TWENTY-FOURTH ANNUAL EASTERN FISH HEALTH WORKSHOP Royal Pavilion Resort, Atlantic Beach, NC MARCH 9-11, 1999 Microaerophilic Edwardsiella ictaluri Isolated From Channel Catfish Andrew J. Mitchell1 and Andrew E. Goodwin2 1Stuttgart National Aquaculture Research Center - United States Department of Agriculture, Agricultural Research Service, P. O. Box 860, 2955 Highway East 130, Stuttgart, AR 72160; 2Aquaculture and Fisheries Center, University of Arkansas at Pine Bluff, P.O. Box 4912, 1200 North University Drive, Pine Bluff, AR 71611 Several cases of channel catfish with deep necrotic lesions were processed at the Stuttgart diagnostic laboratory from 1982 through 1997. Lesions typically covered an area of several cm2, were of a depth sufficient to expose bone, and were located on the head or sides of the fish. In several cases, tissue loss was so extensive that most of the cranium was revealed. Typical lesions had well defined edges with an abrupt transition from necrotic areas to uninflamed normal tissue. Cases usually occurred in food-sized catfish from May to early July, although there were reports by the fish producers of similar lesions on catfish from late winter through spring. The die-offs, consisting of less than 10% of the fish, occurred over several weeks. Six isolates were made anaerobically from 1993 to 1997. The initial isolate only grew anaerobically on TSA agar with blood, but upon passage a limited aerobic growth was observed. In thioglycolate broth there was a typical microaerophilic growth tendency. Isolate S97-133, from May 1997, was sent to the National Veterinary Services Laboratories, Ames, Iowa and identified as Edwardsiella ictaluri. It had to be transferred aerobically for many passages before sufficient growth was obtained for identification because it grew best under anaerobic conditions. The S97-133 isolate and three others from 1994 were also definitively identified as E. Ictaluri using the monoclonal immuno dot blot technique. The two remaining isolates, one from 1993 and one from 1994, had culture characteristics similar to those described above but no attempt was made to characterize them. Return to 24th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page