Development of a real time quantitative PCR assay for the hard clam pathogen Quahog Parasite Unknown (QPX)
Lyons, M. Maille
Smolowitz, Roxanna M.
Dungan, Christopher F.
Roberts, Steven B.
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KeywordQuahog Parasite Unknown; QPX; Thraustochytrids; Mercenaria mercenaria; Real-time PCR; Histology; Marine aggregates; Pseudofeces; Clams
Quahog Parasite Unknown (QPX) is a thraustochytrid pathogen responsible for catastrophic mortalities of the northern quahog (hard clam) Mercenaria mercenaria. A real-time quantitative polymerase chain reaction (qPCR) assay was developed to assist research efforts on QPX ecology and pathology. Sensitivity of the assay was evaluated with serial dilutions of QPX-cultured cells to determine the lowest concentration of DNA that remained detectable in both the presence and absence of extraneous environmental substances. QPX cells were quantified before DNA extraction to calibrate standard curves to cell counts. Based on our results, the qPCR assay is able to quantify QPX within the range of 1 to several thousand organisms per reaction. Specificity of the assay was assessed by testing 29 thraustochytrid-like protists isolated from suspension-feeding bivalves from China, Oregon, Maryland, and Virginia. Application of the assay was demonstrated with positive qPCR results from naturally contaminated environmental samples including marine aggregates (i.e. marine snow), clam pseudofeces, and inflammatory nodules from infected clams. This quantitative assay for QPX will provide a valuable tool for characterizing QPX parasite abundances in coastal environments and for improving clam disease diagnostics.
Author Posting. © Inter-Research, 2006. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Diseases of Aquatic Organisms 72 (2006): 45-52, doi:10.3354/dao072045.
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Epizootiology of Quahog Parasite Unknown (QPX) disease in northern quahogs (=hard clams) Mercenaria mercenaria Lyons, M. Maille; Smolowitz, Roxanna M.; Gomez-Chiarri, Marta; Ward, J. Evan (National Shellfisheries Association, 2007-08)The economically important marine bivalve mollusc, Mercenaria mercenaria, (commonly called a northern quahog or hard clam), has endured considerable mortalities caused by a thraustochytrid pathogen called Quahog Parasite ...
Gast, Rebecca J.; Cushman, E.; Moran, Dawn M.; Uhlinger, Kevin R.; Leavitt, Dale F.; Smolowitz, Roxanna M. (Inter-Research, 2006-06-12)Quahog Parasite Unknown (QPX) is a significant cause of hard clam Mercenaria mercenaria mortality along the northeast coast of the United States. It infects both wild and cultured clams, often annually in plots that are ...
Gast, Rebecca J.; Moran, Dawn M.; Audemard, Corinne; Lyons, M. Maille; DeFaveri, Jacquelin; Reece, Kimberly S.; Leavitt, Dale F.; Smolowitz, Roxanna M. (Inter-Research, 2008-09-24)Quahog Parasite Unknown (QPX) is the cause of mass mortality events of hard clams Mercenaria mercenaria from Virginia, USA, to New Brunswick, Canada. Aquaculture areas in Massachusetts, USA, have been particularly hard ...