-fly visualisation with a local deployment of the gene.iobio platform. DNAscan is implemented in Python. Its code and documentation are available on GitHub: https://github.com/KHP-Informatics/DNAscan . Instructions for an easy and fast deployment with Docker and Singularity are also provided on GitHub. CONCLUSIONS DNAscan is an extremely fast and computationally efficient pipeline for analysis, visualization and interpretation of NGS data. It is designed to provide a powerful and easy-to-use tool for applications in biomedical research and diagnostic medicine, at minimal computational cost. Its comprehensive approach will maximise the potential audience of users, bringing such analyses within the reach of non-specialist laboratories, and those from centres with limited funding available.
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Affiliation(s)
- A Iacoangeli
- Department of Biostatistics and Health Informatics, King's College London, London, UK. .,Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, King's College London, London, UK.
| | - A Al Khleifat
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, King's College London, London, UK
| | - W Sproviero
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, King's College London, London, UK
| | - A Shatunov
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, King's College London, London, UK
| | - A R Jones
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, King's College London, London, UK
| | - S L Morgan
- Department of Molecular Neuroscience, UCL, Institute of Neurology, London, UK
| | - A Pittman
- Department of Molecular Neuroscience, UCL, Institute of Neurology, London, UK
| | - R J Dobson
- Department of Biostatistics and Health Informatics, King's College London, London, UK.,Farr Institute of Health Informatics Research, UCL Institute of Health Informatics, University College London, London, UK.,National Institute for Health Research (NIHR) Biomedical Research Centre and Dementia Unit at South London and Maudsley NHS Foundation Trust and King's College London, London, UK
| | - S J Newhouse
- Department of Biostatistics and Health Informatics, King's College London, London, UK.,Farr Institute of Health Informatics Research, UCL Institute of Health Informatics, University College London, London, UK.,National Institute for Health Research (NIHR) Biomedical Research Centre and Dementia Unit at South London and Maudsley NHS Foundation Trust and King's College London, London, UK
| | - A Al-Chalabi
- Department of Basic and Clinical Neuroscience, Maurice Wohl Clinical Neuroscience Institute, King's College London, London, UK.,King's College Hospital, Bessemer Road, London, SE5 9RS, UK
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7
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Abstract
BACKGROUND Microarray technologies have identified imbalances in the expression of specific genes and biological pathways in Alzheimer's disease (AD) brains. However, there is a lack of reproducibility across individual AD studies, and many related neurodegenerative and mental health disorders exhibit similar perturbations. OBJECTIVE Meta-analyze publicly available transcriptomic data from multiple brain-related disorders to identify robust transcriptomic changes specific to AD brains. METHODS Twenty-two AD, eight schizophrenia, five bipolar disorder, four Huntington's disease, two major depressive disorder, and one Parkinson's disease dataset totaling 2,667 samples and mapping to four different brain regions (temporal lobe, frontal lobe, parietal lobe, and cerebellum) were analyzed. Differential expression analysis was performed independently in each dataset, followed by meta-analysis using a combining p-value method known as Adaptively Weighted with One-sided Correction. RESULTS Meta-analysis identified 323, 435, 1,023, and 828 differentially expressed genes specific to the AD temporal lobe, frontal lobe, parietal lobe, and cerebellum brain regions, respectively. Seven of these genes were consistently perturbed across all AD brain regions with SPCS1 gene expression pattern replicating in RNA-Seq data. A further nineteen genes were perturbed specifically in AD brain regions affected by both plaques and tangles, suggesting possible involvement in AD neuropathology. In addition, biological pathways involved in the "metabolism of proteins" and viral components were significantly enriched across AD brains. CONCLUSION This study identified transcriptomic changes specific to AD brains, which could make a significant contribution toward the understanding of AD disease mechanisms and may also provide new therapeutic targets.
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Affiliation(s)
- Hamel Patel
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- NIHR BioResource Centre Maudsley, NIHR Maudsley Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust (SLaM) and Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London, London, UK
| | - Richard J.B. Dobson
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- NIHR BioResource Centre Maudsley, NIHR Maudsley Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust (SLaM) and Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London, London, UK
- Health Data Research UK London, University College London, London, UK
- Institute of Health Informatics, University College London, London, UK
- The National Institute for Health Research University College London Hospitals Biomedical Research Centre, University College London, London, UK
| | - Stephen J. Newhouse
- Department of Biostatistics and Health Informatics, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- NIHR BioResource Centre Maudsley, NIHR Maudsley Biomedical Research Centre (BRC) at South London and Maudsley NHS Foundation Trust (SLaM) and Institute of Psychiatry, Psychology and Neuroscience (IoPPN), King’s College London, London, UK
- Health Data Research UK London, University College London, London, UK
- Institute of Health Informatics, University College London, London, UK
- The National Institute for Health Research University College London Hospitals Biomedical Research Centre, University College London, London, UK
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Baker E, Iqbal E, Johnston C, Broadbent M, Shetty H, Stewart R, Howard RJ, Newhouse SJ, Khondoker M, Kiddle SJ, Dobson RJ. [O3–10–06]: DEMENTIA SEVERITY AND PROGRESSION: IDENTIFYING PATIENTS AT RISK FOR FASTER COGNITIVE DECLINE. Alzheimers Dement 2017. [DOI: 10.1016/j.jalz.2017.07.362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Elizabeth Baker
- King's College LondonLondonUnited Kingdom
- South London and Maudsley NHS Foundation TrustLondonUnited Kingdom
- South London and the Maudsley NHS Foundation TrustLondonUnited Kingdom
- Mental Health of Older Adults & Dementia CAG, South London & Maudsley NHS Foundation TrustLondonUnited Kingdom
- IOPPNKing's College LondonLondonUnited Kingdom
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Voyle N, Patel H, Folarin A, Newhouse S, Johnston C, Visser PJ, Dobson RJ, Kiddle SJ. Genetic Risk as a Marker of Amyloid-β and Tau Burden in Cerebrospinal Fluid. J Alzheimers Dis 2017; 55:1417-1427. [PMID: 27834776 PMCID: PMC5181674 DOI: 10.3233/jad-160707] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2016] [Indexed: 12/31/2022]
Abstract
BACKGROUND The search for a biomarker of Alzheimer's disease (AD) pathology (amyloid-β (Aβ) and tau) is ongoing, with the best markers currently being measurements of Aβ and tau in cerebrospinal fluid (CSF) and via positron emission tomography (PET) scanning. These methods are relatively invasive, costly, and often have high screening failure rates. Consequently, research is aiming to elucidate blood biomarkers of Aβ and tau. OBJECTIVE This study aims to investigate a case/control polygenic risk score (PGRS) as a marker of tau and investigate blood markers of a combined Aβ and tau outcome for the first time. A sub-study also considers plasma tau as markers of Aβ and tau pathology in CSF. METHODS We used data from the EDAR*, DESCRIPA**, and Alzheimer's Disease Neuroimaging Initiative (ADNI) cohorts in a logistic regression analysis to investigate blood markers of Aβ and tau in CSF. In particular, we investigated the extent to which a case/control PGRS is predictive of CSF tau, CSF amyloid, and a combined amyloid and tau outcome. The predictive ability of models was compared to that of age, gender, and APOE genotype ('basic model'). RESULTS In EDAR and DESCRIPA test data, inclusion of a case/control PGRS was no more predictive of Aβ, and a combined Aβ and tau endpoint than the basic models (accuracies of 66.0%, and 73.3% respectively). The tau model saw a small increase in accuracy compared to basic models (59.6%). ADNI 2 test data also showed a slight increase in accuracy for the Aβ model when compared to the basic models (61.4%). CONCLUSION We see some evidence that a case/control PGRS is marginally more predictive of Aβ and tau pathology than the basic models. The search for predictive factors of Aβ and tau pathologies, above and beyond demographic information, is still ongoing. Better understanding of AD risk alleles, development of more sensitive assays, and studies of larger sample size are three avenues that may provide such factors. However, the clinical utility of possible predictors of brain Aβ and tau pathologies must also be investigated.*'Beta amyloid oligomers in the early diagnosis of AD and as marker for treatment response'**'Development of screening guidelines and criteria for pre-dementia Alzheimer's disease'.
