Manual of Sheep Diseases

Manual of Sheep Diseases

Manual of Sheep Diseases Second Edition J.C. Hindson BVSc, Hon FRCVS Woodhouse Farm, Hatherleigh, Devon Agnes C. Winter BVSc, DSHP, PhD, MRCVS, ARAgS Department of Veterinary Clinical Science and Animal Husbandry, University of Liverpool My flocks feed not, My ewes breed not, My rams speed not, All is amiss. Sonnet to Sundry Notes of Music Shakespeare B I a c kwel I Science

02002 by Blackwell Science Ltd, a Blackwell Publishing Company Editorial Offices: Osney Mead, Oxford OX2 OEL, UK Tel: +44 (0)1865206206 Blackwell Science, Inc., 350 Main Street, Malden, MA 02148-5018, USA Tel: +1781388 8250 Iowa State Press, a Blackwell Publishing Company, 2121 State Avenue, Ames, Iowa 50014-8300, USA Tel: +1515 292 0140 Blackwell Publishing Asia Pty Ltd, 550 Swanston Street, Carlton South, Melbourne, Victoria 3053, Australia Tel: +61 (0)39347 0300 Blackwell Wissenschafts Verlag, Kurfurstendamm 57,10707 Berlin, Germany Tel: +49 (0)3032 79 060 The right of the Author to be identified as the Author of this Work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. First edition published by Wright, an imprint of Butterworth Scientific, 1990 Reissued with amendments by Blackwell Science 1996 Second edition published by Blackwell Science Ltd, 2002 Library of Congress Cataloging-in-Publication Data is available ISBN 0-632-05999-0 A catalogue record for this title is available from the British Library Set in 10/12 Palatino by DP Photosetting, Aylesbury, Bucks Printed and bound in Great Britain by TJ International Ltd, Padstow, Cornwall For further information on Blackwell Science, visit our website: www.blackwel1-science.com

Contents Preface Acknowledgements ix xi 1 2 3 4 5 6 7 8 Introduction Special difficulties of clinical diagnosis in the sheep Routine for clinical examination Further aids to diagnosis Interpretation of clinical signs Suboptimal reproductive performance (SORP) Problems during the mating period Manipulation and monitoring of pregnancy Special problems associated with manipulation of the breeding season or prolificacy Suboptimal lamb numbers Investigations required before next season irrespective of the cause of this episode Abortion Causes of ovine abortion Investigation of an outbreak Guide to diagnosis Dystocia and vagino-cervical prolapse Increase in incidence of dystocia Prolapses Male infertility Routine for the clinical examination of a ram Periparturient ewe losses Postmortem examination Mastitis, udder and teat lesions Nondairy flocks Dairy sheep flocks Perinatal lamb losses Flock investigation 6 9 12 14 16 18 19 20 21 23 33 34 38 42 46 53 55 58 58 63 65 66 V

~ vi Contents 9 10 11 12 13 14 15 Postmortem examination Guide to cause of death Dealing with higher than acceptable perinatal lamb losses Inadequate growth rate Estimation of optimum growth rate Milk dominated feed period Transitional milk to grass period Grass nutrition period to weaning Post-weaning growth retardation (ill thrift) Diarrhoea Lambs from birth to 4 weeks Growing lambs Adult sheep Tenesmus Adult weight loss Mouth disorders Neonatal lambs Growing lambs Adult sheep Mouth disorders usually identified during investigation of a flock problem Lameness Neonatal lambs Young lambs over 2 days of age Growing lambs Adult sheep Individual lame sheep Lame sheep, flock problem Changed behaviour and neurological dysfunction Routine for neurological examination Identification of site of lesion from assessment of neurological examination Common diseases in which neurological abnormalities are seen Neonatal lambs Young lambs (milk dependent) Growing lambs Adults The recumbent ewe 68 69 75 79 79 81 84 85 85 90 91 95 101 103 108 115 116 117 117 119 121 122 122 125 128 128 132 137 140 141 142 143 145 147 150 156

