Veterinary Medicine Textbook PDF - 11th Edition

VetBooks.ir VetBooks.ir VETERINARY MEDICINE A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs, and Goats  This page intentionally left blank VetBooks.ir VetBooks.ir VETERINARY...

VetBooks.ir VetBooks.ir VETERINARY MEDICINE A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs, and Goats  This page intentionally left blank VetBooks.ir VetBooks.ir VETERINARY EDITION MEDICINE 11 A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs, and Goats VOLUME ONE PETER D. CONSTABLE KENNETH W. HINCHCLIFF STANLEY H. DONE WALTER GRÜNBERG VetBooks.ir 3251 Riverport Lane St. Louis, Missouri 63043 VETERINARY MEDICINE: A TEXTBOOK OF THE DISEASES OF CATTLE, HORSES, SHEEP, PIGS, AND GOATS, ELEVENTH EDITION Copyright © 2017 Elsevier Ltd. All Rights Reserved. Previous editions copyrighted: 2007, 2000, 1999, 1994, 1983, 1979, 1974 First published 1960 No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechani- cal, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permis- sions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Main ISBN: 9780702052460 Volume 1 ISBN: 978-0-7020-7057-0 Content Strategist: Penny Rudolph Content Development Specialist: Laura Klein Content Development Manager: Jolynn Gower Publishing Services Manager: Hemamalini Rajendrababu Senior Project Manager: Kamatchi Madhavan Design Direction: Renee Duenow Printed in China Last digit is the print number: 9 8 7 6 5 4 3 2 1  Dr. Otto M. Radostits, August 31, 1934-December 15, 2006, Senior Author, Fifth to Seventh Editions; Lead Author, Eighth to Tenth Editions VetBooks.ir Otto Martin Radostits was a veterinary educator, clinician, and literature and had little regard for those who were not. He could be a researcher who had a profound influence on students and practicing forceful presence in discussions, but Otto was also one of the quickest veterinarians throughout the world through his writings, not the least to recognize new information that negated previous theories concern- this text. Otto was closely involved with writing and editing the Fifth ing a disease, and he was always responsive to reasoned argument. to Tenth Editions of Veterinary Medicine. Otto taught that making a correct diagnosis was the crux to the Otto, the eldest son of Austrian immigrants, was raised on a small solution of a disease problem, and he had a passion for the art and mixed farm in Alberta, Canada. His early farm experiences and those science of clinical examination. Many of his students affectionately obtained from working with a local veterinarian while attending high remember his admonition, “We make more mistakes by not looking school sparked an interest in pursuing a career in veterinary science than by not knowing.” Otto’s insistence on the need for accurate diag- and were the beginning of his lifelong passion for large-animal veteri- nosis did not preclude this realization that what the practicing vet- nary medicine. He was admitted to the Ontario Veterinary College in erinarian needed as the final message from his books was the best 1954, at that time the only English-speaking veterinary school in current information on what to do to cure or prevent the disease in Canada. During his undergraduate years, his clinical interests and question. potential were recognized such that following graduation, he was Otto has authored other texts. In the late 1990s he became con- invited to join the faculty as a member of the ambulatory clinic prac- cerned that the traditional skills of physical clinical examination were tice of the college—at that time a vigorous practice in a rural area. being supplanted by laboratory and instrumental analysis. As a con- Otto spent the next 5 years teaching in this position, with the excep- sequence, he consulted with veterinary clinicians around the world tion of a year spent at the veterinary school at Purdue University in and in 2000 was a senior author of the text Veterinary clinical examina- West Lafayette, Indiana. tion and diagnosis. From his work on farms, Otto recognized that The Western College of Veterinary Medicine in Saskatchewan, disease in farm animals commonly was a population concern, and he Canada, was established under the leadership of Professor D. L. T. recognized the limitations of “fire brigade” medicine. He authored the Smith in the mid-1960s, and Otto was one of the founding faculty first major text in herd health and preventive medicine with its first members. He established the ambulatory practice and helped design edition in 1985. Otto published many other works of significance to the college clinical buildings and finalize the curriculum. He remained global veterinary medical education and presented more than 250 a faculty member at the Western College of Veterinary Medicine until invited lectures and seminars in veterinary medicine in countries he retired in June 2002 and was awarded the title Emeritus Professor. around the world. Here he matured as a clinical teacher to influence students and Dr. Radostits’s contributions have been recognized by many veterinarians locally and internationally through his writings and awards. For him, probably the most important were the award of presentations at veterinary meetings. Master Teacher from his university and, nationally, the Order of Otto’s international recognition in large-animal veterinary medi- Canada. cine rests mainly on the strength of his writing and authorship of veterinary texts. These span the spectrum of large-animal veterinary medicine, from the clinical examination of the individual animal to the epidemiology, diagnosis, treatment, and control of livestock dis- eases, to herd health and preventive medicine. The most notable are his contributions to this textbook, which has been used by veterinary students and practicing veterinarians around the world for over 50 years and through 11 editions, for 6 of which Otto was a senior or lead author. Otto joined the original authors, Doug Blood and Jim Henderson, for the Fifth Edition of this text in 1979 and, in 1994, became the senior author for the Eighth, Ninth, and Tenth Editions. During his sojourn as senior author, the text continued its original design as a student textbook with many student- friendly features. It also continued its importance as a reference book including the available information on all of the diseases of large animals, a truly formidable task. Otto did a large part of the work and would surely have been very proud of this new Eleventh Edition. In the writing of these and his other texts, Otto read the veterinary literature and was a firm believer in evidenced-based medicine. He insisted that all statements in these texts were supported by references in the literature, and he maintained the format of a very large bibli- Dr. Otto Radostits teaching at the Western College of Veterinary ography at the end of each disease description. He believed that other Medicine in Saskatchewan, Canada. (Image courtesy of Mrs. Ruth veterinary educators should also be current with the veterinary Radostits and family.) v  Dr. Clive Collins Gay VetBooks.ir Dr. Clive Collins Gay, DVM (Guelph, 1960), MVSc (Guelph, 1962), transfer” (extension work), which was a cornerstone of his approach MVSc (Ad Uendem Statum, Melbourne, 1970), FACVSc (1977), to epidemiological studies and preventive medicine. Diplomate of the American College of Veterinary Internal Medicine Reflecting his international standing, Dr. Gay had been a Visiting (honorary, 2008), and Doctor of Veterinary Science (Honoris Causa, Research Fellow in the following areas: the Department of Veterinary Melbourne, 2008) has a distinguished career as an agricultural Microbiology, University of Guelph, in 1971; the Department of animal veterinarian, scientist, author, and educator spanning five Veterinary Clinical Studies, University of Cambridge, in 1972; the decades. Department of Veterinary Clinical Sciences, Massey University, in After graduating from Guelph in 1960, he was appointed as an 1993; the Central Veterinary Laboratory, Ministry of Agriculture assistant lecturer in the Department of Veterinary Medicine at the Fisheries and Food, Pirbright, in 1994; and the Department of University of Glasgow from 1962 to 1964. In 1964, he was a George Geospatial Science, RMIT University (Melbourne), in 2001. Aitken Pastoral Research Fellow (Sheep) and worked at the Veterinary Over the years, Dr. Gay contributed actively to national and state Investigation Centre, Edinburgh University (Scotland); the Veterinary veterinary associations, serving as a committee member of the Victo- Investigation Centre, Ministry of Agriculture, Penrith (England); and rian Division of the Australian Veterinary Association (1968–1971); the Nuffield Institute for Medical Research, Oxford University. and editor of the Victorian Veterinary Proceedings (1968–1971); and In 1965, Dr. Gay was recruited by his mentor Professor Douglas an executive committee member of the Washington State Veterinary Blood to the newly reestablished veterinary school at the University Medical Association (1999–2005), where he held the positions of vice of Melbourne as a senior lecturer in agricultural animal medicine. president (2000), and president (2003–2004). Ken Hinchcliff was one of Dr. Gay’s students at the University of Dr. Gay was a contributing author