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Affiliation(s)
- Nicola Voyle
- MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
| | - Hamel Patel
- MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
| | - Amos Folarin
- MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
| | - Stephen Newhouse
- MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
| | - Caroline Johnston
- MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
| | - Pieter Jelle Visser
- Department of Neurology and Alzheimer Center, VU University Medical Center, Amsterdam, The Netherlands
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA
| | - Richard J.B. Dobson
- MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre for Mental Health and Biomedical Research Unit for Dementia at South London and Maudsley NHS Foundation, London, UK
- Farr Institute of Health Informatics Research, UCL Institute of Health Informatics, University College London, London, UK
| | - Steven J. Kiddle
- MRC Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- MRC Biostatistics Unit, Cambridge Biomedical Campus, Cambridge Institute of Public Health, Forvie Site, Robinson Way, Cambridge, UK
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Wu H, Oellrich A, Girges C, de Bono B, Hubbard TJ, Dobson RJ. Automated PDF highlighting to support faster curation of literature for Parkinson's and Alzheimer's disease. Database (Oxford) 2017; 2017:3091736. [PMID: 28365743 PMCID: PMC5467557 DOI: 10.1093/database/bax027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 01/23/2017] [Accepted: 03/08/2017] [Indexed: 12/20/2022]
Abstract
Neurodegenerative disorders such as Parkinson's and Alzheimer's disease are devastating and costly illnesses, a source of major global burden. In order to provide successful interventions for patients and reduce costs, both causes and pathological processes need to be understood. The ApiNATOMY project aims to contribute to our understanding of neurodegenerative disorders by manually curating and abstracting data from the vast body of literature amassed on these illnesses. As curation is labour-intensive, we aimed to speed up the process by automatically highlighting those parts of the PDF document of primary importance to the curator. Using techniques similar to those of summarisation, we developed an algorithm that relies on linguistic, semantic and spatial features. Employing this algorithm on a test set manually corrected for tool imprecision, we achieved a macro F 1 -measure of 0.51, which is an increase of 132% compared to the best bag-of-words baseline model. A user based evaluation was also conducted to assess the usefulness of the methodology on 40 unseen publications, which reveals that in 85% of cases all highlighted sentences are relevant to the curation task and in about 65% of the cases, the highlights are sufficient to support the knowledge curation task without needing to consult the full text. In conclusion, we believe that these are promising results for a step in automating the recognition of curation-relevant sentences. Refining our approach to pre-digest papers will lead to faster processing and cost reduction in the curation process. Database URL https://github.com/KHP-Informatics/NapEasy.
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Affiliation(s)
- Honghan Wu
- Department of Biostatistics and Health Informatics, King's College London, De Crespigny Park, Denmark Hill London SE5 8AF, UK
- School of Computer and Software, Nanjing University of Information Science and Technology, 219 Ningliu Road, Nanjing, China, 210044
| | - Anika Oellrich
- Department of Biostatistics and Health Informatics, King's College London, De Crespigny Park, Denmark Hill London SE5 8AF, UK
| | - Christine Girges
- Farr Institute of Health Informatics Research, UCL Institute of Health Informatics, University College London, London Gower Street, WC1E 6BT, UK
| | - Bernard de Bono
- Farr Institute of Health Informatics Research, UCL Institute of Health Informatics, University College London, London Gower Street, WC1E 6BT, UK
| | - Tim J.P. Hubbard
- Department of Medical and Molecular Genetics, King's College London, Guys Hospital, Great Maze Pond, London SE1 9RT, UK
| | - Richard J.B. Dobson
- Department of Biostatistics and Health Informatics, King's College London, De Crespigny Park, Denmark Hill London SE5 8AF, UK
- Farr Institute of Health Informatics Research, UCL Institute of Health Informatics, University College London, London Gower Street, WC1E 6BT, UK
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Patel H, Sattlecker M, Leirer D, Forti M, Mondelii V, Murray RM, Dobson RJ, Newhouse SJ. P1‐039: Assessment of an Alzheimer’s Gene Expression Signature. Alzheimers Dement 2016. [DOI: 10.1016/j.jalz.2016.06.786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
| | | | | | | | | | | | - Richard J.B. Dobson
- NIHR Biomedical Research Centre for Mental Health and Biomedical Research Unit for Dementia at South London and Maudsley NHS FoundationLondonUnited Kingdom
- Institute of Psychiatry Psychology and Neuroscience King's College LondonLondonUnited Kingdom
| | - Stephen J. Newhouse
- Institute of Psychiatry Psychology and Neuroscience King's College LondonLondonUnited Kingdom
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Proitsi P, Min K, Whiley L, Newhouse S, Johnston C, Soininen H, Kloszewska I, Mecocci P, Tsolaki M, Vellas B, Sham P, Lovestone S, Powell JF, Quigley CL, Dobson RJ. O4‐05‐05: Genetic influences on metabolite levels in Alzheimer's disease. Alzheimers Dement 2015. [DOI: 10.1016/j.jalz.2015.07.373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Affiliation(s)
| | - Kim Min
- King's College LondonLondonUnited Kingdom
| | | | | | | | | | | | - Patrizia Mecocci
- Istituto di Gerontologia e Geriatria, Università degli Studi di PerugiaPerugiaItaly
| | | | | | - Pak Sham
- University of Hong KongHong KongHong Kong
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Voyle N, Baker D, Burnham SC, Covin A, Zhang Z, Sangurdekar DP, Tan Hehir CA, Bazenet C, Lovestone S, Kiddle S, Dobson RJ. Blood Protein Markers of Neocortical Amyloid-β Burden: A Candidate Study Using SOMAscan Technology. J Alzheimers Dis 2015; 46:947-61. [PMID: 25881911 PMCID: PMC4923714 DOI: 10.3233/jad-150020] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/26/2015] [Indexed: 12/18/2022]
Abstract
BACKGROUND Four previously reported studies have tested for association of blood proteins with neocortical amyloid-β burden (NAB). If shown to be robust, these proteins could have utility as a blood test for enrichment in clinical trials of Alzheimer's disease (AD) therapeutics. OBJECTIVE This study aimed to investigate whether previously identified blood proteins also show evidence for association with NAB in serum samples from the Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL). The study considers candidate proteins seen in cohorts other than AIBL and candidates previously discovered in the AIBL cohort. METHODS Our study used the SOMAscan platform for protein quantification in blood serum. Linear and logistic regressions were used to model continuous NAB and dichotomized NAB respectively using single proteins as a predictor. Multiple protein models were built using stepwise regression techniques and support vectors machines. Age and APOEɛ4 carriage were used as covariates for all analysis. RESULTS Of the 41 proteins previously reported, 15 AIBL candidates and 20 non-AIBL candidates were available for testing. Of these candidates, pancreatic polypeptide (PPY) and IgM showed a significant association with NAB. Notably, IgM was found to associate with continuous NAB across cognitively normal control subjects. CONCLUSIONS We have further demonstrated the association of PPY and IgM with NAB, despite technical differences between studies. There are several reasons for a lack of significance for the other candidates including platform differences and the use of serum rather than plasma samples. To investigate the possibility of technical differences causing lack of replication, further studies are required.
