Introduction

 

For many people, raw oysters are a delicacy to be enjoyed regularly or savored on special occasions like birthdays, holidays, or trips to the coast. However, raw or undercooked seafood, meat, or poultry can cause foodborne illness, especially in consumers with weak immune systems or certain health problems.

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Raw or undercooked shellfish, particularly oysters, may contain Vibrio bacteria, which naturally occur in marine waters. Shellfish from the Gulf of Mexico and South Atlantic Ocean are especially vulnerable to these bacteria in warmer weather, from April through November. Vibrio vulnificus bacteria may cause severe, life-threatening illness in people with compromised immune systems who eat raw shellfish or expose open wounds or sores to seawater (e.g., by swimming, wading, or fishing).

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From 2007 - 2015, an average of 120 cases/year of Vibrio vulnificus infection was reported in the U.S. Approximately 23% of cases resulted from eating raw or undercooked seafood (primarily oysters); 52% were linked to exposure (typically of wounds) to saltwater, marine life, or raw seafood drippings; and the remaining 25% of cases were of unknown origin. According to the Centers for Disease Control and Prevention, the overall mortality rate for Vibrio vulnificus infection during this time period was 28%. However, the mortality rate for food infections is approximately 41% and is even higher for people with alcoholism (61%) and liver disease (60%).

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Susceptibility of Consumers to Vibrio vulnificus Infection

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Most people are not at risk for serious V. vulnificus infection. If healthy people become infected, they may experience mild gastroenteritis (nausea, stomach pain, vomiting, and/or diarrhea) after eating raw shellfish or acquire cellulitis (spreading skin infection) from exposing a wound to seawater.

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However, people with weak immunity or with one or more "high-risk" conditions (see list below) are much more likely to develop a life-threatening V. vulnificus infection. In addition, the infection and severity of symptoms usually progresses very rapidly in these people. Death may occur in as few as 24 to 48 hours. In some cases, amputation of limbs is necessary to prevent death.

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Health Conditions that Increase Risk of Serious Infection

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• Alcohol abuse

• Liver disease (from hepatitis, cirrhosis or cancer)

• Diabetes

• Cancer (including lymphoma, leukemia, Hodgkin's disease)

• AIDS/HIV

• Stomach disorders (surgery or taking antacids)

• Kidney disease or disorders

• Iron overload disease (hemochromatosis)

• Other conditions, diseases, or medical treatments that suppress or weaken the immune system, including chemotherapy

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Educate, Don't Frighten Consumers

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Seafood is an important part of a healthy diet. Seafood is a good source of high-quality protein, is generally low in calories and fat, and contains Omega-3 fatty acids, which may decrease risk of stroke and heart disease in adults, and which promote healthy development of young children, infants, and unborn babies. In its Dietary Guidelines for Americans, 2015-2020 edition, the U.S. Department of Agriculture reiterates that adults should eat at least 8 ounces (cooked edible portion) of a variety of seafood each week, which is equivalent to 2 to 3 servings. Unfortunately, the average American consumes only one serving of seafood per week.

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Some consumers hear negative information about one type or species of seafood and avoid all seafood. In addition, food safety messages for certain "at-risk" groups are frequently misunderstood or followed by consumers who are not at risk. Therefore, keep your message simple and remind consumers that eating any raw animal food is risky, but cooking and effective post-cooking handling reduces the risk of foodborne illness.

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Prevention

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Your job responsibilities, food safety outreach activities, and audience will dictate when and how you can educate consumers about the risk of Vibrio vulnificus infection. However, some ideas for consumer education are:

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• Target groups of consumers with weakened immunity (diabetics, dialysis patients, and local support groups for liver, cancer, and AIDS), since they are the most susceptible to Vibrio (and other foodborne) infections, and advise them to eat only thoroughly cooked seafood and avoid consuming raw seafood, especially oysters.

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• Tell consumers to seek immediate medical treatment if they have any symptoms of Vibrio infection or suspect exposure to the bacteria.

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• Include information about the risk of V. vulnificus infection in any general food safety education activities, especially to consumers who live near the Gulf or South Atlantic coasts or in adjacent states.

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• Stress that thorough cooking kills harmful bacteria and viruses in seafood, meat, and poultry. Demonstrate the proper cooking of shellfish and/or provide cooked oyster recipes.

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• Obtain free consumer brochures from the Interstate Shellfish Sanitation Conference (www.issc.org) and distribute them to consumers at health, agricultural, or food fairs, seafood or coast festivals, fundraisers, exhibitions, or other events.

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• Ask physicians and other health care professionals to place ISSC consumer brochures in their waiting rooms and inform high-risk patients about their risk of Vibrio infection. Provide ISSC Vibrio vulnificus Fact Sheets (also available free from www.issc.org) to medical professionals. Refer them to SafeOysters.org for more information.

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Additional Educator Resources

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1. Food and Health Educators Fact Sheet – Univ of GA Marine Extension and Georgia Sea Grant 

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2. To locate your state or regional chapter of the American Liver Foundation and local liver support groups, phone 1-800-GoLiver (1-800-465-4837) or visit www.liverfoundation.org/chapters

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3. U.S. Food and Drug Administration Vibrio vulnificus Education Kit for outreach to the Hispanic community.