Studies On The Pathogen And Immunological Prevention Of Fulminant Septicaemia Ictalurus Punctatus

Fulminant septicaemia of Channel Catfish (Ictalurus punctatns) is a threatening disease with high incidence and mortality in fish-farm. At present, no effective measures has been developed to prevent this disease.The net-cage cultured Channel Catfish occurred fulminant septicaemia disease in Jiayu and Changyang, Hubei province. The prevalent season was from April to October, the fastigium period was from July to August. The appropriate water temperature was 25℃～30℃ and the weight of diseased fish was 150g～300g. The infected fish showed two types of main dead symptoms: acute and chronic. The symptoms of acute dead fish showed fulminant death. It had obviously fastigium period. The mortality was very high. The symptoms of chronic dead fish showed two types: one was large engorgement around the eyes, serious engorgement on the basal of the fin, a white petechial in the cranial cavity between the eyes. The other was distendend abdomen, raised red on the anus and the epidermis developed serious spongiosis. The three strains of bacterial pathogen with high virulence have been isolated from the liver, kidney and spleen of diseased Channel Catfish with typical Fulminant septicaemia. According to the artificial infection and the results of many morphological, physiological and biochemical characteristics tests, comparison to the data of Bergeys Manual of Determinative Bacteriology, we have demonstrated that the three strains belonged to two different species: Aeromonas sobria and Aeromonas hydrophila, respectively.In vitro, all of the strains were tested of drug sensitivity. The results showed that three strains had the resistance to broad-spectrum bacteriophage namely Ampicillin, Penicillin, Cephalexin, Exythromycin et al., but had highly susceptibilities to Ceftriaxone Sodium, Cefuroxime, Fortum et al. Jh-1 and Yh-3 had highly sensitivity to Compound Sulfamethoxazole, Tetracycline, Norfloxacin, Amilcacin and Sulfate, while Jh-2 not. Five antibiotics, namely, Florfenicol, Oxytetracycline, Ciprofloxacin, Norfloxocin, Enoxacin were studied. The efficacies of the antibiotics on three strains were determined as well as minimum inhibitory concentration(MIC) and minimum bactericidal concentrations (MBC). The three strains showed high susceptibilities to Ciprofloxacin and Norfloxacin, but low susceptibilities to the other three antibiotics. It was showed that Ciprofloxacin...