TWENTY-SECOND ANNUAL EASTERN FISH HEALTH WORKSHOP ROYAL PAVILLION RESORT, ATLANTIC BEACH, NC MARCH 18 - 20, 1997 Isolation and Sublethal Effects of Bacillus thuringiensis var kurstaki on Koi Carp (Cyprinus carpio). Phyllis A.W. Martin1. Ana M. Baya2, Rosangela Navarro2 and Joyce Evans3 1 US Dept. of Agriculture, Agriculture Research Service, Insect Biocontrol Lab., Beltsville, MD 2 Maryland Department of Agriculture, Animal Health Diagnostic Lab., College Park, MD 3 Cooperative Oxford Lab., Oxford, MD In 1995, there was an unexplained kill of ornamental fish in a Maryland pond. The fish deaths occurred several days after a large scale spraying of Bacillus thuringiensis. As there is no information available on the effects of B. thuringiensis on Koi carp, we conducted controlled transmission studies with the inoculum being the formulated product (Foray 48B) of B. thuringiensis. Six 55 gallon tanks, each containing 25 koi carp, were used in the experimentation. Two tanks of fish received the formulated product of B. thuringiensis at 1X and 10X the recommended application dose. Fish in two other tanks were fed with the formulated product applied to the food at the same concentrations. A fifth tank of fish was exposed to the predominant B. thuringiensis strain in the product Foray 48B without formulation. The 25 fish in the 6th tank were untreated controls. There were no mortalities during the month-long experiment except for 5 fish that died on day 14 when a filter in one of the tanks failed. We did not recover B. thuringiensis from any of the fish organs examined (brain, kidney, liver, spleen and intestine) but did isolate the inoculated strain from the intestines of some fish in low numbers. Biochemical test results indicated that some of the B. thuringiensis organisms that were isolated were not the same as the B.thuringiensis strain that was applied. The only observed difference between the experimental and control groups was that the body weights of the fish exposed to B. thuringiensis were significantly lower than those of the controls at the end of the study period. Return to 22nd Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page