Comparative susceptibility of representative Great Lakes fish species to the North American viral hemorrhagic septicemia virus Sublineage IVb

Abstract

The present study compared the susceptibility of representative Laurentian Great Lakes fish species to the emerging viral hemorrhagic septicemia virus (VHSV) Genotype IVb. The median lethal dose of infection by intraperitoneal injection (IP-LD 50 ) was obtained from fish that were experimentally infected with the MI03 index strain of VHSV-IVb. Fish were injected at doses ranging from 7 × 10 7 to 7 × 10 -2 plaque-forming units (pfu) and maintained at 12 ± 1°C. The infection trials identified species of high, medium, and low susceptibility based on the IP-LD 50 values. Pathogenicity of VHSV-IVb was highest in largemouth bass Micropterus salmoides, which resulted in an IP-LD 50 of 1.5 × 10 2 pfu, while also demonstrating the clinical diathesis of VHSV-infected fish. The virus was moderately pathogenic in yellow perch Perca flavescens (IP-LD 50 of 2.5 × 10 5 pfu), but also showed the classical signs of VHSV infection. Salmonids were the least susceptible to VHSV-IVb with IP-LD 50 values of no less than 1.4 × 10 6 pfu; however, in fish that succumbed to infection, characteristic VHSV lesions were observed. Histopathologic alterations were most profound in gill, skin, muscle, gonads, and liver of largemouth bass and yellow perch, while in salmonids, hemorrhages in the swimbladder and/or degenerative changes in the liver were the most common lesions noticed. VHSV was isolated from infected fish, and its identity was confirmed by the reverse transcriptase polymerase chain reaction. These results highlight the variations among fish species susceptibility to this emerging strain of VHSV and offer insights into the potential impact of VHSV-IVb on the Laurentian Great Lakes fish community.

Role of Viral Hemorrhagic Septicemia Virus Matrix (M) Protein in Suppressing Host Transcription

“…VHSV-IVb has been isolated from at least 31 fish species, including muskellunge, yellow perch, and walleye (28), and has been detected in all five of the Laurentian Great Lakes (31,32). However, unlike the European Ia sublineage, IVb has low pathogenicity for rainbow trout (33). Despite intensive management and surveillance, VHSV is still detectable among many asymptomatic fish in the Great Lakes region (34).…”

Low prevalence of VHSV detected in round goby collected in offshore regions of Lake Ontario

“…However, these signs are not specific to VHSV and naturally and experimentally infected fish can carry high levels of the virus (up to 10 7 VHSV nucleoprotein gene copies per 50 ng RNA measured by quantitative reverse transcriptase polymerase chain reaction [qRT-PCR]) without showing any gross clinical signs Groocock et al, 2012). The susceptibility of fish to VHSV IVb varies across species (Kim and Faisal, 2010a;Groocock et al, 2012). Although 28 species within the Great Lakes are considered susceptible, some species are highly susceptible to the virus (e.g., tiger muskellunge ♂Esox lucius×♀E.…”

Detection and surveillance of viral hemorrhagic septicemia virus using real-time RT-PCR. I. Initial comparison of four protocols

“…Dependent on the species of fish, infection may result in substantial mortality (Smail & Snow 2011, Kim & Faisal 2010a,b,c, Groocock et al 2012. VHSV can become endemic in fish populations, with some individual fish serving as carriers of the virus and periodically shedding the virus, which causes repeat episodes of disease in naïve fish populations (Hershberger et al 2010.…”