Journal
DISEASES OF AQUATIC ORGANISMS
Volume 143, Issue -, Pages 51-56Publisher
INTER-RESEARCH
DOI: 10.3354/dao03554
Keywords
Tubificinae; Oligochaete; Myxozoa
Categories
Funding
- Alabama Department of Conservation and Natural Resources, Alabama Agricultural Research Station
- North Carolina Wildlife Resources Commission
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This study identified Myxobolus cerebralis in an oligochaete for the first time in the southeastern USA, and also for the first time in an oligochaete other than T. tubifex. These findings suggest that other definitive hosts besides T. tubifex may harbor the pathogen, highlighting the importance of considering alternative hosts for biosecurity in fish hatcheries and monitoring for M. cerebralis and whirling disease in wild trout streams in the southeastern USA.
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.
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