Malassezia yeasts and Malassezia dermatitis have been the subject of almost innumerable publications and anecdotes since the early 1990s. The condition is diagnosed commonly in the dog and uncommonly in the cat.
Malassezia yeasts and Malassezia dermatitis have been the subject of almost innumerable publications and anecdotes since the early 1990s. The condition is diagnosed commonly in the dog and uncommonly in the cat. This presentation will focus on what has been published since the submission of the sixth edition of Muller & Kirk's Small Animal Dermatology in 2001.
Thanks to the advances in molecular biology, the genus Malassezia has undergone extensive investigation and revision. The genus currently contains 13 species: one lipid-dependent, M. pachydermatis; and 12 lipid-independent, M. caprae, M. dermatis, M. equina, M. furfur, M. globosa, M. japonica, M. nana, M. obtusa, M. restricta, M. slooffiae, M. sympodialis, and M. yamatoensis. M. pachydermatis remains the most commonly isolated and studied in dogs and cats.
M. pachydermatis is most commonly isolated, in decreasing order of frequency, from interdigital skin, ears, claw folds, mouth, groin, conjunctiva, axilla, perineum, anus, and circumanal glands of atopic dogs.27 The highest yeast counts are found on lesional skin.
M. pachydermatis produces a large number of substances which may be important in the production of disease: acid phosphatase, alkaline phosphatase, chondroitin-sulfatase, esterase, galactosidase, glucosidase, hyaluronidase, lecithinase, leucine arylamidase, lipoxygenase, peroxidase, phosphoamidase, phosphohydrolase, phospholipase, protease, and urease.16 Multiple M. pachydermatis genotypes and subgenotypes were isolated from healthy dogs or dogs with skin lesions, and those from lesional skin contained significantly higher phospholipase activity.
The variability in adhesive capacity of M. pachydermatis and M. sympodialis to canine, feline, and human corneocytes did not explain the marked difference in Malassezia flora in these three species.7 The in vitro growth of M. pachydermatis was inhibited at pH 1 to 3 and 9 to 10.
M. pachydermatis applied to the skin of healthy dogs produced mild, transient lesions; when the yeast was applied under occlusion, the lesions were more severe, lasted longer, but still spontaneously resolved. Fungal culture was positive much more commonly than cytology when sampling healthy and inflamed skin. Cultures from adhesive tape samples were positive twice as frequently as those from dry swabs.
There was no significant difference in anti-Malassezia IgE levels between atopic dogs with or without Malassezia dermatitis and/or otitis. Neither were there significant differences in anti-Malassezia IgE levels (commercial ELISA test) between atopic dogs with or without Malassezia dermatitis and healthy dogs.18 Passive transfer of type-1 hypersensitivity reactivity confirmed the functionality of anti-Malassezia IgE.
Intradermal test reactions to M. pachydermatis antigen were 4 times more frequently immediate than delayed. Intradermal tests (commercial M. pachydermatis antigen) were positive (immediate reactions) in all atopic dogs with Malassezia dermatitis, 31% of atopic dogs without Malassezia dermatitis, and no healthy dogs. Lymphocyte blastogenesis to M. pachydermatis antigen was positive in atopic dogs with or without Malassezia dermatitis. Patch tests using M. pachydermatis antigen were more often positive in basset hounds with Malassezia dermatitis than in healthy basset hounds and healthy beagles.
Proteins of 45, 52, 56, and 63 kDA were recognized by over 50% of the atopic dogs with Malassezia dermatitis, thus qualifying as major allergens. Results of this study were not in total agreement with those from previous studies. Differences could be due to the fact that there is variation in antigenic expression in different growth phases of M. pachydermatis.
In vitro susceptibility testing of strains of M. pachydermatis from dogs showed that all were susceptible to azoles: ketoconazole > itraconazole > fluconazole. Ketoconazole and itraconazole were equally effective for systemic treatment of Malassezia dermatitis, and there was no difference in efficacy between ketoconazole at 5 mg/kg q24h and 10 mg/kg q24h. There was no difference in the efficacy of itraconazole when administered daily or for two consecutive days/week.Ketoconazole and terbinafine were equally effective for reducing population sizes of Malassezia and for the treatment of Malassezia dermatitis.
