SREL Reprint #0622




Histopathology of Red-sore Disease (Aeromonas hydrophila) in Naturally and Experimentally Infected Largemouth Bass Micropterus salmoides (Lacepede)

H. W. Huizinga, G. W. Esch and T. C. Hazen



The histophathology of red-sore disease, caused by the gram-negative bacterium, Aeromonas hydrophila, is described for largemouth bass, Micropterus salmoides.  Externally, lesions range from those affecting a few scales (pin-point), to those associated with extensive chronic ulcerations; there is focal hemorrhage, oedema and dermal necrosis which exposes underlying muscles producing infiltration of mononuclear and granulocytic inflammatory cells.  Internally, the liver and kidneys are foci for toxic products produced by A. hydrophila with, in the most severe cases, complete destruction of the structural integrity of both organs.  Pathological changes were not serious in either the spleen or heart, even in cases with massive damage in the liver and kidney.  Internal and external lesions were similar in both natural and experimentally induced infections.  The pathobiology of red-sore disease in bass is postulated to be linked to elevated water temperature stimulating increased metabolism, decreased body condition and stress, leading to the increased production of corticosteriods and the concomitant rise in susceptibility to infection.


SREL Reprint #0622

Huizinga, H.W., G.W. Esch, and T.C. Hazen. 1979. Histopathology of red sore disease (Aeromonas hydrophila) in naturally and experimentally infected largemouth bass Micropterus salmoides (Laceped). Journal of Fish Diseases 2:263-277.

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