Equine Respiratory Diseases

Dr Rush gained her DVM degree from The Ohio State University in 1989. She completed her internship training at North Carolina State University in 1990, and her internal medicine residency training at The Ohio State University in 1993. She has been awarded the 1996 and 2003 Carl J. Norden Distinguished Teacher Award and the 2002 Pfizer Award for Research Excellence at Kansas State University. Dr. Rush's research interest is equine respiratory disease, particularly respiratory physiology, immunology, and aerosol drug therapy. Her clinical interest is in equine respiratory, neurologic, and immune-mediated disease.

About the Authors xv

Introduction xvii

Section I: Examination of the Equine Respiratory Tract 1

Chapter 1: Examination of the Upper Respiratory Tract 3

Chapter 2: Examination of the Lower Respiratory Tract 7

Section II: Noncontagious Diseases of the Upper Respiratory Tract 11

Chapter 3: Diseases Causing Airway Obstruction in the Horse 13

Pathophysiology 13

Respiration and Locomotion 14

Respiratory Noise 14

Diagnosis of Airway Obstructions 15

History 15

Palpation tests 15

Endoscopy at rest 15

Radiographic examination 16

Exercise tests 16

Treadmill endoscopy 16

Spectrum analysis of respiratory sounds 17

Further Reading 17

Chapter 4: The Nasal Cavity and Paranasal Sinuses 19

Anatomy 19

Nasal cavity 19

Paranasal sinuses 20

Function 23

Examination of the Nasal Cavity and Paranasal Sinuses 23

Common presenting signs 23

History 23

Physical examination 24

Endoscopic examination 24

Radiographic examination 25

Computed tomography (CT) and magnetic resonance imaging (MRI) 25

Nuclear scintigraphy 27

Percutaneous centesis 27

Surgical exploration and biopsy 27

Treatment Objectives in Nasal and Sinus Disease 27

Medical Management 28

Trephination of the Paranasal Sinuses 28

Bone Flap Surgery 29

Further Reading 31

Chapter 5: Congenital and Developmental Malformations of the Nasal Cavity 33

Wry Nose 33

Nasal Septal Deviation 34

Choanal Atresia/Stenosis 35

Further Reading 35

Chapter 6: Diseases Affecting the Nostrils (External Nares) 37

Hypertrophy of Alar Folds/Redundant Alar Folds 37

Epidermal Inclusion Cyst (“Atheroma”) of the False Nostril 38

Lacerations and Wounds of the Nostrils 39

Alar Cartilage Necrosis 39

Paralysis of the Nostrils 39

Further Reading 39

Chapter 7: Diseases of the Nasal Cavity and Paranasal Sinuses 41

Primary and Secondary Sinusitis and Sinus Empyema 41

Clinical signs 42

Diagnosis 42

Treatment 43

Prognosis 44

Progressive Ethmoidal Hematoma 44

Clinical signs 45

Diagnosis 45

Treatment 47

Prognosis 48

Paranasal Sinus Cysts 48

Clinical signs 48

Diagnosis 48

Treatment 49

Prognosis 49

Fungal Rhinitis and Sinusitis 49

Cryptococcosis 49

Rhinosporidiosis 49

Phycomycosis 50

Coccidioidomycosis 50

Aspergillosis 50

Sinus and Nasal Neoplasia and Polyps 50

Clinical signs 51

Diagnosis 51

Treatment 51

Prognosis 51

Amyloidosis 52

Conchal Necrosis and Metaplasia 52

Intranasal Foreign Bodies 52

Facial and Sinus Trauma 53

Subcutaneous Emphysema 53

Further Reading 54

Chapter 8: The Guttural Pouches 57

Anatomy and Function of the Guttural Pouches 57

Signs of Guttural Pouch Diseases 59

Examination of the Guttural Pouches 59

Palpation 59

Endoscopic examination 60

Radiographic examination 61

Cytology 62

Other diagnostic imaging techniques 62

Surgical approaches to the guttural pouches 62

Hyovertebrotomy 62

Viborg’s triangle 63

Paralaryngeal (Whitehouse) approach 63

Modified Whitehouse approach 64

Topical Treatment of the Guttural Pouches 64

Guttural Pouch Tympany 64

Clinical signs and diagnosis 65

Treatment 66

Prognosis 67

Diverticulitis of the Guttural Pouch 67

Strangles 68

Chronic gutteral pouch empyema and chondroids 68