M. pachydermatis was 11 times more likely to be demonstrated by PCR on the hands of owners of atopic dogs with Malassezia dermatitis or otitis.
Malassezia spp. (mostly M. pachydermatis) were demonstrated (ear canal, anus, claw fold, axilla, and groin were sampled) in 90% of Devon Rex, 50% of domestic shorthair, and 39% of Cornish Rex cats. M. slooffiae (mostly clawbed) and M. nana (mostly ear canal) were occasionally isolated. Frequency of isolation and population sizes of Malassezia spp. (mostly M. pachydermatis) were greater in "seborrheic" Devon Rex than in healthy Devon Rex or domestic shorthair cats.1 The prevalence of Malassezia spp. in clawfolds was greater in Devon Rex (100%; 8.6/oil immersion) than non-Devon Rex (61%; 0.59/oil immersion). The frequency of isolation and population sizes of Malassezia sp. were not significantly different in healthy cats and cats with diabetes mellitus, hyperthyroidism, and neoplasia.
Results of a retrospective histopathological study suggested that the finding of Malassezia yeasts in surface keratin was often associated with the presence of systemic disease (e.g., paraneoplastic alopecia, thymoma). Malassezia yeasts were demosntrated in allergic cats (atopic dermatitis, food allergy) and treatment with itraconazole or ketoconazole resulted in reduced pruritus and dermatitis. Itraconazole administration produced reduced Malassezia counts and dermatitis in "seborrheic" Devon Rex cats.
Ahman S, et al: Carriage of Malassezia spp. yeasts in healthy and seborrhoeic Devon Rex cats. Medical Mycology 2007; 45:449.
Ahman S, et al: Treatment of Malassezia pachydermatis-associated seborrhoeic dermatitis in Devon Rex cats with itraconazole – a pilot study. Veterinary Dermatology 2007; 18:171.
Baksi S, et al: Clinico-therapeutic study of Malassezia dermatitis in dogs. Indian Veterinary Journal 2004; 81:706.
Bensignor E, et al: Comparison of two sampling techniques to assess quantity and distribution of Malassezia yeasts on the skin of basset hounds. Veterinary Dermatology 2002; 13:237.
Bensignor E: Comparison de deux posologies de kétoconazole pour le traitement de la dermatitie � Malassezia chez le chien. Annals de Médecine Vétérinaire 2001; 145:311.
Bensignor E: Oral itraconazole as a pulse therapy for the treatment of canine Malassezia dermatitis: a randomized, blinded, comparative trial. Pratique Médicale and Chirurgicale de L'Animal de Compagnie 2006; 41:69.
Bond R, et al: Adherence of Malassezia pachydermatis and M. sympodialis to canine, feline, and human corneocytes in vitro. Veterinary Record 2000; 147:454.
Bond R, et al: Clinical, histopathological, and immunological effects of exposure of canine skin to Malassezia pachydermatis. Medical Mycology 2004; 42:165.
Bond R, et al: Patch test response to Malassezia pachydermatis in healthy dogs. Medical Mycology 2006; 44:175.
Bond R, et al: Patch test responses to Malassezia pachydermatis in healthy basset hounds and in basset hounds with Malassezia dermatitis. Medical Mycology 2006; 44:419.
Bond R, et al: Carriage of Malassezia spp. yeasts in Cornish Rex, Devon Rex, and domestic short-haired cats: a cross-sectional survey. Veterinary Dermatology 2008; 19:299.
Brito EHS, et al: Phenotypic characterization and in vitro antifungal sensitivity of Candida spp. and Malassezia pachydermatis strains from dogs. Veterinary Journal 2007; 174:147.
Cafarchia C, et al: Genetic variants of Malassezia pachydermatis from canine skin: body distribution and phospholipase activity. FEMS Yeast Research 2008; 8:451.