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Affiliation(s)
- Nicola Voyle
- Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- MRC Social, Genetic and Developmental Psychiatry Centre, King’s College London, London, UK
| | - David Baker
- Janssen R&D, Neurosciences, Titusville, NJ, USA
| | - Samantha C. Burnham
- CSIRO Digital Productivity and Food and Nutrition Flagships: eHealth, Floreat, WA, Australia
| | | | | | | | | | - Chantal Bazenet
- Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre for Mental Health and Biomedical Research Unit for Dementia at South London and Maudsley NHS Foundation, London, UK
| | - Simon Lovestone
- Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- Department of Psychiatry, Oxford University, Oxford, UK
| | - Steven Kiddle
- Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- MRC Social, Genetic and Developmental Psychiatry Centre, King’s College London, London, UK
| | - Richard J.B. Dobson
- Institute of Psychiatry, Psychology and Neuroscience, King’s College London, London, UK
- NIHR Biomedical Research Centre for Mental Health and Biomedical Research Unit for Dementia at South London and Maudsley NHS Foundation, London, UK
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Dobson RJ, Barnes EH, Tyrrell KL, Hosking BC, Larsen JWA, Besier RB, Love S, Rolfe PF, Bailey JN. A multi-species model to assess the effect of refugia on worm control and anthelmintic resistance in sheep grazing systems. Aust Vet J 2011; 89:200-8. [PMID: 21595639 DOI: 10.1111/j.1751-0813.2011.00719.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Develop a computer simulation model that uses daily meteorological data and farm management practices to predict populations of Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia (Ostertagia) circumcincta and the evolution of anthelmintic resistance within a sheep flock. Use the model to explore if increased refugia, provided by leaving some adult sheep untreated, would delay development of anthelmintic resistance without compromising nematode control. PROCEDURES Compare model predictions with field observations from a breeding flock in Armidale, NSW. Simulate the impact of leaving 1-10% of adult sheep untreated in diverse sheep-grazing systems. RESULTS Predicted populations of Tr. colubriformis and T. circumcincta were less than those observed in the field, attributed to nutritional stress experienced by the sheep during drought and not accounted for by the model. Observed variation in faecal egg counts explained by the model (R(2) ) for these species was 40-50%. The H. contortus populations and R(2) were both low. Leaving some sheep untreated worked best in situations where animals were already grazing or were moved onto pastures with low populations of infective larvae. In those cases, anthelmintic resistance was delayed and nematode control was maintained when 1-4% of adult stock remained untreated. CONCLUSIONS In general, the model predicted that leaving more than 4% of adults untreated did not sufficiently delay the development of anthelmintic resistance to justify the increased production risk from such a strategy. The choice of a drug rotation strategy had an equal or larger effect on nematode control, and selection for resistance, than leaving 1-10% of adults untreated.
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Affiliation(s)
- R J Dobson
- School of Veterinary & Biomedical Sciences, Murdoch University, South Street, Murdoch, Western Australia 6150, Australia.
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15
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Dobson RJ, Hosking BC, Besier RB, Love S, Larsen JWA, Rolfe PF, Bailey JN. Minimising the development of anthelmintic resistance, and optimising the use of the novel anthelmintic monepantel, for the sustainable control of nematode parasites in Australian sheep grazing systems. Aust Vet J 2011; 89:160-6. [PMID: 21495986 DOI: 10.1111/j.1751-0813.2011.00703.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To compare the risk of different treatment scenarios on selecting for anthelmintic resistance on Australian sheep farms. DESIGN A computer simulation model predicted populations of Trichostrongylus colubriformis, Haemonchus contortus or Teladorsagia (Ostertagia) circumcincta, and the frequency of anthelmintic resistance genes. METHOD Nematode populations and the progression of drug resistance for a variety of treatment options and management practices in sheep-rearing areas of Western Australia (WA), Victoria (VIC) and New South Wales (NSW) were simulated. A scoring system was devised to measure the success of each option in delaying resistance to each anthelmintic and in controlling nematode populations. RESULTS The best option at all sites was combining the new anthelmintic (monepantel) with a triple mixture of benzimidazole, levamisole and abamectin (COM). The next best option was: in NSW, rotation at each treatment between monepantel, moxidectin and COM; in VIC, rotation at each treatment between monepantel and COM; and in WA, rotation at each treatment between monepantel (used in winter) and COM or moxidectin (used in summer-autumn). In WA, rapid selection for resistance occurred as a consequence of summer-autumn treatments; however, if a small percentage of adult stock were left untreated then this selection could be greatly reduced. Despite purposely assuming relatively high resistance to benzimidazole and levamisole, COM was still effective in controlling worms and delaying resistance. CONCLUSIONS Because of cost constraints, it may not be feasible or profitable for producers to always use the combination of all drugs. However, the second- and third-best options still considerably slowed the development of anthelmintic resistance.
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Affiliation(s)
- R J Dobson
- School of Veterinary & Biomedical Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia.
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16
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Dargantes AP, Mercado RT, Dobson RJ, Reid SA. Estimating the impact of Trypanosoma evansi infection (surra) on buffalo population dynamics in southern Philippines using data from cross-sectional surveys. Int J Parasitol 2009; 39:1109-14. [PMID: 19268471 DOI: 10.1016/j.ijpara.2009.02.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 02/05/2009] [Accepted: 02/05/2009] [Indexed: 11/30/2022]
Abstract
Despite the widespread problem with surra (Trypanosoma evansi) in livestock, there are no published studies on its impact on host populations, probably because of the large financial and time cost involved in performing longitudinal studies. During 2002-6, a cross-sectional survey for T. evansi infection involving 1732 buffaloes from 71 villages in southern Philippines was carried out. Other livestock animals (horses, cattle and goats) in every surveyed village were also tested for infection with T. evansi but domestic buffaloes were the primary survey target. Seroprevalence ranged from 6% to 21% and 13% to 100% for buffaloes in low and high risk areas, respectively. Key demographic parameters were estimated from the age structured distributions of the sampled buffalo population for each sex. All areas were dominated by females (69%) and the annual calving rate for areas of 100% and low seroprevalence was 15% and 47%, respectively. Males were removed at a relatively high annual rate of 27% in all areas. In the main reproductive years (4-10) female removal/mortality was <1% and 10% for low and high risk areas, respectively. Older females were removed/died at a rate similar to males regardless of area. In high risk areas there were consistently more 2-year than 1-year old females and the reverse was true for the low risk areas. This implies that females were imported to the high risk areas for breeding. By assuming a stable age structure and similar size populations in each area, it was estimated that 28% of female calves need to be moved from low to high risk areas to maintain the observed age structure. In high risk areas, surra imposes significant financial losses due to reduced fertility, high mortality/removal rate and the necessity to import replacement buffaloes.
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Affiliation(s)
- A P Dargantes
- School of Veterinary & Biomedical Sciences, Murdoch University, South Street, Murdoch, WA 6150, Australia
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Kotze AC, Dobson RJ, Chandler D. Synergism of rotenone by piperonyl butoxide in Haemonchus contortus and Trichostrongylus colubriformis in vitro: potential for drug-synergism through inhibition of nematode oxidative detoxification pathways. Vet Parasitol 2005; 136:275-82. [PMID: 16325340 DOI: 10.1016/j.vetpar.2005.11.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 10/07/2005] [Accepted: 11/01/2005] [Indexed: 10/25/2022]
Abstract
The anthelmintic properties of rotenone and its activity in combination with the cytochrome P450 inhibitor piperonyl butoxide, were examined in in vitro assays with adults and larvae of Haemonchus contortus and larvae of Trichostrongylus colubriformis. Rotenone was toxic to larvae of both species, with LC(50) values in larval development assays of 0.54 and 0.64 microg/ml for H. contortus and T. colubriformis, respectively. The compound also caused complete cessation of movement in adult H. contortus after 72 h at a concentration of 20 microg/ml. Toxicity of rotenone towards the larvae of both species was increased in the presence of piperonyl butoxide (synergism ratios of 3-4-fold at the LC(50)) and the activity against adult H. contortus was also significantly enhanced following pre-treatment with piperonyl butoxide. This significant synergism suggests that these nematode species are able to utilize a cytochrome P450 enzyme system to detoxify rotenone and indicates that a role may exist for cytochrome P450 inhibitors to act as synergists for other anthelmintics which are susceptible to oxidative metabolism within the nematode.
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Affiliation(s)
- A C Kotze
- CSIRO Livestock Industries, St. Lucia, Australia.
