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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Publications at this Location » Publication #310504
Title: Diagnostic tools for rapid detection and quantification of Weissella ceti NC36 infections in rainbow trout

Author
item Snyder, Anna
item HINSHAW, JEFFREY - North Carolina State University
item Welch, Timothy - Tim

Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2014
Publication Date: 1/19/2015
Citation: Snyder, A.K., Hinshaw, J.M., Welch, T.J. 2015. Diagnostic tools for rapid detection and quantification of Weissella ceti NC36 infections in rainbow trout. Letters in Applied Microbiology. DOI: 10.1111/lam.12365.

Interpretive Summary: Weissellosis is an emerging infectious disease of farmed rainbow trout caused by Weissella ceti, a gram-positive bacterium. This disease can result in high rates of mortality in market-sized fish and therefore can cause significant economic losses. An effective Weissellosis vaccine has been developed and is in limited use in North Carolina. However, methods for detection and monitoring of Weissella ceti NC36 are needed to support efforts in outbreak investigation, disease surveillance, epidemiology and to better advise farmers of infection risk and the need for vaccine use. We developed diagnostic assays for the rapid identification of Weissella ceti and for quantification of pathogen load directly from tissues without the need for bacterial amplification or isolation. These tools are critical for rapid confirmation of Weissellosis diagnosis and for studying the epidemiology of this emerging pathogen.

Technical Abstract: Weissellosis in rainbow trout is caused by the gram-positive bacteria Weissella ceti and has been reported in China, Brazil and the United States. This disease can result in high mortality in market-sized fish and thus causes significant losses. Thus far, phenotypic characterization and 16S rRNA sequencing have been used to confirm a Weissellosis diagnosis. Here, we present the development of the first PCR-based diagnostic tools for the rapid identification and quantification of Weissella ceti within culture and trout tissues. A duplex PCR, which amplifies both genus- and strain-specific targets, positively identifies isolates as Weissella ceti NC36. A qPCR assay was also developed to quantify pathogen load from infected tissues, using a Weissella ceti NC36 unique locus. A proof of concept study was performed to demonstrate that quantification using traditional plate count methods and qPCR were significantly correlated when assessed from infected brain and spleen tissue. These tools were also used to confirm diagnosis of Weissellosis in a commercial rainbow trout farm during an outbreak investigation. To our knowledge, these are the first diagnostic tools developed for identification and quantification of Weissella ceti infection within rainbow trout, contributing to rapid Weissellosis diagnosis, enhanced pathogen surveillance, and epidemiological studies.