The Editor

Kimberly S. Coyner, DVM, DACVD, is a veterinary dermatologist at Dermatology Clinic for Animals in Lacey, WA and a consultant for the Veterinary Information Network.

List of contributors xv

Preface xvii

Acknowledgments xix

About the companion website xxi

1 Dermatology diagnostics 1

1.1 Skin scrapings 1

1.2 Cytology - Skin and ear 4

1.3 Cytology - Mass aspirates 6

1.4 Trichograms 8

1.5 Dermatophyte culture technique 15

1.6 Wood's lamp examination 15

1.7 Dermatophyte culture medium selection and incubation 16

1.8 Identification of dermatophytes 16

1.9 Dermatophyte PCR 18

1.10 Bacterial culture 19

1.11 Skin biopsies 19

1.12 Allergy testing 22

2 Dermatology lesions and differential diagnoses 23

2.1 Primary lesions 23

2.1.1 Macule/Patch 23

2.1.2 Papule/pustule 23

2.1.3 Plaque 26

2.1.4 Vesicle/bulla 27

2.1.5 Wheal 28

2.1.6 Nodule 29

2.1.7 Cyst 30

2.2 Primary or secondary lesions 31

2.2.1 Alopecia 31

2.2.2 Scale 34

2.2.3 Crust 35

2.2.4 Follicular cast 36

2.2.5 Comedo (Comedones) 36

2.2.6 Pigment change 37

2.3 Secondary lesions 40

2.3.1 Epidermal collarette 40

2.3.2 Scar 40

2.3.3 Excoriation 41

2.3.4 Erosion 42

2.3.5 Ulcer 42

2.3.6 Lichenification 43

2.3.7 Callus 44

2.3.8 Fissure 44

3 Lesion location and differentials 47

3.1 Face 47

3.1.1 Nasal planum 47

3.1.2 Lips/Eyelids 47

3.1.3 Muzzle 49

3.2 Ears 56

3.2.1 Pinnal margin 56

3.2.2 Pinna 57

3.2.3 Outer ear canal 57

3.3 Paws 60

3.3.1 Interdigital 60

3.3.2 Palmar metacarpal/plantar metatarsal 63

3.3.3 Paw pad 63

3.3.4 Nailbed 65

3.4 Claws 66

3.5 Perianal/perivulvar 67

3.6 Tail 68

3.7 Pressure points (elbows/hocks) 69

3.8 Trunk (dorsal and/or lateral) 70

3.9 Inguinal/axillary 78

3.10 Oral cavity 81

4 Causes and workup for pruritus in dogs and cats 85

Algorithm 4.1 Pruritic dog - Causes/Workup 86

Algorithm 4.2 Pruritic cats - Causes/Workup 87

5 Causes and workup for alopecia in dogs and cats 89

Algorithm 5.1 Canine non¿inflammatory truncal alopecia - Causes/Workup 90

Algorithm 5.2 Canine multifocal alopecia - Causes/Workup 91

Algorithm 5.3 Feline alopecia - Causes/Workup 92

6 Breed¿related dermatoses 93

Table 6.1 Canine breed¿related dermatoses 93

Table 6.2 Feline breed¿related dermatoses 107

7 Parasitic skin diseases 111

Table 7.1 Canine and feline ectoparasites 112

Demodex 112

Sarcoptes 113

Notoedres 114

Otodectes 114

Cat fur mite 114

Cheyletiella 114

Lice 115

Chiggers 115

Hookworm Dermatitis 115

Cuterebra 115

Myiasis 115

Fly bite dermatitis 116

Pelodera dermatitis 116

Dracunculiasis 116

Spider bite 116

Fleas 117

Ticks 117

Table 7.2 Flea control product options 130

Table 7.3 Tick control product options 130

8 Bacterial, fungal, oomycete, and algal infections 133

Table 8.1 Superficial bacterial skin infections 133

Impetigo 133

Pyotraumatic dermatitis 133

Intertrigo 133

Mucocutaneous pyoderma 133

Bacterial overgrowth syndrome 134

Bacterial folliculitis 134

Algorithm 8.1 Approach to chronic recurrent bacterial pyoderma 143

Table 8.2 Deep bacterial skin infections 144

Bacterial furunculosis 144

Canine acne 144

Callus furunculosis 144

Acral lick dermatitis 144

Pedal folliculitis/furunculosis 145

Post¿grooming furunculosis 145

Table 8.3 Meticillin resistance 150

Table 8.4 Underlying causes for recurrent pyoderma 152

Table 8.5 Commonly used antibiotics for canine pyoderma 152

Table 8.6 Topical antibacterial products 153

Table 8.7 Subcutaneous bacterial infections 154

Subcutaneous abscess 154

Botryomycosis 155

Cellulitis 155

Necrotizing fasciitis 155

Actinomycosis 155

Nocardiosis 156

Plague 156

L¿form infection 156

Table 8.8 Mycobacterial infections 159

Non¿tuberculous mycobacteria 159

Feline leprosy 160

Canine leproid granuloma 160

Obligate mycobacterial infections/tuberculosis 161

Table 8.9 Yeast infections 164

Malassezia 164

Candida 165

Table 8.10 Dermatophytosis 170

Table 8.11 Environmental decontamination in dermatophytosis 180

Algorithm 8.2 Treatment of generalized dermatophytosis 181

Table 8.12 Deep fungal, oomycete, and algal infections 182

Blastomycosis 182

Cryptococcosis 182

Histoplasmosis 183

Coccidioidomycosis 184

Sporotrichosis 184

Phaeohyphomycosis 185

