Malassezia spp

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Greasy exudate in palmar interdigital web in a seborrhoeic Sphinx cat
Greasy exudate and paronychia around the claws in a seborrhoeic Sphinx cat
Paronychia in a 5-month-old Devon rex with chronic paronychia and otitis externa due to generalised Malassezia spp infection. Photo courtesy of Dr Jim Euclid

Malassezia spp are a commensal yeast of skin and mucosa and result in generalized as well as local skin disease in all breeds of cats worldwide[1].

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[2]. It is also seen associated with idiopathic facial dermatitis in Persian and Himalayan breeds[3].

Species of Malassezia which are pathogenic to cats include:

  • Malassezia pachydermatis
  • Malassezia obtusa
  • Malassezia nana[4]
  • Malassezia globosa
  • Malassezia slooffiae[5]
  • 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[6].

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[7].

Clinical signs

Overgrooming may be the only symptom in some cats which present with generalised Malassezia[8], and these cats have characteristic obsessive facial, auricular and foreleg licking, sometimes to the point of excoriations.

Localised infections are more common and 95% of cats with otitis externa have Malassezia infection, either as a primary etiological agent, or secondary to other causes[9][10].

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[11][12].

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.

Diagnosis

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[13].

In Persian cats, this needs to be distinguished from hereditary greasy seborrhoea.

Definitive diagnosis requires laboratory isolation and speciation of the Malassezia species, often requiring PCR assays.

Treatment

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[14] and ketoconazole appear to be satisfactory treatments, but resistance of Malassezia to azoles is emerging as a significant impediment to successful eradication[15].

References

  1. Cafarchia C& Otranto D (2008) The pathogenesis of Malassezia yeasts. Parassitologia 50(1-2):65-67
  2. Bond R (2010) Superficial veterinary mycoses. Clin Dermatol 28(2):226-236
  3. Chung TH et al (2009) Topical tacrolimus (FK506) for the treatment of feline idiopathic facial dermatitis. Aust Vet J 87(10):417-420
  4. Castellá G et al (2011) Molecular characterization of Malassezia nana isolates from cats. Vet Microbiol 148(2-4):363-367
  5. Volk AV et al (2011) Malassezia pachydermatis and M nana predominate amongst the cutaneous mycobiota of Sphynx cats. J Feline Med Surg 12(12):917-922
  6. Bond R et al (2008) Carriage of Malassezia spp. yeasts in Cornish Rex, Devon Rex and Domestic short-haired cats: a cross-sectional survey. Vet Dermatol 19(5):299-304
  7. Khosravi AR, Shokri H, Rad MA, Jamshidi S. (2009) Occurrence of Malassezia Species in Persian and Domestic Short Hair Cats with and without Otitis Externa. J Vet Med Sci Dec 1
  8. Dr Jim Euclid (2012) pers comm
  9. Shokri H et al (2010) Occurrence of Malassezia species in Persian and domestic short hair cats with and without otitis externa. J Vet Med Sci 72(3):293-296
  10. Ahman, SE & Bergstrom, KE (2009) Cutaneous carriage of Malassezia species in healthy and seborrhoeic Sphynx cats and a comparison to carriage in Devon Rex cats. JFMS 11:970-976
  11. Ahman, S et al (2007) Carriage of Malassezia species yeast in healthy and seborrhoeic Devon Rex cats. Med Mycol 45:449-455
  12. Ahman, S et al (2007) Treatment of Malassezia pachydermatitis-associated seborrhoeic dermatitis in Devon Rex cats with Itraconazole - a pilot study. Vet Dermatol 18:171-174
  13. Reche A et al (2010) Cutaneous mycoflora and CD4:CD8 ratio of cats infected with feline immunodeficiency virus. J Feline Med Surg 12(4):355-358
  14. Bensignor E et al (2011) Treatment of Malassezia overgrowth with itraconazole in 15 cats. Vet Rec 167(26):1011-1012
  15. Nijima M et al (2011) An azole-resistant isolate of Malassezia pachydermatis. Vet Microbiol 149(1-2):288-290