Comparative Study On The Protective Effect Of Tilapia Streptococcus Agalactiae Attenuated And Inactivated Vaccines

At present,the production of tilapia culture in China is still at the top of the characteristic freshwater fish,but the frequent occurrence of streptococcus agalactiae disease of tilapia is seriously affecting the healthy development of tilapia farming industry in China.The research and development and application of vaccines is an urgent development direction in the current aquaculture field,and safe,stable and long-acting vaccines will bring huge economic benefits to this industry.Several vaccines have been reported to be effective in preventing tilapia streptococcal disease,but most vaccines are still in the laboratory stage.Based on the natural breeding environment,this paper discusses the effects of fish body size,immune dose and whether adjuvant is used on the immune effect of attenuated vaccines,and compares with inactivated vaccines prepared by wild strong strains,and the main results are as follows:1.The effects of fish size,immune dose and adjuvant use on the immune effect of attenuated vaccines in natural breeding environmentsAfter injecting immunodeficiency vaccines in different fish body sizes,it was found that compared with 10 g fish,50 g and 250 g fish had lower mortality and higher relative immunoprotective rates,and produced higher levels of serum-specific antibodies;discovery after immunot dosage induction1 × 107 CFU/ tail has a lower mortality,high relative immune protection rate and can induce a high level of serum-specific antibody;mixed injectable immunization of attenuated vaccines and adjuvants does not improve the relative immunoprotective rate and the production of specific antibodies.2.Comparison of immune effects of attenuated vaccine and inactivated vaccine in natural environmentWe first prepared an inactivated vaccine for wild strong strains,and the immunization of the immune group,survived the immune group,the survival curve,the relative immune protection rate and the serum-specific antibody test,and the weak toxic vaccine relative to the inactivated vaccine.There is a lower mortality,higher relative immune protection rate,longer protective aging and higher levels of serum-specific antibodies.Inactivating vaccine once immunized aging is 60 d,enhances immunization,it is possible to increase the relative immune protection rate and protection of disinfection vaccines and inactivated vaccines,and inactivating vaccine reinforced immunizations have similar to weak drug vaccines.The antibody level is higher than the immunization of the inactivated vaccine.Head kidney,spleen,and liver tissue pathological sections show that after injection of immunization,the disappearing vaccine has a longer immune time(disappearing vaccine 14 d,inactivating vaccine 7 d),and is enhanced by inactivating vaccine.Providing a persistent antigen that allows the immune system for a long time to activate its immune effect and the weak disinfection vaccine,which may explain the cause of weak disinfection vaccines and enhance immunity to improve the protection effect.