Since infectious pancreatic necrosis virus (IPNV) is the most predominant strain causing fatal viral disease in Iranian fish farms, an inactivated vaccine for this fatal pathogen was developed. Additionally, the effect of the above-mentioned vaccine was investigated against IPNV using Montanide 1312 VG adjuvant. Two hundred and forty healthy fish with an average weight of 3.00±0.45 g were vaccinated using immersion method with ethylene amine-inactivated IPN vaccine in combination with Montanide IMS 1312 VG for 5 min at 11 ± 1°C. The control group was vaccinated with sterile phosphate-buffered saline. The immersed vaccine with Montanide IMS 1312 VG adjuvant increased the expression of immune system genes such as IgM, MX, and CD8 within 30 days of vaccination period. The expression of IgM, Mx (P<0.05) and CD8 (P>0.05) genes was higher for the vaccine containing 10g of Montanide than that of 50g of Montanide. In fish vaccinated with the adjuvant, the relative percent survival was notably higher than of fish vaccinated without the adjuvant and the control group. Results showed that the ethylene amine-inactivated IPNV vaccine by the immersion method with Montanide IMS 1312 VG significantly has a strong protective immunity against IPNV in rainbow trout.

Viral hemorrhagic septicemia virus (VHSV), Infectious hematopoietic necrosis virus (IHNV), and infectious pancreatic necrosis virus (IPNV) are documented as the most considerable viral pathogens in Rainbow trout (Onchorhynchus mykiss). This study aimed to evaluate the frequency of these pathogens in 65 farms with suspected clinical signs in northern Iran from March 2016 to February 2018. Logistic regression analysis used to assess the effect of several determinant factors on the occurrence of these pathogens. In total, 19 (29.23%) farms were positive by a reverse transcription-polymerase chain reaction (RT-PCR). The frequency of VHSV, IHNV, and IPNV was reported 18.5%, 6.2%, and 4.61%, respectively. The most affected farms (78.95%) used river water. Furthermore, our results revealed that using river water raised the chances of viral disease by 5 times (OR= 5.02; P= 0.01). Thus, using river water was a risk factor for the occurrence of viral pathogens. From four weight groups (A to D); fishes in groups A (fish < 1 gr) and B (1 to 20 gr) were more affected but not statistically significant (P>0.05). This study has provided insight into the frequency of these targeted viruses. Collectively, establishing routine rapid diagnostic programs and setting up basic educational practices can be valuable to design the prevention and control strategies.