The effect of heat and low pH on selected viral and bacterial fish pathogens

Abstract

The thermal and pH resistance of five representative salmonid fish pathogens were tested to examine the efficacy of procedures currently used for processing fish viscera to be incorporated into fish diets. Aeromonas salmonicida, Mycobacterium chelonei, Renibacterium salmoninarum, infectious hematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV) were suspended in buffered medium at pH 7.0 or 4.0, or in fish silage at pH 4.0 and their survival at selected temperatures was determined. When suspended in medium at pH 7.0, A. salmonicida, M. chelonei and IHNV were sensitive to temperatures in a range of 40–60°C. Renibacterium salmoninarum and IPNV were both more resistant to that temperature range in the neutral pH medium; however, each was inactivated by conditions simulating pasteurization. The combination of heat and low pH currently used for the processing and pasteurization of fish viscera should ensure that the resulting fish food is safe against spreading infectious diseases.