Exophiala angulospora Causes Systemic Mycosis in Atlantic Halibut: a Case Report

Abstract

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 fishes. 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 seven fish were affected by a combination of an ascending trans-ductual 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 E. angulospora as the causal agent of systemic mycosis in Atlantic Halibut.

Exophiala angulospora infection in hatchery‐reared lumpfish (Cyclopterus lumpus) broodstock

“…Identification has involved examination of growth, the temperature requirements and dimensions of conidia, together with DNA sequencing techniques (Řehulka et al, ). E. angulospora has been identified previously in lumpfish (Řehulka et al, ), and also in several other marine finfish such as cod Gadus morhua (Gjessing et al, ), halibut H. hippoglossus (Overy et al, ) and the Japanese flounder Paralichthys olivaceus (Kanchan, Muraosa, & Hatai, ). Another species of Exophiala, E. psychrophila , has also been diagnosed in lumpfish (Scholz et al, ).…”

Fungal communities in Scandinavian lakes along a longitudinal gradient

“…One OTU was assigned to the black yeasts genus Exophiala (Chaetothyriales), which includes ubiquitous, opportunistic pathogens causing both superficial and systemic mycoses in marine and freshwater fish (e.g. halibut, salmon, cod), although it can also be isolated from substrates such as soil, sediments, decaying wood and plant material (Gjessing et al, 2011;Overy et al, 2015). Similarly, other known yeast-like pathogens recovered in this study closely related to terrestrial fungi and associated with disease in aquatic environment include Trichosporon, Taphrina, Ustilago and Exophiala (Higgins, 2000;Richards et al, 2012).…”

A Novel Exophiala Species Associated With Disseminated Granulomatous Inflammation in a Captive Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis)

“…No observed changes in the hellbender's environment or health justified the change in the masses. Detailed reports of lesions from Exophiala infections are rare and include systemic mycosis with E. angulospora in an Atlantic halibut (Hippoglossus hippoglossus), and disseminated mycosis in a colony of Ornate-horned frogs (Ceratophrys ornata) with cutaneous and visceral lesions Diagnostic techniques used in cases of phaeohyphomycoses include impression smear cytologic exam, histologic exam, culture, molecular identification, and phylogenetic analysis (23,28,29). In the present case, the fungus was identified histologically followed by molecular screening.…”

“…Infections may occur secondary to traumatic percutaneous inoculation (23,27,28). Immunosuppression may be a factor in producing infection, but phaeohyphomycosis has been reported in immunocompetent animals (7,(27)(28)(29).…”