Efficacy of vaccine from whole killed Vibrio alginolyticus cells on the immune response of white shrimp (Litopenaeus vannamei)

Vibrio alginolyticus causes high mortality in white shrimp, leading to significant worldwide losses to the aquaculture industries. Vaccine development has become a priority to prevent the spread of disease by activating the immune responses of aquatic organisms. This study aims to compare the efficacy of two types of whole killed Vibrio alginolyticus cells vaccines; formalin killed cells (FKC) and heat-killed cells (HKC), on the immune responses of white shrimp (Litopenaeus vannamei) via oral administration. The shrimp immunization for seven days, the vaccine provided with food twice per day. All shrimps challenged by injection with 0.1 mL of culture contain 1.5×106 CFU mL-1; of V. alginolyticus and monitored for ten days. Total haemocytes count (THC) and the relative percent of survival (RPS) recorded. The shrimp immunized with HKC showed a significant increase in THC than shrimp immunized with FKC and the shrimp in control groups. In addition, the RPS values show significantly higher survival rates, 82.14% and 60.71%, in the immunized groups with HKC and FKC, respectively, compared to the control group 6.68%. This study found that the HKC vaccine offered a good immunity in shrimp against the infection of virulent V. alginolyticus.