SAUNDERS an Imprint of Elsevier Science 11830 Westline Industrial
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SAUNDERS An Imprint of Elsevier Science 11830 Westline Industrial Drive St. Louis, Missouri 63146 EQUINE DERMATOLOGY ISBN 0-7216-2571-1 Copyright © 2003, Elsevier Science (USA). All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permissions may be sought directly from Elsevier’s Health Sciences Rights Department in Philadelphia, PA, USA: phone: (+1) 215 238 7869, fax: (+1) 215 238 2239, e- mail: [email protected]. You may also complete your request on-line via the Elsevier Science homepage (http://www.elsevier.com), by selecting ‘Customer Support’ and then ‘Obtaining Permissions’. NOTICE Veterinary Medicine is an ever-changing field. Standard safety precautions must be followed, but as new research and clinical experience broaden our knowledge, changes in treatment and drug therapy may become necessary or appropriate. Readers are advised to check the most current product information provided by the manufacturer of each drug to be administered to verify the recommended dose, the method and duration of administration, and contraindications. It is the responsibility of the treating veterinarian, relying on experience and knowledge of the patient, to determine dosages and the best treatment for each individual animal. Neither the publisher nor the editor assumes any liability for any injury and/or damage to animals or property arising from this publication. International Standard Book Number 0-7216-2571-1 Acquisitions Editor: Ray Kersey Developmental Editor: Denise LeMelledo Publishing Services Manager: Linda McKinley Project Manager: Jennifer Furey Designer: Julia Dummitt Cover Design: Sheilah Barrett Printed in United States of America Last digit is the print number: 987654321 W2571-FM.qxd 2/1/03 11:46 AM Page v Preface and Acknowledgments quine skin disorders are common and important. After dogs and cats, horses are the most Ecommon species presented to our Dermatology Service and telephone consultation service for evaluation. In general, the equine dermatoses seen worldwide are similar both in nature and frequency.1-8 Very little information is available concerning the demographics of equine skin disorders. A survey carried out by the British Equine Veterinary Association in 1962 and 1963 indicated that 2% of all cases seen by the membership were presented for skin disease.9 A 1989 survey of the members of the American Association of Equine Practitioners revealed that skin disorders were the fourth most common medical problem encountered (following colic, viral respiratory tract disease, and endometritis).10 The top 10 equine health problems as determined by a survey of horse owners included skin diseases, which ranked number 9.11 Panel reports of veterinary practitioners in 1975, 1981, and 1986 found that dermatophytosis, dermatophilosis, urticaria, insect hypersensitivities, onchocerciasis, eosinophilic granulomas (“nodular necrobiosis”), papillomas (“warts”), sarcoids, photodermatitis, and nutritional “seborrheas” were the most commonly encountered equine skin disorders.4-6 In a 21-year (1979- 2000) retrospective study of equine skin disorders at the College of Veterinary Medicine at Cornell University, 4.1% of all horses examined at the Large Animal Clinic were evaluated by a dermatologist for skin problems (Tables 1 and 2).12 There was no breed predisposition for skin G Table 1 COMMON HORSE BREEDS PRESENTED FOR DERMATOLOGIC DIAGNOSIS12 PERCENTAGE OF PERCENTAGE OF TOTAL BREED DERMATOLOGY CASES HOSPITAL POPULATION Thoroughbred 23.9 22.9 Quarter Horse 16.5 14.6 Standardbred 15.8 24.2 Arabian 6.4 5.2 Appaloosa 5.8 5.4 Morgan 4.5 3.0 Belgian 3.9 2.1 American Paint 1.8 1.8 Percheron 1.1 0.7 American Saddle Horse 0.9 0.6 Clydesdale 0.6 0.4 All other breeds 18.8 19.1 v W2571-FM.qxd 2/1/03 11:46 AM Page vi vi • Preface and Acknowledgments G Table 2 DERMATOLOGIC DIAGNOSES* FOR 900 HORSES OVER A 21- YEAR PERIOD (1979-2000)12 DIAGNOSIS # OF CASES % OF CASES Bacterial folliculitis 106 11.78 Dermatophytosis 80 8.89 Insect hypersensitivity 57 6.33 Dermatophilosis 50 5.56 Drug reaction 37 4.11 Eosinophilic granuloma 35 3.89 Atopy 35 3.89 Vasculitis 30 3.33 Chorioptic mange 24 2.67 Equine sarcoid 23 2.56 Urticaria, idiopathic 22 2.44 Idiopathic pruritus 19 2.11 Pemphigus foliaceus 17 1.89 Erythema multiforme 17 1.89 Onchocerciasis 15 1.67 Ear papillomas 13 1.44 Viral papillomatosis 12 1.33 Alopecia areata 12 1.33 Follicular dysplasia 12 1.33 Pediculosis 11 1.22 Idiopathic seborrhea 11 1.22 Unilateral papular dermatosis 11 1.22 Dermoid cysts 10 1.11 Bacterial pseudomycetoma 10 1.11 Telogen defluxion 10 1.11 Melanoma 9 1.00 Lymphoma 9 1.00 Anagen defluxion 9 1.00 Habronemiasis 9 1.00 Coronary band dysplasia 