Color Atlas of Diseases and Disorders of the Foal

413 Pages·100.506 MB·English

by  Edited by, Siobhan B McAuliffe, MVB DACVIM, and Nathan M Slovis, DVM DipACVIM CHT (Eds.)

An imprint of Elsevier Limited
© Elsevier Limited 2008. All rights reserved.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise, without the prior permission of the Publishers. Permissions may be sought directly from Elsevier’s
Health Sciences Rights Department, 1600 John F. Kennedy Boulevard, Suite 1800, Philadelphia, PA 19103-2899, USA: phone: [phone]
3804; fax: [phone]; or, e-mail: [email protected]. You may also complete your request on-line via the Elsevier
homepage (http://www.elsevier.com), by selecting ‘Support and contact’ and then ‘Copyright and Permission’.
First published 2008
ISBN 978 0 7020 2810 6
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
Library of Congress Cataloging in Publication Data
A catalog record for this book is available from the Library of Congress
Notice
Knowledge and best practice in this fi eld are constantly changing. As new research and experience broaden our knowledge, changes in
practice, treatment and drug therapy may become necessary or appropriate. 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 the practitioner, relying on their own
experience and knowledge of the patient, 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 assume any liability for any
injury and/or damage to persons or property arising out of or related to any use of the material contained in this book.
The Publisher
Working together to grow
libraries in developing countries
www.elsevier.com | www.bookaid.org | www.sabre.org
The
publisher’s
policy is to use
paper manufactured
from sustainable forests
Printed in China
CONTRIBUTORS
Chapters: Nathan M Slovis
McGee Medical and Critical Care Center
Thomas J Divers Hagyard Equine Medical Institute
Lexington, Kentucky
College of Veterinary Medicine
USA
Cornell University
Ithaca, New York
Kimberley A Sprayberry
USA
McGee Medical and Critical Care Center
Brendan T Farrelly Hagyard Equine Medical Institute
Lexington, Kentucky
Irish Equine Centre
USA
Johnstown, Naas
Co. Kildare
Ed Voss
Ireland
Arizona Equine Medical and Surgical Center
Noreen Galvin Gilbert, Arizona
USA
The Phoenix Equine Clinic
Kildare Town, Co. Kildare
J Scott Weese
Ireland
Department of Pathobiology
Caroline Hahn Ontario Veterinary College
University of Guelph
Neuromuscular Disease Laboratory
Guelph, Ontario
Royal (Dick) School of Veterinary Studies
Canada
Easter Bush, Roslin
Scotland, UK
Walter Zent
Siobhan B McAuliffe Hagyard Equine Medical Institute
Lexington, Kentucky
Veterinary Division
USA
Stables of King Abdullah and Sons
Riyadh
Illustrations:
Kingdom of Saudi Arabia
Lucas Pantaleon Monica Aleman
Woodford Equine Hospital Neuromuscular Disease Laboratory, Director
Versailles, Kentucky Veterinary Medical Teaching Hospital
USA Large Animal Clinic
University of California
Dwayne Rodgerson Davis, California
Davidson Surgical Center USA
Hagyard Equine Medical Institute
Lexington, Kentucky
USA
viii
Contributors
Stefania Bucca Deivasigamani Kumaran
Irish Equine Centre Ramz-al-Sharq Equine Services
Johnstown, Naas Riyadh
Co. Kildare Kingdom of Saudi Arabia
Ireland
Celia M Marr
Ursula Fogarty Beaufort Cottage Equine Hospital
Irish Equine Centre Exning, Newmarket
Johnstown, Naas Suffolk
Co. Kildare UK
Ireland
Lisa Neuwirth
Genevieve Fontaine-Rodgerson Hagyard Equine Medical Institute
Hagyard Equine Medical Institute Lexington, Kentucky
Lexington, Kentucky USA
USA
Warren L Schofi eld
Richard Hepburn Troytown Equine Hospital
Willesley Equine Clinic Kildare Town, Co. Kildare
Byams Farm Ireland
Willesley, Gloucestershire
UK
PREFACE
Today’s veterinary curriculum places more demands on both students possessed were the photographs that they took of their patients. These
and teachers and consequently there is generally insuffi cient time photographs and schematics will provide the reader with a large
available to teach all aspects of an expanding knowledge of equine range of images from which to learn and compare, while helping the
pediatric medicine and surgery. practitioner gain confi dence in equine pediatric medicine and
The purpose of this atlas is to provide both the general practitioner surgery.
