Table Of ContentSelf-Assessment Colour Review of
Equine Internal
Medicine
Tim S. Mair
BVSc, PhD, MRCVS
Bell Equine Veterinary Clinic, UK
Thomas J. Divers
DVM, Diplomate ACVIM, Diplomate ACVECC
Cornell University, USA
Manson Publishing/The Veterinary Press
Copyright © 1997 Manson Publishing Ltd
ISBN 1–874545–74–X
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Contributors
John M. King, DVM, PhD,
Douglas Byars, DVM,
NewYork State College of
Diplomate ACVIM,
Veterinary Medicine,
Hagyard–Davidson–McGee
Cornell University,
Associates,
Ithaca,
Director, Equine Internal Medicine
USA
Equine Hospital,
Lexington,
Sandy Love, BVMS, PhD, MRCVS,
USA
Professor of Equine Clinical Studies,
Division of Equine Clinical Studies,
Noah D. Cohen, VMD, MPH, PhD,
University of Glasgow Veterinary
Diplomate ACVIM,
School,
Assistant Professor of Equine
Scotland
Medicine,
Department of Large Animal
Tim Mair, BVSc, PhD, MRCVS,
Medicine & Surgery,
Bell Equine Veterinary Clinic,
College of Veterinary Medicine,
Maidstone,
Texas A & M University,
England
USA
Celia M. Marr, BVMS, MVM, PhD,
Chrysann Collatos, VMD, PhD,
MRCVS,
Diplomate ACVIM,
The Royal Veterinary College,
High Desert Veterinary Service,
University of London,
Reno,
England
USA
William H. Miller, Jr, VMD,
Thomas J. Divers, DVM,
Diplomate ACVD,
Diplomate ACVIM,
New York State College of
Diplomate ACVECC,
Veterinary Medicine,
New York State College of
Cornell University,
Veterinary Medicine,
Ithaca,
Cornell University,
USA
Ithaca,
USA
3
Elspeth M. Milne, BVM&S, PhD, Corinne Raphel Sweeney, DVM
MRCVS, Diplomate ACVIM,
Veterinary Investigation Officer, School of Veterinary Medicine,
SAC Veterinary Services, University of Pennsylvania,
Dumfries, USA
Scotland
J.H. van der Kolk, DVM, PhD,
Christopher J. Proudman, MA, Diplomate EIM RNVA (Royal
VetMB, PhD, Cert EO, FRCVS, Netherlands Veterinary
Division of Equine Studies, Association),
Department of Clinical Veterinary Department of Large Animal
Medicine, Medicine & Nutrition,
University of Liverpool, Faculty of Veterinary Medicine,
England Utrecht University,
The Netherlands
William C. Rebhun, DVM,
Diplomate ACVO, Roel A. van Nieuwstadt, DVM,
Diplomate ACVIM, PhD, Diplomate RNVA (Royal
Professor of Ophthalmology and Netherlands Veterinary
Large Animal Medicine, Association),
New York State College of Department of Large Animal
Veterinary Medicine, Medicine and Nutrition,
Cornell University, Utrecht University,
Ithaca, The Netherlands
USA
Elaine D. Watson, BVMS, MVM,
Johanna M. Reimer, VMD, PhD, FRCVS,
Diplomate ACVIM, Internal Department of Veterinary Clinical
Medicine & Cardiology, Studies,
Rood & Riddle Equine Hospital, University of Edinburgh,
Lexington, Scotland
USA
4
Preface
Presented here are over 230 questions and answers that cover current infor-
mation on a wide and interesting range of the more common, and some of
the less common, equine medical disorders.
Cases have been contributed by specialists in equine medicine from the
United States and Europe. As we read and compared the material, it became
clear that 90% of equine medical disorders are common to most countries
and that, given the frequency and distances that horses travel, it is important
for veterinarians to be familiar with the other 10%.
Our review presents the cases in the form of problems to be solved,
given in random order, just as they may present in practice. The problems
are designed to stimulate readers to make their own differential diagnoses
and appropriate treatment plans. Immediately following each question we
provide an answer and, perhaps more importantly, an explanation of the
case. To help the reader we have also provided a list of cases classified by
broad subject, an abbreviations list and a detailed index.
We take this opportunity to thank the contributors for the cases they
have provided, and Manson Publishing for the speedy publication of the
book. Finally, we thank you for reading the book and hope that the infor-
mation serves as a useful update and review of equine medicine.
