Siniperca chuatsi rhabdovirus derived from Mandarin fish was pathogenic to Largemouth Bass

Abstract Background Siniperca chuatsi rhabdovirus (SCRV) is one of the most important causativea gents of fish viral diseases, especially the virulent strains. SCRVcould cause significant loss and damages in the fish breeding industry. However, the pathogenesis of SCRV is unclear. Methods In the present study, two SCRV strains (SCRV-QY strain, SCRV-GM strain) derived from Mandarin fish was pathogenic to Largemouth Bass and the pathogenicity was revealed. The viral RNA copy numbers and innate immune activity detected by real-time qRT-PCRThe tissue sections were stained with hematoxylin-eosin (HE). And the sections of tissue were then examined by light microscope. Results Both of two strains were lethal to Largemouth Bass, which showed obvious clinical symptoms/pathology. The SCRV-GM strain was more virulent than the SCRV-QY strain and had higher mortality. Largemouth Bass infected with the SCRV-GM strain had higher viral RNA copy numbers than those of fishes infected with the SCRV-QY strain in all tissues. The viral RNA copy numbers were higher in the kidney, brain and spleen, which may be the target organ of virus. Additionally, the expression levels of innate immune activity-related genes, including Viperin, IRF-7, IRAK1 and Mx, were slightly up-regulated in the brain on the 7th and 21st day. Moerover, the Mx was slightly up-regulated in the intestine and spleen on the 7th and 21st day. Conclusions In the study, the two SCRV strains derived from Mandarin fish was lethal to Largemouth Bass and were characterized by systematic elucidation, which can help to understand the virus and diagnose the associated disease.