Salmonella contamination of eel culture ponds.

Abstract

A survey of Salmonella contamination of eel culture ponds was conducted in Shizuoka Prefecture. Samples were collected from an indoor culture pond (A) and an outdoor culture pond (B) in August and December, 1986. A total of 23 samples consisting of pond water, sludge, eel (skin, gill and gut contents), feed etc. were examined.Of the 23 samples examined, 6 were found to be contaminated with salmonellae, 5 of which were collected from the pond A, and only one from the pond B. Regarding the 5 positive samples from the pond A, 3 were collected in summer, and levels of salmonellae of these samples were as follows: pond water was 7.9 cells/ml, sludge, 1.3×104cells/g, and the gut contents of eels, 4.9×102 cells/g, in contrast, 2 samples collected in winter, the level of pond water was as low as 0.02 cell/ml and that of sludge was 2.7 cells/g. Only one sludge sample showing Salmonella positive from the pond B was detected in summer, and the level was 0.45 cell/g. Major serovars of the 56 Salmonella isolates were S. java (43%), S. braenderup (36%) and S. etnnessee (14%). The necessity and possibility for a Salmonella free culture and clean eels were discussed.