Exophiala angulospora causes systemic mycosis in Atlantic halibut (Hippoglossus hippoglossus): A case report

Filamentous black yeasts from the genus Exophiala are ubiquitous, opportunistic pathogens causing both superficial and systemic mycoses in warm- and cold-blooded animals. Infections by black yeasts have been reported relatively frequently in a variety of captive and farmed freshwater and marine fish. In November 2012, moribund and recently dead farm raised Atlantic halibut (Hippoglossus hippoglossus ) were necropsied to determine the cause of death. Histopathology revealed that three of five fish were affected by a combination of an ascending trans-ureter granulomatous mycotic nephritis, necrotizing histiocytic encephalitis, and in one fish the addition of a fibrogranulomatous submucosal branchitis. Microbial cultures of kidney using selective mycotic media revealed pure growth of a black pigmenting septated agent. Application of molecular and phenotypic taxonomy methodologies determined that all three isolates were genetically consistent with Exophiala angulospora. This is the first report of Exophiala angulospora as the causal agent of systemic mycosis in Atlantic halibut.