Distribution of viral hemorrhagic septicemia virus in the nearshore fish community of the St. Lawrence River.

Abstract

Objective: We investigated viral hemorrhagic septicemia virus dynamics in wild fish populations of the St. Lawrence River to compare host competency among five abundant native species and the invasive Round Goby Neogobius melanostomus following two decades of host-pathogen coevolution. To examine species' responses to the virus and identify principal hosts as viral reservoir species, we used viral surveillance among Round Gobies, Yellow Perch Perca flavescens, Rock Bass Ambloplites rupestris, Pumpkinseed Lepomis gibbosus, Bluegill L. macrochirus, and Brown Bullhead Ameiurus nebulosus collected from the nearshore fish community in the upper St. Lawrence River during spring 2020-2021.

Methods: Reverse-transcription quantitative PCR was used to detect and quantify viral nucleoprotein gene genetic material in pooled organ (i.e., liver, kidney, and spleen) and brain tissues of wild fish belonging to several susceptible host species.

Results: Reverse-transcription quantitative PCR detected viral hemorrhagic septicemia virus genetic material in each species during both sampling years. There was significant variation between species in both infection prevalence and median viral titer. Invasive Round Gobies exhibited significantly higher prevalence and titers compared to any of the native species. However, some native fishes (e.g., Yellow Perch and sunfishes Lepomis spp.) presented higher infection prevalence and viral concentrations compared to the others (e.g., Rock Bass and Brown Bullhead).

Conclusions: Multiple species remain susceptible to viral hemorrhagic septicemia virus under enzootic conditions; however, viral infections are distributed unevenly among host species. Invasive Round Gobies have amplified reservoir competence compared to native fish species.