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Affiliation(s)
- C M Robinson
- The Shoulder Injury Clinic, Royal Infirmary of Edinburgh, Edinburgh, Scotland, UK
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Ancheta PB, Dumilon RA, Venturina VM, Cerbito WA, Dobson RJ, LeJambre LF, Villar EC, Gray GD. Efficacy of benzimidazole anthelmintics in goats and sheep in the Philippines using a larval development assay. Vet Parasitol 2004; 120:107-21. [PMID: 15019148 DOI: 10.1016/j.vetpar.2003.10.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2003] [Revised: 09/30/2003] [Accepted: 10/08/2003] [Indexed: 10/26/2022]
Abstract
The negative effects of nematodes in small ruminants can be reduced by use of dewormers but their effectiveness is increasingly limited by the emergence of anthelmintic resistance. The efficacy of benzimidazole (BZ) anthelmintics in the Philippines was estimated by an in vitro larval development assay using worm eggs recovered from faeces collected from goats and sheep. Two hundred and eighteen farms were selected to represent areas of the country with high goat and sheep populations and the full range of farm sizes, from smallholders with just a few animals to commercial and institutional farms with several hundred. Initial surveys of worm control advisers indicated that BZs have been in continuous widespread use for up to 20 years with little use of other chemical groups. A larval development assay (LDA: DrenchRite) was modified for use with BZs alone to allow up to five samples to be analysed on a single microtitre plate. The assay was validated by comparison with the faecal egg count reduction test (FECRT). The dominant nematode genera were Haemonchus and Trichostrongylus with small numbers of Oesophagostomum. The range of BZ efficacy estimated from the LDA results was 0-100% and the distribution of efficacy levels was continuous, with mean efficacy of 82 and 64% for goats and sheep, respectively. There were significant associations between efficacy and parameters measured to characterize the sampled farms: size of animal management group, FEC of sample, recent importation of stock and no access to common grazing were all correlated with decreased efficacy. Likewise, low efficacy was associated with reported frequency and number of years that BZ drenches had been used. The LDA was found to be highly suited to estimate efficacy in nematode populations from small farms where performance of a FECRT for even one chemical would be impractical. Using a larval development assay, we have demonstrated a wide efficacy range for BZs against nematodes from all sizes of goat and sheep farms in the tropics.
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Affiliation(s)
- P B Ancheta
- Central Luzon State University, Muñoz, Nueva Ecija, Philippines
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Tyrrell KL, Dobson RJ, Stein PA, Walkden-Brown SW. The effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus. Vet Parasitol 2002; 107:85-93. [PMID: 12072216 DOI: 10.1016/s0304-4017(02)00092-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The in vivo effects of ivermectin and moxidectin on egg viability and larval development of ivermectin-resistant Haemonchus contortus were examined over time after anthelmintic treatment of sheep. Twenty merino sheep, (12 months old) were allocated to five treatment groups and infected with ivermectin-resistant H. contortus. Thirty one days later, the sheep were treated with intraruminal ivermectin capsules, oral ivermectin, oral moxidectin or injectable moxidectin at the manufacturer's recommended dosages, or left untreated. At various times up to 112 days after treatment, faecal egg counts (FEC) were determined and development rates of infective larvae (L3) cultured in faeces or on agar were measured. Eggs in faecal cultures from ivermectin capsule treated sheep showed reduced L3 development percentages in comparison to faecal cultures from untreated sheep. Eggs from ivermectin capsule treated sheep, isolated from faeces, and cultured on agar showed similar L3 development to eggs from control sheep. These results demonstrate an inhibitory effect of excreted ivermectin in faeces on larval development of ivermectin-resistant H. contortus. L3 development in faecal culture from animals receiving oral ivermectin were reduced for only 3 days after treatment. Faecal egg counts and development of L3 larvae in both culture systems from moxidectin treated sheep were low, due to the high efficacy of the drug. Egg counts in moxidectin treated sheep were reduced by approximately 90% 24h after treatment, before decreasing to almost 100% at 48h, suggesting that the current quarantine recommendation of holding sheep off pasture for 24h after treatment may still lead to some subsequent pasture contamination with worm eggs.
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Affiliation(s)
- K L Tyrrell
- CSIRO Livestock Industries, Locked Bag 1, Armidale NSW, Australia.
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Abstract
OBJECTIVE To provide principles for the appropriate use of avermectin/milbemycin or macrocyclic lactone (ML) anthelmintics in sheep, to ensure effective worm control and to minimise selection for ML resistance. STRATEGY The principles were based on an assessment of the information currently available. The MLs were categorised into three groups (ivermectin [IVM], abamectin [ABA] and moxidectin [MOX]) based on structural differences, persistence and efficacy against ML resistant strains. The reported order of activity or efficacy against ML resistant worm strains was IVM<ABA<MOX. General treatment schemes were considered for Australian conditions and were divided into the following situations: 1. quarantine treatment, 2. treatment on/to clean pasture, 3. treatment on/to safe pasture, 4. treatment on/to moderate/heavily contaminated pasture. For each of these situations a strategy was considered for farms where ML resistance was present or absent. It was assumed that resistance commonly occurs in some or all other broad spectrum anthelmintics, and even where ML resistance has been detected, the ML group remains the most effective. The guidelines provided are general and it is expected that state agencies and sheep/veterinary advisers would give specific advice to suit their environments and drug resistance/worm problems. CONCLUSIONS The primary recommendation is to use a mixture of effective drugs when treating sheep. However, unless the combination treatment is highly effective it is unlikely to delay selection for ML resistance if sheep are being treated and moved to a clean or safe pasture. Where possible, reliance on the ML anthelmintics should be reduced by not using them every year, not using them in low risk stock or by using narrow spectrum and low efficacy drugs such as naphthalophos when appropriate. Anthelmintic treatment should be given as part of a strategic worm control program. It is suggested that IVM-oral and IVM-capsules should not be used when ML resistance is present. In this situation MOX or ABA should be used in combination with other drugs, provided that the chosen ML is effective against the resistant parasite. It is essential to monitor the efficacy of ML and drug combinations by post-treatment worm egg counts, particularly when ML resistance has been detected.
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Affiliation(s)
- R J Dobson
- CSIRO Livestock Industries, McMaster Laboratory, Blacktown, NSW.
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22
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Barnes EH, Dobson RJ, Stein PA, Le Jambre LF, Lenane IJ. Selection of different genotype larvae and adult worms for anthelmintic resistance by persistent and short-acting avermectin/milbemycins. Int J Parasitol 2001; 31:720-7. [PMID: 11336754 DOI: 10.1016/s0020-7519(01)00174-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To understand the factors that influence selection for anthelmintic resistance, it is necessary to examine the impact of drug treatment, particularly persistent drugs, on all phases of the worm life cycle. The efficacy of various avermectin/milbemycin anthelmintics was determined against resident worms, incoming larvae (L3) and development of eggs in faecal culture. Homozygote-resistant and maternal and paternal F1-heterozygote genotypes of Haemonchus contortus were used to infect sheep before or after treatment with ivermectin (IVM) oral, IVM capsule, moxidectin (MOX) oral or MOX injectable. Total worm count and quantitative larval culture were used to determine efficacy against parasitic and free-living stages, respectively. Selection for resistance by IVM capsules occurred at the adult and L3 stages because of poor efficacy against these stages for all resistant genotypes. However, the selective advantage of these surviving worms was reduced due to the low development of their eggs to L3 in faecal culture. For MOX, selection for resistance predominantly occurred after treatment because of high efficacy against resident adult worms of all resistant genotypes but poor efficacy against resistant L3 ingested after drug administration. The results indicated no evidence of sex-linked inheritance for IVM resistance. Mean IVM efficacies against homozygous and heterozygous resistant adult worms were not different, and IVM capsule efficacy against incoming L3 was approximately 70% for all resistant genotypes, consistent with a dominant trait. MOX was highly effective against adults of all resistant genotypes and approximately 76% effective against incoming L3 regardless of resistance genotype, also consistent with a dominant trait. These results will enable the impact of persistent drugs on worm control and anthelmintic resistance to be estimated. The results indicate that IVM capsules should not be used in populations where avermectin/milbemycin resistance is present.
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Affiliation(s)
- E H Barnes
- CSIRO Livestock Industries, McMaster Laboratory, Locked Bag 1, Delivery Centre, Blacktown, NSW 2148, Australia.
