Dynamic Distribution of Infectious Pancreatic Necrosis Virus (IPNV) Strains of Genogroups 1, 5, and 7 after Intraperitoneal Administration in Rainbow Trout (Oncorhynchus mykiss)

Infectious pancreatic necrosis virus (IPNV) is the causative agent of rainbow trout (Oncorhynchus mykiss) IPN and causes significant loss of fingerlings. The currently prevalent IPNV genogroups in China are genogroups 1 and 5. However, in this study, we isolated and identified a novel IPNV, IPNV-P202019, which belonged to genogroup 7. Here, a total of 200 specific-pathogen-free rainbow trout (10 g average weight) were divided randomly into four groups to investigate the distribution of different IPNV strains (genogroups 1, 5, and 7) in 9 tissues of rainbow trout by means of intraperitoneal (ip) injection. Fish in each group were monitored after 3-, 7-, 14-, 21- and 28- days post-infection (dpi). The study showed no mortality in all groups. The distribution of IPNV genogroups 1 and 5 was similar in different tissues and had a higher number of viral loads after 3, 7, or 14 dpi. However, the distribution of IPNV genogroup 7 was detected particularly in the spleen, head kidney, and feces and had a lower number of viral loads. The results of this study provide valid data for the distribution of IPNV in rainbow trout tissues and showed that IPNV genogroups 1 and 5 were still the prevalent genogroups of IPNV in China. Although rainbow trout carried IPNV genogroup 7, the viral load was too low to be pathogenic.