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What is the most common etiologic agent that causes yeast dermatitis and otitis?
Malassezia pachydermitis
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Where is Malassezia found in normal, healthy animals? (7)
ear canal, anal sac, lips, chin, vagina, rectum, and skin [found in low numbers in healthy animals]
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What are pre-disposing factors for Malassezia yeast infections? (6)
host defenses down, excess sebum problems, sebum quality (keratinization problems, allergies), moisture accumulation, disrupted epidermal surface, concurrent dermatoses
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What are predisposing diseases for Malassezia dermatitis? (6)
allergies, keratinization disorders, bacterial skin diseases, metabolic diseases, endocrinopathies, cutaneous or internal neoplasia
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How does Malassezia cause inflammation and clinical signs?
releases enzymes that alter sebum quality and disrupt the epidermal surface, may also activate complement--> inflammation and pruritus
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Describe the clinical presentation of Malassezia dermatitis. (3)
moderate to intense pruritus, rancid odor, generalized or localized (ears, muzzle, interdigital areas, ventral neck, medial thigh, axillae, perianal region- all areas dense with sebaceous glands)
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What skin lesions are common with yeast dermatitis? (6)
[all non-specific] erythema, scaling (greasy or dry) crusts, hyperpigmentation, lichenification, alopecia, red-brown discoloration
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What 3 localized Malassezia infections are most common in cats?
paronychia (nail bed), chin acne, otitis externa
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What underlying conditions commonly predispose cats to generalized Malasseia dermatitis? (4)
FIV/FeLV, neoplasia, diabetes, allergies
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How do you diagnose Malassezia dermatitis? (2)
yeast identification via cytology (cotton swab smear, superficial skin scraping, acetate tape prep) is rather simple, culture/histo not usually necessary unless you suspect an underlying problem
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What method of sample collection is the most sensitive for identifying Malassezia?
acetate tape preparation
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How do you treat yeast dermatitis? (3)
identify and treat underlying cause, degreasing/antiseborrheic products, anti-fungal topical agents
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What antifungal agents are used with yeast dermatitis and what each is useful for? (4)
- Sulphur/Salicylic acid: not good at degreasing, works for less oily cases
- Benzoyl peroxide: degreasing, lacks antifungal component so must add that
- Selenium sulfide: mild antifungal, very degreasing
- Antifungal shampoos: with miconazole, climbazole, ketoconazle, chlorohexidine
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When is systemic therapy considered with yeast dermatitis?
severe cases or when topical therapy is unsuccessful
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What systemic drugs have been efficacious at treating Malassezia dermatitis? (4)
- Ketoconazole (severe side effects)
- Itraconazole (fewer side effects, safer for cats)
- Terbinafine (fewer drug interactions)
- Fluconazole (?)
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What re-check protocol are important when managing Malassezia dermatitis? (4)
re-check every 3-4weeks, cytology re-check, monitor serum liver enzymes if on systemic therapy, topicals can be used prophylactically
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In what circumstances is Malassezia zoonotic?
immunocompromised individuals
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