Thomas J Divers,DVM, Diplomate ACVIM
Diplomate ACVIM
Cornell University
College of Veterinary Medicine
Ithaca, NY, USA
Tim Mair, BVSc, PhD, MRCVS
Bell Equine Veterinary Clinic
Maidstone, Kent, UK
Acknowledgements
The authors are grateful to Williams & Wilkins for permission to publish
101b,174and182a(fromEquine Diagnostic Ultrasonographyby Rantanen
and McKinnon, in preparation), to Mosby–Year Book for permission to
publish 24 (from Atlas of Equine Ultrasonography in preparation), to W.B.
Saunders for permission to publish 239 (from The Horse: Diseases and
Clinical Management by Kobluk, Ames and Geor), and to Dr Corrie Brown,
DVM, PhD, DipACVP, for Figure 85.
5
Broad Classification of Cases
Listed are the questions and answers that deal with particular topics.
Eyes, 19, 41, 56, 74, 111, 116, 119, Nervous system, 1, 5, 6, 9, 17, 55,
122, 147, 151, 167, 176, 209, 213, 58, 64, 89, 110, 116, 123, 133, 137,
221, 230 149, 154, 155, 157, 176, 185, 215,
237
Alimentary tract, 1, 2, 13, 18, 20,
21, 29, 40, 44, 50, 51, 52, 59, 76, Endocrine system, 3, 22, 26, 39, 47,
77, 78, 83, 86, 87, 92, 95, 96, 105, 65, 88, 112, 134, 136, 143, 164,
108, 109, 116, 118, 124, 125, 128, 194, 211, 233
133, 144, 145, 148, 152, 162, 165,
180, 189, 207, 214, 217, 223, 227, Haematopoietic and immune sys-
234 tems, 3, 14, 15, 32, 34, 41, 44, 45,
49, 66, 79, 81, 106, 130, 151, 186,
Respiratory tract, 5, 8, 10, 25, 26, 193, 201, 219, 220, 225, 238
33, 38, 39, 42, 44, 54, 62, 68, 72,
113, 115, 126, 130, 131, 132, 135, Infectious diseases, 1, 2, 3, 7, 19, 21,
140, 145, 146, 151, 153, 170, 179, 23, 24, 30, 31, 35, 46, 50, 54, 55,
195, 200, 212, 222, 224, 228, 235 59, 61, 63, 66, 70, 73, 80, 83, 84,
85, 88, 91, 92, 93, 103, 109, 125,
Cardiovascular system, 22, 26, 53, 127, 130, 131, 133, 138, 139, 140,
75, 102, 107, 116, 132, 158, 174, 146, 149, 152, 159, 165, 168, 169,
184, 203, 205, 208, 226, 239 171, 172, 175, 176, 180, 187, 188,
189, 190, 195, 197, 204, 209, 212,
Liver, 34, 84, 98, 117, 169, 184, 218, 224, 229
193, 211, 225, 232
Parasites, 16, 27, 36, 50, 69, 71,
Reproductive system, 4, 7, 12, 23, 124, 129, 150, 173, 175, 192, 206,
37, 42, 48, 57, 67, 70, 80, 100, 116, 223
121, 143, 156, 166, 181, 188, 198
Foals, 1, 2, 7, 13, 20, 21, 23, 24, 29,
Urinary tract, 11, 28, 49, 90, 97, 99, 43, 44, 50, 54, 60, 61, 79, 84, 86,
101, 116, 120, 142, 153, 161, 177, 95, 97, 101, 108, 116, 130, 131,
183, 194, 199, 231 132, 137, 154, 155, 157, 159, 160,
161, 176, 178, 182, 191, 196, 197,
Skin, 36, 41, 69, 71, 114, 130, 139, 200, 201, 213, 215, 220, 223, 230,
163, 164, 190, 210, 236 237
6
1 & 2: Questions
1 A 23-day-old foal 1
presents with dysphagia,
a stilted gait and muscle
tremors. The tail and
tongue tone are weak.
The vital signs and blood
analyses are normal.
i. What diagnostic
procedure can be used to
best explain the reason
for dysphagia?
ii. Assuming the
condition might be
caused by an infectious
disease, is vaccination available as a preventive measure?
iii. How might this clinical condition be acquired?
iv. What treatments are available?
2 You are called to 2
examine a one-day-old
foal that has diarrhoea.
