Introduction to Vibrio vulnificus
What Shellfish Dealers and Retailers Should Know About Handling Raw Molluscan Shellfish
What is Vibrio vulnificus (V. vulnificus) and where is it found?
Vibrio vulnificus (V. vulnificus) is a naturally occurring bacterium in warm coastal waters such as the Gulf of Mexico and South Atlantic Ocean. Concentration of V. vulnificus and cases of infection follow a seasonal trend, rising in April, peaking in August, and declining in November. V. vulnificus bacteria are not a result of pollution. Oysters feed by filtering water-surrounding areas where Vibrios may thrive and as a result, concentrate V. vulnificus in their tissues. When immunocompromised consumers eat these shellfish raw or undercooked, the bacteria enter their digestive tract and multiply rapidly. Additionally, individuals can become infected when open cuts, burns or sores come in contact with seawater containing V. vulnificus.
Why is Vibrio vulnificus of concern to pubic health officials?
While not potentially life-threatening to most healthy people, symptoms of V. vulnificus infection may occur within 24 to 48 hours of ingestion. Symptoms may include sudden chills, fever, nausea, vomiting, diarrhea, shock and skin lesions. In people with certain medical conditions (i.e., cancer, diabetes, liver or stomach disorders, hemochromatosis, HIV/AIDS) death can occur within two days. According to the US Food and Drug Administration, “the risk of death is almost 200 times greater in those with liver disease than those without liver disease.” Anyone showing signs of any these symptoms after eating raw oysters should immediately seek medical attention. The fatality rate of high-risk individuals with V. vulnificus infections is 50 percent.
Eating oysters from "clean" waters or in reputable restaurants with high turnover does not provide protection. Eating raw oysters with hot sauce or while drinking alcohol does not kill the bacteria, either. Only heat can destroy the bacteria.
Why is Vibrio vulnificus important to oyster dealers (shellstock shipper, shucker-packer, repacker, reshipper, or depuration processor)?
Raw oysters are the major source of food-borne disease caused by V. vulnificus. To minimize the risk of illness from the consumption of molluscan shellfish containing these pathogens, Shellfish Control Authorities place certain controls on the harvest of molluscan shellfish. Naturally occurring pathogens may be present in relatively low numbers at the time that molluscan shellfish are harvested, but may increase to more hazardous levels if they are exposed to time/temperature abuse. In most cases, control for V. vulnificus involves limits on the time from harvest to refrigeration. The length of time is dependent upon the average monthly maximum water temperature (AMMWT) at the time of harvest, which is also determined by the Shellfish Control Authority.
What is the processor’s and retailer's role in minimizing risk of Vibrio infections from raw oyster consumption?
Shellfish Control Authorities require that shellstock intended for raw consumption bear a tag containing a warning about the risk of consuming raw or undercooked shellfish.
Where can processors and dealers obtain additional information regarding handling and marketing of raw oysters to consumers and the required tags and records that are mandated by the Shellfish Control Authority?
Consult the 2005 “National Shellfish Sanitation Program Guide for the Control of Molluscan Shellfish” (http://www.cfsan.fda.gov/~ear/nss3-toc.html).
What advisory information shall the retailer provide to consumers of raw oysters?
All shellstock intended for raw consumption shall include a consumer advisory. The following statement, from Section 3-603.11(C)3 of the 2005 Food Code (p. 95) (http://www.cfsan.fda.gov/~acrobat/fc05-3.pdf), or an equivalent statement, shall be included on all shellstock: "RETAILERS, INFORM YOUR CUSTOMERS" "Consuming raw or undercooked meats, poultry, seafood, shellfish or eggs may increase your risk of foodborne illness, especially if you have certain medical conditions."
- 2005 Food Code, US Food and Drug Administration (http://www.cfsan.fda.gov/~acrobat/fc05-3.pdf)
- Chapter 4, Pathogens From The Harvest Area (A Biological Hazard) in Fish and Fisheries Products Hazards and Controls Guidance. Third Edition June 2001, US Food and Drug Administration (http://www.cfsan.fda.gov/~comm/haccp4d.html)
- Guide for the Control of Molluscan Shellfish, National Shellfish Sanitation Program (NSSP). 2005 Revision (http://www.cfsan.fda.gov/~ear/nss3-toc.html)