Chronic diverticulitis 71

Guttural Pouch Mycosis 72

Clinical signs 74

Diagnosis 74

Treatment 75

Prognosis 77

Other Disorders of the Guttural Pouches 78

Foreign bodies 78

Neoplasia 78

Further Reading 79

Chapter 9: The Pharynx 81

Anatomy 81

Dorsal Displacement of the Soft Palate 82

Extrinsic factors 83

Intrinsic factors 84

Clinical signs 85

Diagnosis 85

Treatment 86

Conservative measures and medical treatments 86

Surgical treatments 87

Staphylectomy 87

Strap muscle resection 87

Llewellyn procedure—Sternothyroid muscle resection and staphylectomy 88

Epiglottic augmentation 88

Tension palatoplasty 88

Laryngeal tie-forward 89

Prognosis 89

Pharyngeal Lymphoid Hyperplasia 89

Clinical signs 90

Diagnosis 91

Treatment 91

Nasopharyngeal Cicatrices 92

Clinical signs 92

Diagnosis 92

Treatment 92

Cleft Palate (Palatoschisis) 93

Clinical signs 94

Diagnosis 95

Treatment 95

Prognosis 95

Subepiglottic, Pharyngeal, and Palatal Cysts 96

Clinical signs 97

Diagnosis 97

Treatment 98

Prognosis 98

Pharyngeal Paralysis 99

Pharyngeal Neoplasia 99

Pharyngeal Trauma 99

Pharyngeal and Retropharyngeal Foreign Bodies 101

Clinical signs 101

Diagnosis 101

Treatment 101

Retropharyngeal Abscess 101

Clinical signs 102

Diagnosis 102

Treatment 103

Prognosis 103

Further Reading 103

Chapter 10: The Larynx 107

Anatomy and Function 107

Idiopathic Laryngeal Hemiplegia/Recurrent Laryngeal Neuropathy 108

Prevalence 111

Clinical signs 112

Diagnosis 112

Treatment 114

Ventriculectomy and cordectomy 114

Prosthetic laryngoplasty 115

Temporary tracheotomy tubing 117

Permanent tracheostomy 117

Arytenoidectomy 117

Laryngeal reinnervation 118

Prognosis 118

Right Laryngeal Hemiplegia 118

Epiglottal Entrapment 119

Clinical signs 120

Diagnosis 120

Treatment 121

Prognosis 122

Arytenoid Chondropathy (Arytenoid Chondritis; Arytenoid Chondrosis) 122

Clinical signs 123

Diagnosis 123

Treatment 124

Prognosis 125

Laryngeal Neoplasia 126

Fourth Branchial Arch Defects 126

Clinical signs 127

Diagnosis 127

Treatment 128

Prognosis 128

Epiglottic Flaccidity 129

Clinical signs 129

Diagnosis 129

Treatment 130

Prognosis 130

Epiglottic Hypoplasia 130

Clinical signs 130

Diagnosis 130

Treatment 131

Prognosis 131

Epiglottitis 131

Clinical signs 131

Diagnosis 131

Treatment 131

Prognosis 131

Dorsal Epiglottic Abscess 132

Persistent Frenulum of the Epiglottis 132

Laryngeal Web 133

Perilaryngeal Accessory Bronchial Cyst 133

Further Reading 133

Chapter 11: Dynamic Airway Collapse During Exercise 137

Pharyngeal Collapse 137

Dynamic Dorsal Displacement of the Soft Palate 138

Intermittent Epiglottal Entrapment 139

Aryepiglottic Fold Collapse (Axial Deviation of the Aryepiglottic Folds) 139

Clinical signs 139

Diagnosis 140

Treatment 140

Prognosis 140

Epiglottic Retroversion 141

Dynamic Rostral Displacement of the Palatopharyngeal Arch 141

Dynamic Laryngeal Collapse 141

Further Reading 141

Chapter 12: Postanesthetic Upper Respiratory Tract Obstruction 143

Nasal Edema 143

Bilateral Laryngeal Paralysis 143

Further Reading 144

Chapter 13: The Trachea 145

Anatomy 145

Tracheal Examination 145

Surgery of the Trachea 146

Tracheotomy intubation 146

Permanent tracheostomy 147

Tracheal resection and anastomosis 148

External prosthesis to stent collapsed tracheal cartilages 149

Laser surgery 149

Congenital Tracheal Collapse (Collapsed Trachea) 149

Clinical signs 150

Diagnosis 150

Treatment 150

Tracheal Stenosis 151

Clinical signs 152

Diagnosis 152

Treatment 152

External Compression and Stenosis of the Trachea 152

Tracheal Wounds 152

Tracheal Neoplasia 153

Intratracheal Prolapse of the Cricotracheal Membrane 153

Tracheobronchial Foreign Body 153

Further Reading 155

Color plates (following page 156)

