Pathology, tissue distribution, and phylogenomic characterization of largemouth bass virus isolated from a wild smallmouth bass (Micropterus dolomieu)

Viruses
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Abstract

We performed a diagnostic disease investigation on a wild smallmouth bass (Micropterus dolomieu) with skin ulcers that was collected from Lake Oahe, South Dakota, following reports from anglers of multiple fish with similar lesions. Gross and histologic lesions of ulcerative dermatitis, myositis, and lymphocytolysis within the spleen and kidneys were consistent with largemouth bass virus (LMBV) infection. LMBV was detected by conventional PCR in samples of a skin ulcer, and the complete genome sequence of the LMBV (99,184 bp) was determined from a virus isolate obtained from a homogenized skin sample. A maximum likelihood (ML) phylogenetic analysis based on the major capsid protein (MCP) gene alignment supported the LMBV isolate (LMBV-SD-2023) as a member of the species Ranavirus micropterus1, branching within the subclade of LMBV isolates recovered from North American largemouth (Micropterus salmoides) and smallmouth bass. This is the first detection of LMBV in wild smallmouth bass from South Dakota. The ultrastructure of the LMBV isolate exhibited the expected icosahedral shape of virions budding from cellular membranes. Viral nucleic acid in infected cells was visualized via in situ hybridization (ISH) within dermal granulomas, localized predominantly at the margin of epithelioid macrophages and central necrosis. Further sampling is needed to determine the geographic distribution, affected populations, and evolutionary relationship between isolates of LMBV.

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Publication type Article
Publication Subtype Journal Article
Title Pathology, tissue distribution, and phylogenomic characterization of largemouth bass virus isolated from a wild smallmouth bass (Micropterus dolomieu)
Series title Viruses
DOI 10.3390/v17081031
Volume 17
Issue 8
Publication Date July 23, 2025
Year Published 2025
Language English
Publisher MDPI
Contributing office(s) Western Fisheries Research Center
Description 1031, 14 p.
Country United States
State South Dakota
Other Geospatial Lake Oahe
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