Edwardsiellosis in Fish

Abstract

Edwardsiellosis in fish caused by Edwardiella tarda and E. ictaluri is reviewed. Genus Edwardsiella belongs to the Enterobacteriaceae family, and E. tarda produces both hydrogen sulfide and indole, whereas E. ictaluri does neither. E. tarda was first isolated from diseased eel in Japan, and infects freshwater fish as well as marine fish. E. ictaluri has been detected in only freshwater fish after described as a new species from diseased channel catfish in the United States. The two pathogens survive in phagocytic cells, and hosts affected with edwardsiellosis die from septicemia. There were no reports about E. ictaluri infection in Japan before E. ictaluri was isolated from diseased wild ayu in 2007. Recently, the vaccine against edwardsiellosis of Japanese flounder was officially approved in Japan.