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23
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Abstract
Diversity of parasite populations was compared between two herds of horses, one a regularly treated herd the other a feral herd which has bad no anthelmintic treatment for at least 25 years. Eggs obtained from fecal samples of both herds were tested for anthelmintic resistance by use of an in-vitro larval hatch/development assay (LDA), DrenchRite. A fecal egg reduction test was also performed with the domesticated herd using fenbendazole, pyrantel pamoate and ivermectin. Cyathostomes were the predominant group of worms present in both herds. Trichostrongylus axei was seen in both herds, but Strongylus equinus, Strongylus vulgaris, Gyalocephalus capitatus, Poteriostomum spp. and Strongyloides westeri were only found in the feral horses. Larvae of Strongylus edentatus were found in a single domesticated horse. Fecal egg reduction tests with the domesticated herd showed a 32% egg count reduction for fenbendazole, a 93% reduction with pyrantel, and a 99% reduction with ivermectin. From the LDA, anthelmintic resistance was evaluated by determining the resistance ratio of the domesticated herd compared with the feral herd. For benzimidazoles in the domesticated herd, 45% of the cyathostome population was 9.4 times more tolerant than the feral herd's parasite population. The parasite population in the domesticated herd was 1.5 times more tolerant to Levamisole, and 1.7 times more tolerant to the benzimidazole/levamisole combination than the parasite population within the feral herd. 9% of the parasite population in the domesticated herd was 90 times more tolerant to avermectins than the feral herd's parasite population, even though a subpopulation of worms in the feral herd were tolerant to low concentrations of avermectins despite never being previously exposed to this class of anthelmintic.
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Affiliation(s)
- K E Young
- Department of Veterinary Pathobiology, Texas A and M University, College Station 77843, USA
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24
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Abstract
Responses of several nematode species to naphthalophos and pyrantel/levamisole were examined using a larval development assay in order to determine the potential of this assay for detection of resistance. Haemonchus contortus and Ostertagia circumcincta showed concentration-dependent responses to naphthalophos, however, the assay was unsuitable for Trichostrongylus colubriformis due to the low toxicity of the drug to the larval stages of this nematode. Measurement of concentration-dependent response to pyrantel in susceptible T. colubriformis was limited by a reduced toxicity against larvae at high drug concentrations, resulting in a parabolic response with a development-inhibition maxima of less than 100%. This limits the usefulness of the assay to detect pyrantel resistance in this species as the presence of a small resistant fraction in a field isolate may be indistinguishable from the parabolic susceptible response. On the other hand, responses of susceptible T. colubriformis to levamisole, and susceptible H. contortus to pyrantel and levamisole showed 100% development inhibition over a range of drug concentrations, indicating that the appearance of a resistant fraction in a field population would be readily discernible from the susceptible response, allowing resistance detection for these drug/parasite combinations. This study has highlighted the varied suitability of the larval development assay technique for resistance detection with different combinations of drugs and parasite species.
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Affiliation(s)
- A C Kotze
- CSIRO Animal Production, McMaster Laboratory, Blacktown, NSW, Australia.
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25
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Abstract
Two morphologically marked strains of Haemonchus contortus, CAVRS (smooth-macrocyclic lactone resistant) and McMaster (linguiform-macrocyclic lactone susceptible), were used to investigate the selection for anthelmintic resistance following exposure to ivermectin (IVM), a non-persistent anthelmintic. and a more persistent anthelmintic, oral moxidectin (MOX). Three types of selection were investigated: (1) selection of resident worms at the time of treatment (Head selection); (2) selection of incoming-larvae post-treatment (Tail selection); and (3) selection of both resident population and incoming larvae (Head + Tail selection). The experimental animals were adult sheep and lambs. In the controls where there was no anthelmintic selection, the proportion of CAVRS in the adult worm population was the same as the proportion in larvae given to both adults and lambs indicating that CAVRS and McMaster H. contortus were equally infective. There was a significant effect of anthelmintic on total worm numbers in adult sheep with MOX treated adults having less worms, but selection type was non-significant. Anthelmintic type had a significant effect on numbers of resistant worms in adult sheep with less resistant worms in the MOX treated groups, but selection type had no effect. Analysis of variance of arcsine-transformed proportions of resistant worms found that the type of anthelmintic had a highly significant effect, with MOX treated adults having a higher proportion of resistant worms, while type of selection was not significant. In the lambs, nil treated controls and IVM Head + Tail and Tail selected groups had similar geometric mean total worm burdens while Head selected had less total worms. In the MOX treated lamb groups the worm burdens were similar within selection type but less than the IVM treated groups. In the lambs, the types of selection that resulted in more resistant worms were IVM Tail, MOX Head + Tail and MOX Tail. Resistant worm numbers were similar in both adult and lamb groups with Head selection by either MOX or IVM. Moxidectin selected out higher proportions of resistant worms than did IVM in the lambs, with Tail and Head + Tail being stronger selectors than Head. Computer simulations were used to estimate the rate at which resistance developed in the field using the information generated in the present study. The anthelmintic treatments used in the simulation followed a strategic parasite control program for H. contortus in which all sheep receive three Closantel (CLS) treatments in summer. all sheep receive a broad-spectrum (BS) drench or capsule at weaning and lambs receive an additional two BS drenches insummer or no further treatment in the case of the capsule. Moxidectin, IVM-capsule and IVM were the broad spectrum anthelmintics simulated. All simulations were run four times assuming high or low efficacy against resident resistant worms and in the presence or absence of CLS resistance. The simulations indicated that the presence of CLS resistance hastened selection for macrocyclic lactone (ML) resistance. While the IVM-capsule will select most rapidly for ML resistance, IVM oral is expected to be least selective. Moxidectin treatment is intermediate, except in simulations with no CLS resistance and when MOX is assumed to be highly effective against resident ML-resistant worms, in which case MOX can be expected to select more slowly than IVM oral treatments.
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Affiliation(s)
- L F Le Jambre
- CSIRO Division of Animal Production, Pastoral Research Laboratory, Armidale, NSW, Australia.
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26
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Faedo M, Barnes EH, Dobson RJ, Waller PJ. The potential of nematophagous fungi to control the free-living stages of nematode parasites of sheep: pasture plot study with Duddingtonia flagrans. Vet Parasitol 1998; 76:129-35. [PMID: 9653997 DOI: 10.1016/s0304-4017(97)00057-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The potential of nematophagous fungi to control the free-living stages of nematode parasites of sheep: Pasture plot study with the fungus Duddingtonia flagrans. Vet. Parasitol. The experiment was designed to test the ability of D. flagrans to reduce infective larval populations on pasture after passage through the gastrointestinal tract of sheep. Merino sheep were given chlamydospores by intra-ruminal infusion at a rate of 5 million chlamydospores/sheep/day and faeces collected from these sheep was deposited on pasture plots. Numbers of larvae recovered from faeces and pasture were both lower on plots from sheep dosed with fungus (P < 0.001 and P < 0.01, respectively) than on plots from control sheep.
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Affiliation(s)
- M Faedo
- CSIRO Division of Animal Production, McMaster Laboratory, Delivery Centre, Blacktown, NSW, Australia
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27
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Abstract
Resistance to the benzimidazole (BZ) anthelmintics is inherited as an incomplete dominant/ incomplete recessive trait and is now widespread in populations of gastrointestinal nematode parasites of sheep. Unlike benzimidazole resistance, which is common in Haemonchus contortus, Trichostrongylus colubriformis and Ostertagia circumcincta, resistance to levamisole is relatively rare in H. contortus, although common in the other 2 species. One explanation for the slow spread of resistance to levamisole in H. contortus is that it is inherited as an autosomal recessive trait, while in T. colubriformis levamisole resistance is inherited as a recessive sex-linked trait. With the introduction of the avermectin/milbemycin class resistance has developed to the relatively short-acting ivermectin, but this time it is inherited as a completely dominant trait. The potentially more serious situation of a persistent anthelmintic selecting a dominant resistance gene was investigated using a simulation model. Efficacy against incoming infective larvae (L3) was assumed to decline or remain high over the period of drug persistence (3 days to 4 weeks), thus allowing the estimation of the relative importance of selecting resistant L3s on the development of resistance in the worm population. These factors were also examined against a background of initial efficacy levels, against adults, and mode of inheritance. Persistence and initial efficacy were found to be far more important in determining the rate of selection for resistance than was selection of resistant L3 as drug efficacy declined.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Production, McMaster Laboratory, Blacktown, NSW, Australia
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28
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Abstract
Twenty-one-week-old, worm-free, pen-reared lambs were infected with either 6000 O. circumcincta L3 per week, or 3000 H. contortus L3 per week, or both (9000 L3 per week). Egg counts were monitored throughout the experiment, and worm burdens and larval establishment rates of both worm species were estimated after 4, 7, 10 and 13 weeks of infection. After 10-13 weeks of infection with H. contortus only, establishment of O. circumcincta was lower than in previously uninfected controls, demonstrating that a high level of immunity to H. contortus affords some cross-protection against O. circumcincta. Total H. contortus worm burdens and egg counts (about 2000 worms and 3000 e.p.g., respectively) in sheep infected with both worm species were less than half those observed in sheep infected with H. contortus alone (about 5000 worms and 10,000 e.p.g., respectively). Cross-protection between the two species was observed, but was probably less important than the reduction in H. contortus establishment that was caused by O. circumcincta disrupting abomasal physiology.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, McMaster Laboratory, Blacktown, NSW, Australia
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29
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Abstract
There are three common questions asked of parasitologists about anthelmintic resistance. Does it matter? How do you prevent it? Can you help me (it's here!)? In short, the respective answers are yes, read on the read on. Elizabeth Barnes, Robert Dobson and Ian Barger examine these issues in the context of nematode parasite control in grazing sheep. With the aid of a model, they examine some important factors that influence drug resistance and how farm management decisions and worm genetics modify these factors. They also explore the likely impact of new technologies on drug resistance and how efficient they need to be to sustain good worm control.