Cafarchia C, et al: Frequency, body distribution, and population size of Malassezia species in healthy dogs and in dogs with localized cutaneous lesions. Journal of Veterinary Diagnostic Investigation 2005; 17:316.
Chen TA, et al: Identification of major allergens of Malassezia pachydermatis in dogs with atopic dermatitis and Malassezia overgrowth. Veterinary Dermatology 2002; 13:141.
Chen TA, Hill PB: The biology of Malassezia organisms and their ability to induce immune response and skin disease. Veterinary Dermatology 2005; 16:4.
Colombo S, et al: Prevalence of Malassezia spp. yeasts in feline nail folds: a cytological and mycological study. Veterinary Dermatology 2007; 18:278.
Farver K, et al: Humoral measurement of type-1 hypersensitivity reactions to a commercial Malassezia allergen. Veterinary Dermatology 2005; 16:261.
Guillot J, et al: Comparative efficacies of oral ketoconazole and terbinafine for reducing Malassezia population sizes on the skin of basset hounds. Veterinary Dermatology 2003; 14:153.
Habibah A, et al: Canine serum immunoreactivity to Malassezia pachydermatis in vitro is influenced by the phase of yeast growth. Veterinary Dermatology 2005; 16:147.
Kumar A, et al: Treatment of dermatitis in dogs associated with Malassezia pachydermatis. Indian Veterinary Journal 2002; 79:730.
Matousek JL, et al: Evaluation of the effect of pH on in vitro growth of Malassezia pachydermatis. Canadian Journal of Veterinary Research 2003; 67:56.
Mauldin EA, et al: Retrospective study: the presence of Malassezia in feline skin biopsies. A clinicopathological study. Veterinary Dermatology 2002; 13:7.
Morris DO, et al: Response to Malassezia pachydermatis by peripheral blood mononuclear cells from clinically normal and atopic dogs. American Journal of Veterinary Research 2002; 63:358.
Morris DO, et al: Malassezia pachydermatis carriage in dog owners. Emerging Infectious Diseases 2005; 11:83.
Nagata M: Cutaneous reactivity to Malassezia pachydermatis in dogs with seborrheic dermatitis. Japanese Journal of Veterinary Dermatology 2003; 9:67.
Nardoni S, et al: Occurrence, distribution, and population size of Malassezia pachydermatis on skin and mucosae of atopic dogs. Veterinary Microbiology 2007; 122:172.
Negre A, et al: Evidence-based veterinary dermatology: a systematic review of interventions for Malassezia dermatitis in dogs. Veterinary Dermatology 2009; 20:1.
Nuttall TJ, Halliwell REW: Serum antibodies to Malassezia yeasts in canine atopic dermatitis. Veterinary Dermatology 2001; 12:327.
Omodo-Eluk AJ, et al: Comparison of two sampling techniques for the detection of Malassezia pachydermatis on the skin of dogs with chronic dermatitis. Veterinary Journal 2003; 165:119.
Ordeix L, et al: Malassezia spp. overgrowth in allergic cats. Veterinary Dermatology 2007; 18:316.
Perrins N, et al: Carriage of Malassezia spp. yeasts in cats with diabetes mellitus, hyperthyroidism, and neoplasia. Medical Mycology 2007; 45:541.
Pinchbeck LR, et al: Comparison of pulse administration versus once daily administration of itraconazole for treatment of Malassezia pachydermatis dermatitis and otitis of dogs. Journal of the American Veterinary Medical Association 2002; 220:1807.
Rosales MS, et al: Comparison of the clinical efficacy of oral terbinafine and ketoconazole combined with cephalexin in the treatment of Malassezia dermatitis in dogs – a pilot study. Veterinary Dermatology 2005; 16:171.
Scott DW, et al: Muller & Kirk's Small Animal Dermatology, 6th ed.. Saunders Elsevier, St. Louis, 2001; p 363.
Morris DO, DeBoer DJ. Evaluation of serum obtained from atopic dogs with dermatitis attributable to Malassezia pachydermatis for passive transfer of immediate hypersensitivity to that organism. American Journal of Veterinary Research 2003; 64:262.