Malassezia species are common inhabitants of the normal skin and oral mucosa of many species including dogs, cats, and birds. Currently, there are at least 11 species of Malassezia yeast; however, with the exception of the ear canal, little is known about the prevalence of yeast on the skin of healthy cats. In this study, cytologic sampling of the front and rear nail folds of 46 cats without a history of skin disease revealed yeast in 61%. Of these, 21 had brown-black debris in the nail fold. When breed distribution was stratified, yeast were found in 100% of all Devon rex cats sampled (mean 8 cells per high-power field, range 5 to 10) and in only 46% of domestic shorthair and Persian cats. When nail fold debris was cultured, Malassezia species were isolated in 11 of 21 cats. The most commonly isolated were M pachydermatis, M furfur, and M sympodialis. Yeast organisms were most commonly isolated from cats with brown nail bed debris. M furfur and M sympodialis were isolated exclusively from cats with brown nail bed debris. 

COMMENTARY: The major clinical question with respect to yeast in the nail fold is "when is treatment needed?" Cats are usually fastidious groomers and nail bed debris is uncommon, except possibly in breeds with unusual hair coats (eg, Devon rex, sphinx). In this author's experience, if the cat is not bothered by the debris then "watchful neglect" may be the best course of action. Devon rex cats are predisposed to seborrheic debris and nail bed debris, and yeast are "normal" findings. Routine bathing of the paws may be helpful in controlling such debris. The author has found that gently scrubbing the nail bed while wearing loofah gloves is an easy and atraumatic way to control and remove the debris. If the cat is traumatizing the paws and/or the area is inflamed, then medical treatment is needed. In these cases, oral itraconazole and topical shampoo therapy is effective. However, inflammation usually has an underlying cause, such as atopy or food allergy. Finally, the development of brown-black nail bed debris is common in cats that are not grooming due to illness, particularly diabetes mellitus and hyperthyroidism.

Prevalence of Malassezia spp. yeasts in feline nail folds: A cytological and mycological study. Colombo S, Nardonia S, Cornegliani L, Mancianti F. Vet Dermatol 18:278-282, 2007.