of Veterinary Medicine, edited Melbourne. Dr. Gay was a genuinely gifted clinician, with an enthu- by Blood, Henderson, and Radostits in 1979, 1983, and 1989, and an siasm for veterinary science that inspired generations of undergradu- author and editor for the Eighth (1994), Ninth (2000), and Tenth ate and postgraduate students and staff alike. His teaching attributes (2007) Editions. His most important contributions to those editions were recognized by various student accolades over the years, both in included diseases of the newborn, infectious diseases of sheep and Australia and North America, and by the Washington State University goats, prion diseases, practical antimicrobial therapy, and selected (WSU) Faculty Award in 2000 from the Washington State Veterinary metabolic and protozoan diseases, emphasizing the important roles Medical Association (WSVMA). that environment, management, host factors, and pathogen virulence In 1979, Dr. Gay became a professor of food animal medicine at factors play in disease occurrence and severity. Dr. Gay was largely WSU, where he concentrated on agricultural animals, establishing the responsible for bringing the Tenth Edition to print when Dr. Radostits, Field Disease Investigation Unit in 1982 and leading the unit until his the lead author and editor, became ill during the final stages of prepa- retirement in 2005. The approach used by the Field Disease Investiga- ration of the text. tion Unit was groundbreaking at the time it was implemented in that it applied a multidisciplinary approach including university and private veterinarians, animal scientists, extension agents, and produc- ers to tackle economically important livestock diseases. Dr. Gay was also one of the earliest proponents of evidenced-based medicine. He served on several committees of the U.S. Department of Agriculture (USDA). In recognition of his extensive contribution in this area, he received the prestigious Calvin W. Schwabe Award for lifetime achievement in veterinary epidemiology and preventive medicine from the American Association of Veterinary Epidemiology and Pre- ventive Medicine in 2007. Dr. Gay became Professor Emeritus at WSU in 2005. His extensive contribution to veterinary medicine was recog- nized with a Distinguished Achievement Award from the Washington State Veterinary Medical Association in 2006, and he was made an Honorary Diplomat of the American College of Veterinary Internal Medicine in 2008. Dr. Gay’s research activities covered the breadth of veterinary science in regard to both species and systems, including topics as diverse as colic in horses, cardiology in dogs, diarrhea in pigs, colos- tral immunity in calves, and trace-element deficiency in ruminants. He supervised 13 PhD students and 14 master’s degree students. This work resulted in more than 90 articles in journals, more than 100 proceedings and abstracts, and the delivery of more than 150 invited presentations to scientific groups, veterinary conferences, and agricul- Dr. Clive Gay and Professor Doug Blood, Veterinary Clinical Centre, tural groups. The latter reflected his commitment to “knowledge University of Melbourne, 1978. (Courtesy of D. Blood’s family.) vi  Professor Douglas Blood VetBooks.ir 1920–2013 Professor Douglas Blood came to Australia in 1926 from East Ham, London. His family settled in Richmond, New South Wales, and toughed out the Great Depression. Through a scholarship, he attended Hurlstone Agricultural High School, where he enjoyed studying animals, especially cows and dogs. Following high school, Doug entered the Bachelor of Veterinary Science program at the University of Sydney. During World War II, he and a group of colleagues con- vinced the university to allow them to complete an accelerated course so that they could graduate in 1942 and then enlist in the armed services. Doug became a captain in a surveillance unit called Curtin’s Cowboys in the Northern Territory. He returned to teach at the Uni- versity of Sydney Veterinary School for 12 years. Then, from 1957 to 1962, Doug taught large-animal medicine at the Ontario Veterinary College at Guelph. It was during this time that he taught and mentored Otto Radostits and Clive Gay, both of whom were subsequently to Professors Ken Hinchcliff, Peter Constable, and Doug Blood (Werribee, become authors, along with Doug, of this text. Australia, 2008). (Source: Hinchcliff K.) In 1962, Doug was appointed Professor of Veterinary Medicine and Founding Dean of Veterinary Science at the University of Mel- bourne. Doug passed on the deanship in 1968, but he continued to teach, retiring in 1985 after 23 years of service. During his time at the University of Melbourne, Doug recruited Clive Gay to a faculty (aca- their education. Throughout subsequent years in his teaching career, demic) position in the School of Veterinary Science and taught both Doug had the ability to inspire students and is viewed with respect, Ken Hinchcliff and Peter Constable, both of whom followed him as admiration, and even veneration by the generations of students he has authors of this text and deans of veterinary faculties—Hinchcliff at the taught. University of Melbourne and Constable at the University of Illinois. The First Edition of this text was published in 1960 and authored In recognition of his service to veterinary science, Doug was the by D. C. Blood and J. A. Henderson. It was entitled Veterinary Medi- recipient of many awards and honorary degrees, including the Scho- cine: A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goats field Medal from the University of Guelph, the Gilruth Prize for Meri- and was based on Doug Blood’s and Jim Henderson’s lectures and torious Service to Veterinary Science from the Australian Veterinary Doug’s teaching and philosophical approach. At that time, there were Association, and an Order of the British Empire. He was involved in few textbooks in the disciplines of veterinary science and up-to-date the formation of the Australian and New Zealand College of Veteri- texts published in English that were primarily concerned with clinical nary Scientists. He also served as a committee member of the Victo- veterinary medicine and diseases in agricultural animal species were rian Division of the Australian Veterinary Association and as a board not available. The original text was divided into two major sections. member of the Veterinary Surgeons Registration Board of Victoria. One section, “General Medicine,” covered system dysfunction, and the In the early years, Doug Blood revolutionized the teaching of clini- other, “Special Medicine,” covered the specific diseases of the large- cal veterinary medicine. For those of us privileged to have been taught animal species. This format was followed until the Eleventh Edition. by him at this time, he was a superlative teacher. Doug was one of the The Second Edition was published in 1963 and had an additional two first teachers in clinical veterinary medicine to recognize that patho- chapters covering parasitic diseases. Subsequently, new editions have physiology was the basis for teaching the disease processes in large been published approximately every 5 years, with major or minor animals. He also concentrated on the principles of pathophysiology changes in format in most editions, such as the addition of chapters in his explanations of disease syndromes and in teaching clinical dealing with new subjects or the addition of material in specific sub- examination and diagnosis. This was an approach that he developed headings to highlight, for example, the epidemiology or zoonotic from the teaching of his mentor, Oxford veterinary scientist H. B. implications of disease. However, always, with each edition, there was Parry, to whom the first edition of this text was dedicated. This an extensive revision of disease descriptions based on current litera- approach to clinical teaching was in marked contrast to the rote learn- ture. Professor Henderson’s involvement with the text ceased with the ing that was common in many of the disciplines taught at that time Fifth Edition, and that edition recruited Professor O. M. Radostits as and in stark contrast to the teaching method in clinical examination senior author and others as contributing authors. Blood coauthored and diagnosis, which primarily relied on pattern recognition. nine editions over a span of 45 years, with coauthors including Doug Blood also taught that the method of clinical examination Radostits, Gay, Hinchcliff, and Constable. should be system based, that it should be conducted in a systematic In the preface to the First Edition, it was stated that the book was manner, and that it should be conducted using all available senses and directed primarily to students of veterinary medicine, although it was techniques. He further taught that the intellectual diagnostic rule-out expected that the book would be of value to practicing veterinarians process should also incorporate a consideration of the presenting and field workers. The latter expectation has certainly proved true, epidemiology of the disease problem, an examination of the environ- and the book has come to be extensively used as a reference by veteri- ment, and an estimation of the probability of disease occurrence, narians in large- and mixed-animal practice around the English- summarized