Disease in Wild Animals: Investigation and Management 2nd Edition Gary A. Wobeser Disease in Wild Animals Investigation and Management 2nd Edition With 17 Figures Prof. Dr. Gary A. Wobeser Department of Veterinary Pathology Western College of Veterinary Medicine University of Saskatchewan 52 Campus Drive Saskatoon, Saskatchewan, S7N 5B4 Canada e-mail: [email protected] The first edition “Investigation and Management of Disease in Wild Animals” (ISBN 0-306-44703-7) was published by Plenum Press, New York, 1994. Library of Congress Control Number: 2006940351 ISBN-10: 3-540-48974-6 Springer Berlin Heidelberg New York ISBN-13: 978-3-540-48974-0 Springer Berlin Heidelberg New York This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permissions for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. Springer is a part of Springer Science+Business Media springer.com © Springer-Verlag Berlin Heidelberg 2007 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Editor: Dr. Dieter Czeschlik, Heideiberg, Germany Desk editor: Dr. Andrea Schlitzberger, Heidelberg, Germany Cover design: WMXDesign GmbH, Heidelberg, Germany Production and typesetting: SPi Publisher Services Printed on acid-free paper SPIN 11562528 31/3100 5 4 3 2 1 0 Preface This book arose out of teaching graduate and undergraduate classes in wildlife diseases. It, in some ways, chronicles my involvement in the investi- gation and diagnosis of diseases in free-ranging wildlife, primarily in western and northern Canada, since the 1960s. It also, perhaps, reflects the develop- ment of wildlife disease study as a discipline. Much of the earlier work in this field was purely descriptive, documenting the occurrence of various diseases in wild animals. I have chosen to retain references to some older and obscure information in this second edition because this body of work provides the foundation for a more analytical approach. The literature on health problems in free-ranging animals is expanding rapidly. I am gratified that the theoret- ical and quantitative aspects of wildlife disease are receiving more attention than in the past, and that role of disease as a factor in population biology is being analyzed. My hope for the first edition of this book was that it would serve as an overview of the study of disease in wild animals and of methods that might be used to manage health problem. It was, and is, not intended to be a how-to book or an encyclopedic reference to the literature on disease; rather it is intended as a seed crystal around which the reader can build. The inquiries I have received about a second edition suggest that it has been useful. The field of wildlife diseases is an interface area between medicine and applied biology. During the past half-century, medical science has become preoccupied with technology and with dissecting disease phenomena at the molecular level in the laboratory. This has resulted in marvelous tools for the study of disease agents. However, study of disease in whole animals and of the population biology of disease became unfashionable, even though such knowledge is essential if the results of high-tech research are to be applied. In contrast, wildlife biology is concerned with populations and, to the wildlife manager, disease is important only when it has an impact on the population. Some basic concepts of epidemiology, such as mortality rate and survival rate of a population, are used more frequently by the average biologist than by the average health practitioner. Medical scientists don’t think of disease in terms of fitness, trade-offs or compensation, but these concepts are fundamental to the ecologist. The role of the “wildlife disease specialist” is to use the tools of biomedical science within an ecological framework to understand how and why disease occurs in free-living populations and when and how it might be managed. vi Preface I thank my wife Amy Grace for her patience and support; my colleagues in the Department of Veterinary Pathology, Western College of Veterinary Medicine, and the Canadian Cooperative Wildlife Health Centre for allowing me to pursue my interests; the students who have tolerated my enthusiasm and served as a sounding board for notions; and the many wildlife biologists I have worked with over the years who have helped me to keep the impor- tance of disease in perspective. Saskatoon, December 2006 Gary A. Wobeser Contents Section I Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 Disease and epizootiology—basic principles . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Disease and diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 A definition of disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3 Disease causation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4 Disease investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.5 Basic epizootiological terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2 Special problems in working with free-living animals . . . . . . . . . . . . . . . . . . 17 2.1 Problems in detecting diseased animals . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.2 Problems in determining numbers and identifying individuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.3 Problems related to lack of knowledge about the animals . . . . . . . . . . . 23 2.4 Problems related to the diversity and intractable nature of wild animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.5 Fitness, trade-offs, and predators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.6 Problems related to people . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Section II Disease investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3 Identifying and defining a disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.1 Temporal distribution of disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.2 Spatial distribution of disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 3.3 Identification of the disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 3.4 Avian vacuolar myelinopathy—an example of defining a disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4 Collecting population data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.1 Basic features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.2 Choosing a method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 4.3 Basic methods for determining animal numbers . . . . . . . . . . . . . . . . . . 56 4.4 Population distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.5 Vital statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 viii Contents 5 Defining environmental factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 5.1 Characteristics of the physical environment . . . . . . . . . . . . . . . . . . . . . 