Study on pathogenesis of bacterial disease in frog, (Rana tigerina Cantor)
1995
Bunchard Siyapong
Aeromonas hydrophila was isolated from liver, kidney and heart of cultured frog. The affected frogs were listless and failed to react to the usual stimuli. The skin of the abdominal area and the flexor region of the legs were pink to deep red in colour and abdominal dropsy was observed. Tadpoles with a weight of 0.9-1.2 gm, small frogs with a weight of 2.0-2.5 gm and large frogs with a weight of 50.0-70.0 gm were used for an LC50 experiment. The three sizes of frogs were infected with bacteria by immersion in different bacterial concentrations. The concentration at which 50 percent of all experimental frogs died (LC50) was 3.98 * 10*[7), 1.12 * 10*[6) and 5.0 * 10*[6) cells/ml at 96 hours, respectively. Large and small frogs were infected by intraperitioneal injection with different bacterial concentrations. The concentration at which 50 percent of experimental frogs died (LD50) was 4.22 * 10*[5) and 6.06 * 10*[4) cells/ml at 96 hours, respectively. The three experimental groups, both immersed with bacterial concentration at LC50 and injected intraperitoneally with bacterial concentration at LD50, showed very similar histopathological changes in various organs. Focal necrosis, hydropic degeneration, blood congestion and haemorrhagic lesions with exudate were found in the liver of infected frogs. Kidney tissue demonstrated hyaline degeneration and necrosis of the epithelial cell lining of the renal tubules, glomerular swelling and glomerulitis. Blood congestion and haemorrhagic lesions with exudate were also observed in the kidney. The heart of the infected frogs showed pericarditis, myocarditis and hypertrophy of endocardial cells.
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