The Primary Pathogen And Treatment Test For The Skin Ulceration Disease Of Anguilla Japonica

Anguilla japonica is one of important species of eel aquaculture in China. In recent years, a new disease is epidemic in aquaculture production- skin ulceration disease. The main symptoms of the skin ulceration disease of Anguilla japonica was desquamation of mucus of body surface with petal-shaped. With the progression of the disease, the body surface lesions expand gradually, the lesions occurred mainly in the head and trunk of eels, and then skin and muscle of eels in lesions ulcerated; fin was hyperemia, trunk skin discoloration, erosion, the physical situation and livingness of the disease eels declined and leaded to death. In present, there were not any research reports about its pathogen, pathology, etc, and no good control technology. In this paper, pathogenic bacteria isolation, purification and preservation; pathogen classification, the growth conditions, histopathology, pathogenicity, the screening experiment of the drug sensitivity and the prevention technology of the eel disease were studied. The main results as follows.1. This thesis studied the isolation and identification of the fungal pathogen of this disease. The fungal strain Js80122 was isolated from diseased eels by cultured on kernels of wheat. Strain Js80122 was confirmed as the causative pathogen of dermal ulceration disease by artificial infection tests. In these tests, healthy eels were injected with spore on dorsal muscle, or marinated with culture after hurting, or daubed with spore on wound, or injected with spore and bacteria on dorsal muscle. The morphology and life history of Js80122 cultured on slide and cover glass showed that Js80122 was the filamentous fungi, its hyphae were aseptate with plentiful branches,the reproductive modes of Js80122 were asexual and sexual. Zoosporangium was clavate or spindly and renewed by internal or cymose proliferation,zoospores were diplanetic. There were more than one oospore per oogonium, the oospores were smooth. According to the morphological characteristics, Strain Js80122 was identified as Saprolegniaceae, Protoachlya Coker, Protoachlya paradoxa.2. 10μL spore suspension was added to the sterilization of wheat water, using citric acid, potassium hydrogen phosphate, sodium hydroxide, boric acid, sodium chloride respectively to regulate pH and salinity of the sterilization of wheat water in the test tube. According growing situation of mycelium in the culture environment,we study the temperature, salinity and pH value for the growth, suitable growth and optimum growth of Protoachlya paradoxa(Js80122), the pathogen of the skin ulceration disease of Japonica eel. The range of growth temperature was 6-41℃, the suitable and optimum growth temperature were15-30℃and 25℃, respectively; The range of growth salinity was 0.0-8.5%, the suitable and optimum growth salinity were 0.0-2.5% and 0.0-0.34% ,respectively; The range of growth pH was 2.0-8.2, the suitable and optimum growth pH were 6.0-7.6 and 6.8 ,respectively; Two-factor orthogonal test showed that optimum growth pH and salinity were 7.0 and 0.0, respectively.3. Taking the ulcers skin of surface , gill, and internal organs , for histopathology slice, studing histopathology of the skin ulceration disease of Anguilla japonica by microscope observation. The mucus of body surface was desquamated, the skin of eels in lesions was ulcerated, and having hemorrhaging and inflammatory exudation,the gill was rotten, the inherent structure of gill filaments collapsed, skin necrosis. Microscope observation of pathology: muscle fibers melt and disappeared; myocardial fibers disordered and necrosis, leukocyte of myenteric infiltrated and thrombosis, liver swelled and necrosis; splenic bleeding, the number of lymphocytes reduced, intestinal epithelial desquamated and necrosis;inherent menbrane leukocyte infiltrated; kidney damaged severely, widespread congestived and hemorrhaged, leukocyte infiltration; tubular swelled and necrosis; glomerular languored, intracavitary bleed.4. The minimal inhibitory concentration(MIC)of the strain Js80122 of the Protoachlya paradoxa which leaded to the skin ulceration disease of japonica eel to 12 kinds of antifungal drug were studied by using the method of the outside tube two-fold dilution. Results showed that Meijunjing,Shuimeitexiaoling and benzalkonium bromide solution were the most effective. Japonica eel and the strain Js80122 were used for clinical evaluation. The formula showed that Meijunjing, Meijunjing with Disulfide cyano-methane could entirely kill the Protoachlya paradoxa in the organisation in 9 d and 14 d. Then, we used MAQQ to control the secondary affection of the Aeromonas hydrophila and finally used potassium permanganate to heal up the wound for the next 2 d. Both survival rate and therapeutic rate reached 100% in water temperature 18±0.5℃. In water temperature 25±0.5℃, the Protoachlya paradoxa in the organisation had been entirely killed between 10d to 12d, with MAQO controling on the secondary affection and potassium permanganate healing wound, both survival rate and therapeutic rate reached 100%. The treatment technology showed effective preventive and therapeutic results, above 95% therapeutic rate.