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Affiliation(s)
- E H Barnes
- Danish Centre for Experimental Parasitology, Royal Veterinary and Agricultural University, Bulowsvej 13. DK-1870 Frederiksberg C, Denmark
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30
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Abstract
Lambs were infected with 6000 Trichostrongylus colubriformis L3 per week for 18, 12 or 6 weeks, beginning at ages 14, 20 and 26 weeks, respectively. At the end of the primary infection subgroups had geometric mean adult worm burdens of 5000, 15,000 and 18,000, respectively. In the remaining sheep the worm population was removed with anthelmintic, and sheep had no further larval intake until challenged with T. colubriformis 1, 6, 12, 18 or 24 weeks later. In the groups given 18 or 12 weeks primary infection, establishment of challenge doses was low (less than 25% of establishment in helminth naive controls) in most animals at all challenge times. However, for the groups given 6 weeks primary infection, establishment was low only at the first two challenge times. Thereafter it had similar mean to control groups, but much greater variance. Other subgroups were challenged with T. colubriformis, Ostertagia circumcincta and Haemonchus contortus 1 week after worm removal. In these animals T. colubriformis establishment was not different to animals challenged at the same time with T. colubriformis alone, however immunity to T. colubriformis afforded little protection against the other species. The results of this experiment were incorporated into a simulation model of the population dynamics of T. colubriformis.
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Affiliation(s)
- E H Barnes
- CSIRO Division of Animal Health, McMaster Laboratory, Glebe NSW, Australia
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31
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Rothwell JT, Sangster NC, Conder GA, Dobson RJ, Johnson SS. Kinetics of expulsion of Haemonchus contortus from sheep and jirds after treatment with closantel. Int J Parasitol 1993; 23:885-9. [PMID: 8314373 DOI: 10.1016/0020-7519(93)90054-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Experiments were conducted in sheep after intramuscular treatment with closantel and in jirds after oral treatment with closantel to determine when expulsion of established H. contortus commences. Expulsion starts at about 8 h in sheep and coincides with the onset of reduced motility in worms recovered from the abomasum. In jirds, expulsion starts by 2 h after treatment. Experiments also conducted in jirds showed that infective larvae are first killed by circulating closantel 3 days after infection, when blood feeding starts, and that by 8 days 80% of larvae are lost.
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Affiliation(s)
- J T Rothwell
- Department of Veterinary Pathology, University of Sydney, Australia
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32
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Dobson RJ, Barnes EH, Birclijin SD, Gill JH. The survival of Ostertagia circumcincta and Trichostrongylus colubriformis in faecal culture as a source of bias in apportioning egg counts to worm species. Int J Parasitol 1992; 22:1005-8. [PMID: 1459776 DOI: 10.1016/0020-7519(92)90060-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
When cultured alone or concurrently with Trichostrongylus colubriformis in sheep faeces, Ostertagia circumcincta produced fewer infective larvae per 100 eggs than did T. colubriformis. Averaged over five trials 60% of T. colubriformis eggs were recovered as infective larvae while for O. circumcincta the figure was only 39%. This result was observed for two strains of O. circumcincta and was independent of when larvae were harvested from culture (days 6-10 at 25 degrees C). The mortalities of both species occurred at the first and second larval stages. These observations are of concern when using larval differentiation from faecal culture to make quantitative estimates of worm egg numbers for each species present. Species such as T. colubriformis which have a low mortality during culture are likely to have their egg numbers overestimated when cultured with a species, like O. circumcincta, that suffers high mortality in culture.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, Glebe, New South Wales, Australia
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33
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Dobson RJ, Barnes EH, Windon RG. Population dynamics of Trichostrongylus colubriformis and Ostertagia circumcincta in single and concurrent infections. Int J Parasitol 1992; 22:997-1004. [PMID: 1459794 DOI: 10.1016/0020-7519(92)90059-t] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Twenty-one-week-old worm-free pen-reared lambs were infected weekly with either 10,000 T. colubriformis larvae, 5000 O. circumcincta larvae, or with both species (15,000 larvae per week). Larval establishment and total worm burdens were estimated after 4, 7, 10 and 13 weeks of infection. Faecal egg counts and lamb bodyweights were measured weekly, and numbers of eosinophils in blood were estimated before infection and at weeks 5, 8 and 14. For both species of worms, the dynamics of infection (establishment, worm burdens, egg counts) were not affected by concurrent or pre-existing infection with the other species. Infection with T. colubriformis alone did not protect against O. circumcincta, but infection with O. circumcincta alone provided slight protection against the T. colubriformis larvae. Blood eosinophils increased between 5 and 8 weeks of infection and were similar for the three infections. This corresponded to the reduction in establishment for both species.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, McMaster Laboratory, Glebe, New South Wales, Australia
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34
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Barnes EH, Dobson RJ. Population dynamics of Trichostrongylus colubriformis in sheep: computer model to simulate grazing systems and the evolution of anthelmintic resistance. Int J Parasitol 1990; 20:823-31. [PMID: 2276858 DOI: 10.1016/0020-7519(90)90019-j] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
A computer model was developed to simulate Trichostrongylus colubriformis populations, their level of resistance to the common anthelmintics, host mortalities and acquired immunity. Predictions were based on sheep management practices such as lambing, weaning, sheep/paddock rotation, anthelmintic treatment, the use of controlled release devices (capsules) for anthelmintic delivery and daily meteorological records to determine the development and survival of infective larvae (L3) on pasture. Evolution of drug resistance was determined by a simple genetic system which allowed for up to three genes, each with two alleles, to give a maximum of 27 genotypes associated with one drug or three genotypes for each of three drugs. The model was validated against egg counts, L3 counts on pasture and host mortalities observed in a grazing trial, however, aspects of the model such as the development of drug resistance and use of the model in a variety of climatic zones have yet to be tested against field observations. The model was used to examine the impact of grazing management and capsule use on anthelmintic resistance and sheep production over 20 years using historical weather data. Predictions indicated that grazing management can play a dominant role in parasite control and that capsule use will reduce sheep mortalities and production losses, and in some circumstances will not cause a substantial increase in anthelmintic resistance for up to 5 years.