and student with a reference guide. The atlas’s emphasis is on normal The chapters are organized according to the body system being
and abnormal fi ndings of different body systems examined by the discussed. Each chapter starts by discussing diagnostic techniques
general equine practitioner. It contains excellent digital images and associated with the given body system accompanied by photographic
illustrations that provide a base of knowledge on which the reader and, where appropriate, schematic representations of normal features.
may build and describes techniques involved in neonatal and pediatric The abnormal fi ndings are then discussed as either congential or
medicine and surgery, so as to make learning easier and more acquired disorders. Acquired disorders are then further broken down
enjoyable. and discussed under various subheadings. We have strived to include
This atlas provides clear, easily accessible information on history, as many images as possible of each disorder so that the reader can be
clinical signs, differentials, treatment and prognosis. It should be guided from presentation, through diagnosis and differentials to the
regarded as a companion to other equine texts that have educated the outcome of the case. We have included case histories and outcomes
reader on the pathophysiology of the various diseases illustrated in in many of the image legends and we hope this is benefi cial to the
the atlas. reader.
We have attempted to emphasize the diagnostic features of those Signifi cant progress has been made in equine pediatric medicine
conditions the general equine practitioner will be frequently exposed over the last two decades and today the public demands more
to but have included some less common conditions for completeness specialized care for their animals. We hope that the images in the
and interest. following pages stimulate interest in further learning and aid in the
Through this book we have oriented many years of clinical timely diagnosis of many foal disorders.
experience in pediatric medicine and surgery by leading specialists.
The editors realized that the most valuable learning resources they Siobhan McAuliffe Nathan Slovis
ACKNOWLEDGEMENTS
Putting together a well-illustrated book obviously requires both text provided us with these images. In particular Dr. Monica Aleman and
and illustrations. Our thanks must fi rst go to all of those who Dr. Genevieve Fontaine-Rodgerson provided us with a large selection
contributed chapters to this book. They have given of their expertise from which to choose. A further thanks has to be extended to Dr.
and time with little in return other than harassing e-mails and the Ursula Fogarty and Dr. Celia Marr, who patiently answered questions
knowledge that they have yet again helped to educate others. We and provided legends for their images.
have tried to use as many practitioners as possible when compiling Our thanks and appreciation also goes to the staff and management
the text in order to give an emphasis to those disorders that are more of the McGee Medical center and The Stables of King Abdullah and
commonly encountered and to present the information in a way in Sons. Their patience and tolerance with our amateur photography
which it is easily accessible. This has however meant that we asked has resulted in many of the images on the following pages.
some very busy people to contribute for us. We cannot adequately The illustration team at Elsevier must be congratulated on the
state how appreciative we are of the time they have dedicated to our magnifi cent job they have done with the drawings throughout. The
endeavour and the enthusiasm they have shown throughout. support staff at Elsevier have shown endless patience and understanding
A special thanks is extended to Dr. Ursula Fogarty, Dr. Stefania from start to fi nish.
Bucca and Dr. Brendan Farelly, who kindly asked us to include their Finally we would like to thank out spouses, Fernando and Stacey
new information on atlanto-occipital ultrasound. for their support and understanding in the four years that it has taken
Obtaining the photographic images for this book has taken many us to put this book together; and our children, Fernando and Riley for
years. We cannot state how grateful we are to those who generously providing us with constant inspiration and joy.
