In winter 1994, a mortality up to70% was observed in cultured silver Carp (H. molitrix) in one of the Khouzestan Province fish farms. Bacteriological studies were carried out on the samples obtained from kidney, liver, eroded tails and gills using Cytophaga medium resulted in isolation of filamenus gram negative bacteria. These bacteria were similar to Flavobacterium psychrophilus from point of chemical characteristics. Histological observations showed some necrosis in skin's layers, tissues or livers, kidneys and some sections of gill filaments. Review of present Literature indicate that there is no pervious report on natural occurence of Flavobacrerium psychrophilus infection in silver carp.
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