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Affiliation(s)
- E H Barnes
- CSIRO Division of Animal Health, McMaster Laboratory, New South Wales, Australia
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35
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Dobson RJ, Waller PJ, Donald AD. Population dynamics of Trichostrongylus colubriformis in sheep: the effect of infection rate on loss of adult parasites. Int J Parasitol 1990; 20:359-63. [PMID: 2358319 DOI: 10.1016/0020-7519(90)90152-d] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Rejection of adult T. colubriformis was examined in lambs given 2000, 1124, 632 or 200 L3 day-1, 5 days per week for up to 20 weeks. Rejection of adults began at approximately the same time for the first three infection rates, and took about 9 weeks to complete. Approximately 20% of adults were rejected by week 10 of infection at the higher infection rates and it was estimated that rejection commenced at about week 7. This coincided with a decline in establishment of larvae to about 1%. For the low infection rate, there was a delay of about 5 weeks before adult worm rejection commenced and reached equivalent levels to those observed at the higher rates. This delay also coincided with an estimated 5-week delay in larval establishment declining to 1% at the low rate.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, McMaster Laboratory, Private Bag, Glebe, New South Wales, Australia
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36
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Dobson RJ, Donald AD, Barnes EH, Waller PJ. Population dynamics of Trichostrongylus colubriformis in sheep: model to predict the worm population over time as a function of infection rate and host age. Int J Parasitol 1990; 20:365-73. [PMID: 2358320 DOI: 10.1016/0020-7519(90)90153-e] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The developing immunity of sheep to Trichostrongylus colubriformis infections was described by a mathematical function. The rate of adult establishment was assumed to be a measure of the host's acquired immunity to this parasite. Prediction of establishment from infection rate and host age was used to estimate worm burden, worm rejection and arrested development.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, McMaster Laboratory, Glebe, New South Wales
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37
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Abstract
A mathematical model was constructed to predict the egg production of Trichostrongylus colubriformis worms as a function of worm age and host experience of infection. The model set egg production at zero until the worm was 14 days old, when a linear increase to maximum egg production levels occurred over 7 days. It was assumed that egg production remained at maximum levels until a threshold total worm burden was exceeded, when an exponential decline in egg production occurred. The rate of decline was assumed independent of worm age or worm burden. The estimated parameters (maximum egg production, threshold, lag and rate of decline) were optimized by fitting values predicted from the model to faecal egg counts observed in continuously infected sheep, giving R2 = 0.80. The model was validated against faecal egg counts obtained in two other continuous infection experiments, one performed at the same laboratory and the other in Britain.
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Affiliation(s)
- E H Barnes
- CSIRO Division of Animal Health, McMaster Laboratory, New South Wales, Australia
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38
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Dobson RJ, Waller PJ, Donald AD. Population dynamics of Trichostrongylus colubriformis in sheep: the effect of infection rate on the establishment of infective larvae and parasite fecundity. Int J Parasitol 1990; 20:347-52. [PMID: 2358317 DOI: 10.1016/0020-7519(90)90150-l] [Citation(s) in RCA: 95] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The establishment of Trichostrongylus colubriformis was estimated in helminthologically naive 20-week-old Merino sheep given third stage infective larvae (L3) at rates of 2000, 632 or 200 L3 per day, 5 days per week. After varying periods of continuous L3 intake, a levamisole-susceptible strain of T. colubriformis was replaced with a highly resistant strain for 1 week. The animals were then treated with levamisole to remove the susceptible population, and establishment of the cohort of resistant worms was estimated. In previously uninfected sheep, approximately 65% of the L3 given in the first week became established as adults. This fell to low levels (less than 5%) after 7, 10 and 14 weeks of continuous L3 intake for the high, medium and low infection rates, respectively. At the low infection rate, establishment remained at maximum levels for the first 4 weeks, but then fell at a rate similar to that observed for the higher infection rates. This implied that a threshold of worm exposure was required before resistance to establishment developed. Parasite egg production, expressed as eggs per gram of faeces, was proportional to infection rate and is explained by higher worm burdens occurring at high infection rates. However, estimates of fecundity in eggs per female per day showed the opposite relationship with rate of infection. Fecundity stayed high (approximately 600) for 5 weeks at the low infection rate but only maintained this level for 3 weeks and 1 week at the medium and high rates, respectively. This suggests that fecundity, like establishment, was similarly affected at threshold levels of immunological recognition.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, McMaster Laboratory, Glebe, New South Wales, Australia
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39
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Dobson RJ, Waller PJ, Donald AD. Population dynamics of Trichostrongylus colubriformis in sheep: the effect of host age on the establishment of infective larvae. Int J Parasitol 1990; 20:353-7. [PMID: 2358318 DOI: 10.1016/0020-7519(90)90151-c] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Sheep, reared worm-free in pens and aged 12-36 weeks, were infected each weekday with 2000 infective T. colubriformis larvae (L3). Establishment was measured at various times during the course of infection and the rate of development of resistance to new infection was found to be faster in older than in younger hosts. In addition arrested development at the exsheathed L3 stage was found to be less marked in older hosts. Sheep which had experienced natural infection on pasture up to 20 weeks of age before exposure, in pens, to the same experimental infections as their worm-free counterparts showed similar immune responses. However, at 36 weeks of age, pasture-reared sheep had acquired a high level of resistance to infection with T. colubriformis.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, McMaster Laboratory, Glebe, New South Wales, Australia
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Affiliation(s)
- P J Waller
- CSIRO Division of Animal Health, McMaster Laboratory, New South Wales
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Waller PJ, Donald AD, Dobson RJ, Lacey E, Hennessy DR, Allerton GR, Prichard RK. Changes in anthelmintic resistance status of Haemonchus contortus and Trichostrongylus colubriformis exposed to different anthelmintic selection pressures in grazing sheep. Int J Parasitol 1989; 19:99-110. [PMID: 2707967 DOI: 10.1016/0020-7519(89)90027-1] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
This experiment was designed to study, over a 5-year-period, the effect of different frequencies of treatment with three different anthelmintic groups, namely, benzimidazoles, levamisole and ivermectin, and different frequencies of alternation between them, on existing levels of anthelmintic resistance in the nematode parasites Haemonchus contortus and Trichostrongylus colubriformis of grazing sheep. No evidence of ivermectin resistance emerged, even in suppressively treated groups. Likewise, H. contortus failed to develop resistance to levamisole under a similar selection regimen. Thiabendazole was shown to select positively against levamisole resistance in T. colubriformis resulting in significantly greater susceptibility to this drug than for the natural reversion which occurred in the untreated control. There was no evidence that an anthelmintic treatment combined with a movement of sheep to pastures of low infectivity selected more rapidly for resistance than where the same number of treatments were given to set-stocked sheep. Rotation between anthelmintic groups at yearly intervals appeared to be more beneficial in delaying resistance than rotation of drugs with each treatment.
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Waller PJ, Dobson RJ, Axelsen A. Anthelmintic resistance in the field: changes in resistance status of parasitic populations in response to anthelmintic treatment. Aust Vet J 1988; 65:376-9. [PMID: 3223850 DOI: 10.1111/j.1751-0813.1988.tb14276.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Changes in anthelmintic resistance in nematode parasites were monitored in sheep grazing on 2 separate farms, but with the same anthelmintic treatment program, over 16 years. High levels of benzimidazole resistance emerged in Ostertagia and Trichostrongylus spp populations on both farms following 9 years of continuous use of this class of drug. Subsequently, variations in the levels of resistance occurred for the same species between farms and between species on the same farm. A change to levamisole for 2 years resulted in a significant reversion towards benzimidazole susceptibility, but a concomitant rise in levamisole resistance, in Ostertagia on one farm. However, benzimidazole resistance increased rapidly following the re-introduction of oxfendazole into the anthelmintic treatment program. Results from both farms illustrate the pitfalls of using one anthelmintic class for an extended period and provide indirect support for the alternation of anthelmintic classes at approximately yearly intervals.