Contents vii 16 17 18 19 20 21 22 Eye disorders/visual defects Neonatal lambs Growing lambs and adults Anaemia Young lambs (<4 weeks) Growing lambs Adults Jaundice Investigation of jaundice Young lambs Growing and adult sheep Abdominal distension and abdominal pain Abdominal distension Abdominal pain Wool loss and skin lesions Neonatal and very young lambs Grazing lambs and adults Respiratory disease Antemortem diagnosis of respiratory disease Postmortem diagnosis of respiratory disease Found dead and sudden death Sudden death at any age Common causes of sudden death or found dead Other causes of death 158 159 160 163 166 167 167 169 170 171 171 173 173 177 179 179 181 196 198 205 210 210 211 212 Appendix 1 Postmortem examination Appendix 2 Sample taking and sample sending Appendix 3 Nutrition Appendix 4 Internal parasite control Anthelmintic resistance Control of diseases caused by endoparasites Appendix 5 Health plans and vaccination programmes Appendix 6 Poisons Plant poisons Chemical poisons 220 223 228 241 241 242 249 252 252 256

viii Contents Appendix 7 Zoonoses Appendix 8 Anaesthesia and common surgical procedures Sedation Analgesia Local and regional anaesthesia General anaesthesia Common surgical procedures 260 264 264 265 265 267 269 Appendix 9 Possible new production and disease patterns 276 Appendix 10 Standard reference values Appendix 11 Abbreviations 278 280 Appendix 12 Further reading Index 283

This book, although it has a different title, is an updated and expanded version of our previous book, Outline of Clinical Diagnosis in Sheep. It is written at a time when farmers are having to adapt to a very different political and economic environment following noticeable changes that took place during the 1990s. Perhaps the most significant of these changes is the imposition of oppressive but necessary bureaucratic controls. The setting up of the Food Standards Agency and its concerns about spongiform encephalopathies have led to the imposition of identification and marketing rules, and the National Scrapie Plan has been introduced. The 2001 epidemic of foot and mouth disease and European Union regulations have introduced identification and movement recording. These changes are here permanently. When these regulations are superimposed on the increasing vertical integration of the sheep industry, which gives rise to the movement of millions of sheep annually, the result is a tightly controlled enterprise very different from that which has, perhaps, been one of the attractions of sheep farming in the past. Looking ahead, the possibility of climate change may influence the pattern of production and disease, although any effects on the sheep industry may be less than on other types of livestock farming. Indeed, the high dependence of sheep farming on grassland may mean that areas of the country where grass production is currently limited by adverse climatic conditions may in future see increased output. This could, however, be offset by the arrival of diseases at present limited to southern Europe, and the spread to our country of insect vectors from southern Europe or even North Africa. In the last few years, changes to the economics of sheep production have led to a situation where many farm animal practitioners have had neither the opportunity nor the incentive to acquire the knowledge and expertise on this species that their clients have a right to expect. Although a number of texts on sheep diseases are available, ranging from comprehensive coverage of diseases on a global basis, to shorter ones aimed at students and/or farmers, we now feel that there is a need for a text to which the practitioner can refer for information not only on diagnosis, but also on treatment and prevention strategies. This new edition, aimed particularly at the nonspecialist veterinarian, is designed to update and expand the information in the first edition to cover not only diagnosis, but also treatment and prevention of diseases and poor production in sheep. The format is, as in the first edition, based on specific and accurate diagnosis, since without this, treatment and prevention will be a lottery. ix

X Preface We have found it difficult to decide how much detail to include on prevention and, in particular, treatment. Sometimes these are so obvious or simple that no comment is needed, for example treatment of a simple infection with antibiotic. In other cases brief details are included at the most logical point in the text. In the case of major influences on flock productivity, new sections have been written and included as appendices. In particular, new sections have been added on nutrition (which has a significant effect on all aspects of production), health programmes and parasite control. New information is also included on poisons, zoonoses, anaesthesia and some common surgical techniques. Unless there is a particular reason, we have tried to avoid referring to specific commercial products since new products come on the market, old products disappear and drug companies merge, making this particular information soon out of date. One further difficulty is the reclassification and name changes of some bacteria and parasites that are important in sheep - notably, Chlamydia psittaci is now known as Chlamydophila abortus and Pasteurella haemolytica type A as Mannheimia haemolytica. In the case of the latter, though, the disease it causes is still referred to as pasteurellosis. We have tried to use the most recent names, but doubtless further changes will occur. We hope the expanded text will be of help to all veterinarians, particularly those inexperienced in dealing with sheep. We hope also that it will assist in some small way in safeguarding the health and welfare of the national flock. Jim Hindson Agnes Winter

Acknowledgements Few textbooks are the result of the authors working in isolation. We are very happy to acknowledge the help and support of colleagues in the production of both this new edition and the first edition. In particular Professor Michael Clarkson and other colleagues in the Veterinary Faculty, University of Liverpool, Judith Charnley, Colne and Neil Spedding, Ripon, commented on the content of the first edition, and Charles Stone and Kate Phillips gave advice on the nutrition section of this edition. Without the help of these and other colleagues, friends and families, the production of this book would have been a much more difficult undertaking. xi