Malassezia dermatitis is a common pruritic, often malodorous, skin condition caused by an opportunistic yeast that is typically considered a normal inhabitant of the dog's skin and ear canals.
Common name: Yeast infection, Malassezia dermatitis Scientific name: Malassezia dermatitisDiagnosis
Malassezia Signalment Any dog is susceptible to developing the skin condition; however basset hounds, west Highland white terriers, poodles, cocker spaniels and dachshunds are predisposed.
Malassezia Incidence/prevalence Malassezia dermatitis is a common cause of pruritic seborrheic dermatitis in dogs. (Seborrheic dermatitis is a skin inflammation characterized by excessive or abnormal sloughing of skin cells and excessive or abnormal oily secretions by glands in the skin. This type of dermatitis causes a greasy skin and haircoat).
Actual incidence of Malassezia dermatitis during a given period is unknown. Increased prevalence is associated with previous antibacterial, glucocorticoid or combination therapy.
Malassezia Geographic distribution Malassezia dermatitis is common in all regions of the world. However, increased frequency may be seen in climates of high humidity and temperature, and during warm weather in temperate areas.
Malassezia Clinical signs (primary, most to least frequent, scientific term, synonyms) Pruritis (itchiness) is intense and characterized by scratching, rubbing, chewing and scooting.
Erythema (redness of the skin) is visible in affected areas. Scaley skin, which are generally yellow or grey in color and have a foul, unpleasant odor, are a common complaint with the disease.
Alopecia (hair loss) can be severe. Otitis externa (ear infection) with a dark moist waxy exudate can also occur, especially in floppy eared dogs.
Malassezia Clinical signs (secondary, most to least frequent, scientific term, synonyms) Hyperpigmentation (increased darkening of the skin) is common in chronic cases. Lichenification (skin thickening) occurs with persistent scratching.
Malassezia Cause (scientific, common term) Malassezia pachydermatis, Pityrosporum canis (synonym).
Malassezia Organ system affected (most to least affected) Skin, haircoat, nails.
Malassezia Diagnostic tests Microscopic examination of skin scraping, response to therapy, skin biopsy, culture (M. pachydermatis usually grows well on routine media).
Malassezia Differential Diagnosis Allergic dermatitis (atopy, flea allergy, food allergy), superficial pyoderma, Demodicosis, Sarcoptic mange, ringworm, defects in keratination.Overview
Malassezia dermatitis is a moderately to intensely pruritic (itchy), malodorous skin disease caused by the opportunistic yeast, Malassezia pachydermatitis.
This yeast is typically found in low numbers on the skin, in the ear canals and at mucosal/skin interfaces such as around the mouth and anus. Disease results when either a hypersensitivity reaction to the organism or yeast overgrowth occurs. Underlying factors such as a food allergy, atopy (inhalant skin allergy), flea allergy, endocrine disorder and prolonged antibiotic or corticosteroid therapy can predispose the dog to overgrowth conditions.
Besides the notable itchiness and unpleasant odor, variable degrees of erythema (redness), alopecia (hair loss) and scales which are usually yellowish grey and greasy are apparent.
Persistent scratching, rubbing, chewing and scooting in chronic cases results in hyperpigmentation (darkening) and lichenification (thickening) of the skin. While generalized disease does occur, infection is typically localized to the lips, muzzle, ventral neck, axillae, groin, feet and skin fold areas. When present on the feet, inflammation in the nail folds can cause a dark brown nail discharge and discoloration of the nail. Often a concurrent yeast infection of the external ear canal is present, as exhibited by head shaking and tilting.
Any dog is susceptible to Malassezia dermatitis; however basset hounds, west Highland white terriers, poodles, cocker spaniels and dachshunds are predisposed. Increased incidence may be seen in high humidity and high temperature climates.Treatment
Malassezia Home Care Since Malassezia yeast are not considered contagious to other animals or to humans, and unless an individual is immunocompromised, environmental cleaning and disinfecting is not required. Treatment requires veterinary intervention.
Malassezia Professional Care Cytology, a microscopic examination of skin samples taken from imprints, scrapings or smears of the skin surface, is a reliable, quick, easy and inexpensive method of identifying the yeast.
Malassezia has a distinctive round to oval budding appearance that looks like peanut shells. Since the organisms are part of the dog's natural skin flora, cytological results are interpreted in conjunction with the animal's disease history and clinical signs. Diagnosis is then based on response to therapy. A skin biopsy may be performed additionally to determine any underlying disease in yeast overgrowth cases.
A treatment plan is developed to meet the needs of the individual patient, with consideration of predisposing factors and diseases. Mild localized infections often respond to topical antifungal creams or ointments. For generalized disease, medicated shampoos, rinses and possibly dips are beneficial.
In moderate to severe cases, oral antifungal therapy is required. Most animals will also need systemic antibiotics for concurrent bacterial pyoderma (skin infection).
Malassezia Action Diagnosis and development of a treatment plan should be made by a veterinarian. Oral antifungal medications which may include ketoconazole or itraconazole may have serious side effects and require blood screening during the course of treatment. Therapy should continue until lesions resolve and follow-up skin cytology reveals no organisms (approximately two to four weeks).
Malassezia Outcome Prognosis is good if an underlying cause is identified and controlled. Otherwise, routine bathing once or twice weekly, with antifungal-antibacterial shampoo combinations may be needed to decrease or prevent recurrence.
Matousek, JL. Infectious Skin Diseases. In: Morgan, RV, ed.al. Handbook of Small Animal Practice, 4th Ed. Philadelphia: Saunders, 2003; 853-855.
Wilkinson, GT & Harvey, RG. Color Atlas of Small Animal Dermatology A Guide To Diagnosis, 2nd Ed. London: Mosby-Wolfe, 1995; 123-124.
Medleau, L & Hnilica, KA. Small Animal Dermatology A Color Atlas and Therapeutic Guide. Philadelphia: W.B. Saunders Company, 2001; 41-43.
Tilley, LP & Smith, FWK, Jr. The 5 Minute Veterinary Consult Canine and Feline, 2nd Ed. Philadelphia: Lippincott Williams & Wilkins, 2000; 926-927.
Donna Lohman, DVM
Steven Hansen, DVM, MS, MBA