Fungal Skin Diseases Malassezia Dermatitis – Small Animals Dr.Kedar Karki A. General Considerations: 1. Malassezia sp is probably a secondary colonizer/invader in seborrhea conditions. 2. Many primary diseases may predispose the animals to Malassezia infection: a. Atopy/food allergy. b. Endocrinopathies. c. Ectoparasites. 3. The role of Malassezia organism as a primary pathogen on skin or in ear is unclear. An immunologic reaction to the yeast should be considered. 4. Antibiotic therapy may predispose to disease. B. Etiology: 1. Malassezia pachydermatis is the most common agent in dogs and cats. 2. Malassezia sympodialis has been isolated from cat skin. 3. Malassezia pachydermatis is a lipophilic yeast that is commonly found on normal and abnormal skin, in normal and abnormal ear canals, and in the anal sacs, rectum, and vagina of normal dogs and cats. C. Clinical Signs: 1. Clinical signs are quite variable: a. Greasy seborrhea is more often seen in terriers and hounds. b. Interdigital erythema and/or seborrhea is a common clinical presentation. It can be seen in many breeds, especially cocker spaniels. These dogs are 1 often extremely pruritic and, they do not lick at their feet but, they chew at them! c. Mucocutaneous junctions can be affected. d. Intertriginous – axilla, groin. 2. Pruritus is variable but, usually severe. 3. Character of the exudate – it may be dry or greasy. D. Diagnosis: 1. Cytologic examination is the most useful and readily available diagnostic tool. a. Samples of surface scale or grease are gathered by 1) making a superficial scraping (do not use oil on scalpel); 2) vigorously rubbing a cotton swab on the skin surface; 3) pressing a piece of clear cellophane tape onto lesional skin several times; 4) or pressing a section of a clean glass microscope slide on the skin. b. Scraping and tapping appear to be more effective than swabbing. c. All material is transferred to a glass slide, heat fixed (but not if cellophane tape has been used), and stained with new methylene blue or Diff Quick for cytologic examination. d. Examine your glass slide under oil immersion. If cellophane tape prep has been used, put first a drop of oil on the glass slide then the tape, and again apply another drop of immersion oil on the tape surface. e. Find budding yeast often associated with squamous cells. 2. Culture – not easy to perform. Sabouraud’s media can be used. 3. Skin biopsy. a. Yeast organisms may be seen in stratum corneum. b. Organisms may also be present in the infundibulum of hair follicles. c. Skin biopsy is less reliable than cytologic examination for demonstrating yeasts. d. Do not scrub or use alcohol on skin surface before the biopsy. 2 E. Treatment: 1. Topical shampoos: a. Selenium sulfide shampoos. 1. 1.0% selenium in Selsun Blue or veterinary selenium shampoos. 2. Contact time of at least 10 minutes is important. 3. It may be a contact sensitizer. b. Chlorhexidine containing shampoos. 1. Not a good degreasing shampoo. c. Nizoral shampoo – by prescription for human use. 1. Expensive ($ 15-25 for 4 oz). 2. Generally less expensive than systemic ketoconazole. d. Dermazole shampoo 1. Miconazole and chlorhexidine are the active ingredients. 2. It is not degreasing. 2. Systemic therapy: a. Ketoconazole 5 to 10 mg/kg/day for 21 days. Give it with food. b. Itraconazole 5 mg/kg/day for 21 days. 3. Other treatment options: a. Most important! Identify and treat the underlying cause. b. Use antiseborrheic baths. 3 c. In occasions when only the feet or a focal area is affected, you can use topical creams or ointments containing antifungal agents (such as clotrimazole, miconazole). I like to use Otomax (contains clotrimazole, gentamicin and betamethasone valerate) in between the digits and in between the footpads to manage malassezia pododermatitis. 4