Abstract:Vibrio anguillarum is a pathogen that can infect a variety of fish and causes highly fatal hemorrhagic septicemia. Its O1, O2, and O3 serotype strains are prevalent in the mariculture environment of China, causing great economic loss. However, the study of polyvalent vaccines of different pathogenic serotypes of V. anguillarum has not been undertaken. For this purpose, a trivalent inactivated vaccine V. anguillarum was made, and its antibody duration and immune protection period were evaluated. The trivalent vaccine was administered to turbot (80.2±4.7 g) at a dose of 108 cells/individual via intraperitoneal injection; booster vaccination was given at 60 days post vaccination (dpv), and the serum antibody titer and RPS of the vaccinated group and control group were compared. Fish vaccinated only once were observed for 150 days, and the results showed that during 14~150 dpv, the antibody level of the vaccinated V. anguillarum group was significantly higher than that in the control group (P<0.05), and rose to 1∶6.7 at 7 dpv, reached peak value at 28 dpv, and during 28~150 dpv hovered between 1∶106.7~1∶320. RPS of three serotype V. anguillarum were 16.7%~43.8% for 7 dpv, then reached 100% at 28 dpv; during 28~120 dpv was 70%~100%, 35%~100% for 150 dpv. The fish vaccinated twice were observed for 90 days; during 3~60 days post-second vaccination (dpsv), their antibody titer was significantly higher (P<0.05) than those vaccinated only once, then went down and was not significantly different (P>0.05) than that of those vaccinated only once. RPS of three serotype V. anguillarum were still higher than 70% and higher than those of fish only vaccinated once. All in all, antibody durability and efficient immune protection period (RPS>70%) of fish vaccinated with V. anguillarum trivalent inactivated vaccine once was longer than 150 days and 120 days respectively, and 150 days for fish that were vaccinated twice. Control group fish reached higher weight in comparison to the vaccinated fish, while SGR between groups for the whole period was not statistically significant (P>0.05).
