Equine Pathology

512 Pages·1999·51.958 MB·English

by  James R. Rooney, John L. Robertson

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JA M ES R. ROONEY,

dvm
JOHN L. ROBERTSON,
, PhD
v m d
IO W A STATE U N IVER SITY PRESS / AM ES
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James R. Rooney
received his AB degree from Dartmouth
College and his D V M from Cornell University. Dr. Rooney also
has an M S degree from Virginia Polytechnic Institute and State
University and an M A degree from the University of Pennsyl­
vania. His life's work has been devoted to the study of equine
species, and he is recognized worldwide as an expert in
equine pathology. Dr. Rooney is a Diplómate of the American
College of Veterinary Pathologists, and is retired from the
University of Kentucky.
John L. Robertson
received his BS degree from the State
University of New York at Stony Brook and his M S, VMD, and
PhD degrees from the University of Pennsylvania. Dr. Rooney
was his mentor while at the University of Pennsylvania. Dr.
Robertson is presently Associate Professor of Anatomic
Pathology in the Department of Biomedical Sciences and
Pathobiology at Virginia-Maryland Regional College of
Veterinary Medicine in Blacksburg, Virginia. He has had a
lifelong interest in diseases of horses and other species. His
current research is in the fields of oncology and immunology.
© 1996 Iowa State University Press, Ames, Iowa, 50014
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©Printed on acid-free paper in the United States of America
First edition, 1996
Library of Congress Cataloging-in-Publication Data
Rooney, James, R.
Equine pathology/James R. Rooney, John L. Robert­
son.— 1st ed.
p. cm.
Includes bibliographical references and index.
ISBN 0-8138-2334-X (alk. paper)
1. Horses— Diseases. I. Robertson, John L. II. Title
SF951.R6835 1996
636.1 0 8 9 6 0 7 -d c 2 0 96-4630
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Illustrations, vii
Preface, xiii
Acknowledgments, xiii
Introduction, xv
1 Cardiovascular System, 3
2 Respiratory System, 23
3 Gastrointestinal Tract and Adnexa, 57
4 Endocrine System, 115
5 Ryes and Ears, 121
6 Locomotor System, General, 133
1 Fore Leg, 152
8 Rear Leg, 198
9 Vertebral Column, 216
1 0 Stability Theory and Pathogenesis of Lameness, 224
11 Female Reproductive System, 233
1 2 Neonate, 250
13 Male Reproductive System, 264
14 Urinary Tract, 273
287
1 5 Integument,
16 Nervous System, 308
1 7 Shock. 344
348
1 8 Hemolymphatic System,
1 9 Autopsy Method, 367
2 0 Forensics. 378
Bibliography, 389
455
Index,
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Illustrations
Cardiovascular System
2.11. Section of lung showing bleeding into the pulmonary
parenchyma, which is characteristic of exercise-
on valve cusps of semilunar valves induced hemorrhage, 54
(arrows), 5
Several inti mal bodies (arrows) in a small muscular
Gastrointestinal Tract
artery in cecal submucosa, 6
A jet lesion in an artery (arrow) consists of endothe­
\ 3 .
lial thickening due to turbulent blood flow, 7 Schematic drawing of retained permanent 3rd man­
1.4. Rupture at the base of the aorta may be overlooked dibular premolar, 60
without meticulous examination of valve cusps; from 3.2. Cement hypoplasia of the 4th upper cheek tooth.
a horse that died suddenly, 8 Food material is impacted, 62
A focus of vegetative endocarditis between the cusps Jaw movements, Leue molograph. See the text for
of the aortic valve, 11 description, 66
A plaque of fibroelastosis in a medium-sized artery, 3.4. Middle power, H & E of asteroid concretions in the
14 inttma of an Intestina] submucosal artery, 72
Aplasia of the origin of the left coronary artery with 3.5. Middle power, H & E of intestinal submucosal artery
foci of ischemia in the epicardium, 16 with lacy, loculated media, 73
A focus of infarction and hemorrhage on the right 3.6. Lower power of apex of cecum with Peyer’s patch
atrium, 21 (accumulation of lymphoid tissue). 73
Acute verminous arteritis of cranial mesenteric and
ileocecocolic artery caused by S. vulgaris. (Photo­
Respiratory System
graph courtesy of E. Lyons and H. Drudge.), 76
3.8. Hemamelasma ilei: ileum, 76
. .
2 1 Angiomatosis of the ethmoid is a congenital anomaly 3.9. Infarction of the jejunum. Photo taken during sur­
or vascular malformation commonly known as gery, 77
’‘ethmoidal hematoma,” 28 3.10. Infarction of cecum and ventral colon in experimen­
Squamous cell carcinoma of the nasal passage tal S. vulgaris infestation of a pony. 78
(arrow) must be differentiated from ethmoidal 3.11. Infarction of the small intestine. The duodenum and
adenocarcinoma, 29 first part of the jejunum (above), are normal, while
2.3. Muscles controlling the movement of the soft palate infarction becomes progressively more severe in
and ihe pharynx can most easily be examined by distal jejunum and ileum, 78
splitting the skull, 31 3.12. S. edentatus. Massive infiltration of the liver in
Entrapment of the epiglottis is usually associated experimental infection. With survival many of these
with epiglottic hypoplasia, 32 infiltrations become scars. (Photograph courtesy of
2.5. Inspissated debris in the guttural pouch may form E. Lyons and H. Drudge.), 79
balls of caseous material known as Hluftsackstein,H 3.13. Anoplocephalaperfoliate around the ileocecal orifice,
33 81
Guttural pouch mycosis is usually seen grossly as a 3.14. Stomach of a foal. The normal stratum corneum
tough, yellow plaque near the hyoid bone. 34 partially coats the esophageal portion of the stomach.
2.7. A portion of the lung from a horse with chronic There are several fundic ulcerations, one of which
