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Diseases of Aquatic Organisms

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DAO 143:51-56 (2021)  -  DOI: https://doi.org/10.3354/dao03554

Detection of Myxobolus cerebralis (Bivalvulida: Myxobolidae) in two non-Tubifex tubifex oligochaetes in the southeastern USA

Steven P. Ksepka1,*, Jacob M. Rash2, Wenlong Cai3, Stephen A. Bullard1

1Aquatic Parasitology Laboratory, School of Fisheries, Aquaculture, and Aquatic Sciences, College of Agriculture, Auburn University, 203 Swingle Hall, Auburn, AL 36849, USA
2North Carolina Wildlife Resources Commission, 645 Fish Hatchery Road, Marion, NC 28752, USA
3Department of Pathology and Microbiology, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave, Charlottetown, PEI C1A 4P3, Canada
*Corresponding author:

ABSTRACT: Myxobolus cerebralis (Hofer, 1903), the etiological agent of salmonid whirling disease, reportedly matures in only the oligochaete ‘Tubifex tubifex’. The concept of ‘T. tubifex’ is problematic because it is renowned as a species complex (or having ‘strains’), and many sequences ascribed to this taxon in GenBank are misidentified or indicate several cryptic species. These facts cast doubt on the long-held notion that M. cerebralis is strictly host-specific to the single definitive host, T. tubifex. Herein, as part of an ongoing regional whirling disease monitoring project, oligochaetes (452 specimens) were collected from 31 riverine sites in western North Carolina (August through September 2015) and screened for infection by M. cerebralis. The species-specific nested PCR for M. cerebralis was positive for 8 oligochaete specimens from the French Broad River Basin (Mill Creek and Watauga River) and New River Basin (Big Horse Creek). We individually barcoded these M. cerebralis-positive oligochaete specimens using cytochrome oxidase 1 (CO1) primers and then conducted a Bayesian inference phylogenetic analysis. We identified 2 oligochaete genotypes: one sister to a clade comprising Limnodrilus udekemianus (Haplotaxida: Naididae) and another sister to Limnodrilus hoffmeisteri. This is the first detection of M. cerebralis from an oligochaete in the SE USA and the first detection of M. cerebralis from an oligochaete other than T. tubifex. These results suggest that other non-T. tubifex definitive hosts can harbor the pathogen and should be considered in the context of fish hatchery biosecurity and monitoring wild trout streams for M. cerebralis and whirling disease in the southeastern USA.


KEY WORDS: Tubificinae · Oligochaete · Myxozoa


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Cite this article as: Ksepka SP, Rash JM, Cai W, Bullard SA (2021) Detection of Myxobolus cerebralis (Bivalvulida: Myxobolidae) in two non-Tubifex tubifex oligochaetes in the southeastern USA. Dis Aquat Org 143:51-56. https://doi.org/10.3354/dao03554

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