ETIOLOGIC CHARACTERIZATION OF ACUTE INFECTIOUS ABDOMINAL DROPSY OUTBREAK AFFECTING INDIAN MAJOR CARP, CIRRHINUS-MRIGALA IN SOUTH-ANDAMAN

The causative agent of severe acute infectious abdominal dropsy outbre ak in Indian major carp, Cirrhinus mrigala was investigated, The etiol ogical agent was identified as a highly virulent strain of Aeromonas h ydrophila. No virus could be isolated from the affected fishes in home othermic cell lines, viz. BHK21, Vero, L929 and NTH3T3 and poikilother mic cell lines namely RTG-2 and RTH-149. The abdominal transudate of t he affected fishes and the culture filtrate contained heat-stable hemo lytic proteolytic, amylolytic and dermonecrotic exotoxin activity. Amm onium sulphate precipitated partially purified extracellular preparati ons (ECPs) were highly cytotoxic when tested in same cell lines, The f lagellar 'H' antigen was common to other moderate and avirulent strain s of Aeromonas sp, as well as Edwardsiella tarda and Yersinia rukeri, whereas the somatic 'O' antigen was very specific to the isolated stra in only when tested by agglutination test using polyclonal antisera ag ainst these organisms, Soluble antigens of the strain were cross-react ing with these organisms when tested for humoral response by agar gel immunodiffusion (AGID) test, The partially purified ECPs showed Type I V hypersensitivity in rabbits immunized with homologous and heterologo us antigens, when tested for cell mediated immune response (CMIR).