Seafood poisoning in red tides alert

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THE China Food and Drug Administration recently warned consumers to take special care before eating shellfish and other seafood because right now ocean creatures can contain saxitoxin, a neurotoxin responsible for paralytic shellfish poisoning.
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THE China Food and Drug Administration recently warned consumers to take special care before eating shellfish and other seafood because right now ocean creatures can contain saxitoxin, a neurotoxin responsible for paralytic shellfish poisoning.

Alexandrium catenella, an alga that produces the toxin, has been proliferating in China’s southern waters at an alarming rate. Explosive growth of aquatic bacteria, protozoa, and phytoplankton can give water a dark red tint and is therefore called red tides. Unfortunately, according to the Food and Drug Administration, the current wave of red tide features the toxin-producing Alexandrium catenella. Shellfish and other marine organisms may consume the alga, and saxitoxin accumulates within the animals over time. Though harmless to shellfish, saxitoxin can quickly block the transport of sodium ions across cell membranes in human neurons, impede the transmission of electrochemical signals within the nervous system, and cause paralysis. Mild paralytic shellfish poisoning can immobilize limbs and induce numb or tingling sensations in the mouth and on the lips. In its most severe form, the toxin can kill by causing respiratory paralysis. Saxitoxin has no known antidote.

Worse still, the virulent toxin is easily absorbed by the human digestive system, and hardly decomposes even in the presence of heat and digestive enzymes. One may develop paralytic shellfish poisoning after ingesting only 600 micrograms of saxitoxin and may die after taking in 3,000 micrograms. As one of the most common toxins found in red tides, saxitoxin accounts 87 percent of poisoning caused by algae.

However, the human body can deal with smaller amounts of saxitoxin, so limited and occasional intakes of seafood present hardly any risk. The Food and Drug Administration still advise that one cooks shellfish thoroughly and avoid eating any part that appears dark-colored, including innards, sex organs, and eggs.

Experts also recommend companies, food providers, and consumers to avoid purchasing shellfish and other seafood produced in areas suffering from the red tide and only go to large malls and markets that meet safety standards. If any symptom of paralytic shellfish poisoning occurs, one should seek medical attention immediately.



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