with his often repeated adage “common diseases occur speaking world. Editions of the text have also been translated into commonly.” Although these approaches might seem obvious to recent French, Italian, Spanish, Portuguese, Japanese, Chinese, and Russian. graduates, in the 1950s and early 1960s, they were revolutionary. In In addition to his passion for the method and accuracy of diagno- fact, they set the foundation for current teaching principles in large- sis of disease in individual animals and herds, Doug Blood also had animal clinical veterinary medicine. Students of that older vintage a passion for preventive medicine and was a firm proponent of recall with great appreciation the understanding of clinical veterinary the thesis that subclinical disease is economically more important medicine imparted by Doug Blood and his particular contribution to than clinical disease in agricultural animal populations. With other vii  viii Professor Douglas Blood colleagues at the University of Melbourne, he developed health pro- agement. These herd health programs have been successfully com- grams for dairy cattle, beef cattle, and sheep and conducted practical mercially adopted in several countries. VetBooks.ir trials of these programs in private herds and flocks. These programs Doug had a formidable intellect combined with an inexhaustible were based on a whole-farm approach and centered on the concept work ethic. He was a generous family man who had a zest for life and that performance targets could be tracked through computer-based dry wit and who was so proud of his family and their achievements. productivity monitoring to detect deviation from target performance. He loved his morning runs/walks with his beloved Border Collies, Doug Blood was a very early proponent of the use of computers to music, and literature, and Doug had a passion for baking bread, manage and analyze data in clinical diagnosis and herd health man- brewing beer, photographing birds, and wearing bow ties.  Contributors VetBooks.ir The authors’ names, degrees, and contact emails are below. Authors Contributing Authors Peter D. Constable BVSc(Hons), MS, PhD, Docteur Honoris Causa (Université de Liège), Dipl.ACVIM, Dipl.ACVN (Honor- D.D. (Doug) Colwell BSc, MSc, PhD; (Doug.Colwell@AGR. ary), AssocMember.ECBHM; ([email protected]) Professor GC.CA) Livestock Parasitology/Parasitologie du betail, Agricul- and Dean, College of Veterinary Medicine, University of Illinois, ture and Agri-Food Canada/Agriculture et Agroalimentaire Urbana, Illinois, USA Canada, Lethbridge Research Centre, Alberta, Canada Kenneth W. Hinchcliff BVSc(Hons), MS, PhD, Dipl.ACVIM; Sara Connelly, DVM, MS, Dipl.ACVCP; ([email protected]) [email protected]; President and Chief Executive Officer, Clinical Assistant Professor, Department of Pathobiology and Vet- Trinity College, University of Melbourne, Royal Parade, Parkville, erinary Diagnostic Laboratory, College of Veterinary Medicine, Victoria, 3052, Australia; past Dean Faculty of Veterinary and University of Illinois, Illinois, USA Agricultural Sciences, University of Melbourne, Werribee, Victo- ria, Australia Levent Dirikolu DVM, MVSc, PhD; ([email protected]) Profes- sor and Director of the Equine Medication Surveillance Labora- Stanley H. Done BA, BVetMed, DVetMed, Dipl.ECPHM, tory, School of Veterinary Medicine, Louisiana State University, FRCVS, FRCPath; ([email protected]) Animal Health Baton Rouge, Louisiana, USA and Veterinary Laboratories Agency (AHVLA), Thirsk, United Kingdom. Contact [email protected] Robin Gasser Tierarzt, DVM, PhD, DVSc; (robinbg@unimelb. edu.au) Professor in Veterinary Parasitology, Veterinary Preclini- Walter Grünberg DrMedVet, MS, PhD, Dipl.ECBHM, Dipl. cal Centre, Faculty of Veterinary Science, University of Melbourne, ECAR, AssocDipl.ACVIM; ([email protected]) Parkville, Victoria, Australia Farm Animal Internal Medicine Specialist, University of Veterinary Medicine Hannover, Foundation Clinic for Cattle, Lynn Hovda RPh, DVM, MS, Dipl.ACVIM; (lhovda@safetycall. Hannover, Germany com) Adjunct Professor, University of Minnesota College of Vet- erinary Medicine, Director of Veterinary Services, SafetyCall International and Pet Poison Helpline, Bloomington, Minnesota, USA Basil Ikede DVM, PhD, Diagn Path, FCVSN; ([email protected]) University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada John Larsen BVSc, PhD, Grad Dip Bus Admin; (j.larsen@unimelb. edu.au) Associate Professor of Ruminant Production Medicine and Director, The Mackinnon Project, Veterinary Clinical Centre, Faculty of Veterinary and Agricultural Sciences, University of Mel- bourne, 250 Princes Highway, Werribee, Victoria, Australia William Witola BVetMed, MSc, PhD; ([email protected]) Assistant Professor of Parasitology, Department of Pathobiology, College of Veterinary Medicine, University of Illinois, Urbana, Illinois, USA Amelia R. Woolums DVM, MVSc, PhD, Dipl.ACVIM, Dipl. ACVM; ([email protected]) Professor, Department of Pathobiology and Population Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi, USA ix  Preface to the Eleventh Edition VetBooks.ir We are delighted to present the Eleventh Edition of Veterinary Medi- We continue to emphasize the epidemiology and pathophysiol- cine, 56 years since the first “Blood and Henderson” Veterinary Medi- ogy of each disease, which are important in understanding the ratio- cine was published in 1960 and 9 years since the Tenth Edition was nale for the diagnosis, treatment, and control. This means that we published in 2007. Veterinary Medicine focuses on diseases of rumi- strive to maintain an optimum balance between published research nants, horses, and swine, and it is the most extensively cited textbook and what field veterinarians find useful in their daily work. To make in veterinary medicine, with a recent total of 4,267 citations (Google it easier for the reader to find particular pieces of information, long Scholar, May 2016). Because the demand for this book remains strong, passages of prose have been divided into smaller sections using head- we assume that we have developed a philosophy, format, and price ings and subheadings. Key words, terms, and phrases have been that are attractive and meet the demands of undergraduate veterinary emboldened for emphasis and to make it easier for the reader to students and graduate veterinarians working in the field of large- identify important points. We also continue to include the zoonotic animal medicine. and bioterrorism implications of many diseases and how the large- Substantial changes were made to the format of the book for the animal veterinarian is becoming more involved in the control of dis- Eleventh Edition to keep current with the continuing expansion of eases transmissible to humans. The use of individual diagnostic tests, knowledge about the diseases of large animals. The book has been described under Clinical Pathology for each disease, continues to be a extensively revised and reorganized based on the major organ system challenge for all of us, especially with the increased availability of affected. The organ systems approach reflects the profound impact genomic or genetic testing and point-of-care testing. We have contin- that Dr. D. C. Blood had on the practice of large-animal medicine ued to concentrate on those tests that are accepted through common worldwide (see Foreword); he emphasized that the clinical examina- use, to discuss their limitations if they are known, and to provide a tion procedure should be a systems-based method. We have extended reference to newer tests that have future promise in diagnosis. A the systems approach implemented in the First Edition through the common limitation of publications describing new diagnostic tests is assignment of diseases to the primary organ system affected or the the absence of, or inadequate, information on the characteristics (sen- most obvious clinical sign referable to an organ system. As a result, sitivity, specificity, accuracy) of the test in the population of animals the Eleventh Edition contains 21 chapters, compared with 36 chapters in which it will be used. in the Tenth Edition. Thirteen chapters deal with specific organ Consistent with our deep commitment to practicing evidenced- systems, including the alimentary tract of ruminants and nonrumi- based veterinary medicine, relevant references from 2006 onward nants; the liver and pancreas; and the cardiovascular, hemolymphatic/ have been cited, and important review and scientific papers, including immune, respiratory, urinary, nervous, musculoskeletal, and repro- Internet sites, are identified as Further Reading. We refer readers to ductive systems; in addition to metabolic/endocrine abnormalities, previous editions of the book for references to earlier works. diseases of the mammary gland, and, finally, diseases of the skin, eye, When permitted by the quality and number of peer-reviewed pub- and ear. Each of these chapters is organized in the following manner: lications, we have applied the Grading of Recommendations Assess- general diseases; infectious diseases, listed in order of cause (bacterial, ment, Development and Evaluation (GRADE) process (see Foreword) viral, prion, protozoal, fungal, metazoan) and species affected (all to provide a summary of treatment and control recommendations in