85 5.2 Characteristics of the biotic environment . . . . . . . . . . . . . . . . . . . . . . . 91 5.3 Human effects on disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 6 Formulating and testing hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 6.1 Hypotheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 6.2 Collecting information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 6.3 Use of indicator or sentinel species . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 6.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 7 Samples, sampling and sample collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 7.1 Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 7.2 Collection and analysis of biological specimens . . . . . . . . . . . . . . . . . . 128 7.3 Sampling and data collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134 7.4 Is disease present? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 7.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 8 Investigation of disease outbreaks and chronic or inapparent disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 8.1 Investigation of outbreaks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 8.2 Investigation of chronic or inapparent disease . . . . . . . . . . . . . . . . . . . 155 8.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 9 Records and recordkeeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 9.1 Designing a record system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166 9.2 Logging information for retrieval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 9.3 Collecting information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 9.4 Filing and storing information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 9.5 Specimen collections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178 9.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 Section III Disease management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 10 Disease management—general principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 10.1 Is management desirable? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 10.2 Is management feasible? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 10.3 Who is management for? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188 10.4 Costs and benefits of management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190 10.5 How will management be done? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191 10.6 A management matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 10.7 How far will the program be taken? . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196 10.8 How will success be measured? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 10.9 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198 Contents ix 11 Management of the causative agent/factor or its vector . . . . . . . . . . . . . . . . . 199 11.1 Elimination of the cause of non-infectious diseases . . . . . . . . . . . . . . . 200 11.2 Attacking the cause of infectious diseases . . . . . . . . . . . . . . . . . . . . . . . 205 11.3 Management of invertebrates involved in disease transmission . . . . . 211 11.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216 12 Disease management through manipulation of the host population . . . . . . 217 12.1 Defining the population(s) of interest . . . . . . . . . . . . . . . . . . . . . . . . . . 218 12.2 Manipulation of animal distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . 218 12.3 Selective removal of diseased animals from the population . . . . . . . . 224 12.4 Reduction of population density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227 12.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244 13 Disease management through treatment and immunization . . . . . . . . . . . . . 247 13.1 Therapy of diseased animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248 13.2 Immunization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254 13.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 14 Disease management through environmental modification . . . . . . . . . . . . . 271 14.1 General considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271 14.2 Abiotic elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273 14.3 Biotic factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277 14.4 Predicting, preventing, and mitigating . . . . . . . . . . . . . . . . . . . . . . . . . 286 14.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289 15 Disease management through influencing human activities . . . . . . . . . . . . . 291 15.1 Movement of animals and disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292 15.2 Modifying human activities by regulation and legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302 15.3 Modifying human activities through education . . . . . . . . . . . . . . . . . . 304 15.4 Integrating disease management in planning . . . . . . . . . . . . . . . . . . . . 306 15.5 Disease transmitted from humans to wildlife . . . . . . . . . . . . . . . . . . . . 307 15.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308 16 Emergency and integrated management programs . . . . . . . . . . . . . . . . . . . . . 309 16.1 Emergency disease control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309 16.2 Integrated disease management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320 16.3 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324 17 Assessing the effectiveness of a disease-management program . . . . . . . . . . . 325 17.1 Choosing suitable parameters to measure . . . . . . . . . . . . . . . . . . . . . . . 326 17.2 Collecting the data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329 17.3 The method of assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331 17.4 The time frame for assessing effectiveness . . . . . . . . . . . . . . . . . . . . . . 335 17.5 Assessing the economics of disease management . . . . . . . . . . . . . . . . . 336 17.6 Using models to predict and assess effectiveness of programs . . . . . . 338 17.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339 x Contents Common and scientific names of animals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389 Section I Introduction “Up to the present time it has been customary to believe that wild animals pos- sess a high standard of health, which is rigidly maintained by the action of natural selection, and which serves as the general, though unattainable, ideal of bodily health for a highly diseased human civilization. This belief is partly true and partly false.” (Elton 1931)