Similar but different emerging adomaviruses are associated with blotchy bass syndrome in largemouth and smallmouth bass: Evidence of phylogeographic diversity [abstract]

Authors: Iwanowicz, Luke; RAINES, CLAYTON - Us Geological Survey (USGS); YOUNG, KELSEY - University Of Georgia; BLAZER, VICKI - Us Geological Survey (USGS); ADAMS, CYNTHIA - University Of Pittsburgh School Of Medicine; SMITH, GEOFFREY - Pennsylvania Game Commission, Bureau Of Wildlife Management; JONES, TOM - Vermont Agency For Natural Resources; WALSH, HEATHER - Us Geological Survey (USGS); BIGGS, MORGAN - Us Geological Survey (USGS); CORNMAN, ROBERT - Us Geological Survey (USGS)

Submitted to: American Fishery Society (Fish Health Section) Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/5/2023
Publication Date: 7/25/2023
Citation: Iwanowicz, L.R., Raines, C.D., Young, K.T., Blazer, V.S., Adams, C.R., Smith, G., Jones, T.E., Walsh, H.L., Biggs, M.A., Cornman, R.S. 2023. Similar but different emerging adomaviruses are associated with blotchy bass syndrome in largemouth and smallmouth bass: Evidence of phylogeographic diversity [abstract]. American Fishery Society (Fish Health Section) Proceedings. 7 24-27.

Interpretive Summary:

Technical Abstract: Blotchy bass syndrome has been reported in largemouth bass since the late 1980’s. This condition is characterized by hallmark hyperpigmented melanistic lesions (HPMLs) on the body surface, fins or margins of the oral cavity. Until recently, this idiopathic condition had been ascribed to best guess causes ranging from recessive genetic traits, exposure to ultraviolet light or contaminant exposure. During 2012, anglers and fish resource managers in Pennsylvania began reporting smallmouth bass with clinical signs characteristic of blotchy bass syndrome. These reports followed a few years of substantial mortality events which included skin lesions in smallmouth bass within the Susquehanna River drainage. Visible HPMLs quickly led to public speculation about the health of PA fisheries. Interestingly, blotchy smallmouth bass were first reported around this same time (2008) in Lake St. Clair, MI and more recently in Vermont. Extensive efforts followed to conclusively identify the cause of blotchy bass syndrome in smallmouth bass. We have now recovered complete viral genomes of novel, emerging adomaviruses associated with blotchy bass syndrome using a next generation sequencing workflows. These efforts have identified similar, but different (69.5% nucleotide identity) adomaviruses associated with the same clinical signs in largemouth and smallmouth bass. Non-lethal, minimally invasive methods utilizing buccal swabs to sample HPMLs of affected bass collected across the United States have provided a means to confirm the presence of virus and determine genomic variability. While River’s Postulates have not been satisfied, the association of these viruses and corresponding skin lesions provide compelling evidence of causation. Furthermore, sequencing data supports evidence of phylogeographic genomic diversity in the largemouth bass adomavirus-1 confirming that it has been present in specific aquatic environments for some time. Analysis of smallmouth bass adomavirus-1 similarly suggests phylogeographic signatures. It is not yet clear what led to the relatively recent reports of blotchy bass syndrome in smallmouth bass in areas where it had not been observed previously. More comprehensive analyses are in progress to augment molecular epidemiological investigations.