9 1.00 Ventral midline dermatitis 8 0.89 Cannon keratosis 7 0.78 Contact dermatitis† 7 0.78 Verrucous hemangioma 6 0.67 Linear keratosis 6 0.67 Trichorrhexis nodosa 6 0.67 Vitiligo 6 0.67 Bacterial cellulitis 6 0.67 Traumatic alopecia 5 0.56 Blackfly bites, pinna 5 0.56 Sterile eosinophilic folliculitis 5 0.56 Secondary seborrhea, hepatic 5 0.56 Pseudolymphoma 5 0.56 Epidermal nevus 5 0.56 Schwannoma 5 0.56 Sterile pyogranuloma 4 0.44 Sterile panniculitis 4 0.44 Sarcoidosis 4 0.44 Tick bite granuloma 4 0.44 Hyperadrenocorticism 4 0.44 Food hypersensitivity 4 0.44 Behavioral self-mutilation 4 0.44 W2571-FM.qxd 2/1/03 11:46 AM Page vii Preface and Acknowledgments • vii G Table 2 DERMATOLOGIC DIAGNOSES* FOR 900 HORSES OVER A 21- YEAR PERIOD (1979-2000)12—cont’d DIAGNOSIS # OF CASES % OF CASES Mane and tail seborrhea 3 0.33 Idiopathic pastern dermatitis 3 0.33 Discoid lupus erythematosus 3 0.33 Epitrichial sweat gland neoplasm 3 0.33 Spotted leukotrichia 3 0.33 Amyloidosis 3 0.33 Barbering 3 0.33 Burns 2 0.22 Bullous pemphigoid 2 0.22 Lymphangitis, bacterial 2 0.22 Photodermatitis, hepatic 2 0.22 Systemic lupus erythematosus 2 0.22 Epitheliotropic lymphoma 2 0.22 Squamous cell carcinoma 2 0.22 Idiopathic delayed shedding 2 0.22 Sporotrichosis 2 0.22 Eumycotic mycetoma 2 0.22 Photic headshaking 2 0.22 Pressure sores 2 0.22 Multisystemic eosinophilic epitheliotropic disease 2 0.22 Aplasia cutis congenita 1 0.11 Malignant fibrous histiocytoma 1 0.11 Carcinosarcoma 1 0.11 Halicephalobiasis 1 0.11 Phaeohyphomycosis 1 0.11 Cutaneous asthenia 1 0.11 Mast cell tumor 1 0.11 Arsenic toxicosis 1 0.11 Hypotrichosis 1 0.11 Trichoepithelioma 1 0.11 Pili torti 1 0.11 Strawmite dermatitis 1 0.11 Organoid nevus 1 0.11 Lichenoid keratosis 1 0.11 *Where more than one dermatosis was present at the same time in one horse, only the most important are listed. †Contact reactions associated with topical medicaments are included under Drug Reaction. disease as a whole. Due to the referral nature of our practice, the types and frequencies of the various dermatoses documented would not be expected to be those seen in general equine practice. The “Top 10” equine dermatoses seen at our clinic were bacterial folliculitis, dermato- phytosis, insect hypersensitivity, dermatophilosis, drug reaction, eosinophilic granuloma, atopy, vasculitis, chorioptic mange, and equine sarcoid. In a 16-year (1978-1994) retrospective study of biopsy specimens submitted to the Diagnostic Laboratory, College of Veterinary Medicine, at Cornell University, 23.4% of all equine submissions were skin lesions.12 Interest in equine dermatology has resulted in its being reviewed in a number of textbooks13- 36,46 and continuing education articles.37-44 Of particular note is the special issue of Veterinary Dermatology dedicated to the late Dr. Tony Stannard.45 Skin diseases are a source of animal suffering—through annoyance, irritability, pruritus, disfigurement, secondary infections, myiasis, and increased susceptibility to other diseases. In addition to compromising the animal’s comfort W2571-FM.qxd 2/1/03 11:46 AM Page viii viii • Preface and Acknowledgments and appearance, skin diseases can interfere with the horse’s ability to function in riding, working, or show. Economic losses through the financial burdens of diagnostic, therapeutic, or preventive programs can be sizable. Rarely, zoonotic dermatoses may be a source of human disease and suffering. We wholeheartedly echo the conclusion reached by the 1989 survey of the members of the American Association of Equine Practitioners: “Dermatologic disorders in horses are common problems that need emphasis in veterinary curricula and research endeavors.”8,10 We cannot overstate our appreciation for those who have contributed to this text. We couldn’t have done it without you! If we have failed to acknowledge anyone, please forgive us and send us your correction! Special thanks go out to Drs. Bill McMullen and Reg Pascoe for their many years of observation, investigation, and reporting. We remember and salute our greatest teacher in equine dermatology, the late Tony Stannard. We have purposely used many of Tony’s slides that he so graciously donated to us over the years. Held up for special praise and recognition are those who have given so much in terms of love, patience, and support during this endeavor: Kris, Travis, and Tracy (DWS) and Kathy, Steven, Julia, and Andrew (WHM). Yo Lexi (Alexis Wenski-Roberts) . thanx for your photomicrographic expertise! A big kiss for Denise LeMelledo, Jennifer Furey, Ray Kersey, and the whole W. B. Saunders gang. I (DWS) first began working on the idea of an equine dermatology textbook in 1984. It has gone through many starts and stops, ups and downs, and incarnations in the subsequent 18 years.