A 5-year-old intact male silky bantam chicken (Gallus gallus) was presented with a history of chronic epidermal cysts within the comb. Results of diagnostic tests and histopathologic examination of biopsy specimens revealed epidermal cysts associated with Aspergillus fumigatus and an Alternaria sp. Physical removal and treatment with systemic itraconazole (Sporonox®, Janssen Pharmaceutica, Beerse Belgium) and miconazole nitrate (Micazole lotion, 1% Burns Veterinary Supply, Inc., Rockville Centre, New York, NY 11570 USA) resolved the lesions.
Epidermal cysts are generally benign lesions observed within the dermis or subcutis. They are lined with stratified squamous epithelium and filled with keratin.4 In avian species, epidermal cysts have been observed in budgerigars.4 Fungal infections of the integument are uncommonly reported problems in avian species, although Candida albicans, Rhodotorula, Microsporum gallinae, Aspergillus and Mucor spp. have been observed.1,3,9 Aspergillus and Alternaria spp. are commonly encountered pathogens of the respiratory system in birds.2,6,7
A 5-year-old male silky bantam chicken was presented with a 1-month history of having numerous firm, yellow, keratinized masses measuring 4–15 mm in diameter involving the tissues of the comb. The bird was housed with two conspecific chickens in an outdoor farmyard exhibit with indoor access to a 3 m × 4 m chicken coop bedded with straw. Commercial poultry feed and fresh water was provided on a daily basis.
A blood sample obtained for a complete blood count (CBC) and select serum chemistries revealed elevations in aspartate aminotransferase (AST) and creatinine phosphokinase (CPK) values. Fecal direct, flotations and Gram’s stain evaluations were within normal limits.
The bird was anesthetized with isoflurane (Iso-thesia, Vetus Animal Health, Abbott Laboratories, North Chicago, IL 60064 USA) and multiple full-thickness biopsies were obtained and placed in either 10% neutral buffered formalin or sterile saline. The biopsy sites were closed with simple interrupted absorbable sutures, and supplemental SC fluids were administered. The bird recovered uneventfully.
Histopathologic examination of formalin-fixed tissues revealed epidermal cysts characterized by orthokeratotic hyperkeratosis. In some sections the hyperkeratotic stratum corneum contained branching fungal mycelia. Aerobic bacterial cultures revealed heavy growth of Aspergillus fumigatus and an Alternaria sp. on Sabouraud dextrose agar (REMEL, Inc., Lenexa, KS 66215 USA). Anaerobic bacterial cultures revealed no growth.
Treatment was initiated with 10 mg/kg itraconazole (Sporonox, Janssen Pharmaceuticals, Beerse, Belgium) PO BID and a topical 1% miconazole nitrate solution (Micazole lotion, Burns Veterinary Supply, Rockville Centre, New York, NY 11570 USA) applied BID. Serum itraconazole levels were analyzed at day 30 and day 35 of treatment. Samples obtained 5 hours after the morning dose demonstrated serum itraconazole levels of 1.4 µg/ml; serum sample levels of itraconazole obtained 9 hours after the morning dose were 0.7 µg/ml (Fungus Testing Laboratory, University of Texas Health Science Center, Department of Pathology, San Antonio, TX 78284-7750 USA). Noticeable improvement was noted as treatment progressed.
After day 45 of treatment the bird was anesthetized as before and several full thickness wedge biopsies were obtained and prepared as before. Results of histopathologic examination revealed no evidence of fungal mycelia or hyperplastic epidermis. Aerobic bacterial cultures were negative for fungal organisms. A CBC and select serum chemistries at that time revealed no abnormalities.
Elevated CPK values can be associated with tissue necrosis and would be compatible with damage to the comb caused by toxins associated with Aspergillus and Alternaria.2 Alternaria spp. are ubiquitous in nature, common in corn and agricultural commodities. In poultry this organism is known to cause hemorrhage and death from tenuazonic acid.5
It is possible that the unique recesses of the rose type comb provided a warm, moist environment that predisposed to growth of Aspergillus and Alternaria organisms. As opposed to most birds, silky chickens sleep with their head resting close to the ground, rather than tucked over their backs. Prolonged contact with contaminated bedding probably predisposed this chicken to infection. Toxins produced by each of these mycotic organisms may have caused irritation and subsequent development of epidermal cysts. Minimum inhibitory concentrations (MIC) values for itraconazole against Aspergillus fumigatus have been reported to range from 0.01–1.0 µg/ml.10 MIC values for Alternaria spp. were not found in the literature. Miconazole is a commonly utilized azole class of antifungal drug. It has a broad spectrum of activity and is most commonly utilized as a topical agent.8
The combination of physical removal, systemic itraconazole, and topical miconazole resolved this case. To date, 11 months after treatment, the bird remains clinically normal.
The authors would like to thank Ms. Lani Stark, RVT, and Ms. Jennifer Pollard, RVT, for their care of the chicken.
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