An investigation on protective effects of the new killed vaccine against nervous necrosis virus (NNV) using histopathology and immunohistochemistry approach on the brain and eye tissues of Acipenser stellatus Pallas 1771.

The objective of this study was to analyze the efficiency of the killed vaccine against nervous necrosis virus on Acipenser stellutus. Heat inactivated VNN vaccine was administrated in 7 g juveniles of Acipenser stellutus as a laboratory model and it was included in three different adjuvants that were used as injection and immersion forms with different doses. Ten groups consisting of 30 A. stellutus fish in each group (group 1-4 with 3 replications, others with no replicate) were divided totally into 18 aquariums. Two steps of vaccination were done with a one-month interval and after that, all treatments and control groups were challenged by the virulent VNN virus. The mortality rate of immersion and injection groups were 12.9% and 19.8% respectively, compared to 100% mortality in the control group. Histopathology and immunohistochemistry findings were evaluated. According to the mortality rate one month after challenging, a low range mortality of 12.5% was seen in group 2 with no pathological lesion and negative IHC test in the brain and eye tissues, whereas 100% of the control group (unvaccinated group) died with severe vacuolation in the brain and eye tissues and also positive IHC test. The correlation assay between these results concluded that the immersion form with 75% of aquatic-specific Montanide IMS 1312 Seppic adjuvant made better immunization with no pathological sign or forming the complex of antigen-antibody in IHC assay. These findings are important because of the impossibility of injection in the larval stage and also due to the occurrence of the disease in the first stage of sturgeon life which could cause high mortality in susceptible fish in the larval stage.

Effect of dietary supplementation with zinc enriched yeast (Saccharomyces cerevisiae) on immunity of rainbow trout (Oncorhynchus mykiss).

Zinc (Zn) is an essential trace element in all living organisms, and the first eukaryotic Zn uptake transporter was discovered in the yeast, Saccharomyces cerevisiae. Zinc-enriched yeast is a currently available Zn supplement. The purpose of the investigation was to compare and evaluate the effect of Zn enriched yeast in rainbow trout. The fish (mean body weight 10 ± 0.5 g) were fed a commercial diet supplemented with 0 (control), 1 × 10(6), 1 × 10(7) and 1 × 10(8) CFU/g of Zn-enriched yeast for 60-days. Results showed that significant increase in serum lysozyme activity, complement activity and total immunoglobulin were seen in all treatment groups during feeding trial when compared to the control group. On the basis of our findings, Zn-enriched improved rainbow trout growth, some immune parameters and disease resistance.