Abstract
Outbreaks of motile aeromonad disease occurred among crucian carps, Carassius auratus, in game-fish ponds. Aeromonas hydrophila which produced strong β-hemolysin was isolated from the diseased fish. A histopathological study was made on the infected fish. The fish showed hemorrhage on the body surface, accumulation of red-colored ascitic fluid and enteritis with bacterial invasions. Hemosiderosis was observed in the liver, spleen and kidney. Deposition of hematoidin crystals was found in the spleen, kidney and blood vessels. Experimental infections were carried out by intraperitoneal injection with the isolate into crucian carp and resulted in manifestation of similar pathological signs to those of the naturally infected case.
