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Ichthyophonus parasite phylogeny based on ITS rDNA structure prediction and alignment identifies six clades, with a single dominant marine type

July 7, 2016

Despite their widespread, global impact in both wild and cultured fishes, little is known of the diversity, transmission patterns, and phylogeography of parasites generally identified as Ichthyophonus. This study constructed a phylogeny based on the structural alignment of internal transcribed spacer (ITS) rDNA sequences to compare Ichthyophonus isolates from fish hosts in the Atlantic and Pacific oceans, and several rivers and aquaculture sites in North America, Europe, and Japan. Structure of the Ichthyophonus ITS1–5.8S–ITS2 transcript exhibited several homologies with other eukaryotes, and 6 distinct clades were identified within Ichthyophonus. A single clade contained a majority (71 of 98) of parasite isolations. This ubiquitous Ichthyophonus type occurred in 13 marine and anadromous hosts and was associated with epizootics in Atlantic herring, Chinook salmon, and American shad. A second clade contained all isolates from aquaculture, despite great geographic separation of the freshwater hosts. Each of the 4 remaining clades contained isolates from single host species. This study is the first to evaluate the genetic relationships among Ichthyophonus species across a significant portion of their host and geographic range. Additionally, parasite infection prevalence is reported in 16 fish species.

Citation Information

Publication Year 2016
Title <i>Ichthyophonus</i> parasite phylogeny based on ITS rDNA structure prediction and alignment identifies six clades, with a single dominant marine type
DOI 10.3354/dao03017
Authors Jacob Gregg, Rachel L. Thompson, Maureen K. Purcell, Carolyn S. Friedman, Paul Hershberger
Publication Type Article
Publication Subtype Journal Article
Series Title Diseases of Aquatic Organisms
Series Number
Index ID 70175023
Record Source USGS Publications Warehouse
USGS Organization Western Fisheries Research Center