Widespread Seropositivity to Viral Hemorrhagic Septicemia Virus (VHSV) in Four Species of Inland Sport Fishes in Wisconsin.

Serological assays were conducted for anti-viral hemorrhagic septicemia virus (VHSV) antibodies in four species of fish in Wisconsin (Bluegill Lepomis macrochirus, Brown Trout Salmo trutta, Northern Pike Esox lucius, and Walleye Sander vitreus) to examine spatial and temporal distributions of exposure. Sera were tested for non-neutralizing anti-nucleocapsid antibodies to VHSV by blocking enzyme-linked immunosorbent assay (ELISA). Results (percent inhibition [%I]) were analyzed for differences among species, across geographic distance, and among water management units. Positive fish occurred in 37 of 46 inland water bodies tested, including in water bodies far from reported outbreak events. Using highly conservative species-specific thresholds (mean %I of presumptive uninfected fish + 2 SDs), 4.3% of Bluegill, 13.4% of Brown Trout, 19.3% of Northern Pike, and 18.3% of Walleye tested positive for VHSV antibodies by ELISA. Spatial patterns of seropositivity and changes in %I between sampling years were also analyzed. These analyses explore how serology might be used to understand VHSV distribution and dynamics and ultimately to inform fisheries management.

Novel reovirus associated with epidemic mortality in wild largemouth bass (Micropterus salmoides).

Reoviruses (family Reoviridae) infect vertebrate and invertebrate hosts with clinical effects ranging from inapparent to lethal. Here, we describe the discovery and characterization of Largemouth bass reovirus (LMBRV), found during investigation of a mortality event in wild largemouth bass (Micropterus salmoides) in 2015 in WI, USA. LMBRV has spherical virions of approximately 80 nm diameter containing 10 segments of linear dsRNA, aligning it with members of the genus Orthoreovirus, which infect mammals and birds, rather than members of the genus Aquareovirus, which contain 11 segments and infect teleost fishes. LMBRV is only between 24 % and 68 % similar at the amino acid level to its closest relative, Piscine reovirus (PRV), the putative cause of heart and skeletal muscle inflammation of farmed salmon. LMBRV expands the known diversity and host range of its lineage, which suggests that an undiscovered diversity of related pathogenic reoviruses may exist in wild fishes.