MS Thesis Defense: Rachel Canty

The Master’s Thesis Defense of Rachel Canty is presented by the University of North Carolina at Chapel Hill Department of Marine Sciences and Institute of Marine Sciences. This event is scheduled for Friday, March 15th, at 1:00 pm in room 222 of UNC’s Institute of Marine Sciences in Morehead City, NC. This seminar will be simultaneously broadcast live to both UNC’s Department of Marine Sciences in the 3rd floor conference room (3204) of Murray Hall in Chapel Hill and online via Zoom (Meeting ID: 252-726-6841).

Title: Comparison of Vibrio sp. populations in farmed, suspended and wild, on-bottom oysters in eastern North Carolina

Abstract: Oysters can be harvested from the wild or they can be farmed, in which case they are grown using a variety of aquaculture systems including suspension farming where oysters are grown in floating bags or cages. In North Carolina (NC) and throughout the United States (US), shellfish aquaculture is growing rapidly in an attempt to meet increasing seafood demands. Vibrio vulnificus and Vibrio parahaemolyticus are important human bacterial pathogens often associated with farmed and wild oysters. Even though these species can cause infections via ingestion or through open wounds, the infections caused by these bacteria are most often acquired by eating raw or undercooked oysters. Oysters and other shellfish are filter-feeders and can concentrate Vibrio bacteria from the water up to 100-fold, posing a serious risk to consumers who consume shellfish that contain pathogenic forms of Vibrio sp. Historically in NC, wild oysters can only be harvested and consumed during the open oyster season, which begins October 15 and closes March 31, resulting in a wild harvest summer closure. This period of closure is the season in which human pathogenic Vibrio concentrations tend to be the highest in oysters in NC, and therefore consumers are at the highest risk of infection. Conversely, oysters grown via farmed aquaculture are not restricted by season and can be harvested and sold at any time. In this study, we compared the total Vibrio, total and potentially pathogenic V. vulnificus, and total and potentially pathogenic V. parahaemolyticus concentrations of wild (on-bottom) and farmed (suspended) oysters harvested during the summer season of 2018. This study found that total confirmed V. vulnificus, as well as potentially pathogenic V. vulnificus, concentrations were lower in suspended oysters (unpaired t-test, p=0.0334). Over the short duration of this study, total V. parahaemolyticus concentrations were not substantially different in wild on-bottom versus suspended oysters (unpaired t-test, p=0.2202). Furthermore, the rate of potentially pathogenic V. parahaemolyticus found in this study across all types of oysters was less than 1%. Aside from some discrepancies, culture methods were accurate for quantifying Vibrio populations, but molecular methods were necessary for evaluation of potential pathogenicity. Although this study found some interesting patterns, the results would be best supplemented by another study with a larger geographical range and longer period of study.