Abstract
Tilapia, Tilapia mosambica, were experimentally infected by intramuscular injection with 108 CFU/ml of Edwardsiella tarda (J3N strain) isolated from diseased tilapia, and examined on 24, 48, 96 and 120 hours after injection. Fish 24 and 48 hours after the injection showed swollen and erosious lesions and muscular necrosis with bacterial multiplication and inflammatory calls at the injected areas, and focal necrosis with bacteria-laden inflammatory cells in the liver, spleen, kidney and heart. Fish 96 and 120 hours after injection were moribund showing swollen and ulcered lesions at the injected areas, small white nodules in the liver and spleen. The injected lesions showed muscular necrosis with bacterial multiplication and inflammatory cells. The liver, spleen and hematopoietic tissue showed focal accumulation of macrophages and production of granulomas in the infected lesions. The heart showed focal necrosis with bacterial multiplication and inflammatory cells. Gills showed bacterial embolism in lamellae. These histopathological signs of experimentally infected tilapia resembled to those of naturally infected fish.