1
CHAPTER
The pregnant mare
Walter Zent DVM and Lucas Pantaleon MV, MS, DACVIM
Introduction 1 Leptospirosis abortion 13
Placentitis 1 Salmonella abortion 13
Hydrallantois 6 Other causes of abortion 13
Ventral body wall hernias and prepubic tendon rupture 7 Cord torsion 13
Uterine torsion 9 Trauma 13
Infectious abortion 11 Fetal abnormalities 15
Equine herpes virus abortion 11 Twins 15
Equine infectious anemia abortion 11 Fetal monitoring 17
Equine viral arteritis abortion 12 Predicting parturition 20
Introduction Placentitis (Figs 1.1–1.20)
The breeding success of a mare can no longer be judged on her ability
History
to conceive alone but rather on her ability to produce a live, viable
foal. Advances in theriogenology have resulted in high conception
• Placentitis is an important cause of abortion, stillbirth and perinatal
rates and improvements in neonatal medicine have resulted in greater
death in horses. Different etiologic agents such as viruses (equine
survival rates of foals. However disease processes are often advanced
viral arteritis and equine herpes virus 1), bacteria (β-hemolytic
when presented as they may have started in utero. Awareness of an
Streptococci, Escherichia coli, Pseudomonas aeruginosa, Klebsiella
existing problem prior to parturition facilitates early intervention and
pneumoniae, Leptospira spp and Crossiella equi) and fungi (Aspergillus
treatment and consequently will aid in decreasing perinatal deaths
spp and Mucor spp) have been implicated as causative agents.
which account for a signifi cant percentage of foal mortality. Increas-
• Depending on the microorganism involved, several routes of
ing awareness of fetal wellbeing and the impact that it has on neonatal
infection are possible:
viability has led to closer monitoring of the peripartum mare and
improved techniques in fetal monitoring. ♦ Ascending infections are common, resulting in infl ammation and
detachment of the chorioallantois at the level of the cervical star.
Complications in late gestation ♦ Hematogenous infection of the fetal membranes has also been
described. This is the primary route of infection for Leptospira spp.,
which cause a diffuse or multifocal placentitis. Viruses also gain
It is estimated that 10–15% of mares undergo embryonic or fetal
access to the placenta and fetus via the hematogenous route.
loss at some point in gestation. Most occurs in the fi rst 40 days of
pregnancy, when the primary corpus luteum is the sole source ♦ A unique form of placentitis is caused by the bacteria Crossiella
of progesterone. Thus, once confi rmed to be 45–60 days pregnant equi (nocardioform placentitis). It has been suggested that the
most mares can be expected to carry the fetus to term. However, organism gains access to the mare’s uterus during breeding and
abortions that occur during the last trimester can be particularly remains latent until later in gestation. The characteristic lesions
stressful for the owner as there is a sense of being so near and yet so are localized at the level of the uterine body.
far. Every effort should be made to diagnose the cause of an abortion
as some agents such as equine herpes virus may occur in storms and
Clinical signs
preventative measures may be taken to limit further loss.
In addition to fetal loss through abortions, life-threatening
situations for the mare may develop in late gestation such as • Clinical signs of placentitis may include premature udder
ventral body wall ruptures, uterine torsion and hydrops of the fetal enlargement and lactation, cervical relaxation, vaginal discharge,
membranes. Accurate diagnosis and timely intervention may not abortion, stillbirth and premature delivery.
only save the life of the mare but may also result in the birth of a viable • Most mares with placentitis do not become systemically ill and the
foal in cases of ventral body wall ruptures and uterine torsions. This hemogram remains within normal ranges.
chapter reviews some of these late gestation complications and causes • Placentitis can also result in the birth of immature or dysmature
of abortion. foals, small for gestational age foals or neonatal sepsis.
2
Color Atlas of Diseases and Disorders of the Foal
Figure 1.1: Ascending placentitis viewed from the allantoic surface, note the Figure 1.2: Ascending placentitis, same placenta as Fig 1.1 viewed from the chorionic
thickening and discoloration of the placenta around the cervical star. surface. Note the absence of villi and presence of exudates in the affected area.
Figure 1.4: Fungal placentitis, note the thickened leathery appearance.
Figure 1.3: Ascending placentitis with extensive exudate (courtesy of the Irish Equine
Centre – IEC)
A B

Figure 1.5: (a) & (b) Fungal placentitis, note the fungal plaques evident on both the allantoic and chorionic surfaces of the placenta from a fresh abortion at 5 months of gestation.
3
The pregnant mare
Figure 1.7: Chronic diffuse placentitis with marked thickening of the placenta
(courtesy of IEC).
