Neurotoxic shellfish poisoning is caused by brevetoxin, a neurotoxin secreted by certain dinoflagellates found worldwide, with most generated by Karenia brevis in the Gulf of Mexico. Symptoms include numbness, tingling, and gastrointestinal discomfort, with treatment focusing on supportive care. Shellfish consumption is linked to the condition due to bioaccumulation, and red tides can cause toxic cargo release. Harvesting and consumption of shellfish is prohibited during red tide events in affected areas.
Neurotoxic shellfish poisoning (NSP) is a condition caused by the ingestion of brevetoxin, a neurotoxin secreted by certain dinoflagellates, microscopic marine organisms found throughout the world. Most of the brevetoxin is generated by Karenia brevis, a dinoflagellate that prefers the Gulf of Mexico. This condition is closely associated with paralytic shellfish poisoning (PSP), a much more serious condition also caused by exposure to a marine toxin.
In neurotoxic shellfish poisoning, symptoms usually appear within one to three hours of ingesting the toxin. The patient may experience numbness, tingling and gastrointestinal discomfort as the body processes the toxin. Death from neurotoxic shellfish poisoning is extremely rare, unless a patient is already in a compromised state of health. Treatment focuses on supportive care to help the patient feel comfortable.
This condition is specifically linked to shellfish consumption because shellfish are filter feeders, so they tend to bioaccumulate any harmful toxins in the waters around them. However, neurotoxic shellfish poisoning is also linked more generally to seafood consumption and can be harmful to birds and marine mammals as well as human shellfish enthusiasts.
The brevetoxin is closely linked to the algal blooms known as red tides. Dinoflagellates and diatoms use the red tide to feed, exploiting the proliferation of algae. If these organisms are driven ashore, they often burst open in the surf, releasing their toxic cargo, meaning any shellfish in the area will ingest the toxin. This is why eating shellfish in a region experiencing a red tide event is not recommended.
Cases of neurotoxic shellfish poisoning have been documented in Florida and the Gulf of Mexico since at least the 1800s. In these areas, when a red tide occurs, the harvesting and consumption of shellfish is prohibited until the event is over and testing they confirmed it is safe to eat shellfish again. Because the brevetoxin cannot be eliminated through cooking or freezing, if a shellfish meal makes someone in the house ill, the leftovers should be discarded.
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