Although there is no foolproof way to completely avoid food poisoning from shellfish, there are steps to take to make consumption relatively safe. Food poisoning from shellfish most often happens when consuming shellfish from water that may be contaminated by red tides or that have recently been contaminated. The commercial shellfish industry is regulated, and operations are inspected regularly, making most commercially prepared shellfish safe to eat. Most food poisoning from shellfish happens when amateurs collect and eat contaminated shellfish. It’s also risky to eat raw or undercooked shellfish.
Like any other food, shellfish can become contaminated with bacteria and harmful microorganisms through improper handling. Shellfish should always be obtained from reputable sources. Never eat any shellfish if unsure of the source. Any seafood should be prepared with washed hands and clean utensils and in a clean workspace. Cooking shellfish thoroughly will kill many harmful microorganisms.
Sometimes shellfish may contain toxins that are heat stable and cannot be removed through cooking. It’s best to avoid eating shellfish during warm summer months, especially if red tides have been severe. During a red tide, populations of phytoplankton become so numerous that their bodies cause the water to appear reddish. Natural toxins are produced that can be ingested by shellfish. As shellfish are filter feeders, their bodies can accumulate toxins and cause illness to humans or animals who eat them.
Food poisoning from shellfish may also occur when shellfish are contaminated with hepatitis A or Norwalk viruses. In addition, there are four recognized types of shellfish poisoning from natural toxin accumulation. Amnesiac and neurotoxic shellfish poisoning may cause illness, but there are no known deaths. A 1987 outbreak of amnesiac shellfish poisoning in eastern Canada had a 3-percent mortality rate. Paralytic shellfish poisoning is the most deadly, with a 1- to 12-percent mortality rate.
Certain populations are at increased risk of food poisoning from shellfish. These include children and the elderly, especially if they have a compromised immune system. Most cases of shellfish poisoning resolve on their own, but medical attention should be sought if food poisoning from shellfish is suspected. Symptoms from some types of poisoning may appear within minutes of consuming shellfish and include tingling or burning of lips and tongue, nausea, and abdominal pain. Other types of shellfish poisoning, like hepatitis A, may take several weeks for symptoms to appear.
Although the incidence of red tides continues to increase, it’s important to remember that most shellfish consumption is perfectly safe. As commercially obtained shellfish are subject to strict regulations regarding practices, the public continues to enjoy shellfish without excessive concern. In general, the nutritional benefits of consuming shellfish tend to outweigh any risk of poisoning, especially if shellfish are obtained commercially and cooked thoroughly.