Experimental Infection of Rainbow Trout, Oncorhynchus mykiss, and Hybrid Striped Bass, Morone chrysops ♂ × Morone saxatilis ♀, with Viral Hemorrhagic Septicemia Virus Genotype IVb

Abstract The emergence of a new sublineage of viral hemorrhagic septicemia virus ( VHSV ) within the Laurentian Great Lakes has caused concern for aquaculture in the United States. Because of the occurrence of VHSV in a new geographic location, new host species have been identified and the complete host range has not been determined. This study confirmed the high resistance of rainbow trout, Oncorhynchus mykiss , to VHSV type IVb infection. In addition, the experimental susceptibility of hybrid striped bass, Morone chrysops ♂ × Morone saxatilis ♀, to VHSV type IVb infection was examined but determined to be highly dependent on age of fish and exposure temperature. No mortality was observed in adult fish infected via intraperitoneal ( IP ) injection at 15 C, whereas yearling fish infected via IP injection under the same conditions experienced 20.8% mortality. Among yearling fish infected via IP injection, mortality increased to 100% when exposure to VHSV occurred at 10 C. An LD 50 for yearling hybrid striped bass exposed to VHSV at 10 C by IP injection was determined to be 1.4 × 10 4 pfu ( SE = 2.1). Thus, at 10 C, yearling hybrid striped bass experience a high mortality when exposed to VHSV IVb by IP injection.