DAO prepress abstract  -  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. Ruiz, Jacob M. Rash, Cova R. Arias, Doug A. Besler, Raphael Orélis-Ribeiro, Matthew R. Womble, Jackson R. Roberts, Micah B. Warren, Candis L. Ray, Stacey Lafrentz, Stephen A. Bullard*

*Email: ash.bullard@auburn.edu

ABSTRACT: Herein, we use 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 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 trout and brown trout from the Watauga River Basin. Those infections were confirmed using the prescribed nested polymerase chain reaction (PCR; 18S rDNA), which detected infections also in rainbow trout, brown trout, 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 (8.8 ± 0.6; 104) wide, and 6.0−7.5 (6.9 ± 0.5; 15) thick and had polar capsules 4.0−6.0 (5.0 ± 0.5; 104) long, 2.5−3.5 (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.