Research On Fulminant Epidemic Disease Of Cultured Mud Crab Scylla Serrate

Since Autumn 2004,several serious mud crab disease happened in Sanmen county, Zhejiang province, with a high mortality and large economic losses.According incompletely stat.1.5 billion RMB economic lost during the accident in Sanmen county 2004.But still without an effective solution to control it by far, the thesis mainly concentrate about the epidemic disease on mud crab in recent years in Sanmen county.Mycoplasma can't be cultured from tissue of disease mud crab, but mass mycoplasma microbe were found in the gill and intestine under the transmission electron microscopy, further more they are differ shape and sizes, for instance, sphericity ,egg shpericity and some club-shaped, protonema etc, most of which are present as hollow bubble.As far as the researching of disease mud crab tissue is developing, the gill, hepatopancreas, inintestine, stomachus and hear were all pathological changes in differ grade, this shows us the gill, hepatopancreas, inintestine, stomachus and hear are target apparatus that pathogenic bacterium will attack.From the ultrastucture pathology, virus particles were observed in some of the disease mud crab from the following sample tissues: gill, inintestine, stomachus, heart. The complete viral particle present approximately sphericity, 70nm in diameter, icosahedral and nonenveloped. Greater concentration electron in nuclear, about 50nm in diameter. Mass mature virus particles are crystalline arrangement within the infected tissue cells, base on its morphology characteristics, primary confirmed as reovirus.WSSV were found in the gill and inintestine according PCR, but this can't be found in the other tissue, from the investigation of epidemic, WSSV electropositive is coherence with the disease taken time of mud crab.According the investigation on quantity of microorganism and bacterial flora of the mud crab circumstance, bacteria and virus are present abundance, the bacteria could reach 1.37×10~5cells/ml. Regarding the extensity of ammonifier, denitrify bacteria and sulfate reduction bacteria, the quantity in mud is higher than water and the quantity in Sep and Oct are all generally higher than Aug and Nov.