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Title: Detection of Nucleospora salmonis in steelhead,Oncorhynchus mykiss (Walbaum), using quantitative polymerase chain reaction(qPCR)

Author
item FOLTZ, JOHN - UNIV OF ID, HAGERMAN, ID
item Overturf, Kenneth - Ken
item PLANT, KAREN - UNIV OF ID, HAGERMAN, ID
item CLEMENS, KAREN - U.S. FISH & WILDLIFE SE
item POWELL, MATT - UNIV OF ID, HAGERMAN, ID

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2009
Publication Date: 4/12/2009
Citation: Foltz, J., Overturf, K.E., Plant, K., Clemens, K., Powell, M. 2009. Detection of Nucleospora salmonis in steelhead,Oncorhynchus mykiss (Walbaum), using quantitative polymerase chain reaction(qPCR). Journal of Fish Diseases. 32:551-555.

Interpretive Summary: Nucleospora salmonis is a parasite found in salmonid fishes. The parasiste principally infects blood cells resulting in leukemia-like conditions. N. salmonis generally weakens immune system function allowing for other, opportunistic infections, but it can also be fatal. N. salmonis occurs naturally in the northwestern United States in Chinook salmon and steelhead and has also been reported in Europe and South America. This salmonid pathogen, however, poses its greatest threat within commercial and conservation aquaculture hatchery operations where fish rearing densities are higher than those found in the wild. As with other pathogens, identifying N. salmonis at low levels or among asymptomatic carriers before observable illness occurs is fundamentally important to prevent spread of the disease. N. salmonis infection is generally confirmed by chemical staining for the organism and laborious microscopic examination. Fortunately, several molecular techniques such as polymerase chain reaction (PCR) have been developed which speeds identification and facilitates detection in animals not displaying symptoms of the disease. Here we describe a real-time quantitative PCR method to identify N. salmonis in fish tissues at very low levels. We demonstrate that this method is more sensitive than current methods for the identification of this parasite and that detection of the organism is better in some tissues than others.

Technical Abstract: Nucleospora salmonis is an intranuclear microsporidian found in salmonid fishes. The parasiste principally infects lymphoblast cells resulting in chronic severe lymphoblastosis and leukemia-like conditions. N. salmonis generally weakens immune system function allowing for other, opportunistic infections, but it can also be fatal. N. salmonis occurs naturally in the northwestern United States in Chinook salmon and steelhead and has also been reported in Europe and South America. This salmonid pathogen, however, poses its greatest threat within commercial and conservation aquaculture where fish rearing densities are higher than those found in the wild. As with other pathogens, identifying N. salmonis at low levels or among asymptomatic carriers before observable illness occurs is fundamentally important to prevent spread of the disease. N. salmonis infection is generally confirmed by histochemical staining and laborious microscopic examination. Fortunately, several polymerase chain reaction (PCR) methods have been developed which speeds identification and facilitates detection in asymptomatic animals. Here we describe a real-time quantitative PCR(qPCR) method to identify N. salmonis in fish tissues at very low levels. We demonstrate that qPCR is more sensitive than current histochemical methods and nested PCR methods for the identification of this parasite and that detection of the organism is better in some tissues than others.