Study on the immune enhancers against <i>Micropterus salmoides</i> rhabdovirus infection

Micropterus salmoides rhabdovirus (MSRV) is one of the most serious pathogens harming M. salmoides juvenile, which had brought huge economic losses to farming industry. Studies involving candidate genes to the clinical diseases, however, are limited. In this study, the viral target and clinical manifestation of MSRV on M. salmoides juvenile were analyzed, and the protective effects of a single immune enhancer and a compound immune enhancer were evaluated. The results showed that the brain, liver, intestine and muscle of M. salmoides showed obvious lesions after infection with MSRV. The relative expression levels of nucleoprotein (N) and matrix protein (M) genes showed a trend of increasing at first and then decreasing and reached the peak in each tissue at 36 h post-infection. The mortality rate of M. salmoides was over 90% after 7 days of MSRV infection. The immune enhancers containing free nucleotides and Astragalus polysaccharide added to the diet effectively inhibited the replication of N and M genes in M. salmoides and increased the survival rate by 25% to 28%. This study provided basic data and theoretical reference for the analysis of the pathological mechanism and prevention and treatment of MSRV.