title: Comparison of small subunit ribosomal RNA gene and internal transcribed spacer sequences among isolates of the intranuclear microsporidian Nucleospora salmonis.
abstract: Nucleospora salmonis is an intranuclear microsporidian associated with a proliferative disorder of the lymphoid cells of captive salmonid fish in the northwestern and northeastern regions of North America, in France, and in Chile. Newer diagnostic approaches have used the polymerase chain reaction (PCR) to detect the parasite in fish tissues. The target sequences for these assays lie in the small subunit ribosomal RNA (ssu rRNA) gene or internal transcribed spacer (ITS) as determined from N. salmonis from chinook salmon (Oncorhynchus tshawytscha) from the Pacific Northwest of North America. The lack of sequence data on parasites from diverse geographic origins and hosts led us to compare several isolates of N. salmonis. There was a high degree of similarity in the ssu rDNA sequences (> 98%) among all the isolates of N. salmonis examined, regardless of host or geographic origin. The greatest sequence differences were found between isolates from the Pacific regions of America. Isolates from Chile shared sequences with one or both geographic groups from North America. A similar distribution of sequence types was observed when ITS-1 sequences of selected isolates were analyzed. Sequence data from two N. salmonis-like isolates from marine non-salmonid fish showed one closely related and the second less closely related to N. salmonis isolates from salmonid fish. These results provide evidence for a homogeneous group of aquatic members of the genus Nucleospora found among salmonid fish (N. salmonis) that can be detected using diagnostic PCR assays with ssu rDNA target sequences. The presence of parasites related to N. salmonis among marine fish suggests a potentially broad host and geographic distribution of members of the family Enterocytozoonidae.
authors.affiliation: Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California at Davis, 95616, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Gresoviac
authors.forename: J S
authors.initials: JS
authors.lastname: Khattra
authors.forename: S A
authors.initials: SA
authors.lastname: Nadler
authors.forename: M L
authors.initials: ML
authors.lastname: Kent
authors.forename: R H
authors.initials: RH
authors.lastname: Devlin
authors.forename: C P
authors.initials: CP
authors.lastname: Vivares
authors.forename: E
authors.initials: E
authors.lastname: De La Fuente
authors.forename: R P
authors.initials: RP
authors.lastname: Hedrick
mesh_terms: D000818:Animals; D021903:DNA, Ribosomal Spacer / Q000235:genetics*; D005393:Fish Diseases / Q000469:parasitology; D020459:Genes, rRNA; D006801:Humans; D016814:Microsporidia / Q000235:genetics*; D016881:Microsporidiosis / Q000469:parasitology / Q000662:veterinary*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012335:RNA, Ribosomal / Q000235:genetics; D012487:Salmonidae / Q000469:parasitology*; D017422:Sequence Analysis, DNA
chemical_list: D021903:DNA, Ribosomal Spacer; D012335:RNA, Ribosomal