Shedding of the Salmonid Herpesvirus-3 by Infected Lake Trout (Salvelinus namaycush)

Salmonid Herpesvirus-3, commonly known as the Epizootic Epitheliotropic Disease virus (EEDV), causes a disease of lake trout (Salvelinus namaycush) that has killed millions of fish over the past several decades. Currently, most aspects of EEDV disease ecology remain unknown. In this study, we investigated EEDV shedding in experimentally challenged (intracoelomic injection) lake trout that were individually microchipped. In order to assess viral shedding, each infected fish was placed in individual static, aerated aquaria for a period of 8 h, after which the water was assessed for the presence of EEDV DNA using quantitative PCR. Water sampling was conducted every seven days for 93 days post-infection (pi), followed by additional sampling after one year. Results demonstrated that lake trout began shedding EEDV into the water as early as 9 days pi. Shedding peaked approximately three weeks pi and ceased after nine weeks pi. In contrast, mortalities did not occur until 40 days pi. Although mortality reached 73.9%, surviving fish ceased shedding and continued to grow. However, additional shedding was detected 58 weeks after infection in 66% of surviving fish. Findings of this study demonstrate that EEDV is shed into the water by infected lake trout hosts for extended periods of time, a mechanism that favors virus dissemination.