bronchiolitis. There are extensive areas of atelectasis has perforated. 82
and pulmonary fibrosis; raised areas are foci of air 3.15. Draschia megastoma nodule adjacent to die margo
entrapment, 48 plicatus. (Photograph courtesy of E. Lyons and H.
2 .8 . A bronchiole filled with mucus and cellular debris. Drudge.), 83
49 3.16. Massive ulceration of the stomach of a foal. (Photo
A dilated bronchiole filled with mucus and cell courtesy of Helen A d and.), 84
debris; there is also mucus filling in the adjacent 3.17. Acute gastritis involving the portion of the fundus to
alveoli, 50 the right. There are multiple ulcers in the esophageal
2.10. Squamous metaplasia of the lining of a bronchiole in mucosa adjacent to the margo plicatus. The two
a horse with chronic bronchiolitis, 51 conditions have no necessary relationship, 85
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viii
ILLUSTRATIONS
3.18. Chronic gastritis. Habronema. Esophageal mucosa medial canthus of the eye leads to partial obstruction
and margo plicatus are at bottom. The cardiac and of the nasolacrimal duct and epiphora, 123
fundic mucosa is normal adjacent to the margo
plicatus (though decomposed). The fundic mucosa
Locomotor System, General
becomes progressively thicker and more cobblestone
toward the pylorus. 86
3.19. Meckel’s diverticulum, incidental finding, 88 6.1. Low power, H & E of early osteochondrosis. There
3.20. Distended, discolored proximal jejunum in duodeni- is necrosis and loss of chondrocytes in the inner third
tis/proximal jejunitis syndrome, of the articular cartilage. Necrotic debris can be seen
89
3.21. Focus of intense hyperemia and hemorrhage verging in the space, and reparative cloning of chondrocytes
on infarction of the small intestine, S. vulgaris, 90 is apparent at lower left in the cartilage still in
3.22. Impaction of the descending colon, 91 continuity with bone, ¡47
3.23. Figure 3.22 with the colon opened to show the 6 .2. Nonmarginal osteochondrosis of the radial carpal
impacted bolus, 91 bone. The lesion extends into the subchondral bone
3.24. The bolus removed revealing an elongate focus of and would, in principle, appear on radiographs, 148
hemorrhage with a pale center in the mucosa, infarc­ 6.3. Diagrams of the development of marginal (above),
tion. S. vulgaris, 92 and nonmarginal osteochondrosis (left to right), 149
3.25. Marked thickening of the mucosa of the distal 6.4. Epiphyseal compression, distal region of third
jejunum in granulomatous enteritis. A few less- metacarpal (Mc3) and proximal region of proximal
involved patches are present among the thickened phalanx (arrows), 149
folds, 94 6.5. Early lesion of epiphyseal compression. The vessels
3.26. Low power of Figure 3.25 showing the infiltration of crossing the epiphyseal plate are apparent. There is
the mucosa with mononuclear inflammatory cells, 95 hyperemia in the subchondral bone of the articular
3.27. Schematic of volvulus of the small intestine in situ, cartilage, on the epiphyseal side of the epiphyseal
96 plate, and as a pressure wedge or cone on the met­
3.28. Incarceration of the jejunum through the epiploic aphyseal side of the epiphyseal plate. This was a
foramen. 96 three-legged lame foal, 750
3.29. Lipoma strangulation of the jejunum, 98 6.6 Cleared, india ink-injected, slab of the distal end of
3.30. Intussusception of the jejunum of a foal. In fact, this the third metacarpal (Mc3) showing the numerous
is a double intussusception, the first forming the area blood vessels crossing the epiphyseal plate, 150
of ileus for the development of the second, 98 6.7 A transilluminated ground section of distal third
3.31. Torsion of the colon at the sternal -diaphragmatic metacarpal (Mc3) with epiphyseal compression. The
arrowheads indicate the sclerosis in epiphysis and
flexure. 102
3.32. Tyzzer’s disease in a foal, 109 metaphysis that accompanies increased pressure and
3.33. Middle power, H & E of Theiler’s disease of the loss of stability of the damaged epiphyseal plate, 151
liver. There are virtually no viable hepatocytes, only
shattered remnants adjacent to portal triads, 110
Fore Leg
3.34. Cirrhosis of the liver caused by pyrrolizidinc alka­
loid. Crotalaria, 111
3.35. Acute pancreatitis caused by migration of S. equinus, 7.1. Distal end of humerus with a synovial fossa and
113 scoring or wear lines, 155
3.36. Chronic pancreatitis, S. equinus. Some reasonably Proximal and distal row of carpal bones with ero-
normal lobules remain, 113 sion/ulceration of the distal face of radial carpal bone
three (RC3) (arrowheads), and the mirror lesion on
the proximal surface of the third carpal bone (C3),
Endocrine System
157
Ulcerative arthrosis of the proximal surface of third
Colloid, iodine-deficiency type, goiter in an aborted
carpal bone (C3) (arrowhead). The forceps hold the
fetus (left) compared to age-matched control (right),
joint capsule showing "pannus~ extending from
116
capsule to the damaged joint surface, 158
4.2. Adenoma, adenomatous hyperplasia of the thyroid of
Radiograph of carpus subjected to multiple injections
an old horse, 117
of steroids. Characteristic explosion of osteophytes
4.3. Adenoma of the intermediate lobe of the pituitary
accompanying massive articularcartilagc destruction.
gland in an old mare, 119
158
Proximal rows of carpal bones from a foal. The set
Eyes and Ears on the left is hypoplastic, 759
Macerated specimen of single-event fracture (arrow­
5.1. The growth of a small sarcoid (arrow) near the head) of the third carpal bone (C3), 759
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