Malasezzia spp yeast can result in feline paronychia, seborrhoeic dermatitis in the Sphinx, generalized dermatitis and paronychia in the Devon rex and otitis externa in most breeds of cats. It is also seen associated with idiopathic facial dermatitis in Persian and Himalayan breeds.
Species of Malassezia which are pathogenic to cats include:
- Malassezia pachydermatis
- Malassezia obtusa
- Malassezia nana
- Malassezia globosa
- Malassezia slooffiae
- Malassezia sympodialis
- Malassezia furfur
- Malassezia restricta
Interestingly, M. nana appears to be more frequently isolated from the ear canal, whereas M. slooffiae more often isolated from the claw of cats.
In most cases Malassezia spp infection is a secondary problem. It can occur in conjunction with allergies, immune mediated disease, chronic bacterial infections, long-term antibiotic use and seborrhea. It may also occur as a primary infection such as the sphinx. It also has been reported in cats treated for Pseudomonas spp infection, probably because treatment for that condition requires long term antibiotic use with broad spectrum antibiotics.
Overgrooming may be the only symptom in some cats which present with generalised Malassezia, and these cats have characteristic obsessive facial, auricular and foreleg licking, sometimes to the point of excoriations.
Malassezia species are frequently isolated from younger cats (1 to 4 years of age), suggesting that feline otitis externa may be associated with lipid-dependent Malassezia species in addition to the non lipid-dependent species M. pachydermatis (Khosravi et al, 2009).
Sphinx often have a greasy exudate, which to a varying degree accumulates on the surface as a thin sticky, dark brown or reddish brown layer. Accumulation of greasy material may be particularly noticeable around the claws and in the palmar and/or plantar interdigital web. Within the breed there are many individuals with a varying degree of dark brown, greasy exudate around their claws, and at other sites, including axillae, groin and sometimes ears.
Sphinx cats carry significantly higher numbers of Malassezia spp yeast than other breeds of cats, excepting the Devon rex. No correlation between Malassezia spp infection and diet, housing conditions and genetics of individual Sphinx lines has as yet been reported. Many Sphinx owners bathe their cats regularly, often every 7-14 days, to remove the excessive greasiness from the body, claws and ears. For many Sphinx cats, greasiness becomes increasingly obvious the longer it has been since their bath.
It can take extensive diagnostic work to correctly identify the underlying cause of yeast infections when they are recurrent. Tests for immune system disorders like feline leukemia (FeLV) or feline immunodeficiency virus (FIV), hormonal disease, allergies, bacterial infections, parasites (ear mites, Demodectic mange, etc.) and careful review of medication histories may be necessary to establish the diagnosis of the primary problem, as retroviral infections do make cats more prone to Malasezzia infection.
Definitive diagnosis requires laboratory isolation and speciation of the Malassezia species, often requiring PCR assays.
Topical therapy is arguably more efficacious, considering this yeast is relatively innocuous and long-term treatment with azoles may not be without side-effects. In nonfractious cats, twice weekly bathes in Malaseb or similar antifungal washes for 4 - 6 weeks will eventually clear the skin of this commensal parasite.
If generalised overgrooming is present, indicative of secondary bacterial infection, a broad-spectrum antimicrobial course may be indicated. Cefovecin is a popular and effective therapy in such situations as it avoids long-term oral medication, especially in fractious cats. Corticosteroids are contraindicated, as many cats are immunosuppressed, or in purebred cats, have defective dermal immunity.
Azole-based medications may be required if cases do not respond to medicated shampoos. Itraconazole and ketoconazole appear to be satisfactory treatments, but resistance of Malassezia to azoles is emerging as a significant impediment to successful eradication.
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