Introduction

Classification

Taxonomy

• Kingdom: Fungi- yeast.
• Order: Cryptococcales.
• Genus: Malassezia.

Active Forms

Clinical Effects

Epidemiology

Habitat

• Commensal on skin and in ear canal of dogs.

Lifecycle

• Yeasts multiply by budding to produce blastoconidia. Blastoconidia may be produced in a linear fashion without separating to form pseudohyphae; this occurs under conditions of reduced oxygen supply.

Transmission

• Infection is probably endogenous from host's own commensal population.

Pathological effects

• Possible pathogenic role in cases of otitis externa and inflammatory skin disease in dogs.
• Pathology may be associated with higher levels of yeast and/or disruption of the barrier function of the skin.
• Predisposing conditions: breed, hot humid weather, floppy ears, foreign bodies, seborrhea, parasites, repeated use of antibiotics may allow yeast proliferation.
• Animals predisposed to allergies such as atopic dermatitis Skin: atopy , may develop hypersensitivity to Malassezia therefore severe clinical signs may be observed even in the absence of an increased number of yeasts.

Other Host Effects

• Usually commensal - skin and mucosal sites.

Control

Control via animal

• Aeration and drainage of the ear (surgery may be necessary).
• Control of parasites and intercurrent infection.
  Repeated use of antibiotics and glucocorticoids may allow yeast proliferation.

Control via chemotherapies

• Topical antifungal treatment, eg nystatin Nystatin , natamycin Natamycin , miconazole Miconazole.
• Skin disease:
  • Miconazole-chlorhexidine shampoo.
  • Oral ketoconazole Ketoconazole (5 mg/kg BID PO with food for 21 days).
    Due to the ability of Ketoconazole to suppress cytochrome P450, special care should be used when other drugs depending on the same pathways for metabolism are given concurrently (eg cyclosporine). Dosage of these drugs should be decreased to account for the decreased metabolism.
  • Itraconazole Itraconazole (5 mg/kg SID PO for 10-21 days depending on the severity of the disease.
  • Fluconazole Fluconazole (2.5 mg/kg SID for 7-21 days, depending on the severity of disease.
• Otitis externa:
  • 1% pimaricin suspension - unlicensed in cats.
  • Thiabendazole Tiabendazole (Tresaderm in USA).
  • Miconazole suspension Miconazole.
  • Clotrimazole suspension Clotrimazole.
• The most effective OTC preparations are those containing either miconazole or clotrimazole.

Diagnosis

Further Reading

Publications

Refereed papers

• Recent references from PubMed and VetMedResource.
• Kiss G, Radványi S & Szigeti G (1997) New combination for the treatment of canine otitis externa I. Microbiology of otitis externa. JSAP 38 (2), 51-56 PubMed.
• Bond R & Lloyd D H (1996) Comparison of media and conditions of incubation for the quantitative culture of Malassezia pachydermatis from canine skin. Res Vet Sci 61 (3), 273-274 PubMed.
• Bond R, Ferguson E A, Curtis C F et al (1996) Factors associated with elevated cutaneous Malassezia pachydermatis populations in dogs with pruritic skin disease. JSAP 37 (3), 103-107 PubMed.
• Akerstedt J & Vollset I (1995) Malassezia pachydermatis with special reference to canine skin disease. Br Vet J 152 (3), 269-281 PubMed.