IMPROVING DISEASE RESISTANCE FOR SHRIMP THROUGH APPLICATION OF PROBIOTICS IN FEED

Abstract

Diseases affecting shrimp contribute to billions of dollars of economic loss yearly to the aquaculture industry. Recently, one of the primary causative agents of disease has been Vibrio parahaemolyticus; in 2009, a new strain causing Early Mortality Syndrome (EMS) or acute hepatopancreatic necrosis disease (AHPND) in shrimp emerged. Shrimp losses attributed to pathogens can be greatly reduced through probiotic use, which are known to act as natural immune enhancers and promote pathogen resistance. However, research on probiotic treatment against EMS disease is lacking. The overall project goal was to improve intensive shrimp production through direct application of probiotics in aquaculture feeds.

The value of probiotics for the shrimp industry was evaluated by (1) reducing severity or mortality of V. parahaemolyticus disease in shrimp, (2) qPCR confirmation of Bacillus spore germination in shrimp gut, and (3) probiotic effectiveness evaluation for improving disease resistance. The virulence of several Vibrio spp. strains was examined and it was concluded the V. parahaemolyticus strain identified as the causative agent of EMS was the most lethal; EMS-infected shrimp exhibited 100% mortality within 36-hours of feed inoculation. The number of bacterial cells added to feed directly correlated with pathogenicity and only cells, not filtrate, was capable of causing death. Probiotic strains were evaluated and it was concluded that probiotic strains A, A/B blend, and B were the best candidates for promoting disease resistance against EMS. This research will provide the shrimp farming industry with information vital to developing a means for reducing economic loss from Vibrio-infected shrimp.