Clinical and histopathological changes in rainbow trout Oncorhynchus mykiss experimentally infected with fungus Bradymyces oncorhynchi

Bradymyces oncorhynchi is a poorly known melanised fungal species that has been isolated only from a hyperaemic focus near the enlarged spleen of a rainbow trout. Although the pathogenicity of this species to fish is suspected, it has not been fully confirmed. Four laboratory experiments were conduc...

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Bibliographic Details
Published in:Folia microbiologica 2020-12, Vol.65 (6), p.1025-1032
Main Authors: Řehulka, J., Kolařík, M., Hubka, V.
Format: Article
Language:English
Subjects:
Abdominal wall
Anorexia
Appetite loss
Applied Microbiology
Ascites
Atrophy
Biomedical and Life Sciences
Eating disorders
Environmental Engineering/Biotechnology
Epithelium
Fish
Fungi
Gills
Granulomatous hepatitis
Hemorrhage
Hepatitis
Hepatocytes
Hyphae
Immunology
Inoculum
Lesions
Lethargy
Life Sciences
Microbiology
Muscles
Mycelia
Oncorhynchus mykiss
Original Article
Pathogenicity
Pathogens
Phaeohyphomycosis
Salmon
Spleen
Statistical analysis
Survival
Trout
Weight reduction
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Summary:Bradymyces oncorhynchi is a poorly known melanised fungal species that has been isolated only from a hyperaemic focus near the enlarged spleen of a rainbow trout. Although the pathogenicity of this species to fish is suspected, it has not been fully confirmed. Four laboratory experiments were conducted to test the effect of the fungus on the health of rainbow trout fingerlings. Mycelia were cultivated under different conditions to increase inoculum variability and to test the impact of the conditions on the pathogenicity. The inoculum was subsequently administered by the intraperitoneal route. The clinical manifestations, gross pathological lesions and histopathological changes were identical in all experimental groups, i.e. lethargy, inappetence, anorexia, weight reduction, pale gills, full-thickness ulceration of the abdominal wall, muscle atrophy, haemorrhagic or pale liver, fat-altered pyloric region with haemorrhages, enlarged spleen, haemorrhagic ascites, systemic granulomatous lesions with the presence of melanised hyphae (phaeohyphomycosis), multifocal granulomatous hepatitis, perivascular lymphocytic infiltration, vacuolation of hepatocytes and vacuolation of the kidney tubule epithelium. No statistically significant differences were found in the survival of the fish with respect to experimental settings. The survival period ranged between 3 and 135 days.
ISSN:0015-5632
1874-9356
DOI:10.1007/s12223-020-00813-5