Evaluation of killed vaccine efficacy on hematology parameters and IgM assay of Acipenser stellatus (Pallas, 1771) challenged with Nervous Necrosis Virus (NNV)

Vaccination is considered the most effective, environmentally friendly and cost-effective way of protecting commercial finfish species against infectious diseases with high economic impacts. Efficacy of a new inactivated VNN vaccine through heat-inactivated nervous necrosis virus (NNV) combined with three types of adjuvants was assessed in 7 g juvenile of Acipenser stellatus Pallas, 1771 as a laboratory model. Ten groups of 30 numerical were considered in 18 aquariums using both immersion and injection routes in the form of 4 types of vaccines.Vaccination was performed in two stages one month apart, and one month after the second replication, exposure to the live virus was performed. During this period, the mortality rate of immersion and injection groups was 12.9% and 19.8%, respectively, compared to 100% mortality in the control group. Sampling was performed in four stages before the first vaccination in the adaptation period, after the first vaccination, after the second replication and after exposure to live virus. Blood samples were measured to evaluate changes in blood factors (red blood cell count, white blood cell count, hematocrit and hemoglobin) and immunity factors (immunoglobulin, superoxide dismutase, lysozyme).In order to prove the virulence of the viral sample (supernatant) used in exposure, the pathogenicity of VNN virus isolated from infected Caspian Sea mullet with (TCID50 ) was examined in several guppies. One month after the second repetition of fish, all treatments were exposed to the acute virus sample (supernatant) and after one month, their survival percentage, blood factors and safety were measured.The results of this study showed that immersion vaccination in the vaccinated group containing IMS 1312 SEPPIC adjuvant significantly showed higher levels of IgM compared to other groups equal to 0/35   (P<0.05). This is consistent with the results of hemoglobin 40.6  (P<0.05), which proves the better efficacy of this type of vaccine compared to other vaccines tested in this study.Based on the results of this study, a vaccine killed with 75% IMS 1312 SEPPIC adjuvant can be recommended for vaccination against VNN.