Diagnosis and long-term management of blastomycosis in two ferrets (Mustela putorius furo)

Background: Blastomycosis is an uncommon fungal infection endemic to certain parts of Eastern North America. Blastomycosis has been reported twice before in ferrets, but both cases died shortly after diagnosis. Case description: Two male neutered ferrets (Mustela putorius faro) from the same household, 4 and 11/2-years of age, presented for respiratory signs. The diagnostic work-up included thoracic radiographs and ultrasound, advanced imaging, and cytology of a pulmonary mass, which led to a diagnosis of pulmonary blastomycosis in both cases. Both ferrets developed central nervous system (CNS) clinical signs. Ferret 1 developed signs referable to CNS lesions 3 months after initial presentation, and the second ferret 27 months after initial presentation. The magnetic resonance imaging study and cerebrospinal fluid analysis were performed on the first case. Both ferrets were treated with combinations of antifungal therapy and short-term prednisolone with a total follow-up period of 35 and 31 months, respectively. Both cases responded favorably to antifungal therapy and supportive care. Response to therapy and the dynamics of infection were monitored with serial urinary Blastomyces antigen assays, thoracic radiographs, and routine blood work. The first ferret was euthanized 3 years after diagnosis due to an abdominal neoplasia. An exocrine pancreatic carcinoma, a cervical chordoma, and pulmonary blastomycosis were diagnosed on histopathology. Conclusions and case relevance: This report constitutes the first to document CNS blastomycosis in ferrets, long-term medical management of both pulmonary and suspected CNS blastomycosis in ferrets, and the use of serial urinary Blastomyces antigen assays to monitor disease progression in this species.