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Diseases of Aquatic Organisms

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DAO 149:59-70 (2022)  -  DOI:

Diffuse large B cell lymphoma and a novel gammaherpesvirus in northern elephant seals Mirounga angustirostris

Margaret E. Martinez1,*, Nicole I. Stacy2, James F. X. Wellehan Jr.2, Linda L. Archer2, Salvatore Frasca Jr.3, Carlos Rios1, Emily J. Trumbull1,4, Michelle Rivard1, Emily R. Whitmer1, Cara L. Field1, Pádraig J. Duignan1

1The Marine Mammal Center, Sausalito, California 94965, USA
2College of Veterinary Medicine, University of Florida, Gainesville, Florida 32608, USA
3Connecticut Veterinary Medical Diagnostic Laboratory, Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, Connecticut 06269, USA
4SeaWorld, San Antonio, Texas 78251, USA
*Corresponding author:

ABSTRACT: Two emaciated male northern elephant seal (NES) Mirounga angustirostris pups were admitted to The Marine Mammal Center (Sausalito, California, USA) and treated for malnutrition. Complete blood counts showed a progressive moderate to marked leukocytosis characterized by a predominance of large monomorphic mononuclear cells of probable lymphoid origin, frequently with flower-shaped nuclei. Both seals were euthanized due to suspected lymphoid neoplasia. At necropsy, most lymph nodes in both pups were markedly enlarged, some with distinct white nodules, the spleens were diffusely enlarged, and the intestinal mucosae were thickened. Histopathologic features consistent with disseminated large cell lymphoma were identified to varying degrees of severity in lymph nodes, bone marrow, liver, tonsils, spleen, liver, intestines, kidneys, lower urinary tract, and several other organs. Immunohistochemical staining of neoplastic cells was most consistent with B lymphocyte origin, with most cells staining positively for Pax 5 and CD20 with admixed small CD3-positive T lymphocytes and CD204-positive macrophages. PCR and sequencing identified a novel gammaherpesvirus, herein called miroungine gammaherpesvirus 3, from affected tissues. This virus is in a clade outside of named genera that utilize hosts in the suborder Caniformia. The present study is the first description of diffuse large B cell lymphoma with leukemic manifestation and concomitant detection of a novel gammaherpesvirus in free-living NESs. Further research regarding the prevalence of this new gammaherpesvirus and its associated pathogenesis in this species is indicated.

KEY WORDS: Northern elephant seal · Mirounga angustirostris · Lymphoma · Gammaherpesvirinae · Leukemia · B cell · Immunohistochemistry

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Cite this article as: Martinez ME, Stacy NI, Wellehan JFX Jr, Archer LL and others (2022) Diffuse large B cell lymphoma and a novel gammaherpesvirus in northern elephant seals Mirounga angustirostris. Dis Aquat Org 149:59-70.

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