Yeast-associated skin disease in captive king penguins (Aptenodytes patagonicus) caused by an undescribed Malassezia species in a Swiss zoological garden

Malassezia spp. are lipophilic yeasts that form part of the normal skin flora in many warm-blooded vertebrates but can act as opportunistic pathogens under certain conditions. While commonly implicated in dermatoses in domestic animals, Malassezia-associated skin infections in birds, especially aquatic species, are rarely reported. In avian species, diagnostic criteria and treatment protocols are poorly defined, with most knowledge extrapolated from mammals or limited to isolated case reports. Further documentation is needed to better understand host susceptibility, clinical presentation, and management strategies in exotic birds. Three out of 24 king penguins (Aptenodytes patagonicus) housed at Zoo Basel developed bilateral, greasy, light brown deposits on feather tracts at the dorsal and ventral axillary base of the wings and periocular regions. The lesions were non-pruritic and caused no apparent discomfort. Co-housed gentoo penguins (Pygoscelis papua) under identical conditions remained unaffected. Histopathology of affected feathers revealed numerous PAS-positive, budding yeast-like organisms measuring 2–3 μm in diameter, consistent with Malassezia. Fungal culture and molecular analyses identified a previously undescribed Malassezia species, closely related to M. slooffiae and M. gallinae. A high load of Staphylococcus kloosii was also isolated but considered a secondary colonizer. Topical therapy with 0.1% chlorhexidine and 1% terbinafine spray led to clinical improvement in two affected adult penguins. In the third affected penguin, a subadult, oral terbinafine (Terbinafin-Mepha® 250 mg tablets, Mepha-Pharma AG, 16.6 mg/kg SID for 28 days, via medicated feed fish) was initiated due to persistent lesions, poor response to topical therapy, and stress-related intolerance to repeated handling, which also led to anorexia in parts of the colony. However, no clinical improvement was observed. Subsequent treatment with oral itraconazole (Sporanox® 100 mg capsules, Jannsen-Cilag AG; 13.3 mg/kg SID for 28 days, via medicated feed fish) resulted in rapid and complete resolution of clinical lesions in this animal. This publication expands the host range and clinical spectrum of Malassezia skin infections with associated disease to include king penguins. The species-specific occurrence, lesion distribution, and variable therapeutical response highlight the importance of recognizing fungal integumental infections in exotic avian species. It also underscores diagnostic challenges and management considerations, including stress-induced immunosuppression and the need for species-appropriate therapeutic protocols in zoological settings.