Pathogenicity of Vibrio alginoliticus on Giant Freshwater Prawn, Macrobrachium rosenbergii Post-Larvae

In recent years, aquaculture sector including prawn industry has developed rapidly in Malaysia. Malaysia government has pay high attention on this sector due to the static fisheries production and the potential of aquaculture to serve as national food. However, aquaculture sector has also facing issue and challenges including low quality of seed, depleted of wild stock population and also disease infection. In prawn industry, microbial disease are reported affects its production. Usually, diseases in prawn in ponds are caused by microorganism such as viruses, fungi, protozoan and bacteria. Vibrio bacteria are one of the primary pathogens reported to cause serious mortality in prawn hatcheries in Malaysia. In this study, the post larvae Macrobrachium rosenbergii were conducted with Vibrio alginoliticus to test the pathogenicity of bacteria in this prawn and to determine the median lethal concentration ( LC 50) of the bacteria. The present study showed that Vibrio alginoliticus were isolated from the fish diseases and was immersed to post larvae Macrobrachium rosenbergii at four different concentration 1.0x104 , 1.0x105 , 1.0x106 and 1.0x107 CFU/ml. Most of the infected post larvae Macrobrachium rosenbergii were died within 4 days. Based on pathogenicity test result, LC 50 was determined as 1.0x103 CFU/mL, while 1.0x104, 1.0x105, 1.0x106 and 1.0x107 CFU/ml. were started to convinced 100% mortality in the immersion challenge .The clinical sign were observed during the experiment including hepatopancreas and gross appearance of post larvae Macrobrachium rosenbergii such as lethargy, anorexia and slow growth development.