On Unknown Disease of Pond-Cultured Ayu Characterized by the Swollen Kidney

Abstract

Recently a disease which is characterized by swelling of the kidney has been observed among pond-cultured ayu, Plecoglossus altivelis in Tokushima Prefecture. Yeasts were frequently isolated from the kidney of diseased fish. These yeasts were identified as Candida tropicalis and C. sake.
The swollen lesion of the kidney was histopathologically showing necrosis of renal tubules, edematous dissociation of hematopoietic tissue and dilatation of sinusoids.
Histopathological observation could not find the relationship between swelling of the kidney and these yeasts. Thus, occurrence of yeasts in the kidney is very likely to be the result of secondary invasion.
We could not make clear the cause of this unknown disease.