ABSTRACT
Most of the bacteria presently recognized were not isolated from wild populations, but were from fish used in artificial propagation. Fish maintained in this manner are frequently crowded and under conditions that impose additional stress. Conditions of propagation also provide an opportunity to observe animals for specific alterations resulting from disease and for potential mortality. Transmission by water-borne infection from wild populations to cultured fish also occurs. The genus Edwardsiella is comprised of three species, two of which are pathogens of fish. Fish infected withE. tarda sometimes become lethargic and orient vertically at the surface of the water or swim erratically in a spiral pattern. External signs in channel catfish may begin as small cutaneous lesions and progress to deep abscesses of the body musculature in the postero-lateral region. Control of disease caused by species of Edwardsiella is by therapeutic administration of antimicrobials.
