Abstract

On March 2, 2007, an adult male beluga whale presented with a fluctuant bulla on the dorsal aspect of the melon, approximately 16 cm cranial to the blowhole. The lesion had a one cm umbilicated center that by March 8, had increased markedly in size, eventually ulcerating to reveal a large cavity bordered deeply by exposed dermis. Necrotic epithelium was debrided back to viable margins and submitted for culture and histopathological evaluation. Microscopic examination revealed multifocal coagulative necrosis, with the formation of small intraepithelial vesicles containing necrotic cellular debris and rare degenerate neutrophils. Necrotic foci and adjacent epithelia were infiltrated by fungal hyphae with thin non-parallel walls exhibiting infrequent septation and branching. Hyphae were evident with hematoxylin and eosin, but were better visualized with silver stains. Acid-fast stains were negative. The fungus, identified as Fusarium solani, grew readily in culture. At the time of diagnosis, the animal was being treated orally (PO) with minocycline (2 mg/kg BID) and itraconazole (1.5 mg/kg BID) for previously diagnosed Mycobacterium marinum and Candida guilliermondii infections in other organ systems. As part of the mycobacteriosis treatment, clarithromycin (5 mg/kg BID PO) was also started on March 14. Prior to obtaining sensitivity results, itraconazole was discontinued and posaconazole (2 mg/kg BID PO) started based on literature and personal communications indicating greater efficacy again F. solani from the latter. However, the lesion continued to expand and the treatment regimen was changed to voriconazole (1.7 mg/kg BID PO 14 days, then 1.7 mg/kg once weekly) after sensitivity results became available April 6. Throughout the course of systemic therapy, the lesion was cleaned and debrided daily followed by application of the antimicrobial potentiator, Tricide. By April 24, tissue sloughing ceased and an area of central healing was noted. The lesion resolved completely by July 2007.