large animals, ruminants, horses, pigs); metabolic diseases; nutritional a box at the end of the section. This process distills information down diseases; toxicologic diseases and environmental agents; neoplastic to one of four recommendations that reflect “a judgment that most diseases; congenital and inherited diseases; and, finally, diseases of well-informed people would make”: R1, “do it”; R2, “probably do it”; unknown etiology. The remaining eight chapters deal with specific R3, “probably don’t do it”; and R4, “don’t do it.” We believe that the medicine topics, as follows: clinical examination and making a diag- GRADE approach will prove helpful to large-animal veterinarians, nosis; examination of the population; biosecurity and infection and we look forward to expanding this approach in future editions of control; general systemic states; disturbances of free water, electro- this book. lytes, acid-base balance, and oncotic pressure; practical antimicrobial Constraining the size of the book has been a constant preoccupa- therapeutics; perinatal diseases, and systemic and multi-organ dis- tion and a difficult task with the ever-increasing volume of published eases. A comprehensive index permits the reader to easily access rel- information and the constantly growing list of diseases. Our intention evant information in different chapters of the book. has always been to provide information on all recorded diseases. We have attempted to ensure that the book continues to have an Despite of reductions in reference lists and extensive editing to mini- international scope by including clinically important diseases occur- mize repetition, the book is still large, necessitating a move to two ring in large animals worldwide. The book notes the eradication of volumes. More than 150 new figures have been added to the book to Rinderpest in 2011 and includes new or extensively revised sections assist in presenting information. on a variety of topics, such as biosecurity and infection control; the We continue to subscribe to the practice and philosophy of earlier Schmallenberg and bluetongue viral epidemics of ruminants in editions of this book in having a small number of authors contribute Europe; Wesselsbron disease in cattle and hypokalemia in adult cattle; the majority of the text, with contributions from content specialists equine multinodular pulmonary fibrosis; Hendra virus infection; for particular topics. We believe that analysis and review of the rele- multisystemic, eosinophilic, epitheliotropic disease of horses; hypo- vant literature by a small number of authors with a broad knowledge glycin A intoxication and equine metabolic syndrome; porcine repro- and global perspective of large animal medicine assures a consistency ductive and respiratory syndrome; porcine epidemic diarrhea and of approach to each topic. Our authors are based in the United States, circovirus, and malignant catarrh in pigs; Torque teno, Menangle, and Australia, Europe, the United Kingdom, and Canada and have exten- Japanese B viruses in pigs; and numerous recently identified congeni- sive experience in international veterinary medicine. tal and inherited disorders of large animals. Dr. Peter Constable, Dean of the College of Veterinary Medicine, Reflecting the international scope of the book, the four University of Illinois, USA, has assumed the responsibilities of senior authors and nine coauthors were educated or have practiced vet- author. He revised a number of sections related to specific ruminant erinary medicine in 12 countries covering five continents, including diseases, in addition to major sections of the chapters on general Australia, Austria, Canada, Germany, Japan, the Netherlands, systemic states and diseases of the ruminant alimentary tract, cardio- Nigeria, Turkey, Switzerland, the United Kingdom, the United vascular system, urinary system, musculoskeletal system, nervous States, and Zambia. system, and mammary gland. Dr. Constable also revised the chapters x  Preface to the Eleventh Edition xi on examination of the population and disturbances of free water, State University, USA joined our book as a contributor by revising electrolytes, and acid-base balance. the chapter on practical antimicrobial therapeutics. Dr. Robin VetBooks.ir Dr. Kenneth Hinchcliff, CEO of Trinity College, University of Gasser, Professor of Veterinary Parasitology, Faculty of Veterinary Melbourne, and former Dean of the Faculty of Veterinary and Agri- and Agricultural Sciences, University of Melbourne, Australia, is a cultural Sciences, University of Melbourne, Australia, revised all the new contributor who revised the coverage of protozoal diseases. Dr. equine diseases and major sections of the chapters on diseases of the Lynn Hovda, Director of Veterinary Services, PLLC and Pet Poison respiratory system, nonruminant alimentary tract, hemolymphatic Helpline, Minnesota, USA also joined our book by revising the sec- and immune systems, endocrine abnormalities, and diseases of the tions related to diseases caused by toxins in plants, fungi, cyano- neonate. Dr. Hinchcliff also revised the chapter on clinical examina- phytes, clavibacteria, and venoms in ticks and vertebrate animals. tion and making a diagnosis and the Foreword of the book. Dr. Hinch- Dr. Basil O. Ikede, recently retired from the Atlantic Veterinary cliff acknowledges the support of St. John’s College, Cambridge, in College in Prince Edward Island, Canada, once again revised the appointing him as Overseas Visiting Scholar in 2013 during prepara- sections on the major exotic viral and protozoan diseases. Dr. John tion of parts of this text. Drs. Constable and Hinchcliff are responsible Larsen, Director of the Mackinnon Project, Faculty of Veterinary for the revised format of the book. and Agricultural Sciences, University of Melbourne, Australia, is a Dr. Stanley Done, recently retired from the Animal Health and new contributing author and revised many chapters related to dis- Veterinary Laboratories Agency, Thirsk, United Kingdom, joined our eases of sheep and goats. Dr. William Witola, Assistant Professor of book as a coauthor and revised all the sections on diseases of pigs. Parasitology, College of Veterinary Medicine, University of Illinois, This was a major task given the very large literature base on infectious USA, is also a new contributor to the book, revising chapters related diseases of pigs on a worldwide basis. to nematode, trematode, and tapeworm parasitic infection. Dr. Dr. Walter Grünberg, Farm Animal Internal Medicine Specialist, Amelia Woolums, Professor of Pathobiology and Population Medi- Tieräerztliche Hochschule, University of Veterinary Medicine, cine, College of Veterinary Medicine, Mississippi State University, Hannover, Germany, is also a new coauthor. He revised a number of USA, joined the Eleventh Edition by authoring a new chapter on sections related to specific ruminant diseases and extensive sections biosecurity. of the chapters on diseases of the liver and pancreas and the skin, We believe that we have completed another authoritative and com- eye, conjunctiva, and ear. prehensive review of the peer-reviewed literature of large-animal The legacies of Drs. D. C. Blood, C. C. Gay, J. A. Henderson, medicine, at a standard at least equal to that of the previous 10 edi- and O. M. Radostits continue in this edition of Veterinary Medicine. tions. We hope that the Eleventh Edition of Veterinary Medicine pro- Dr. Doug Colwell, Principal Research Scientist at Agriculture and vides the information necessary to meet the needs of veterinary Agri-Food Canada, once again revised the sections on diseases students and large animal clinicians for the next 5 to 8 years. caused by arthropod ectoparasites. Dr. Sara Connelly, Clinical Assis- tant Professor of Clinical Pathology, College of Veterinary Medicine, P. D. Constable University of Illinois, USA, revised the appendices dealing with con- K. W. Hinchcliff version tables and reference laboratory values. Dr. Levent Dirikolu, S. H. Done Professor of Pharmacology, School of Veterinary Medicine, Louisiana W. Grünberg  Introduction VetBooks.ir The first edition of this book established its role as a textbook of the Concentrations of major greenhouse gases—carbon dioxide, diseases of traditional farm animals in the Western world, those being methane, and nitrous oxide—are at their highest levels for at cattle, horses, sheep, pigs, and goats. The primary objective of this least the past 800,000 years. book was to offer the veterinary student and the practitioner the The global temperature continues to rise above long-term knowledge and information necessary to provide animal health man- historic levels, driving changes in climate and weather patterns. agement for farm animals. Although this intent has not changed, the These changes have a profound impact on human and animal context of veterinary medicine and large-animal practice has changed health, as evidenced by altered geographic distributions of diseases, markedly in the 56 years since publication of the first edition. emergence of new diseases, and reemergence of previously controlled or repressed diseases. Anthropogenic changes in the environment VETERINARY MEDICINE IN THE ANTHROPOCENE influence animal health by affecting the productivity of agricultural and animal production