Virulence of Vibrio parahaemolyticus to Shrimp Juvenile

Abstract

Shrimp aquaculture in the world is depressed by various diseases, especially bacterial and viral diseases. Using antibiotics in aquaculture found ineffective and results in increased virulence of pathogens and residual effect of drugs. Cinnamaldehyde and indole can provide a good solution of these problems. This experiment was conducted to investigate the virulence of Vibrio parahaemolyticus to shrimp juvenile and finding an effect of indole and cinnamaldehyde on the survival of Penaeus monodon against Vibrio parahaemolyticus. The challenge test was conducted with 10 shrimp juvenile (14.36±3.48 g/juvenile) in 30 L plastic tanks and at ±10⁶ CFU/ml bacterial inoculation, and the indole and cinnamaldehyde concentrations were 100 μM respectively. The experimental treatments were C1 (juvenile and feed), C2 (juvenile, feed and bacteria), T1 (juvenile, feed and indole), T2 (juvenile, feed and cinnamaldehyde), T3 (juvenile, feed, bacteria and indole), T4 (juvenile, feed, bacteria and cinnamaldehyde) and T5 (juvenile, feed, bacteria, and both indole and cinnamaldehyde). The results of this experiment represented that the survival of Penaeus monodon was found highest(86.67%) in C1compared to C2 and others group, which was lowest (26.67%) in T5. Nevertheless, the probability of cumulative hazard to mortality of shrimp in this experiment was found to higher in T1 and T3 compared to other treatments. Similarly, it was higher in C2 than that of other groups. C1 was found to have lowest hazardous. However, lower probability of cumulative hazards is in T2, T4 and T5. Total bacterial count was found higher ((2.07±1.31)×10⁸ CFU/g) in group T4 and lower in T5 ((3.28±2.43)×10⁷ CFU/g). Moreover, Vibrio spp. load was found to be higher inT4 (1.31±1.29)×10⁶CFU/g) and lower in T2 ((12.07±6.82)×10⁴CFU/g). Hence, Vibrio parahaemolyticus might have putative virulence activity to shrimp juvenile and cinnamaldehyde and indole might have impact on reducing their virulence activity.