Pathogens may be present at low levels when fish or shellfish are harvested, and others may be introduced during handling and processing or by unsanitary practices. To control bacterial pathogens it is important to keep seafood cold (as close to 32°F as possible) at all times to limit the potential for pathogens to grow and multiply in the product. Viruses cannot grow in food, but can cause illness if they are present in food when it is eaten. Proper cooking of raw seafood to an internal temperature of at least 145°F for at least 15 seconds will significantly reduce or eliminate any bacterial, viral or parasitic organisms that may be present.
Bacteria in food may cause illness in humans by infection or intoxication. Examples of some of the types of bacteria that may be found in seafood that cause foodborne illness by infection are Vibrio, Salmonella, Shigella, and Listeria. Foodborne intoxications occur when patients consume pre-formed toxins that are produced by certain types of bacteria when they grow and multiply in the food. Clostridium botulinum can produce a potent neurotoxin during growth under anaerobic conditions (absence of oxygen) usually associated with vacuum packed, improperly canned, or fermented products. Bacteria such as Staphylococcus aureus can produce enterotoxins that cause foodborne illness, but less than 5% of the seafood associated outbreaks and illnesses were associated with this pathogen over the past three decades. Preventing the growth of these bacterial pathogens is important to prevent infection or intoxication when seafood is eaten.
Preventing Foodborne Illness
Keeping seafood cold at temperatures below 40°F will help prevent the growth of pathogenic bacteria, and adequate cooking will destroy any pathogens that may be present. Proper sanitation and hygiene are also key elements of food safety. Bad food handling practices and sanitation may lead to cross contamination during food preparation causing foodborne illness. Cross contamination involves transferring harmful bacteria from one food to another, from cutting boards, utensils, or your hands. To prevent cross contamination when storing or cooking seafood, keep raw seafood and their juices away from already cooked or ready-to-eat foods. It is also essential to wash your hands after touching raw food or non-food surfaces or other dirty objects, and after using the toilet.
The US Food and Drug Administration believes that prevention is the best way to avoid foodborne illness. Consumers can prevent foodborne illnesses at home by using safe food handling practices including:
- washing hands, utensils, and cooking surfaces often,
- cooking seafood to a minimum of 145°F for 15 seconds,
- keeping raw and cooked seafood separate to avoid cross-contamination, and
- storing seafood in the refrigerator below 40°F or in the freezer below 0°F.
Higher Risk Consumers
Some consumers have an increased chance of getting a type of foodborne illness called listeriosis caused by exposure to Listeria. High risk individuals include those who may have a compromised or weak immune system because of health conditions such as liver disease, cancer, chemotherapy patients, HIV infection, stomach or intestinal problems (low stomach acidity), and certain groups such as the elderly, pregnant women and young children. These groups should avoid certain types of seafood and other foods to reduce the chance of getting listeriosis. High risk consumers should avoid refrigerated types of smoked seafood such as salmon, trout, whitefish, cod, tuna, or mackerel. These products can be labeled as “nova–style,” “lox,” “kippered,” “smoked,” or “jerky” and are found in the refrigerated section of grocery stores and delicatessens. There is no concern of getting listeriosis if these products are cooked in a dish such as a casserole or if they are canned or shelf-stable (do not require refrigeration).
Furthermore, to reduce risks of illness from bacteria in food, the U.S. Department of Agriculture (USDA) advises that persons at risk do not eat the following foods:
- Raw fin fish and shellfish, including oysters, clams, mussels, and scallops.
- Raw or unpasteurized milk or cheese.
- Soft cheeses such as feta, Brie, Camembert, blue-veined, and Mexican-style cheese. (Hard cheeses, processed cheeses, cream cheese, cottage cheese, or yogurt need not be avoided.)
- Raw or lightly cooked egg or egg products including salad dressings, cookie or cake batter, sauces, and beverages such as egg nog. (Foods made from commercially pasteurized eggs are safe to eat.)
- Raw meat or poultry.
- Raw sprouts (alfalfa, clover and radish.)
- Unpasteurized or untreated fruit or vegetable juice (These juices will carry a warning label.)
The following tips can help seafood consumers and recreational fishermen minimize potential food safety concerns.
To reduce your risk of food borne illness:
- Keep fish frozen or refrigerated below 40°F until ready to use.
- Separate cooked and raw seafood. Wash utensils, cutting boards and any surfaces that comes into contact with raw seafood or other foods before re-using.
- Wash hands before and after handling raw or cooked food.
- Cook seafood thoroughly to an internal temperature of 145°F for at least 15 seconds. Check temperatures with a food thermometer in the thickest part of the fillet or steak. Properly cooked seafood should be moist and solid-color throughout.
- Keep hot foods hot and cold foods cold. Avoid keeping seafood products at temperatures between 40–140°F.
- Purchase seafood from retailers that have high standards for quality and sanitation.
To reduce your risk from contaminants:
- Higher risk individuals including women of childbearing age, pregnant women and children should not eat sport caught fish from contaminated waters.
- All individuals should check with their state health department’s fish consumption advisories or go to this web site before eating sport caught fish.
- Individuals who chose to eat fish that may contain contaminants can reduce their exposure to PCBs, pesticides or other chemicals by removing the skin from fish and trimming the fat.
- Higher risk individuals including pregnant women, women who intend to become pregnant, and children should not eat swordfish, tilefish , shark, or king mackerel because they have higher levels of mercury.