Dermatophytosis in Domestic Animals (Santoro) Flashcards
Dermatophytes
“Ringworm”. Fungi that infect keratinized tissues (skin, hair, claws/hooves, feathers, quills)
Dermatophyte species affecting the dog & cat
- Microsporum canis (reservoir: cats)
- Microsporum gypseum (reservoir: soil)
- Trichophyton mentagrophytes (reservoir: rodents, rabbits, pocket pets)
- Microsporum persicolor
Predisposing factors for dermatophytosis
- Decr. grooming
- Microtrauma
- Excessive hydration/maceration
- Warm, humid
- Lack of sun exposure
- Strong cell-mediated immunity
Predilections for dermatophytosis
- White Persians and Himalayans
- Terriers
- Young animals
- Sick & emaciated animals
Clinical signs of dermatophytosis in dogs & cats
- Cutaneous signs
- extremely variable
- absent to moderate pruritis
- erythema/alopecia
- crusting/scaling/pustules
- miliary dermatitis (cats)
- dermal nodules/plaques
- muzzle & feet most affected
Clinical signs of dermatophytosis in horses
- Follicular pustules
- Variable-sized annular alopecic areas
- Severe scaling, crusing, pustules, ulcers, pruritis
- Saddle & tack regions
- Urticaria-like lesions
Clinical signs of dermatophytosis in cattle
- Circular, alopecic areas
- Severe scaling, crusting, suppuration
- Pain and pruritis - variable
Kerion
Well-circumscribed nodular mass
Dermatophytosis diagnosis
- Hx & physical exam
- Wood’s lamp (black light)
- Trichogram (hair pluck)
- Fungal culture (ID macroconidia)
- Skin biopsy/histopath
MacKenzie technique
- Useful for feline asymptomatic carriers of dermatophytosis
- Use hairs collected from brush or cut brush bristles and place them on the media
Slide preperation
Use clear scotch tape to dab colony w/ sticky side. Place tape onto slide that already has a drop of stain on it.
Principles for treatment of dermatophytosis
- Elimination of infection from host
- Prevention of further dissemination of infective spores
- Removal of infective spores already in environment
Treatment of dermatophytes
- Healthy animals can self-cure in 12-17 wks if infective spores are removed from the environement
- Systemic, topical, and environmental therapy
- Treat all animals in contact
Topical therapies for dermatophytosis
- Ketoconazole
- Miconazole
- Chlorohexidine
- Lime sulfur
- Clipping hair controversial
- Removes contaminated hair
- Creates microlesions
Systemic therapies for dermatophytosis
- Ketoconazole
- Itraconazole
- Fluconazole
- Terbinafine
- Griseofulvin
Griseofulvin (general info)
- Fungistatic
- Variable oral absorption
- Incr. fatty meal
- Only effective against dermatophytes
Griseofulvin side effects
- Vomiting
- Diarrhea
- Anorexia
- Bone marrow suppression
- Siamese, himalayans, abyssinians
- Monitor CBC, FIV, FeLV and other viruses
- Teratogenic
Ketoconazole (general info)
- Fungistatic
- Good oral absorption
- Incr. fatty meal
- Decr. non-acid gastric environment
Ketoconazole side effects
- Vomiting
- Diarrhea
- Anorexia
- Interfere w/ steroid synthesis
- Inhibit cytochrome P450
- Better tolerated in dogs than cats
- Contraindicated in pregnant animals
Itraconazole (general info)
- Fungistatic (low) - fungicidal (high)
- Preferred for feline fungal infections
- Good oral absorption
- Incr. fatty meal
Itraconazole side effects
- Uncommon
- GI upset (rare)
- Hepatotoxicity (rare)
- Reversible, dose-dependent cutaneous vasculitis in dogs at higher doses
- Mild inhibition of cytochrome P450
- Not recommended in pregnant animals (teratogenicity, embriotoxicity)
Fluconazole
- Fungistatic
- Broad antimycotic spectrum
- Side effects uncommon (GI upset)
- Mild inhibition of cytochrome P450
- Recommended for patients w/ hepatic dz
Terbinafine
- Fungicidal
- Residual effect (accumulates in keratinized tissue)
- Vomiting & facial pruritis in cats
- Incr. liver enzymes
- NO inhibition of cytochrome P450
Immunotherapy for dermatophytosis
- Killed M. canis vax
- licensed for prevention and treatment of lesions, but not the dz
- causes slightly decr. severity of initial infection
- Cattle
- success in prophylactic or therapeutic use
Environmental decontamination of dermatophytosis
- Swiffer/vacuum
- Detergent
- Bleach (1:10)
- Enilconazole
- Lime sulfur
Duration of dermatophytosis therapy
- No growth on 2 sequential weekly cultures
- 2 negative cultures one month apart
Onychomycosis
- Fungal infection of nail
- Prognosis for cure is guarded, will take several months (6-12+) if at all
- Itraconazole and terbinafine
- Onychectomy (declaw) may be indicated
Large animal dermatophytosis therapy
- Infections usually self-limiting
- Topical (lime sulfur spray)
- Treat 2 wks past clinical cure
- Isolation
- Environmental decontamination
- Decr. crowding, incr. UV light exposure
