28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Prevalence of Vibrio harveyi In Cultured Juvenile Summer Flounder (Paralicthys dentatus) Marta Gomez-Chiarri1, Roxanna M. Smolowitz2, Kevin Uhlinger2, Eric Gauger1   1University of Rhode Island, Department of Fisheries, Animal, and Veterinary Sciences 20A Woodward Hall, Kingston, RI 02881; 2Marine Resources Center, Marine Biological Laboratory, 7 MBL St., Woods Hole, MA 02534 Vibrio harveyi is an important marine pathogen that infects numerous marine species including summer flounder (Paralicthys dentatus).  In 1998, an epizootic of V. harveyi at a Rhode Island grow-out facility caused heavy mortalities and permanent intestinal deformities. The disease was named Flounder Infectious Necrotizing Enteritis (FINE).  We are currently conducting a monitoring program at a flounder hatchery to evaluate the potential threat that V. harveyi poses to the expansion of the summer flounder aquaculture industry.  This program consists of regularly sampling and examining fish, live-feed, and tank water at various stages of culture.  Bacterial populations were monitored by culture on several selective and non-selective media. Culturable bacteria were identified to the species level by biochemical analysis (API20E) and rDNA sequencing.  Additionally, gross and histological examinations were conducted at each sampling period to monitor signs of disease.  At 12 and 27 days post hatch (dph), which coincided with feeding on rotifers and artemia respectively, bacterial diversity was relatively high. Vibrio harveyi was detected as a minor component of the bacterial population in fish samples at these stages.  Gross and histological examinations at these collections showed no major abnormalities. A decrease in bacterial diversity and a dramatic increase in the abundance of V. harveyi characterized collections at 50 and 100 dph, when fish were fully weaned onto a commercial pellet diet. Mortalities remained low through these sampling periods indicating that even high levels of V. harveyi do not necessarily result in major fish losses.  Histological examination at the third collection revealed no major problems, however, at the fourth collection some fish showed inflammation in the submucosa of the colon/cloaca.  Histological analysis at 155 dph found several fish with mild to moderate enteritis and mild to severe peritonitis.  An outbreak of FINE with approximately 35% cumulative mortality occurred when fish (155dph) were transported to the University of Rhode Island. A number of survivors also had blind-sac-guts, a unique clinical sign observed in the first V. harveyi epizootic at the Rhode Island grow-out facility. This survey shows that V. harveyi is a major pathogen of juvenile summer flounder.  Recommendations for management of the disease will be discussed. Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page