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Study on bacterial white muscle disease of freshwater giant prawn (Macrobrachium rosenbergii )
|Publication Year :||1997|
於初步的採集中在病蝦體內病灶部位發現有細菌的存在，因此自1995年8月至10月及1996年7月至11月，在屏東?港、麟洛、潮卅及高雄美濃進行病蝦的採集，將採集到的病蝦做細菌的分離及固定，總共採集到120株細菌，將這些細菌純化後進行生化鑑定以確定菌種，發現95％的細菌在分類上屬於腸內菌科(Enterobacteriaceae)，而其中弗羅恩得氏桿菌(Citrobacter freundii)佔了40%，為最顯著的菌種。此株細菌不產生??(Indole)、可產生硫化氫(H2S)、無賴胺酸去羧基酵素(Lysine decarboxylase)活性、可利用檸檬酸鹽(Citrate)做為碳源、VP試驗陰性、可在氰化鉀(KCN)培養基中生長、不能利用丙二酸(Malonate)及在無氧狀態下無法利用核糖醇(D-Adonitol)等特性。以C. freundii進行病原性試驗，LD50為4x106 CFU/每克蝦體重。而這些注射C. freundii的蝦子產生肌肉白濁，在病理切片上也可發現細菌及肌肉壞死、萎縮與溶解，並形成許多大小不一的血球包被癤結(hemocyte encapsulated nodule)，而肝胰腺當中也同樣在sinus中發現到有hemocyte encapsulated nodule，除此之外sinus有擴張、組識液浸潤、有大量血細胞聚集等病變產生，因此本實驗的研究結果顯示C. freundii的感染會造成淡水長臂大蝦罹患肌肉白濁症。
The freshwater giant prawn (Macrobrachium rosenbergii) is one of the most important aquatic cultured shellfish in Taiwan. Since 1994, the freshwater giant prawns were often found to be suffering from white muscle disease in the spring and autumn seasons. The infected prawns were frequently found around bank of pond. Diseased prawn reveals symptoms of less activity, anorexia and white muscle. The prawn died soon after harvesting which may cause an economic loss for cultured farmers.
Histopathological observation showed that several rod bacteria were observed in the muscle. 120 strains of bacterial samples were collected from a period between August to October, 1995 and July to October, 1996 from Likang, Lingro, Chaocho and Meilong, Taiwan. The results showed that over 95% the bacteria strains were Enterobacteriaceae, and 40% belongs to Citrobacter freundii. The major characteristics for C. freundii are indole negative, H2S positive, Lysine decarboxylase negative, citrate utilization positive, VP test negative, positive on grow of KCN medium, inability of using Malonate and non-fermentation for D-Adonitol. The challenge test showed the lethal dose50 (LD50) was 4x106 CFU/g body weights. An experiment performed on histopathology showed that the bacteria was observed in the infected muscular tissue. The infected muscular tissue showed necrosis, atrophy or lysis. Several hemocyte encapsulated nodules were also observed in the necrotic sites of infected muscle and hepatopancreas. In hepatopancreas, the dilated sinus and expended tissue fluid and increasing of hemocytes were found.
According to the above results it is therefore suggested that C. freundii is probably the main cause for white muscle disease for cultured freshwater prawns.
|Appears in Collections:||漁業科學研究所|
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