systems and increasing the likelihood of Anthropocene is the proposed name for a new, and the current, geo- spread of diseases from animals to humans. One-half of the global logical epoch following on from the Holocene and demarcated as the emerging infectious disease events of zoonotic origin between 1940 time when human activities began to have a substantial global effect and 2005 are estimated to be the result of changes in land use, agri- on the Earth’s systems.1,2 Although not universally accepted, the pro- cultural practices, and food production practices.5 There is evidence posal recognizes that human activity has become the primary deter- of an increased risk of zoonotic disease transmission in disturbed and minant of Earth’s biophysical conditions, influencing global systems degraded habitats, as exemplified by the emergence of two diseases and having profound effects on local and regional environments. The caused by henipaviruses in animals and humans. Both Nipah and Anthropocene is also associated with marked political and economic Hendra henipaviruses “spill over” from bats to pigs and horses, changes, including regional instability and reductions in political or respectively, and subsequently infect humans. In both instances, economic barriers to trade. All of these factors have influenced, and disease is associated with altered habitats, including land clearing that will continue to influence, veterinary practice and the management of creates a pathway for the repeated transmission of virus from fruit bat the health, well-being, and productivity of animals used for produc- reservoirs, emphasizing the role of intact ecosystems and the suit- tion of fiber and human food.3 ability of climatic conditions in regulating the transmission of The concept of the Anthropocene allows veterinarians to consider diseases.6-8 how the veterinary profession will adapt to our changing environment Change in weather systems and climate can profoundly influence and associated social, political, environmental, and economic chal- the distribution of vectors for important pathogens. Climate is a major lenges to animal and human health. The challenges include, but are factor in determining the geographic and temporal distribution of not limited to the following:4 arthropods, characteristics of arthropod life cycles, dispersal patterns A changing climate with flow-on effects on the geographic of associated arboviruses, the evolution of arboviruses, and the effi- distribution of diseases, emergence or reemergence of infectious ciency with which arboviruses are transmitted from arthropods to and noninfectious diseases, and extension of diseases into vertebrate hosts.9 For example, emergence of bluetongue virus infec- species not historically affected tion and disease in Europe has been attributed to climate change– Altered farming patterns, and hence use of animals, as climatic induced alterations in distribution of hematophagous midges that changes force farmers to abandon decades or centuries old land transmit the virus, although this concept is disputed, and the impor- and animal management practices tance of other anthropogenic, vector, or virus factors in the spread of Increasing internationalization of trade and freedom of the disease is unclear.10-13 movement of people, animals, and potential fomite, with There is concern that changes in land-use patterns and climate important implications for the biosecurity of countries, regions, might provide for the spread of Rift Valley fever into new locations, and industries including more frequent or deeper incursions into the Arabian Pen- Political instability, with subsequent loss of animal health insula.14 The emergence of Schmallenberg virus, an orthobunyavirus, monitoring and disease control as a cause of disease in ruminants in Germany and the Netherlands Economic pressures to produce more and safer food with no in late 2011, and its subsequent rapid spread across Europe, highlights increase in water or land use the potential for emergence of new diseases. The virus is apparently Societal expectations for increased animal welfare and the spread by culicoides midges, but its origin remains unknown. associated mandated changes in farm animal management Its roughly concurrent occurrence with new strains of bluetongue practices, for example, housing of dairy cattle or mulesing of virus (e.g., BTV-6) in the same region might be more than a lambs coincidence.15 As noted by the “Safeguarding Human Health in the Anthropo- International transport of animals and animal products has the cene Epoch: Report of the Rockefeller Foundation-Lancet Commis- proven potential to introduce disease into areas in which it was not sion on Planetary Health,”2 the scale of human impact on the planet present. Introduction of African horse sickness into regions with is immense and includes the following changes: populations of susceptible horses and competent midge (Culicoides About a third of the ice-free and desert-free land surface of the spp.) vectors can result in spread of the disease, as occurred in the planet has been converted to cropland or pasture. Iberian Peninsula in 1987.16-18 Equine influenza virus was inadver- Annually, roughly half of all accessible freshwater is appropriated tently introduced into Australia in August 2007 by importation of for human use. infected horses from Japan, with spread occurring because of appar- More than 2.3 million km2 of primary forest has been cleared ently inadequate quarantine procedures.19 Incursion of the virus, since 2000. which was subsequently eliminated from the continent, had an More than 60% of the world’s rivers are dammed, affecting in adverse economic impact.20 excess of 0.5 million km of river. Similarly, political instability and conflict, which might or might Extinction rate of species is more than 100 times that observed not be associated with climate change but in either case is clearly in the fossil record, and many remaining species are decreasing human-related, results in altered patterns of human movement, loss in number. of control and eradication programs, and absence of surveillance, with xii  Introduction xiii resultant resurgence of previously repressed diseases. Examples genome of a pathogen. Polymerase chain reaction tests now allow include the incursion of rinderpest into Turkey from Iraq in the after- detection of infinitesimally small quantities of DNA or RNA with VetBooks.ir math of the first Gulf War in the early 1990s, and spread of bovine great rapidity and absolute specificity, often permitting detection of contagious pleuropneumonia in Angola and the Horn of Africa as a the presence of pathogen genetic material on the same working day result of civil wars.21 as the samples were collected. Additionally, analysis of part (such as It is not just in infectious diseases that we will see changes in the single-nucleotide polymorphisms, or SNIPs) or all of the genome of Anthropocene. Increasing global temperatures and altered rainfall an animal or pathogen provides information critical to understanding conditions will increase the potential for heat- and drought-associated the pathogenesis, pathogenicity, or epidemiology of the organism. The illnesses in farm animals and for disruption to social systems by utility of this type of information is evident in discussion of many of altered rainfall patterns causing flooding, droughts, and an increase the diseases—from detection of mutations in the genome of animals in extreme weather events.4 For instance, heat stress profoundly influ- that cause them to display particular diseases, for example, bovine ences milk production, weight gain, and fertility of cattle, with these leucocyte adhesion deficiency, or, conversely, decrease their suscepti- effects extending beyond the period of actual exposure to heat.4 Heat bility to infectious diseases, such as occurs with scrapie in some breeds stress is a concern for dairy, feedlot, and range cattle in temperate and of sheep; to understanding of the pathogenicity of microbes, such as tropical regions of much of the world and has led to the introduction equine herpesvirus 1 neuropathic and less neuropathic strains, or of management systems to accommodate the changes in weather.3,22,23 their epidemiology, such as in strain typing of equine influenza Increases in mean global temperature will increase the number of days H3N8 viruses. annually, in some instances by over 100%, on which cattle are exposed to conditions that will cause heat stress.4 VETERINARY CLINICAL EPIDEMIOLOGY Veterinary input to animal productions systems will need to reflect these complex and changing climatic, political, social, and economic Important to our understanding of the basis of disease has been the environments that represent the nature of contemporary livestock emergence of clinical epidemiology as a means of interrogating the production of fiber and food for human consumption. patterns of disease and disease spread and identifying risk factors for development of disease. Understanding patterns of disease spread is CONTEMPORARY LIVESTOCK PRODUCTION fundamental to developing and implementing sensible and effective biosecurity and control measures. Similarly, knowing the risk factors Although traditional farms incorporating multiple livestock systems for development