The foal appeared
normal at birth but
became lethargic,
depressed and developed
diarrhoea (2). Within
several hours, the
diarrhoea had become
haemorrhagic and the
foal’s clinical condition
(heart rate, respiratory
rate, colour and moisture of mucous membranes, lethargy and frequency of
diarrhoea) had deteriorated.
i. What cause(s) of diarrhoea do you suspect in this foal?
ii. What diagnostic steps should be taken to prove your presumptive
diagnosis?
iii. What preventive measures could you propose?
7
1 & 2: Answers
1 i.Endoscopy. The procedure should reveal no mechanical obstructions of the phar-
ynx or oesophagus. Pharyngeal paresis is present in this foal. This finding, along with
the presence of decreased tongue tone, is consistent with a neuromuscular disorder.
ii.Yes. These clinical signs are consistent with botulism. A vaccine has been avail-
able in the USA for Type B for a number of years, and a multivalent vaccine is being
developed for commercial use.
iii.Botulism in foals is most likely the result of the toxicoinfectious form, whereby
the actual organism is present in the gastrointestinal tract and the toxin is being
absorbed through intestinal sites. The disease can also be acquired by infection of
anaerobic wounds and by ingestion of preformed toxins (in feedstuffs such as
silage).
iv.Botulism antisera can be given to protect unaffected myoneural junctions. The
antibiotics of choice are aqueous forms of penicillin. Nursing care and supportive
care are essential for survival.
2 i.Clostridial agents have been documented as causing severe, generally fatal diar-
rhoea of neonatal foals. Clostridial diarrhoea is often haemorrhagic. Clostridium
perfringenstypes A, B and C have been associated with enteritis, colic and death in
foals. The disease appears to be sporadic, rapidly progressive and generally fatal.
Affected foals are usually less than seven days old, and signs are often seen in one-
day-old foals. In the USA, Clostridium difficilewas initially associated with haemor-
rhagic diarrhoea and necrotizing enterocolitis in four foals, all less than three days
old. Subsequently, Cl. difficileand its toxin(s) have been identified in faeces of foals
of various ages with mild to moderate diarrhoea. Thus, the spectrum of disease for
Cl. difficile may be broader than that of Cl. perfringens.
ii.Diagnosis of Cl. perfringensis based on isolation of the organism and demonstra-
tion of toxin(s) in faeces or intestinal contents. This can be difficult, and only certain
laboratories provide this diagnostic service. Unlike Cl. perfringens, demonstration of
Cl. difficilein faeces appears sufficient to attribute diarrhoea to the organism because
shedding by asymptomatic foals appears to be rare.
iii.Conclusive evidence of effective methods for prevention are lacking. One farm
may have had cases in sequential years. Veterinarians at that farm administered types
C and D toxoid for ruminants to pregnant mares and no ensuing cases occurred. The
benefit of administering toxoid for ruminants is unclear and speculative. No evidence
exists that administering antitoxin developed for sheep is beneficial.
8
3 & 4: Questions
3 This two-year-old Quarter- 3a
horse filly (3a) presents with an
acute onset of severe swelling
of the head and distal limbs.
She is slightly depressed, with
normal vital signs. The
swelling developed suddenly,
two weeks after spontaneous
drainage of bilateral
submandibular abscesses had
occurred. Many horses on the
farm were exhibiting signs of
purulent nasal discharge, fever, depression 3b
and submandibular abscessation. This filly
had received no treatment for the lymph
node abscessation.
i. Upon closer inspection (3b) you notice
petechial to ecchymotic haemorrhages, as
well as areas of cyanosis, on the muzzle, and
multiple petechial haemorrhages on the oral
mucous membranes. What pathophysiologic
process is most likely responsible for these
signs, and what is the most likely aetiology
of this process in this particular individual?
ii. Assuming that your primary differential
diagnosis is correct, what would be the two
most important components of your
treatment plan for this filly?
iii. What are two reasons, in addition to
elimination of the Streptococcus equi pathogen, why antimicrobial
treatment is warranted in this filly?
iv. Would you expect this filly’s haemogram to have any abnormalities?
4 A six-year-old Thoroughbred mare is presented for artificial insemination
with frozen semen from a Warmblood stallion. She is in oestrus and has
two large pre-ovulatory follicles on her right ovary – one is 35mm and the
other 38mm in diameter. At 40 days, unicornuate twins are diagnosed –
how would you manage her pregnancy?
9
