THE EFFECT OF HEAT AND LOW PH ON SELECTED VIRAL AND BACTERIAL FISH PATHOGENS

The thermal and pH resistance of five representative salmonid fish pat hogens were tested to examine the efficacy of procedures currently use d for processing fish viscera to be incorporated into fish diets. Aero monas salmonicida, Mycobacterium chelonei, Renibacterium salmoninarum, infectious hematopoietic necrosis virus (IHNV) and infectious pancrea tic 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 tem peratures was determined. When suspended in medium at pH 7.0, A. salmo nicida, M. chelonei and IHNV were sensitive to temperatures in a range of 40-60-degrees-C. Renibacterium salmoninarum and IPNV were both mor e resistant to that temperature range in the neutral pH medium; howeve r, each was inactivated by conditions simulating pasteurization. The c ombination of heat and low pH currently used for the processing and pa steurization of fish viscera should ensure that the resulting fish foo d is safe against spreading infectious diseases.