of disease and quantifying the relative importance of still exist, much more important economically and in terms of the each (“relative risk” or “odds ratio,” depending on the context) are key numbers of animals involved are farms that concentrate on one or two to determining which of these factors can be modified to reduce risk livestock systems or species. For example, witness the almost absence of the disease and whether it is economical to do so. in developed countries of farms on which pigs are run in extensive The importance of use of applied and analytical epidemiology in systems on pastures or fields shared with cattle, horses, or sheep. Much large-animal practice and veterinary medicine is clear. The tools of more common, and economically important, are the large piggeries epidemiology are now readily available to allow the veterinarian to that house hundreds to thousands of pigs, often with farms focusing identify and quantify the risk factors associated with the disease, to on breeding pigs that are then transferred to other farms or facilities provide a more accurate prognosis, to accurately assess treatment for finishing. Or consider the ascension of feedlots in which some- responses and not depend on clinical impressions, to scientifically times massive numbers of cattle are aggregated from the many indi- evaluate control procedures, and to conduct response trials. There is vidual farms on which they were bred, or the change in dairies from a large and challenging opportunity for veterinarians to become small (50–100 cows) farms to large operations with thousands of involved in clinical research in the field where the problems are occur- cows. The disease issues confronting managers and their veterinary ring. It will require that they become knowledgeable about the use of advisors in these facilities are much different from those encountered computerized databases. These now provide an unlimited opportunity by a veterinarian responding to a call for a sick cow in a small dairy to capture and analyze data and generate useful information, which herd on a family-run farm that also produces sheep, pigs, and poultry. heretofore was not considered possible. The technique of decision This edition of Veterinary Medicine reflects these changing circum- analysis is also a powerful tool for the veterinarian who is faced with stances, which are discussed in more detail in this Introduction. making major decisions about treatment and control procedures. Another important change confronting veterinarians is the increasing value of some individual animals, particularly horses. The VETERINARY SCIENTIFIC LITERATURE AND manner in which this book deals with medicine of horses is discussed HOW TO USE IT in detail during the planning of each edition. Increasing value of individual horses and desire by owners to protect the health or per- Perhaps the single greatest advance in veterinary medicine has been formance of these animals have driven the veterinary profession to the collective increase in knowledge. The large increase in knowledge develop sophisticated, and expensive, diagnostic and therapeutic of animal diseases and animal health, including information about modalities and interventions directed toward care of individuals. efficacy of diagnostic and therapeutic techniques and interventions, However, this is offset by the recognition that preservation of the coupled with the ease of access of this information through online health of bands of horses on studs or in stables, or in whole popula- databases and web-based search engines, presents challenges in tions in a country, is economically important and based on a thorough assessing the quality of information and in collating the information understanding of epidemiology and biosecurity—just as for food- and into a useable form. fiber-producing animals. For this latter reason, equine medicine Development of formal methods for assessing information and in this book is dealt with as much from a population perspective providing a recommendation have led to the term evidence-based as it is from the perspective of diagnosis and treatment of an veterinary medicine.24-26 Evidence-based veterinary medicine is individual horse. defined as the use of best relevant evidence in conjunction with clini- It is stating the obvious that veterinary medicine has advanced in cal expertise to make the best possible decision about a veterinary ways that were unimaginable 56 years ago. For example, our under- patient, taking into account the circumstances of each patient and the standing of the genetic, and increasingly the genomic, basis of produc- circumstances and values of the owner/carer.27 The questions related tion and susceptibility to disease is something that is now included in to use of an evidence-based approach can be summarized as follows: discussions of almost every disease, and not just those diseases with Why do we need evidence of effectiveness of our clinical actions a clear monogenetic basis. Associated with this is the incalculable (assessment of clinical signs, diagnostic tests, interventions, value of use of diagnostic tests based on detection of all or part of the prognostication)?  xiv Introduction What are the levels of evidence, and how good are they? From Evidence to Recommendation How does one translate evidence into a recommendation or The approach of using evidence to guide clinical decision making has VetBooks.ir decision? been formalized in the last two decades in human medicine and is What factors contribute to the weighting of evidence? gaining traction in veterinary practice. As veterinary clinicians, we Does weak evidence allow us to make a strong have ethical and legal obligations to use methods and practices that recommendation? are most likely to provide the “best” outcomes for the animals we treat Does strong evidence not always allow us to make a strong and their owners. A traditional approach to deciding on the “best” recommendation? treatments, diagnostic tests or methods, and preventative measures How do I use this in practice? has been to identify the highest-quality evidence of effectiveness and There are five steps to evidence-based veterinary medicine:27 to adopt the approach with the strongest evidence of efficacy. The 1. Ask the pertinent question and thereby define what it is Cochrane Collaboration and the Cochrane Reviews exemplify and that needs to be known to allow for the most lead this approach in human medicine (http://www.cochrane.org/ appropriate action. cochrane-reviews). 2. Acquire the evidence, usually by a review of the available This “evidence-based” approach has the implicit assumption that literature or, less commonly, performing a new research one should rely on the highest-quality evidence and that high-quality study. evidence of efficacy necessarily leads to the adoption of that treatment, 3. Appraise the quality of evidence and its external validity diagnostic test, or prophylaxis. However, this approach falls short (evidentiary value for the question being asked). when formulating recommendations for use in clinical practice. What 4. Apply the evidence to practice, where appropriate. See practitioners need is recommendations that are based on the available comments that follow about the GRADE process. evidence but that also take into account the other factors that must be 5. Audit—Assess whether the application of the new evidence considered when advising an owner or trainer on the “best” approach has affected the outcome of interest. to dealing with their animal’s (and their) problem. This methodology has been developed in human medicine as the GRADE (Grading Quality of Evidence of Recommendations Assessment, Development, and Evaluation) The confidence we have in our evidence-based approach to veterinary process.35 GRADE fundamentally works by providing a framework to practice depends on our assessment of the quality of the evidence determine a final recommendation on an intervention through use of available to us.28 Not all evidence is of equal merit or utility, and the following: although there are slight differences in the ratings of quality of evi- 1. The quality of evidence (Cochrane and similar evaluations of dence from different sources, an approximate hierarchy of evidence quality of evidence stop here), from lowest to highest in terms of value of evidence for practical use 2. Seriousness of the outcome, is as follows: 3. Magnitude of the treatment effect, Expert opinion/editorials/nonstructured consensus statements or 4. Precision of the treatment effect, opinion pieces 5. Risk of the target event (how frequent), Case reports and case series 6. Risk of adverse events associated with the intervention, In vitro studies with an appropriate control group 7. Cost of the intervention, and Animal models of the disease of interest (induced disease in 8. The values and preferences of the end users (patients). species other than the species in which the disease occurs All of these criteria have at least some applicability in veterinary naturally, e.g., mouse model of a disease in horses) medicine. Briefly, judgments about the quality of recommendations Case-control or cross-sectional studies require consideration of the following factors: Nonrandomized trials, cohort studies, or models of induced The quality of