DAO 126:211-227 (2017)  -  DOI: https://doi.org/10.3354/dao03171

Complete sequences of 4 viral hemorrhagic septicemia virus IVb isolates and their virulence in northern pike fry

Rodman G. Getchell1,*, Emily R. Cornwell1,5, Steven Bogdanowicz2, Jose Andrés2, William N. Batts3, Gael Kurath3, Rachel Breyta3, Joanna G. Choi1, John M. Farrell4, Paul R. Bowser1

1Aquatic Animal Health Program, Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
2Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
3US Geological Survey, Western Fisheries Research Center, 6505 NE 65th Street, Seattle, WA 98115, USA
4Department of Environmental and Forest Biology, College of Environmental Science and Forestry, State University of New York, 250 Illick Hall, Syracuse, NY 13210, USA
5Present address: Muddy Branch Veterinary Center, Gaithersburg, MD 20878, USA
*Corresponding author:

ABSTRACT: Four viral hemorrhagic septicemia virus (VHSV) genotype IVb isolates were sequenced, their genetic variation explored, and comparative virulence assayed with experimental infections of northern pike Esox lucius fry. In addition to the type strain MI03, the complete 11183 bp genome of the first round goby Neogobius melanostomus isolate from the St. Lawrence River, and the 2013 and 2014 isolates from gizzard shad Dorosoma cepedianum die-offs in Irondequoit Bay, Lake Ontario and Dunkirk Harbor, Lake Erie were all deep sequenced on an Illumina platform. Mutations documented in the 11 yr since the MI03 index case from Lake St. Clair muskellunge Esox masquinongy showed 87 polymorphisms among the 4 isolates. Twenty-six mutations were non-synonymous and located at 18 different positions within the matrix protein, glycoprotein, non-virion protein, and RNA polymerase genes. The same 4 isolates were used to infect northern pike fry by a single 1 h bath exposure. Cumulative percent mortality varied from 42.5 to 62.5%. VHSV was detected in 57% (41/72) of the survivors at the end of the 21-d trial, suggesting that the virus was not rapidly cleared. Lesions were observed in many of the moribund and dead northern pike, such as hemorrhaging in the skin and fins, as well as hydrocephalus. Mean viral load measured from the trunk and visceral tissues of MI03-infected pike was significantly higher than the quantities detected in fish infected with the most recent isolates of genotype IVb, but there were no differences in cumulative mortality observed.

KEY WORDS:  Esox lucius · Experimental infection · Illumina sequencing · Northern pike · Viral hemorrhagic septicemia virus · VHSV IVb

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Cite this article as: Getchell RG, Cornwell ER, Bogdanowicz S, Andrés J and others (2017) Complete sequences of 4 viral hemorrhagic septicemia virus IVb isolates and their virulence in northern pike fry. Dis Aquat Org 126:211-227. https://doi.org/10.3354/dao03171

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