Amnesic Shellfish Poisoning (ASP) is a very rare form of food-borne illness caused by a toxin called domoic acid which is secreted by diatoms in the genus Pseudo-nitzschia. This condition is also sometimes known as Domoic Acid Poisoning (DAP), in a reference to the toxin which causes it. ASP was first observed in 1987, and since then, a handful of cases have been observed around the world; the condition also appears to be on the rise due to growing numbers of harmful algae in the ocean.
This condition is called Amnesic Shellfish Poisoning because memory loss and other neurological symptoms are very common. When someone is afflicted with this condition, he or she typically experiences gastrointestinal distress including vomiting, cramps, and diarrhea within 24 hours. If the patient has ingested enough domoic acid or the body is especially vulnerable, neurological symptoms like headaches, dizziness, impaired coordination, and short-term memory loss will emerge within three days.
In the long term, Amnesic Shellfish Poisoning can cause brain damage, and sometimes even death, in elderly patients or patients with impaired kidney function. Because there is no known antidote to domoic acid, treatment focuses on providing supportive care to the patient to ensure that he or she is comfortable. Supportive care may also include long-term measures like physical therapy to address lingering neurological problems.
While domoic acid can reach especially high levels in shellfish, because they are filter feeders, it can also be present in other seafood, and sometimes it jumps up the food chain to marine birds, as well. This means that during a period of algal bloom, when harmful diatoms and dinoflagellates can also proliferate, it is generally advisable to avoid all seafood until the area has been certified as safe. If consumers purchase seafood and someone becomes ill, the leftovers should be discarded, because domoic acid cannot be eliminated through freezing or cooking. Because seafood is often shipped great distances, it pays to be alert to recall announcements.
Some researchers have suggested that shorebirds affected by DAP may become crazed; the 1961 invasion of birds in Santa Cruz, California which notably inspired Alfred Hitchcock, for example, might have been caused by DOP. Marine mammals can also be affected by Amnesic Shellfish Poisoning, with rising rates of problems in shorebirds and marine mammals suggesting that the diatoms which produce domoic acid are growing more plentiful. Amnesic Shellfish Poisoning can cause animals and birds to become extremely confused, resulting in strandings, starvation, drowning, and other unusual events.