evidence on which the recommendation is disease in the species of interest (target species, e.g., induction of based. The quality of evidence is assessed on the type of study viral diarrhea in calves) (with systematic reviews being designated a priori as the highest Randomized controlled trials under field conditions level of evidence and observational studies providing a lower Systematic review of randomized controlled trials quality of evidence), imprecision of the results over a number of Systematic review, including meta-analysis studies, inconsistency of the studies, indirectness, reporting bias, The higher the quality of evidence, the greater is our confidence in magnitude of the effect, biological plausibility, and strength of making decisions based on this evidence. The highest-quality evi- association.36-40 dence is provided by systematic reviews, which might include a meta- The balance between benefits and harms. Will the intervention analysis. Systematic reviews differ from narrative reviews, which do more good than harm? What is the extent of the benefit and have much lower evidentiary value, in that systematic reviews are of the potential harm? approached in a manner and with methodology designed to ensure Feasibility of translating the evidence into the circumstance in the validity of the conclusions.29 Systematic reviews should be based which the intervention will be made. Can I apply this in my on a clearly defined question and prespecified criteria for inclusion practice? Is it affordable? and evaluation of the literature, among other factors. Criteria and Certainty of the baseline risk. How important is the problem? methodology for performing systematic reviews are available.30-32 Cost. Both monetary costs and expenditures in terms of Assessment of the quality of evidence provided by scientific resources must be considered. articles is dependent on the authors of the article reporting exactly The balance between benefit and harm (the trade-off) can be catego- what they did and how they did it. It is clear from studies in human rized as follows: medicine and small animals that poorer reporting of methodology in Net benefits = the intervention clearly does more good than articles is associated with a greater proportion of positive outcomes, harm. leading one to suspect that reports that are less well documented Trade-off = there are important trade-offs between the benefits are more likely to provide unreliable evidence of efficacy.33 There and harms. are increasing numbers of guidelines that provide advice for authors Uncertain trade-offs = it is unclear whether the intervention on how to adequately report on trials, and these guidelines are also does more good than harm. useful as checklists for readers of articles. Available guidelines are No net benefits = the intervention clearly does more harm than CONSORT, REFLECT, STARD, STROBE, and others, which are avail- benefit. able through the EQUATOR website (http://www.equator-network. The quality of evidence informing the recommendation can be org/reporting-guidelines/).34 categorized as follows:  Introduction xv High: We are very confident that the true effect lies close to that elective procedures themselves. From firsthand experience and of the estimate of the effect. In other words, we can be very extension courses provided for them, they have also learned how to VetBooks.ir confident that both the direction of the effect and its magnitude diagnose and treat many of the common diseases of farm livestock. are known with reasonable certainty and that the magnitude of Many veterinary pharmaceuticals antimicrobials and biologicals can the effect is clinically relevant. now be purchased by producers from either veterinary or nonveteri- Moderate: We are moderately confident in the effect estimate. nary sources. The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. In other INDUSTRIALIZED ANIMAL AGRICULTURE words, the direction of the effect is likely known, although the magnitude might change with further research. The magnitude The intensification of animal agriculture has created complex animal of the effect is likely clinically significant. health and production problems for which there are no simple and Low: Our confidence in the effect estimate is limited. The true reliable therapeutic and preventive procedures, and this has made the effect could be substantially different from the estimate of the task of the veterinarian much more challenging. For example, acute effect. In other words, both the direction of the effect and its undifferentiated respiratory disease is a common disease of feedlot magnitude are very likely to change with further research. cattle that is difficult to treat and control effectively because the etiol- Very low: Any estimate of the effect is very uncertain, and the ogy and epidemiology are complex. Acute diarrhea of calves under 30 direction and magnitude of the real effect of the intervention are days of age may be caused by several different enteropathogens, but a unknown. knowledge of the risk factors or epidemiologic determinants, such as Finally, all of the considerations just described can be distilled colostral immunity and population density, is probably more impor- down to the following recommendations being “a judgement that tant for effective clinical management and control of the disease. The most well-informed people would make”:41 rearing of pigs intensively and in complete confinement has exagger- “Do it”—there is high-quality evidence of net benefits within ated a number of disease problems, many exacerbated by inadequacies appropriate resource constraints (costs) for a problem that has of the environment. significant importance (a judgment that most well-informed Suboptimal reproductive performance resulting from a variety of people would make). management and environmental factors is common, and pneumonia “Probably do it” = when the strength of evidence is moderate or in growing and finishing pigs may be almost impossible to eradicate when the benefit : harm trade-off is unclear or marginal. unless the herd is depopulated and repopulated with minimal-disease “Probably don’t do it” = when the strength of evidence is low or breeding stock. Infectious diseases such as porcine reproductive and very low, when the benefit : harm trade-off is unclear or respiratory syndrome are difficult to control. The solutions to these marginal, or when the baseline risk is low. complex problems are not always readily apparent, in part because of “Don’t do it” = there is high-quality evidence of harm clearly insufficient research on etiology and epidemiology and different exceeding benefits, the cost is too great compared with benefits, or control strategies in the herds where the problems are occurring. The the baseline risk is very low (i.e., the problem is not important). veterinarian must be knowledgeable and skillful in the principles of The GRADE guidelines, although not well established for veteri- epidemiology, applied nutrition, and animal housing; the education nary medicine, have been used and provide the opportunity to make and training of animal attendants; and the analysis of production evidence-based recommendations to practitioners.42 indices, including profit and loss, which includes the use of comput- ers, in addition to being skilled in the traditional veterinary disciplines FOOD- AND FIBER-PRODUCING ANIMALS of medicine, reproduction, pharmacology, and pathology. Thus, the food-producing-animal practitioner must become more skilled in Veterinary practice with food-producing animals provides service the simultaneous management of animal health and production; the primarily to the owners of the meat-, milk-, and fiber-producing modern livestock producer is cost-conscious, and anything veterinar- animals such as dairy and beef cattle, pigs, sheep, and goats. Veterinar- ians do or recommend must be cost-effective. ians also provide service to owners of captive ungulates, such as red deer, elk, and bison, which are being raised under farm conditions for COMPANION-ANIMAL PRACTICE the production of meat and byproducts such as hides. Although some commercially processed horsemeat is consumed by humans, the In contrast, developments in companion-animal medicine (small market is small compared with that for beef and pork, and horses are animals) have followed in the footsteps of human medicine, with an not usually included in discussions about food-producing animal vet- ever-increasing emphasis and reliance on extensive use of clinical erinary practice. Poultry, fish, and rabbits are also important sources pathology for the in-depth evaluation of the hematology, clinical of human food but are not the subject of this book. chemistry, enzymology, immune status, and many other body func- For the past several decades, the major activity in food-producing- tions of the individual animal. animal practice, and a major source of income for veterinarians, was Diagnostic techniques such as ultrasonography, endoscopy, the provision of emergency veterinary service to the owners of herds nuclear imaging, and computed tomography are being used both in or flocks in which a single animal was affected with one of the common veterinary teaching hospitals and in referral veterinary practices. diseases. Occasionally, outbreaks of