DAO 126:185-198 (2017)  -  DOI: https://doi.org/10.3354/dao03170

Morphological and molecular confirmation of Myxobolus cerebralis myxospores infecting wild‑caught and cultured trout in North Carolina (SE USA)

Carlos F. Ruiz1, Jacob M. Rash2, Cova R. Arias3, Doug A. Besler2, Raphael Orélis-Ribeiro1, Matthew R. Womble1, Jackson R. Roberts1, Micah B. Warren1, Candis L. Ray3, Stacey Lafrentz3, Stephen A. Bullard1,*

1Aquatic Parasitology Laboratory, School of Fisheries, Aquaculture, and Aquatic Sciences and Southeastern Cooperative Fish Parasite and Disease Laboratory (SCFPDL), Auburn University, Auburn, AL 36849, USA
2North Carolina Wildlife Resources Commission (NCWRC), Marion, NC 28752, USA
3Aquatic Microbiology Laboratory, Auburn, AL 36832, USA
*Corresponding author:

ABSTRACT: We used microscopy and molecular biology to provide the first documentation of infections of Myxobolus cerebralis (Myxozoa: Myxobolidae), the etiological agent of whirling disease, in trout (Salmonidae) from North Carolina (USA) river basins. A total of 1085 rainbow trout Oncorhynchus mykiss, 696 brown trout Salmo trutta, and 319 brook trout Salvelinus fontinalis from 43 localities across 9 river basins were screened. Myxospores were observed microscopically in pepsin-trypsin digested heads of rainbow and brown trout from the Watauga River Basin. Those infections were confirmed using the prescribed nested polymerase chain reaction (PCR; 18S rDNA), which also detected infections in rainbow, brown, and brook trout from the French Broad River Basin and the Yadkin Pee-Dee River Basin. Myxospores were 9.0–10.0 µm (mean ± SD = 9.6 ± 0.4; N = 119) long, 8.0–10.0 µm (8.8 ± 0.6; 104) wide, and 6.0–7.5 µm (6.9 ± 0.5; 15) thick and had polar capsules 4.0–6.0 µm (5.0 ± 0.5; 104) long, 2.5–3.5 µm (3.1 ± 0.3; 104) wide, and with 5 or 6 polar filament coils. Myxospores from these hosts and rivers were morphologically indistinguishable and molecularly identical, indicating conspecificity, and the resulting 18S rDNA and ITS-1 sequences derived from these myxospores were 99.5–100% and 99.3–99.8% similar, respectively, to published GenBank sequences ascribed to M. cerebralis. This report comprises the first taxonomic circumscription and molecular confirmation of M. cerebralis in the southeastern USA south of Virginia.


KEY WORDS: Trout · Salmonid · Southeastern USA · Whirling disease · Morphology · Molecular diagnostics


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Cite this article as: Ruiz CF, Rash JM, Arias CR, Besler DA and others (2017) Morphological and molecular confirmation of Myxobolus cerebralis myxospores infecting wild‑caught and cultured trout in North Carolina (SE USA). Dis Aquat Org 126:185-198. https://doi.org/10.3354/dao03170

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