Retrospective study of phaeohyphomycosis in aquarium‐housed fish, with first descriptions of Exophiala lecanii‐corni and Neodevriesia cladophorae in fish

Abstract

A broadening fish host range is affected by novel and known pigmented fungal pathogens. A review of 2,250 piscine submissions received by the Aquatic Pathology Service, University of Georgia, revealed 47 phaeohyphomycosis cases (2.1%), representing 34 bony and cartilaginous fish species. The majority involved bony fish (45/47, 95.7%) and were predominantly marine (41/47, 87.2%), with only a few freshwater species (4/47, 8.5%). Cartilaginous fish cases included two zebra sharks ( Stegostoma fasciatum ) (2/47, 4.3%). Northern seahorses ( Hippocampus erectus ) had the highest incidence overall (7/47, 14.9%). Culture and sequencing of the internal‐transcribed spacer region of the rDNA (ITS), large ribosomal subunit gene D1/D2 domains ( LSU ) and the DNA polymerase II gene ( RPB2 ) were performed for fungal identification when fresh tissue was obtainable. Exophiala, Ochroconis and Neodevriesia spp. were identified, with Exophiala as the most common fungal genus (8/11, 72.7%). Exophiala lecanii‐corni and Neodevriesia cladophorae were described for the first time from fish. Microscopically, lesions were characterized by necrosis, granulomatous inflammation and angioinvasion most frequently affecting the skin/fin, skeletal muscle and kidneys. In this study of diverse aquarium‐housed fish species, phaeohyphomycosis cases occurred sporadically and in rare outbreaks with variable pathologic presentations, tissue distributions and severities.

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