Seafood Safety : Seafood Sicknesses, Part 3

by Food and Drug Administration (FDA)

(Page 3 of 4)

Human sewage can also contain bacteria that cause cholera and other illnesses, and mollusks can pick up those microbes. While cholera has been all but wiped out in waters around more developed countries, it is almost a constant in some Third World areas and has been a particular problem for Peru this year.

Yet another legacy of untreated sewage that finds its way into shellfish is the virus that causes hepatitis A. The symptoms are relatively mild, but some people can be left with severe liver damage.

Two other diseases that can result from consuming even well-cooked shellfish are paralytic shellfish poisoning (PSP) and neurotoxic shellfish poisoning (NSP). Both are extremely rare; however, PSP can be fatal. Symptoms can appear within 30 minutes of ingestion; they include tingling, numbness or burning sensations in the lips, gums, tongue, and face. NSP is similar to PSP but milder. Symptoms include tingling in the extremities, vomiting and diarrhea.

Both NSP and PSP occur in humans after they've eaten mollusks that have fed in some "bloomed" waters. These blooms, more commonly known as "red tides," contain plankton (dinoflagellates) in such numbers as to discolor the water. The plankton are nontoxic to the shellfish, but may be dangerous to humans. Not all "blooms" contain toxic dinoflagellates, but when they do the shellfish may be carrying the plankton several days before the water changes color.

As with shellfish, a few species of fin fish can also be the source of illness even if thoroughly cooked. Dinoflagellates can also cause ciguatera poisoning, although the plankton doesn't need to be present in such numbers as to add hues to the water. Found mostly in warmer waters, the toxic plankton moves up the food chain to predatory reef fish, notably groupers, snappers, barracuda, and Spanish mackerel. Ciguatera causes an estimated 30 percent of all fin fish-borne food poisonings in the United States, some 3,000 cases annually. Most cases occur in Hawaii, Guam, Puerto Rico, and the Virgin Islands.

Symptoms are called "moderately severe," affecting both the gastrointestinal and neurological systems. The symptoms include diarrhea, nausea, vomiting, chills, and sweating.

FDA hopes to test a kit that could detect ciguatera contamination this year.

Scombroid poisoning is usually associated with tuna, bluefish and mahi-mahi (dolphin fish). These fish naturally contain high levels of histamine, which is released as the fish decompose. The disease runs its course, and the usually mild symptoms include nausea, vomiting, diarrhea, rash, and tingling and burning sensations around the mouth.

Sports Fishing

Ciguatera and scombroid poisonings point up another area of concern for health officials — recreational fishing. It's estimated that people casting lines in water and digging clams along the seashore may add 3 to 4 pounds to the nearly 16 pounds of seafood that each American, on average, consumes each year. The reef fish associated with ciguatera are prized by sport fishers, as are the scombroid-susceptible bluefish and, to a lesser extent, tuna.

State health officials often issue advisories to warn anglers of the poisoning possibilities in the fish they catch and to caution them against trying to sell such disease-prone fish to vendors or the public.

Sport fishers also need to be careful about doing their thing in waters contaminated by chemicals and metals. These contaminants may include pesticides (such as DDT and dioxin) mercury, and PCBs (polychlorinated biphenyls). The latter were widely used in the past as insulators in transformers and were generously dumped into any convenient body of water after use.

Mercury (or ,more correctly, the form known as methylmercury) and PCBs are the main pollution problems. Both can cause birth defects, and both have been the subject of numerous advisories to anglers. (Swordfish are particularly known for accumulating methylmercury, and consumption of that fish on a regular basis may not be advisable for women who are pregnant or likely to become pregnant.)

In its recent report, the National Academy of Sciences concluded that "only a small portion of seafood is contaminated with appreciable concentrations ..." of chemicals. But the academy cautioned that the area had not been studied well enough, and it called for better efforts to alert fishermen and the rest of the public about contaminated waters.

What Consumers Can Do

While FDA is working to ensure that the seafood sold to the public is safe, consumers themselves can do a lot to make sure that their seafood doesn't cause illness. Indeed, it is estimated that as much as half of all seafood problems could be eliminated by better handling and preparation in the home and in restaurants and other food service establishments. Two accompanying articles give tips on how to select and store seafood.

As to seafood preparation, the household chef can't go wrong by following good sanitation practices, such as washing hands thoroughly before starting to prepare a meal and after handling foods — such as meat and fish — that contain bacteria, keeping equipment such as knives and cutting boards clean, and keeping hot foods hot and cold foods cold. (For more on safe food preparation, see "The Unwelcome Dinner Guest: Preventing Food-Borne Illness" in the January-February 1991 FDA Consumer.)

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.