Atlantic Salmon Alevins Experimentally Exposed to Salmon Gill Poxvirus Become Infected, With the Virus Targeting Epithelial Cells in the Gills, Oral Cavity and Skin

Infection with salmon gill poxvirus (SGPV) can cause severe gill pathology, leading to respiratory distress and high mortality rates in salmon hatcheries, known as salmon gill poxvirus disease. While the infection has been documented in salmon at sea, broodfish and wild salmon, its occurrence in salmon alevins remains unreported. This study presents four trials aiming to infect salmon alevins with SGPV, focusing on variations in storage conditions, processing of the infectious material and cohabitation. Utilising RNAscope in situ hybridisation and PCR techniques, we show that epithelial cells in the gills, oral cavity and skin of Atlantic salmon alevins can indeed be infected with SGPV. Moreover, our findings revealed that storing the challenge material at - 20°C compromises the virus infectivity. In contrast, preservation at - 80°C retains infectivity, even in the supernatant of homogenised infected gills.