Type of event:
Presenter: Associate Professor Claudia Hase
Institution: Oregon State University
The shellfish industry in the United States is largely dependant on hatchery and nursery production of high quality, disease free larvae and juvenile bivalves mollusks (e.g. oysters, clams, mussels). Loss of seed in marine hatcheries to widespread disease-causing bacteria, such as Vibrio tubiashii and its relatives, causes severe economic loss. Losses due to vibriosis have affected shellfish culture on all coasts of the US and extend to other species groups including fish and shrimp. In 2007, the re-emergence of V. tubiashii closed one key shellfish hatchery in Oregon and markedly reduced production (estimated decrease of 59%) at nursery and various growout sites in the Pacific Northwest of the US.
Vibrio tubiashii is a recently re-emerging pathogen of larval and juvenile bivalve mollusks, causing a disease called bacillary necrosis. In spite of the economic importance of V. tubiashii in the cultivation of larval and juvenile bivalves in shellfish hatcheries, little is known about the virulence mechanisms employed by this organism. Marine Vibrio species typically produce an array of extracellular products (ECPs) that are potential pathogenicity factors. Culture supernatants of V. tubiashii had been shown to be toxic to oyster larvae and were reported to contain several ECPs, such as a zinc-metalloprotease and a cytolysin/hemolysin. Work by our team over the past few years identified some of the genetic basis of Vibrio toxicity to shellfish larvae. Furthermore, we investigated the regulation of potential virulence factors in V. tubiashii by environmental conditions.
Detailed research to date shows that the impact of vibriosis on marine hatcheries can be prevented in many cases and greatly reduced in nearly all cases if early detection is possible. Thus, the primary impediment today for marine hatcheries to make effective management decisions is the lack of diagnostic method for the early detection of pathogenic Vibrio bacteria. We have developed a quantitative PCR (qPCR) assay for the detection of the V. tubiashii metalloprotease gene and are currently developing specific antibody-based detection methods usable on-site in hatcheries. This technology can be expected to markedly advance the productivity and efficiency of marine hatcheries.