disease affecting several animals These in-depth “diagnostic workups” presumably lead to a greater occurred. In addition, routine elective veterinary services, such as understanding of the etiology and pathophysiology of disease, with castration, vaccination, dehorning, and deworming; the testing for the ultimate aim of a more accurate and early diagnosis that allows diseases, such as brucellosis and tuberculosis; and the dispensing of much more effective medical and surgical therapy than is economi- veterinary drugs, pharmaceuticals, and biologicals accounted for a cally possible or necessary in food-producing animals. There is not significant source of revenue for the veterinarian. Since about the early the same emphasis on the efficiency of production, epidemiology, and 1970s, there has been a shift from emphasis and dependence on emer- cost-effectiveness that constantly faces the food-producing-animal gency veterinary medicine and routine procedures to more attention practitioner. More and more companion-animal owners, because of being paid by the veterinarian and the producer to planned animal the sentimental value of their animals and the growing importance of health and production management using the whole-farm approach. the human–companion animal bond, are willing to pay for the costs Livestock producers are now much more knowledgeable about animal associated with extensive laboratory and sophisticated diagnostic tests agriculture and are concerned about the cost-effectiveness and the and intensive and prolonged veterinary hospital care. Palliative care scientific basis of the recommendations made by veterinarians and for dogs and cats affected with diseases that may not be curable over agricultural advisors. More and more producers are doing the routine the long term is now a recognized fact in small-animal practice.  xvi Introduction EQUINE PRACTICE Providing the most economical method of diagnosis and treatment of sick and injured animals and returning them to VetBooks.ir Equine practice has evolved along similar lines to small-animal prac- an economically productive status, or to a point where tice. Some aspects of it, such as reproduction, intensive clinical care slaughter for salvage is possible, in the shortest possible time. of the newborn foal, and the treatment of medical and surgical dis- The financially conscious producer wants to know the eases of valuable athletic and competitive horses, have advanced a probability of success following treatment of a disease in an great deal. The great strides that have been made in our understanding animal and to minimize the costs of prolonged convalescence of the diagnosis, prognosis, and medical and surgical therapy of colic and repetitive surgery. in the horse are a result of the in-depth diagnostic laboratory work Monitoring animal health and production of the herd on a and the medical and surgical expertise that have been used. Our regular basis so that actual performance can be compared improved understanding of the prognosis of equine colic is in part with targets and the reasons for the shortfalls in production attributable to prospective studies of the clinical and laboratory find- or increases in the incidence of disease can be identified as ings in horses with colic. However, the large advances in improvement soon as possible, so that appropriate and cost-effective action in survival made in the early years of surgical and intensive medical can be taken. The routine monitoring of production records treatment of colic have not continued, and there is an urgent need for and the regular monitoring of bulk-tank milk somatic cell appropriately designed prospective clinical trials to determine optimal counts in dairy herds are examples. treatment regimes in these horses. The same is true for intensive treat- Recommending specific disease control and prevention ment of sick foals. In addition to the advanced diagnostic and thera- programs, such as herd biosecurity, vaccination of cattle peutic procedures being done on valuable horses at veterinary teaching against several important infectious diseases that occur under hospitals, there are now many privately owned equine veterinary a variety of conditions, and the strategic use of anthelmintics centers that provide the same service. Undoubtedly the high financial in cattle and sheep. value of some horses has provided the impetus for the development Organizing planned herd and flock health programs for the of these services. individual farms with the objective of maintaining optimum Although the increasingly sophisticated diagnostic and therapeutic productivity through animal health management. techniques used in equine practice are readily noted, advances in the Advising on nutrition, breeding, and general management understanding of infectious and contagious diseases of horses have practices. Food-producing-animal practitioners must be also increased markedly. This is particularly true for economically interested in these matters when they affect animal health. It important diseases that have the potential to affect large numbers of is a large part of production-oriented health management, horses, consequently causing disruption to important athletic events and it is now common for veterinarians to expand their and the sale and shipment of horses. These diseases are typically the health-oriented animal husbandry advisory service to include infectious respiratory diseases and those diseases, such as African an animal-production advisory service. To do so is a matter horse sickness, that are exotic to most of the horse population world- of individual preference, an option that some veterinarians wide. The economic incentive to control these diseases has resulted in take up and others do not. Some veterinarians will rely on considerable increases in knowledge of their etiology (and conse- consultation with agricultural scientists. However, quently vaccinology), epidemiology, immunology, diagnosis, and pre- veterinarians still require a working knowledge of the vention. Few advances have been made in treatment of what are, for relevant subjects, at least enough to know when to call in the the most part, self-limiting diseases with low case-fatality rates. collaborating advisor for advice. Members of both groups should be aware of the extensive list of subjects and species- CONTRASTING OBJECTIVES oriented textbooks on these subjects, which should be used to support this kind of service. It is clear that there are major differences between the objectives and principles of companion-animal practice and those of food- ANIMAL WELFARE producing-animal practice. In companion-animal practice, the objec- tive is the restoration of the clinically ill animal to a normal state, if Encouraging livestock producers to maintain standards of animal possible, or in some cases a less-than-normal state is acceptable pro- welfare that comply with the views of the community is emerging as vided it is a quality life, using all the readily available diagnostic and a major responsibility of the veterinarian. The production of food- therapeutic techniques that can be afforded by the client. In sharp producing animals is an animal welfare concern that practitioners contrast, in food-producing-animal practice, the objective is to face and an area in which they must become proactive.43,44 Increas- improve the efficiency of animal production using the most economi- ing public concern for the welfare of animals, including those that cal methods of diagnosis, treatment, and control, including the dis- produce food and fiber for human consumption, must be addressed posal by culling or slaughter of animals that are difficult to treat and using high-quality scientific evidence and a sound understanding are economic losses. of the arguments of individuals and groups opposed to such use This growing dichotomy in the delivery of veterinary services to of animals. the food-producing-animal owner and to the companion-animal owner prompted us to present a short introductory commentary on ZOONOSES AND FOOD SAFETY the objectives and principles of food-producing-animal practice. Promoting management practices that ensure that meat and milk are free of biological and chemical agents capable of causing disease in The Objectives of humans must also become a preoccupation for food-producing- animal veterinarians. This is because the general public is concerned Food-Producing-Animal Practice about the safety of the meat and milk products it consumes, and the EFFICIENCY OF LIVESTOCK PRODUCTION most effective way to minimize hazards presented by certain infec- tious agents and chemical residues in meat and milk is to control these The most important objective in food-producing-animal practice is agents at their point of entry into the food chain, namely, during the the continuous improvement of the efficiency of livestock production production phase on the farm. Veterinarians will undoubtedly become by the management of animal health. This involves several different involved in the surveillance of the use of antimicrobial compounds but related activities and responsibilities, which include the and other chemicals that are added to feed supplies to promote growth following: or prevent infections, and they will be expected to minimize the risk  Introduction xvii