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Diseases of Aquatic Organisms

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DAO 122:1-11 (2016)  -  DOI:

Genetic characterization of esocid herpesvirus 1 (EsHV1)

Jared T. Freitas1, Kuttichantran Subramaniam2, Karen L. Kelley3, Susan Marcquenski4, Joseph Groff5, Thomas B. Waltzek2,*

1College of Agriculture and Life Science, University of Florida, Gainesville, FL 32610, USA
2Department of Infectious Diseases and Pathology, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA
3Electron Microscopy Core, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL 32611, USA
4Bureau of Fisheries Management, Wisconsin Department of Natural Resources, 101 South Webster Street, Box 7921, Madison, WI 53707, USA
5College of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA
*Corresponding author:

ABSTRACT: Blue spot disease, believed to be caused by esocid herpesvirus 1 (EsHV1), has been observed in wild northern pike Esox lucius in a number of cold-water locations, including the northern USA, Canada, and Ireland. In the spring of 2014, a northern pike was caught in Wisconsin displaying the characteristic bluish-white circular plaques on the dorsum and fins. Microscopic examination of hematoxylin and eosin-stained sections of the proliferative cutaneous lesions revealed a focally extensive abundance of panepidermal, megalocytic keratinocytes with karyomegaly. Enlarged nuclei stained basophilic, and an abundance of coarse eosinophilic granules were observed in the expanded cytoplasm. Transmission electron microscopy revealed aggregates of enveloped virus particles with electron-dense, hexagonal nucleocapsids surrounded by a uniformly staining ellipsoidal tegument layer within cytoplasmic vacuoles of megalocytic epidermal cells. More than 7000 bp of the EsHV1 genome were sequenced from infected skin tissues. Phylogenetic and phenetic analyses, based on the partial DNA-dependent DNA polymerase and terminase gene sequences, revealed EsHV1 forms a novel branch within the family Alloherpesviridae as the sister group to the clade that includes members of the genera Ictalurivirus and Salmonivirus. The gross, microscopic, and ultrastructural lesions reported in our study were identical to previous reports of blue spot disease in northern pike; however, here we provide the first molecular evidence supporting EsHV1 as a new species in the family Alloherpesviridae.

KEY WORDS: Esox lucius · Northern pike · Blue spot disease · Alloherpesviridae

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Cite this article as: Freitas JT, Subramaniam K, Kelley KL, Marcquenski S, Groff J, Waltzek TB (2016) Genetic characterization of esocid herpesvirus 1 (EsHV1). Dis Aquat Org 122:1-11.

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