Figure 1.6: Aspergillus spp cultured from the placenta in Fig 1.4.
Figure 1.8: Aborted foal at 10 months of gestation (placenta in Fig 1.7). Note the
dehydrated appearance of the foal. Foals from mares with chronic placentitis are
frequently delivered or aborted with this appearance (courtesy of IEC).
Figure 1.9: Crossiella equi placentitis (nocardioform placentitis). Note the necrotic
area of placentitis at the junction of the body and horn (courtesy of IEC).
Figure 1.10: Crossiella equi placentitis (nocardioform placentitis), same placenta as Fig
1.9 viewed from the allantoic surface (courtesy of IEC). Figure 1.11: Premature lactation in a mare with ascending placentitis.
4
Color Atlas of Diseases and Disorders of the Foal
Figure 1.12: Discharge of the cervical plug at 9 months of gestation in a mare with
ascending placentitis.
Figure 1.14: In utero growth retardation (IUGR) of a foal from a mare that had
Crossiella equi placentitis (nocardioform placentitis).
• Normal complete cell count and fi brinogen.
• Samples obtained from the vaginal or cervical discharge should be
submitted for culture and cytological examination.
• Transrectal ultrasonography is performed in order to image the
area at the level of the cervical star. Ultrasonography may show
an increase in the combined thickness of the uterus and the
placenta (CTUP), edema of the allantochorion and placental
separation. The CTUP should be measured in the ventral part of the
uterine body as placenta in the dorsal part is often thicker, with
edema of the dorsal placenta being found in a number of normal
mares in the last month of gestation. The normal CTUP values by
gestational age are:
<5 mm <270 days
<8 mm 271–300 days
<10 mm 310–330 days
<12 mm 330+ days
• Transabdominal ultrasonography is an important tool to assess
the placenta at the level of the body where nocardioform
placentitis occurs. The mean utero–placental thickness as measured
Figure 1.13: Vaginal discharge from a mare with cervical placentitis. by transabdominal ultrasound should be 11.5 ± 2.4 mm in late
gestation. Another very important use of transabdominal
ultrasonography is to assess the fetal wellbeing in mares with
suspected placentitis. Fetal heart rate (FHR), movement, and growth
Differential diagnosis
can be checked and the turbidity of the amniotic fl uid can be assessed
(see p. 17).
Other causes of abortion, stillbirth or premature delivery. Placental
changes may not be evident to the naked eye and a complete
postmortem examination should be performed on any aborted fetus Treatment
with samples of placenta and appropriate fetal organ samples taken
for histopathology. • Broad-spectrum antibiotics such as trimethroprim-sulfadiazine or a
gentamicin and penicillin combination are good initial choices and
Diagnosis have been shown to achieve acceptable levels within the fetal
fl uids.
• Clinical signs. Any mare with premature udder development • Non-steroidal anti-infl ammatory drugs (fl unixin meglumine or
or a vaginal discharge should be regarded as having placentitis phenylbutazone) are used with the objective of decreasing the level
until proven otherwise. of infl ammatory mediators released during placentitis.
5
The pregnant mare
Figure 1.15: Ultrasonographic image of the uteroplacental unit at the area of the Figure 1.16: Ultrasonographic image of the uteroplacental unit at the area of the
cervical star demonstrating thickening and separation (arrow) of the placenta. cervical star demonstrating thickening and separation (arrow) of the placenta. Note the
retroplacental exudates.
Figure 1.18: Ultrasonographic image of the cervical area demonstrating placental
separation with retroplacental exudate. Note the foal in the bottom right hand corner
Figure 1.17: Same mare as in Fig 1.16 following 3 weeks of therapy. Note that the of the image.
volume of retroplacental exudate has decreased.
Figure 1.19: Transabdominal ultrasonographic image of the uteroplacental unit
demonstrating separation with retroplacental exudates. The measurements are as
follows: 1 = placental thickness, 2 = exudate thickness, 3 = thickness of combined Figure 1.20: Transabdominal ultrasonographic image of the uteroplacental unit
uteroplacental unit including exudate. demonstrating separation (arrows) and folding of the placenta.