Lake Trout (Salvelinus namaycush) Naturally Infected with Salmovirus salmonidallo3 (SalHV-3; Family Alloherpesviridae) Continue to Harbor the Virus for Nearly a Decade.

Salmovirus salmonidallo3 (SalHV-3) causes Epizootic Epitheliotropic Disease (EED), which has resulted in the death of millions of lake trout (Salvelinus namaycush) over the past 40 years. Although advancements in understanding this virus's pathogenicity and control strategies have been made, the duration and effects of chronic SalHV-3 infections remain unknown. This study focused on lake trout that survived a natural outbreak of EED in 2012 and were maintained under quarantine conditions until 2021. Following exposure to either repeated or intermittent handling stress designed to mimic typical hatchery practices, SalHV-3 was detected (via a SalHV-3-specific quantitative PCR assay) in multiple tissues from multiple fish. Non-lethally collected tissues revealed the highest prevalence and virus loads in the fin and mucus. SalHV-3 was detected in these tissues throughout the study period (49 days, 8 sampling events), with some fish having detectible virus on each study day and others only intermittently (n = 1-7 sampling days). Tissues collected lethally yielded SalHV-3 detections in multiple nervous tissues, as well as in the cornea of several fish. Experiments to evaluate virus shedding revealed that SalHV-3 was intermittently detectable in fish holding water. Collectively, results indicate that lake trout can remain SalHV-3 infected for nearly a decade and intermittently shed the virus, constituting a threat to hatchery-based lake trout conservation efforts in the Great Lakes basin.