Evaluation of Pathogenicity of Edwardsiella ictaluri to Riverine Fish Species Using an Immersion Infection Method

Experimental infection trials of six riverine fish species with Edwardsiella ictaluri were performed using an immersion method at three water temperatures, 20°C, 25°C, and 30°C. ​At 20°C, mortalities were recorded only in ayu Plecoglossus altivelis and amur catfish Silurus asotus. ​Whereas, at 25°C or 30°C, mortality events occurred in other species including Japanese dace Tribilodon hakonensis, gibachi Tachysurus tokiensis, and Japanese eel Anguilla japonica, except for common carp Cyprinus carpio, and high (≥80%) cumulative mortalities were recorded in ayu, amur catfish, and gibachi. ​These results suggest that many riverine fishes are at risk of E. ictaluri infection during periods of high water temperature.