Abstract

Studies were conducted to determine the potential pathogenicity of Edwardsiella ictaluri to economically important nonictalurid fishes in California, USA. White sturgeon Acipenser transmontanus , striped bass Morone saxatilis , and chinook salmon Oncorhynchus tshawytscha were immersion-challenged in parallel with channel catfish Ictalurus punctatus . During a 14 d period, chinook salmon and channel catfish succumber to infections with E. ictaluri but the other species did not. An immersion exposure to 4.0 and 7.9 x 10 super(8) cfu/ml of E. ictaluri) for 30 s resulted in a 92 and 48% mortality among chinook salmon and rainbow trout O. mykiss , respectively. A Gram-negative septicemia occurred in infected fishes, and pure cultures of E. ictaluri were recovered from dead and surviving fish. There was a moderate to severe necrosis of the liver and kidney in both salmonids and channel catfish. Intracellular bacteria occurred within mononuclear inflammatory cells and hepatocytes. Results suggest that E. ictaluri is a potential pathogen of salmonid fishes.