Abstract
Blastomycosis occurs most commonly in humans, dogs, and cats, but cases have also been reported in a variety of non-domestic species, including pinnipeds1,4,8, exotic felids7, and ursids2,3,5. Pathology typically includes thoracic disease with occasional spread to other viscera, the central nervous system, bone, eyes, and skin. Three previous cases of blastomycosis have been reported in Ursidae including one case in a free-ranging American black bear (Ursus americanus)3 and two in zoo-housed polar bears (Ursus maritimus)2.
A 2.5-year-old female polar bear presented with a mild left rear leg lameness that progressed to a localized draining abscess. Histopathology of granulomas collected at surgical debridement demonstrated a necrotizing pyogranulomatous lymphadenitis with intralesional fungal yeast morphologically consistent with Blastomyces dermatitidis. Additional diagnostics demonstrated a marked leukocytosis and fungal pneumonia. Four days after initiation of treatment with itraconazole, the bear became profoundly weak, anorexic, dyspneic, and unwilling to move. In humans, acute respiratory distress syndrome (ARDS) can be a complication during treatment of blastomycosis, especially in immunocompromised patients. Corticosteroids have been shown to reduce mortality in human blastomycosis patients suffering from ARDS.6 Addition of corticosteroids to the treatment regimen resulted in marked improvement in the bear. This particular bear was likely immunologically naïve, as it was wild born and recovered after being abandoned by its dam in northern Alaska.
Results of this case report show the importance of considering blastomycosis as a possible etiology in musculoskeletal disease in polar bears, the benefits of anti-inflammatory doses of corticosteroids as an adjunct to treatment, and the application of antigen detection testing to monitor disease status and assist with determining treatment length.
Acknowledgments
The authors thank Drs. Aric Applewhite, Forrest Cummings, Scott Rizzo, Al Legendre, Karen Campbell, Erica Tolar, and Ed Ramsay for their consultations and the staff of the Louisville Zoo for their skills in animal care.
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