Influence of Round Gobies on VHSV Disease Ecology in the Upper St. Lawrence River.

Haws, Anna L.¹*, Rodman G. Getchell², John M. Farrell¹, ¹SUNY College of Environmental Science and Forestry, Syracuse, NY, ²Cornell University College of Veterinary Medicine, Ithaca, NY

Piscine novirhabdovirus, or Viral Hemorrhagic Septicemia Virus (VHSV), is a World Organization for Animal Health (OIE) reportable fish pathogen found across the northern hemisphere. A novel lineage, VHSV-IVb, was detected in the Great Lakes basin following sizeable fish kills in the mid-2000’s. Through IVb’s history, researchers have documented more than 30 species vulnerable to infection, high rates of genetic mutation, recurrent outbreaks, and expanding geographic range. Sensitivity to infection is extremely variable between fishes, and factors that influence VHSV persistence are not well understood. In the St. Lawrence River (SLR), the invasive round goby (Neogobius melanostomus) is regarded as essential for the amplification, spread, and evolution of VHSV, attributed to their high susceptibility, population density, widespread distribution, and trophic significance for native piscivores. Surveillance of VHSV in round gobies in the SLR from 2010 to 2022 has demonstrated strong endemicity of the pathogen in this region. However, other native fish hosts exist that can maintain this virus, therefore comparisons are needed to examine relative host competency and factors influencing viral persistence and evolution. We are using molecular techniques including RT-qPCR and Illumina sequencing to compare round gobies to several native host species in their epidemiological characteristics (i.e., prevalence, viral titer, viral genomic sequence). Our data illustrates that round gobies experience significantly higher viral prevalence rates and titers relative to native hosts, exposing the amplified role this invasive species has in influencing the trajectory of VHSV persistence in the St. Lawrence River.