Pathogenetic Investigation of The Gill Disease of Common Carp( Cyprins carpio )

Ye Yuantu Li Linggui Chen Zhehua (Southwest Agricultural University,Chongqing 630716 China)

Myxococcus Gill disease Cyprinus carpio Chemical control

A strain of Myxococcus was isolated from the gill-deseased carp two years ago.This paper discribed a series of tests and observations in relation to the pathogenesis of the gill disease.When water temperature rises over 20℃,and the carp's gill or surface of body were wounded, the gill or the muscle was easily infected with the pathogenetic Myxococcus. Myxococcus on the infected tissue began to proliferate rapidly.In 1 g gill or internal organs,the number of bacteria(mostly Myxococcus was 10 5-10 8 for diseased carp from net cages and artificial injection, but 0-10 2 for normal ones from net cages and ponds.Both exotoxin and endotoxin were not found in the culture liquid of the pathogenetic Myxococcus and the extraction of the Myxococcus. The activities of protease in the culture liquid was tested and reached the highest at 22 hours.According to these results,the toxicity of the pathogenetic Myxococcus depends on the of increase of number of Myxococcus. Myxococcus in the carp gill caused the gill funtional disorder and the shortage of oxygen in blood,then the gill was decomposed and the diseased fish died.The bactericidal tests of 13 kind medicines were also carried out.