1983 Volume 18 Issue 2 Pages 107-110
From July through September 1982, an epizootic occurred in a population of young cultured red sea bream, Pagrus major, in Nagasaki Prefecture. Some moribund fish without any significant lesions (average body weight 10 g) were submitted to bacteriological examination.
The organism isolated from the kidney or spleen of the specimens was identified as Pasteurella piscicida. The characteristics were identical to those of the isolates from pseudotuberculosis in cultured yellowtail, Seriola quinqueradiata, in Nagasaki Prefecture in the period 1980-1982.
The present isolate showed pathogenicity not only for red sea bream but also yellowtail, and LD50 for red sea bream was between 0.001 mg and 0.01 mg cells per fish. The injection of the isolate caused consistently white spots in the internal organs of yellowtails, whereas their formation in red sea breams was scarcely observed.