Section III: Contagious Respiratory Diseases 157

Chapter 14: Strangles 159

Etiology and Pathogenesis 159

Epidemiology 160

Clinical signs 160

Complications and sequela 162

Diagnosis 164

Treatment 167

Control of an outbreak 169

Prevention 169

Further Reading 170

Chapter 15: Equine Herpesvirus (Rhinopneumonitis) 171

Equine Herpesvirus 4 (EHV-4) 171

Equine Herpesvirus 1 (EHV-1) 172

Diagnosis 173

Treatment 173

Prevention 174

Equine Herpesvirus 2 (EHV-2) 175

Chapter 16: Equine Influenza 177

Diagnosis and Treatment 178

Prevention of Influenza 179

Chapter 17: Equine Viral Arteritis (EVA) 181

Diagnosis and Treatment 182

Prevention of EVA 182

Chapter 18: Other Contagious Respiratory Diseases 183

Hendra Virus (Equine Morbillivirus) 183

Adenovirus 184

African Horse Sickness 184

Further Reading 185

Section IV: Noninfectious Pulmonary Diseases and Diagnostic Techniques 187

Chapter 19: Noninfectious Pulmonary Diseases 189

Recurrent Airway Obstruction (Heaves) 189

Diagnosis 190

Treatment 192

Respiratory Distress at Rest 194

Systemic corticosteroid therapy 194

Bronchodilator therapy 195

Mild to Moderate Airway Obstruction 197

Aerosolized corticosteroids 197

Adrenal suppression 198

Long-acting bronchodilator therapy 199

Maintenance therapy 199

Response to therapy 200

Stable hygiene 200

Summer Pasture-Associated Obstructive Pulmonary Disease 201

Interstitial Pneumonias 202

Lungworms 205

Inflammatory Airway Disease (IAD) 206

Diagnosis 207

Treatment 210

Exercise-Induced Pulmonary Hemorrhage (EIPH) 211

Diagnosis 213

Treatment 215

Thoracic Neoplasia 217

Smoke Inhalation 219

Diagnosis 220

Treatment 220

Immunostimulant Therapy 222

Bacterial and Viral Products 223

Propionibacterium acnes 223

Mycobacterium 224

Parapoxvirus ovis 226

Synthetic Immunostimulants 227

Levamisole phosphate 227

Interferon-alpha 227

Further Reading 229

Chapter 20: Techniques: Noninfectious Lower Respiratory Tract 233

Endoscopic Examination of the Lower Respiratory Tract 233

Arterial Blood Gas Evaluation 234

Bronchoalveolar Lavage 237

Technique 238

Complications 240

Lung Biopsy 240

Technique 240

Complications 241

Advanced Respiratory Techniques 241

Aerosol Delivery Devices 244

Mechanical nebulizers 246

Dry powder inhalant (DPI) devices 247

Further Reading 248

Section V: Lower Respiratory Tract Infectious Disease and Diagnostic Techniques 249

Chapter 21: Juvenile Pneumonia 251

Rhodoccocus equi 254

Clinical signs 255

Diagnosis 257

Treatment 260

Prevention 262

Pneumocystis carinii 263

Bronchointerstitial Pneumonia 265

Further Reading 269

Chapter 22: Pneumonia in Adult Horses 271

Bacterial Pneumonia/Pleuropneumonia 271

Clinical signs 273

Diagnosis 274

Thoracic ultrasound 275

Thoracocentesis 276

Thoracic radiographs 279

Treatment 280

Thoracostomy 282

Complications 283

Prognosis 285

Fungal Pneumonia 285

Pulmonary Metacestode Infection 287

Further Reading 289

Chapter 23: Techniques for Infectious Respiratory Disease 291

Transtracheal Aspiration 291

Thoracic Ultrasound 294

Thoracocentesis 296

Thoracic Radiography 299

Further Reading 303

Index 305