The combined protective effect of inactivated Vibrio Parahemolyticus and irradiated white spot syndrome virus on Litopenaeus vannamei by two routes of administration (injection and immersion)

Abstract

White spot syndrome virus (WSSV) is one of shrimp and other crustaceans' most significant infectious agents. This research isolated WSSV from infected shrimp samples collected from Bushehr’s farms. It was confirmed by PCR and multiplied in Astacus leptodactylus crayfish hemolymph. Titration of WSSV was obtained in postlarvae by the Karber method as 10 5.4 LD50/mL and the virus were inactivated by the electron beam irradiation. The electron beams D10 value and optimum dose was obtained at 1.85 and 13 kGy. Electron beam irradiated WSSV (EBI-WSSV) was used as an electron vaccine to immunize L. vannamei. Gamma-irradiated inactivated Vibrio Parahaemolyticus (GIVP) was used as an immune stimulant. PD50 was calculated 5.62, 6.30 and 2.87 for the injected groups with EBI–WSSV vaccine, EBI-WSSV vaccine+ GIVP and GIVP alone, respectively. The relative percent survival (RPS) values were calculated 64%, 72% and 22% for the EBI-WSSV vaccine, EBI-WSSV+ GIVP and GIVP groups by injection route and 75%, 85% and 12.5% for these three vaccine groups in immersion route, respectively. A significant difference in cumulative mortalities was observed between both vaccination groups (EBI-WSSV and EBI-WSSV+ GIVP), and the GIVP group (P<0.05). Therefore, two vaccine groups 1 and 2 induced productivity responses in shrimp against WSSV infection and GIPV enhanced this response. The conclusion showed the irradiated Vibrio Parahaemolyticus can be used as an immune stimulator and can enhance the protective effect of electron WSSV vaccine. The RPSs in the vaccinated groups by injection and immersion routes are without any significant differences.

Keywords

• shrimp
• white spot syndrome
• electron beam
• vibrio parahaemolyticus
• vaccine