Heterosporosis is an increasingly important microsporidian disease worldwide, impacting wild and farmed raised fishes in both marine and freshwater environments. A previously undescribed species (Heterosporis sp.), with widespread distribution in the Great Lakes region, was the subject of this study. Three angler-caught fish were submitted to the Minnesota Veterinary Diagnostic Laboratory from 2009-2010 with lesions caused by intracellular proliferation of parasitic spores, resulting in destruction and eventual widespread necrosis of the host skeletal muscles. Mature ovoid (5.8 × 3.5μm) spores of a microsporidian parasite, consistent with the genus Heterosporis, were observed by light and electron microscopy. Molecular identification was performed using primer walking to obtain a near-complete rRNA gene sequence (∼3,600 bp). A unique species of Heterosporis was identified, demonstrating less than 96% sequence identity to other published Heterosporis sp. on the basis of partial rRNA gene sequence analysis. Heterosporis sutherlandae n. sp. (formerly Heterosporis sp.) was identified in yellow perch (Perca flavescens), northern pike (Esox lucius) and walleye (Sander vitreus) from inland lakes in Minnesota and Wisconsin. Previous research suggests this species may be even more widespread in the Great Lakes region and should be reexamined using molecular techniques to better understand the distribution of this novel species.
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We sincerely thank the Minnesota Department of Natural Resources Pathology Laboratory (Ling Shen, Ranjit Bhagyam, Paula Phelps, and Tim Monahan), field biologists (Dave Weitzel, Steven Geving, and Molly Negus), and fishermen for submitting fish to the MVDL for this study. We also thank the US Fish and Wildlife, La Crosse Fish Health Center (Becky Lasee and Corey Puzak) for submission of archived samples. We thank Don Ariyakumar and Dean Muldoon for TEM preparations. We recognize Dr. Daniel Sutherland, Dr. Donald Cloutman, Peggy Miller, and Nate Hodgins for their preliminary work on Heterosporis sp. This study was funded in part by the Minnesota Environmental and Natural Resources Trust Fund.
© 2015 Phelps et al.