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Affiliation(s)
- P J Waller
- CSIRO Division of Animal Health, McMaster Laboratory, New South Wales
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Barnes EH, Dobson RJ, Donald AD, Waller PJ. Predicting populations of Trichostrongylus colubriformis infective larvae on pasture from meteorological data. Int J Parasitol 1988; 18:767-74. [PMID: 3192348 DOI: 10.1016/0020-7519(88)90117-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Waller PJ, Axelsen A, Donald AD, Morley FH, Dobson RJ, Donnelly JR. Effects of helminth infection on the pre-weaning production of ewes and lambs: comparison between safe and contaminated pasture. Aust Vet J 1987; 64:357-62. [PMID: 3452301 DOI: 10.1111/j.1751-0813.1987.tb09600.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Comparison was made of the performances of cross-bred ewes and their lambs on pastures of low helminth infectivity ("safe" pastures) or contaminated pastures and at high or low stocking rates. Ewes grazing the safe, but not the contaminated, pastures were given a single pre-lambing drench. The largest difference in parasite infection between treatments was the level of exposure of sheep to Trichostrongylus spp, which was negligible on the safe pastures. The effects of parasite control on lamb growth were significant only in twins during the last 2 months before weaning. However, 22% of lambs on contaminated plots became soiled in the breech area and 38% were flystruck, compared with 8% and 10% respectively for lambs on the safe pastures. Ewe bodyweight gains were greater at low than at high stocking rate and were not affected by the parasite control treatments; differences in breech soiling and fly strike were similar to those in the lambs. Most importantly the parasite treatment produced a highly significant effect on ewe fleece weight at weaning. Ewes drenched and lambing on the safe pastures produced an extra 0.43 kg of wool, calculated to represent an increase of at least 40% during this period at the low-level of parasitic infection.
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Affiliation(s)
- P J Waller
- Division of Animal Health, CSIRO McMaster Laboratory, Glebe, New South Wales
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Waller PJ, Donnelly JR, Dobson RJ, Donald AD, Axelsen A, Morley FH. Effects of helminth infection on the pre-weaning production of ewes and lambs: evaluation of pre- and post-lambing drenching and provision of safe lambing pasture. Aust Vet J 1987; 64:339-43. [PMID: 3447577 DOI: 10.1111/j.1751-0813.1987.tb06062.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The pre-weaning production of ewes and lambs in spring on pastures grazed during the previous autumn and early winter by either weaner sheep, adult sheep, or cattle was investigated together with estimating the benefits of pre- and post-lambing drenches to ewes. These treatments were compared with one in which parasitism was uncontrolled in ewes lambing on pastures grazed previously by untreated weaner sheep, and another where parasitism was suppressed by 2-weekly drenching of the weaner sheep and also of the ewes and their lambs. Prior grazing by cattle effectively eliminated infection of pastures with intestinal Trichostrongylus and Nematodirus spp, but less so for Ostertagia spp. Worthwhile reductions in contamination were also achieved by grazing by adult sheep compared with grazing by undrenched weaners. Despite differences in the parasitological status of the pastures, there were no indications that pre-weaning growth rates of lambs were affected. However, wool growth in ewes was reduced by 10 to 20% by parasite infection. Wool growth of ewes on pastures grazed by cattle during the pre-experimental period exceeded that on any other treatment, and was significantly greater than that of ewes on pastures grazed by undrenched weaners. There was no production benefit in giving a pre-lambing drench to ewes on plots contaminated by weaners, or in giving the additional post-lambing drench to ewes grazing on plots contaminated by weaners, adult sheep or cattle.
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Affiliation(s)
- P J Waller
- Division of Animal Health, CSIRO McMaster Laboratory, Glebe, New South Wales
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Dobson RJ, Griffiths DA, Donald AD, Waller PJ. A genetic model describing the evolution of levamisole resistance in Trichostrongylus colubriformis, a nematode parasite of sheep. IMA J Math Appl Med Biol 1987; 4:279-93. [PMID: 3503094 DOI: 10.1093/imammb/4.4.279] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Data from 21 generations of selection on a levamisole-resistant strain of Trichostrongylus colubriformis, either exposed to selection with the anthelmintics levamisole (LEV) or thiabendazole (TBZ), or unexposed, were used to fit a genetic model describing the evolution of LEV resistance in this parasite species. A statistical model describing the dose-response relationship for a mixed population of susceptible and resistant parasite eggs exposed to anthelmintic was fitted to egg-hatch assay data for each generation and for each selection regimen. Estimated parameters from the statistical model provided the input for the genetic model from which were obtained estimates of the relative fitness of susceptible and resistant genotypes under each selection regimen. The experimental data and the genetic models both indicated that, in this parasite strain, LEV resistance was determined by a single dominant gene, and that TBZ selects for LEV susceptibility. A variety of drug alternation programmes was simulated for this genetic system. The programme that minimized the development of LEV resistance involved alternating the drugs (LEV and TBZ) between each worm generation.
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Affiliation(s)
- R J Dobson
- CSIRO Division of Animal Health, McMaster Laboratory, Glebe, NSW, Australia
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Waller PJ, Dobson RJ, Obendorf DL, Gillham RJ. Resistance of Trichostrongylus colubriformis to levamisole and morantel: differences in relation to selection history. Vet Parasitol 1986; 21:255-63. [PMID: 3776078 DOI: 10.1016/0304-4017(86)90051-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Two field strains of Trichostrongylus colubriformis were tested by in vitro and in vivo methods for resistance to morantel, levamisole and thiabendazole and compared with an anthelmintic-naive laboratory-passaged strain (McM). One field strain (TAS) was isolated from a dairy goat herd which had experienced severe helminthiasis despite intensive anthelmintic usage. The other (BCK) was isolated from sheep which had been treated solely with levamisole over a 6-year period. The BCK strain had very high levels of both levamisole and morantel resistance. In contrast the TAS strain was resistant to morantel but highly susceptible to levamisole. This finding is contrary to the expectation that selection with morantel automatically confers resistance to levamisole, the converse of which was shown to apply in the BCK strain. Although the TAS strain was exposed to levamisole prior to isolation, examination of the drug's pharmacokinetics in goats indicated that it exerted little if any anthelmintic effect, and therefore selection pressure, on the parasite population. This study suggests that the mechanism of levamisole resistance covers a wide spectrum, and embraces that for morantel. It also suggests that in order to conserve the effectiveness of the levamisole/morantel group of broad spectrum anthelmintics, morantel should be used to the exclusion of levamisole until resistance is detected, at which time levamisole may be introduced to re-establish high levels of control.
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Axelsen A, Waller PJ, Donald AD, Dobson RJ, Nadin JB. Grazing management and nematode parasite control in cattle in the temperate climatic zone of Australia. ACTA ACUST UNITED AC 1986. [DOI: 10.1071/ea9860267] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Over 2 years, 1979 and 1981, yearling cattle were grazed from July to December/January on phalaris- or annual ryegrass-based pastures that had been previously grazed by either weaners, cows or cattle drenched every 2 weeks. All yearlings had previously been drenched at weaning in autumn, and from July were either set-stocked, or moved once or twice on to pastures previously grazed by cows. The experiment was conducted at Ginninderra. near Canberra. If a portion of the pasture was saved in winter for grazing in early spring, increased liveweight gains were observed while yearlings grazed the saved area. However, the greater gains during this period were not enough to compensate for previous weight losses or lower gains, so that saving pasture was no better than set-stocking over the total period. In 1979, a year of low rainfall and pasture growth, yearlings drenched 2-weekly gained no more weight than undrenched yearlings, despite much lower worm burdens. In 1981, with average pasture growth, yearlings drenched in July before moving on to pastures previously grazed by cows, and drenched again in September, gained as much weight as those drenched every 2 weeks and significantly more than those undrenched and set-stocked. It is recommended that weaners or yearlings should be moved in July on to improved pastures of low infectivity (obtained by previous grazing with cows or sheep). If combined with one or two drenches, this single move would be as effective for optimising weight gains as more complicated management schemes.
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Abstract
An in vitro technique is described for detecting resistance of nematodes to the anthelmintic levamisole hydrochloride. Samples of eggs are developed under controlled temperature conditions until just prior to the commencement of hatching. They are then exposed to different concentrations of the drug and, when hatching is almost complete, the test samples are killed and preserved. The proportion of unhatched eggs at each drug concentration can then be counted at leisure. Provided a suitable range of drug concentrations is chosen for each test isolate, this assay provides results which may be satisfactorily fitted to a log-concentration-probit regression model. Comparisons with in vivo anthelmintic assays have shown that the technique provides an accurate reflection of the resistance status of parasite populations.
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Waller PJ, Dobson RJ, Donald AD, Griffiths DA, Smith EF. Selection studies on anthelmintic resistant and susceptible populations of Trichostrongylus colubriformis of sheep. Int J Parasitol 1985; 15:669-76. [PMID: 4093238 DOI: 10.1016/0020-7519(85)90014-1] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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