The Pathology Research Of Mass Mortality Of Farmed Acipenser Schrenckii In South

Sturgeon was introduced to China more than about 10 years ago in which the disease was simple. And because the intestine structure sturgeon is simple, so the common disease was mainly enteritis in a lower incidence. Compared with the early aquaculture with almost no morbidity, after a long time of culture, due to the deterioration of culture environment, bacterial diseases, protozoan diseases and viral diseases have been found in each process of sturgeon aquaculture, such as eyed eggs hatching, fry rearing and commercial fish farming. And now it is more likely to burst some comprehensive diseases that are fatal, infectious and difficult to treatment, so it's urgent to combat diseases of Acipenser Schrenckii. The diseased fish of this paper is from one artificial breeding farm in Xiamen, in which there were a large number of death of Acipenser Schrenckii.From the sampled fish, the main symptoms could be found as abdominal wall bleeding and ascites, enlarged spleen, and the liver was tended to flower liver or gray liver, and the kidneys were severe swelling and there were lots of white spots. The pathological changes were found such as a large number of eosinophilic blood cells in the spleen, and there were liver cells with loose or dense cytoplasm of hepatocytes and also necrosis of liver cells, and then the nucleolus of urinary tubule epithelial atrophy, deformed, necrosis and came off; and there were also a large number of eosinophilic leucocyte in renal interstitium and volume expansion on glomerular.With sterile conditions, the liver, kidney, spleen and other lesions were took from diseased fish, and streak inoculation were made in the ordinary nutrient medium plates with the inoculation needles, then they were cultivated for 20 ~ 24 hours at 37℃constant. And then the colony of dominant bacteria was isolated again which were cultured till purebred and then the purebred was stored in the slant medium. Washing the isolated bacterial strain which have been cultured for 20 hours with sterile saline and made it into bacterial suspension with concentration of 3.0×108. Then injected 0.3 mL of bacterial suspension to the base muscle of dorsal fin of healthy Acipenser Schrenckii, while control group were injected 0.2 mL of sterile saline, and then observed the disease symptoms and death. The diseased fish with typical symptoms after artificial infection were picked up to re-infection using the bacterial suspension that have been purified and cultured.The pathogenic strains were obtained for directional tests such as Gram staining, microscopy and oxidative enzymes. Through the basic physiological and biochemical determination and bacteria form colonies observed,then automatic identify the pathogens with the VITEK-AMS-32 Automatic microbial analysis system and the GNI identify card (BioMerieux, France), and finally determined it as Aeromonas hydrophila. And using the susceptibility paper (Hangzhou Tianhe Microorganism Reagent Co.Ltda) to made the standard decision of pathogens sensitivity to drugs in nutrient agar plates at 37℃constant for 24h. Experimental results show that the antibiotics such as erythromycin, ciprofloxacin, gentamycin, streptomycin have stronger bacteriostasis.