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Red Tide (Paralytic Shellfish Poisoning)

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Red Tide (Paralytic Shellfish Poisoning) MASSACHUSETTS DEPARTMENT OF PUBLIC HEALTH | BUREAU OF ENVIRONMENTAL HEALTH Red Tide (Paralytic Shellfish Poisoning) Conversely, toxic plankton may be numerous enough to toxify shellfish, but not sufficiently abundant to discolor water. Discolored water should always be regarded with suspicion. However, it should be noted that even during high concentrations during a red tide event caused by Alexandrium fundyense, there is no risk with regard to swimming in the water. WHAT SEAFOODS ARE UNSAFE TO EAT FROM WATERS WHERE RED TIDE OCCURS? Only a few marine animals accumulate these toxins. Shellfish, including hard-shell clams, soft-shell clams, oysters, mussels, and WHAT IS RED TIDE? scallops, are particularly prone to Red Tide is caused by a "population explosion" contamination as they feed by filtering of toxic, naturally occurring microscopic microscopic food out of the water. If toxic plankton (specifically, a subgroup known as planktonic organisms are present, they are dinoflagellates). "Blooms" of the poison- filtered from the water along with other producing plankton are coastal phenomena nontoxic foods. Whelks and moon snails can caused by environmental conditions that also accumulate dangerous levels of the toxin promote explosive growth. Factors that are during red tide as they feed on contaminated especially favorable include warm surface shellfish. temperatures, high nutrient content, low salinity, and calm seas. Rain followed by sunny During red tide blooms, hard-shell clams, soft- weather in the summer months is often shell clams, oysters, mussels, whelks, and associated with red tide blooms. Organisms moon snails harvested from areas affected by that cause theses blooms around the United the blooms are not safe to eat. Since toxins are States are as follows: stored in the digestive tract (stomach) and Alexandrium fundyense, along the Northeast viscera (intestines) of these animals, scallops Atlantic coast, ranging from the Canadian are safe to eat as long as only the cleaned Maritimes to Southern New England; adductor muscle (the only part generally eaten) Alexandrium catenella, on the Pacific West is consumed. Lobster meat, crab, shrimp, and Coast from California to Alaska; and most finfish do not normally accumulate toxin Karonia brevis, in the Gulf of Mexico along and are safe to eat from affected waters. the West Florida coast. Lobster tomalley (the green part or liver) is not safe to eat in general, but particularly during DOES IT REALLY COLOR THE WATER? red tide events because this part of the lobster Yes, water in coastal areas can be colored red can build up high levels of toxins and other by the algae, thus the term "red tide." Although pollutants. toxic blooms often turn the water reddish brown, many nontoxic species or reddish brown plankton cause the same discoloration. WHAT HAPPENS IF TOXIC SHELLFISH ARE the Division of Marine Fisheries (DMF) is CONSUMED? responsible for year-round testing of shellfish Eating toxic shellfish can cause paralytic andd shellfish growing areas. Monitoring efforts shellfish poisoning (PSP) in humans. PSP is are more intensive in the spring, summer, and caused by saxitoxin, which is produced by fall. The DMF nnotifies officials of affected cities Alexandrium fundyense and is one of the most andd towns of closures. When blooms subside, potent toxins known to scientists. After shellfish purifyy themselves of the toxin, and ingestion, this poison immediately affects the when testing indicates a return to safe levels, nervous system, with symptoms usually the areas are reopened. Monitoring programs occurring within 30 minutes. Severity depends may differ in other states. on the amount of toxin consumed. Initial reactions are tingling of the lips and tongue, WHHAT PRECAUTIONS SHOULD which spreads to the face, neck, fingertips, and RECREATIONAL FISHERMAN TAKE? toes. Headache, dizziness, and nausea follow. Recreational shellfish gatherers should look for These symptoms may be mistaken for drunken posted warnings and pay close attention to conditions and are further aggravated by local media announcements. Also, it is alcohol consumption. In severe cases, advvisable to contact appropriate state agencies muscular paralysis and respiratory difficulty andd local shellffish constables for current news may occur within 5 to 12 hours. Fatalities from on closures. respiratory paralysis have been reported. Under no circumstance should individuals harvest shellfish from any area closed to WHAT SHOULD ONE DO IF ACCIDENTAL shellfishing. INGESTION OF TOXIC SHELLFISH IS SUSPECTED? Tox ic shellfish will taste and appear no different Seek proper medical attention immediately. If a than nontoxic shellfish, and cooking does not family doctor or other physician cannot be destroy the red tide toxin. Testing is the only reached, the person should be taken to the way to determine if shellfish contain unsafe nearest hospital emergency room or medical levels of toxin. clinicc. If none of these options are available, contact the nearest poison control center. The SHOULD CONSUMERS FEEL SAFE WHEN diagnosis of PSP is a reportable disease. PURCHASING SHELLFISH AT SEAFOOD Cases of suspected PSP poisoning should be MARKETS? reported to the Center for Environmental Yess, consumers should feel confident about Health, Food Protection Program, at 617-983- purchasing shellfish from established markets. 6712 or to the Center for Hospitals and Clinical Harvesting regulations for shellfish are strictly Laboratories, Bureau of Communicable enforced. Even during periods of red tide, Disease Control, at 617-983-6800. clams, oysters, mussels, and whelks in seafood markets are harvested from clean HOW IS RED TIDE MONITORED SO THAT wateers. The U.S. Food and Drug Administration TOXIC SHELLFISH ARE NOT MARKETED? visits state labs to observe routine testing All shellfish-producing states have monitoring procedures, and public health officials regularly programs that test water, sediments, and monitor shellfish markets to ensure that only shellfish for contamination. The action level for safe, nontoxic shellfish are available to humans is 80 micrograms per 100 grams of consumers. shellfish meat. In Massachusetts, for instance, For More Info rmation: Bureau of Environmental Health MA Department of Public Health 250 Washington Street, 7th Floor, Boston, MA 02108 Phone: 617-624-5757 | Fax: 617-624-5777 | TTY: 617-624-5286 Food Protection Program 617-983-6712; or the Bureau of Communicable Disease Control 617-983-6800. Your local board of health (listed in the phone book under local government) Your local Shellfish Constable or Warden Massachusetts Division of Marine Fisheries 617-626-1520 or 508-563-1779; you may also visit the DMF website at www.mass.gov/eea/agencies/dfg/dmf/ .
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