Lipoidosis, steatitis, and streptococcosis in mariculture of silver perch (Bidyanus bidyanus).

摘要

A disease outbreak with 15 percent mortality was reported in a perch farm located in the Hsinchu County, Taiwan. The moribund fish showed signs of lethargy and frequent surfacing behaviour before death. Post-mortem examination revealed petechial haemorrhages at the base of abdominal girdle. The head kidney and liver were swollen and distorted due to infiltration of transparent, whitish, irregular semi-solid material. The epicardium was thickened and rough. The microscopic lesions included deposition of variable-sized nests of adipose tissue in the head kidney and liver, necrotic adipose tissue in the kidney, and inflammation with adipocyte infiltration at the epicardium of the bulbous arteriosus. Streptococcus iniae was isolated from the moribund fish and its identity was confirmed by the biochemical properties and the nucleotide sequence of the 16S rRNA gene. Based on these findings, a disease of lipidosis, steatitis and streptococcosis was suggested. This is the first report of lipoidosis, steatitis, and streptococcosis in mariculture of silver perch in Taiwan.