Pythiosis 185

Lagenidiosis 186

Zygomycosis 187

Protothecosis 187

9 Viral, rickettsial, and protozoal dermatologic diseases 199

Table 9.1 Viral dermatologic diseases 200

Feline herpesvirus dermatitis 200

Feline calicivirus dermatitis 201

Viral papillomas - Dogs/Cats 201

Cowpox virus 203

Feline infectious peritonitis (FIP) 203

Canine distemper 203

Table 9.2 Rickettsial diseases 208

Rocky Mountain Spotted Fever 208

Ehrlichiosis 208

Table 9.3 Protozoal diseases 210

Leishmaniosis 210

Toxoplasmosis 211

10 Allergic skin diseases in dogs and cats 215

Table 10.1 Hypersensitivity disorders and treatment of allergic skin diseases 216

Algorithm 10.1 Canine atopic dermatitis treatment 231

Table 10.2 Allergy treatment toolkit 232

Table 10.3 Allergy testing: Intradermal and serologic methods 235

Table 10.4 Considerations in allergen formulation 236

Table 10.5 Protocols for allergen specific immunotherapy (ASIT) 237

Table 10.6 Performing an adequate diagnostic hypoallergenic diet trial 239

Table 10.7 Feline manifestations of cutaneous allergy 244

Table 10.8 Eosinophilic granuloma complex 248

11 Autoimmune and immune¿mediated dermatologic disorders 255

Table 11.1 Autoimmune and immune¿mediated dermatologic disorders 256

Discoid lupus erythematosus 256

Pemphigus foliaceus 256

Pemphigus vulgaris 256

Vesicular cutaneous lupus erythematosus 257

Mucocutaneous lupus erythematosus 257

Alopecia areata 257

Uveodermatologic syndrome 257

Autoimmune subepidermal blistering diseases 258

Vasculitis 259

Post¿vaccination injection site alopecia 259

Drug eruption 260

Erythema multiforme 260

Toxic epidermal necrolysis 261

Sterile panniculitis 261

Sterile granuloma/pyogranuloma 261

Juvenile cellulitis 262

Plasma cell pododermatitis 262

Pseudopelade 262

Symmetric lupoid onychitis 263

Nasal arteritis 263

Metacarpal/metatarsal fistulas 264

Canine sterile neutrophilic dermatitis (Sweet's¿like syndrome) 264

Canine acute eosinophilic dermatitis with edema (Well's¿like syndrome) 264

Superficial suppurative necrolytic dermatitis 265

Systemic lupus erythematosus 265

Algorithm 11.1 Treatment of canine pemphigus foliaceus 269

Algorithm 11.2 Treatment of feline pemphigus foliaceus 270

Table 11.2 Typical glucocorticoid doses for treatment of autoimmune and immune¿mediated disorders 286

Table 11.3 Non¿steroidal immunosuppressant or immunomodulatory drugs as adjunctive or primary treatments of autoimmune/immune¿mediated diseases 287

12 Endocrine skin diseases 291

Table 12.1 Canine endocrine skin diseases 292

Hypothyroidism 292

Spontaneous hyperadrenocorticism (HAC, Cushing's disease) 292

Iatrogenic hypercortisolemia 293

Atypical Cushing's disease (ACD) 293

Food¿induced Cushing's disease 293

Topical corticosteroid application 293

Pituitary dwarfism 293

Calcinosis cutis 294

Exogenous estrogen¿related alopecia 294

Spontaneous hyperestrogenism 294

Spontaneous hyperandrogenism 295

Tail gland hyperplasia 295

Table 12.2 Trilostane treatment and monitoring 303

Table 12.3 Endocrine skin diseases of cats 304

Hyperthyroidism 304

Hypothyroidism 304

Hyper adrenocorticism (HAC) 304

Feline acquired skin fragility 305

Diabetes mellitus (DM) 305

Acromegaly 305

13 Non¿endocrine alopecia 309

Table 13.1 Non¿endocrine alopecia of dogs 310

Localized Alopecia 310

Post¿clipping alopecia 310

Traction alopecia 310

Congenital follicular/ectodermal dysplasia 310

Regional to Multifocal Alopecia 310

Color dilution alopecia 310

Black hair follicular dysplasia 310

Non¿color, breed¿related follicular dysplasia 310

Cyclic flank alopecia 311

Pattern alopecia 311

Follicular lipidosis 311

Generalized Alopecia 311

Alopecia X 311

Anagen/telogen effluvium 312

Non¿color breed¿related follicular dysplasia 312

Table 13.2 Non¿endocrine alopecia of cats 318

Congenital hypotrichosis 318

Hair shaft disorder of Abyssinian cats 318

Pili torti 318

Feline preauricular "alopecia" 318

Feline pinnal alopecia 318

Feline psychogenic alopecia 318

Mural folliculitis 319

Mucinotic mural folliculitis 319

Pseudopelade 319

Trichorrhexis nodosa 319

Feline paraneoplastic alopecia 319

14 Diagnosis and treatment of acute and chronic otitis 323

14.1 Approach to...