Studies On Pathogen And Pathology Of "Emulsification" Disease Of Portunus Trituberculatus

An explosive epidemic disease named "Emulsification " consecutively happened in cultured Portunus trituberculatus during these years in Zhoushan of Zhejiang province, which caused high mortality and resulted in great economic loss. In order to make sure the pathogen of the disease and find the way of prevention, we studied the epidemiology, the pathogenic bacteria, the histopathological features of the disease, and the agents for the prevention and cure of this disease in this paper.The study on the disease breaking out in low water temperature period ranging from October to February of next year showed that the infected crab was thin; when the leg cut transversely or the lid opened, milky liquid would flow out or be seen. In addition, a great deal of uniform microbes were found in the milky liquid under light microscope, the same microbe can also be isolated from muscle, heart and hepatopancreas of the disease crab. Artificial infection experiment showed that it could cause the healthy crab to be diseased, and the symptom was same as that of the natural sick crab. Same strain was isolated from the artificial infection crab, which proved to be the pathogen of the disease. By challenge test, the pathogen was identified to be the yeast Candida oleophila.The histopathological features of cultured Portunus trituberculatus infected by "Emulsification " disease was also examined. The results showed that the number of the haemolymph cells in body fluid of the crab decreased sharply and was replaced by large amount of yeast, and the blood cannot agglomerate. There were pathological changes in different degree in gills, heart and hepatopancreas of the diseased crabs. The pathological characteristics mainly appeared as cells swelling, necrosis, and nucleus condensation and collaspe. Budding of yeast was present here and there within the hemolymph vessels throughout the whole body. Based on the pathological changes, the nosogenesis was also analysed.In order to study the physiological and biochemical characteristics of Portunustrituberculatus with etnusification disease, the activities of some enzymes involving in immune defense, such as hydrolases enzymes, antioxidant enzymes, enzymes within cell and MDA, in 4 kinds of tissues (heart, muscle, gill, and liver) of the healthy and diseased Portunus trituberculatus were measured. The results showed that the differences of lysozyme activities in healthy and diseased groups were notable. It is considered that isozymes activities can be used as a physiological as well as pathological index in the emusification disease.The effectiveness of 10 anti-epiphyte agents on the yeast Candida oleophila was evaluated. The results showed that 5 chemotherapeutants (mycostatin, benzalkonium bromide, formaldehyde, goldthread root, garlic) were the most effective agents against the yeast Candida oleophila, with the MICs and MBCs of 4ug/mL, 8ul/mL; 4ug/mL andl6ug/mL; 31.27uL/mLand 62.54uL/mL; 1:640 and 1:160: 1:20 and 1:10, respectively.