By David P. Green, North Carolina State University

When the U.S. Food and Drug Administration announced in October 2009 that, beginning with the 2011 season, it would require post-harvest treatment of live Gulf Coast oysters harvested in summer months for control of pathogenic Vibrios, the industry was taken by surprise. Gulf Coast processors and politicians rallied around the cause and went straight to Washington D.C. to voice their opposition to the plan. Consequently the FDA has agreed to work with the industry on potential post-harvest treatments, such as high-pressure processing and freezing techniques. While the industry is pleased that the FDA has paused to reflect on its raw oyster policy, they still insist that traditional Gulf Coast oysters must be made available to consumers under any future plan.

What’s the issue?

Vibrio species are ubiquitous to the marine environment. Current methods used for classifying harvesting waters do not correlate to the presence or levels of the environmental Vibrios. The primary human illnesses caused by Vibrios are wound infection, primary septicemia and gastroenteritis. Both Vibrio vulnificus and Vibrio parahaemolyticus cases occur sporadically the former almost always sporadic, while the latter also occurs in outbreaks. Epidemiological data has shown that 91 percent of primary septicemia and 86 percent of the wound infections occur from April through October, with 48 percent of those with primary septicemia reporting pre-existing liver disease. Fatality rates were only 1 percent for gastroenteritis, but were 5 percent for wound infection and 44 percent for septic disease. The FDA cited the state of California, which prohibited Gulf Coast oysters from entering the state in 2003 unless they had undergone post-harvest processing, in reducing the number of deaths attributed to raw oyster consumption to zero in the past six years compared to 40 reported deaths between 1991 and 2001.

What’s at stake?

The proposed policy change may affect one-quarter of the annual harvest from the Gulf Coast states. According to industry, the FDA plan would effectively ban the sale of live oysters for up to eight months per year. Repercussions for the harvesting industry and wholesale distributors go well beyond the Gulf Coast states and would affect consumers across the entire nation. Various state shellfish authorities are working to better prepare their industry members for the potential change in the FDA oyster policy. Many industry members are looking to adopt available methods or identify new post-harvest treatment techniques. Any post-harvest treatment method must be validated to reduce the presence of Vibrio to non-detectable levels.

What’s the solution?

Currently the industry is relying on temperature control and refrigeration to reduce human infections. Considerable effort also has been directed toward consumer-education programs designed to alert at-risk consumers, but these efforts have failed to reduce the number of reported illnesses. Other solutions acceptable to the FDA have been freezing and frozen storage, high hydrostatic pressure and heat treatment. The FDA requested industry to increase its capacity to perform post-harvest treatments for control of Vibrio in raw oysters. And now that the Gulf Coast industry appears to have the capacity to meet the post-harvest treatment demand, the FDA has moved to take action. While the issues are still being hotly debated from the waterfront to the Congressional halls, the Gulf Coast industry and wholesale distributors should no longer be surprised that the agency still intends to require post-harvest processing in the near future.

David P. Green is Professor and Extension Seafood Specialist in the Department of Food, Bioprocessing and Nutrition Sciences at North Carolina State University. For more information contact him at dpg@ncsu.edu.