Infectious necrotizing enteritis and mortality caused by Vibrio carchariaein summer flounder Paralichthys dentatus during intensive culture

An epizootic causing mortality among cultured summer flounder Paralichthys dentatus occurred in summer of 1998 at a land-based facility on Narraganset t Bay, Rhode Island, USA. The disease, flounder infectious necrotizing ente ritis (FINE), was characterized by reddening around the anal area, distende d abdomens filled with opaque serosanguineous fluid, enteritis and necrosis of the posterior intestine. In extreme cases of the disease, the posterior intestine was detached from the anus and was observed coming out the vent. The intestine of individuals that recovered from the disease ended in a bl ind-sac; the abdomens of these fish were distended, due to food and water i nside the intestinal blind-sac. A bacterium was isolated from ascites fluid and kidney of moribund flounder and identified as the causative agent in c hallenge experiments. The pathogen was identified as Vibrio carchariae by m orphological and biochemical characteristics and sequence of the 16S rRNA. The LD50 estimate was 5 x 10(5) colony-forming units injected intraperitone ally into 100 to 200 g summer flounder.