Thesis or Dissertation Regulation of infectious diseases of Pacific white shrimp (Litopenaeus vannamei) by galangal (Alpinia galanga Linn.) extract

Chaweepack, Tidaporn  ,  Chaweepack, Surachart  ,  Muenthaisong, Boonyee  ,  Ruangpan, Lila  ,  Khomvilai, Chutima  ,  Nagata, Kei  ,  Kanaori, Kenji  ,  Kamei, Kaeko

In this study, galangal extract was tested for its efficacy for controlling shrimp pathogens, using Pacific white shrimp (Litopenaeus vannamei) which is the main product of penaeid shrimp. We discovered that the galangal (Alpinia galanga Linn.), ethanol extract suppressed the growth of 8 pathogenic Vibrio species, V. parahaemolyticus (EMS/AHPND) in particular. We also found that antibacterial compounds of the galangal extract were trans-p-hydroxy cinnamaldehyde, trans-p-acetoxy cinnamic alcohol and trans-p-coumaryl diacetate with the half maximal inhibitory concentrations (IC50) against V. harveyi of 0.0740 ± 0.0095, > 5 and 0.7200 ± 0.0190 ?mol/ml, respectively. A commercial diet mixed with galangal extract was fed to shrimp. At the end of the feeding trial, the numbers of total Vibrio spp. and the incidence of fungi infestation in the hepatopancreas and intestines of shrimp were significantly lower than that in the control group. Furthermore, the survival rates for the treatment groups, after injections with V. parahaemolyticus (EMS/AHPND), V. harveyi or white spot syndrome virus were significantly higher than that of the control group. The number of V. harveyi in the hemolymph of the galangal diet group was significantly lower than that in the control diet group, indicating the higher clearance ability of the galangal diet group. The intramuscular injection of either galangal extract or trans-p-coumaryl diacetate to Pacific white shrimp showed significant increases in the relative expression level of the six immune-related genes compared with a control group. Furthermore, by the oral administration of galangal extract, similar inducible effects of the expression of immune-related genes in shrimp were obtained, which led to an enhanced survival rate from V. harveyi infection. Based on these results, the galangal extract might be useful for the treatment of shrimp diseases in the aquaculture industry. Moreover, this studies can solve the problem of antibiotic residual in shrimp product and make it safe for consumers.

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