Amnesic shellfish poisoning (ASP) is an illness caused by consumption of

shellfish Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater environ ...

that contain the marine biotoxin called domoic acid. In

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

s, including humans, domoic acid acts as a

neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature nerv ...

, causing permanent short-term memory loss,

brain damage Neurotrauma, brain damage or brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating t ...

, and death in severe cases. This toxin is produced naturally by marine

diatom A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...

s belonging to the genus ''

Pseudo-nitzschia ''Pseudo-nitzschia'' is a marine planktonic diatom genus that accounts for 4.4% of pennate diatoms found worldwide. Some species are capable of producing the neurotoxin domoic acid (DA), which is responsible for the neurological disorder in huma ...

'' and the species '' Nitzschia navis-varingica''. When accumulated in high concentrations by shellfish during filter feeding, domoic acid can then be passed on to birds, marine mammals, and humans by consumption of the contaminated shellfish. Although human illness due to domoic acid has only been associated with shellfish, the toxin can

bioaccumulate Bioaccumulation is the gradual accumulation of substances, such as pesticides or other chemicals, in an organism. Bioaccumulation occurs when an organism absorbs a substance at a rate faster than that at which the substance is lost or eliminated ...

in many marine organisms that consume

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. ...

, such as anchovies and sardines. Intoxication by domoic acid in nonhuman organisms is frequently referred to as domoic acid poisoning.

Symptoms and treatment

In the brain, domoic acid especially damages the

hippocampus The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...

and

amygdaloid nucleus The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex vert ...

. It damages the

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa ...

s by activating AMPA and kainate receptors, causing an influx of

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

. Although calcium flowing into cells is a normal event, the uncontrolled increase of calcium causes the cell to degenerate. Gastrointestinal symptoms can appear 24 hours after ingestion of affected molluscs. They may include

vomiting Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Vomiting can be the result of ailments like food poisoning, gastroenter ...

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin w ...

, abdominal cramps, and haemorrhagic gastritis. In more severe cases, neurological symptoms can take several hours or up to 3 days to develop. These include

headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result ...

dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...

disorientation Orientation is a function of the mind involving awareness of three dimensions: time, place and person. Problems with orientation lead to ''dis''orientation, and can be due to various conditions, from delirium to intoxication. Typically, disorient ...

, vision disturbances, loss of short-term memory, motor weakness,

seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with lo ...

s, profuse respiratory secretions,

hiccup A hiccup (scientific name ''singultus'', from a Latin word meaning "to catch one's breath while sobbing"; also spelled hiccough) is an involuntary contraction ( myoclonic jerk) of the diaphragm that may repeat several times per minute. The hi ...

s, unstable blood pressure, abnormal heart rhythms, and

coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to respond normally to painful stimuli, light, or sound, lacks a normal wake-sleep cycle and does not initiate voluntary actions. Coma patients exhi ...

. People poisoned with very high doses of the toxin or displaying risk factors such as old age and

kidney failure Kidney failure, also known as end-stage kidney disease, is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney failure is classified as eit ...

can die. Death has occurred in four of 107 confirmed cases. In a few cases, permanent

sequela A sequela (, ; usually used in the plural, sequelae ) is a pathological condition resulting from a disease, injury, therapy, or other trauma. Derived from the Latin word, meaning “sequel”, it is used in the medical field to mean a complication ...

e included short-term memory loss and peripheral

polyneuropathy Polyneuropathy ( poly- + neuro- + -pathy) is damage or disease affecting peripheral nerves (peripheral neuropathy) in roughly the same areas on both sides of the body, featuring weakness, numbness, and burning pain. It usually begins in the hand ...

. No antidote for domoic acid is known, so if symptoms fit the description, immediate medical attention is advised. Cooking or freezing affected fish or shellfish tissue does not lessen the toxicity. Domoic acid is a heat-resistant and very stable toxin which can damage kidneys at concentrations that are 1/100th of those that cause neurological effects.

Discovery

ASP was first discovered in humans late in 1987, when a serious outbreak of food poisoning occurred in eastern

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by to ...

. Three elderly patients died and other victims suffered long-term neurological problems. Because the victims suffered from memory loss, the term "amnesic" shellfish poisoning is used. Epidemiologists from

Health Canada Health Canada (HC; french: Santé Canada, SC)Health Canada is the applied title under the Federal Identity Program; the legal title is Department of Health (). is the department of the Government of Canada responsible for national health poli ...

quickly linked the illnesses to restaurant meals of cultured mussels harvested from one area in

Prince Edward Island Prince Edward Island (PEI; ) is one of the thirteen provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has several nicknames: "Garden of the Gulf", ...

, a place never before affected by toxic algae. Mouse bioassays on aqueous extracts of the suspect mussels caused death with some unusual neurotoxic symptoms very different from those of paralytic shellfish poisoning toxins and other known toxins. On December 12, 1987, a team of scientists was assembled at the

National Research Council of Canada The National Research Council Canada (NRC; french: Conseil national de recherches Canada) is the primary national agency of the Government of Canada dedicated to science and technology research & development. It is the largest federal research ...

laboratory in Halifax,

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

. Integrating bioassay-directed fractionation with chemical analysis, the team identified the toxin on the afternoon of December 16, only four days after the start of the concerted investigation.

Possible animal effects

On June 22, 2006, a California brown pelican, possibly under the influence of domoic acid, flew through the windshield of a car on the Pacific Coast Highway. The

phycotoxin Phycotoxins (from Greek, ''phykos'', "seaweed"; and ''toxikon'', "toxin") are complex allelopathic chemicals produced by eukaryotic and prokaryotic algal secondary metabolic pathways. More simply, these are toxic chemicals synthesized by photosy ...

is found in the local coastal waters. Since March 2007, marine mammal and seabird strandings and deaths off the Southern California coast have increased markedly. These incidents have been linked to the recent and dramatic increase of a naturally occurring toxin produced by algae. Most of the animals found dead tested positive for domoic acid. According to the Channel Islands Marine and Wildlife Institute,

It is generally accepted that the incidence of problems associated with toxic algae is increasing. Possible reasons to explain this increase include natural mechanisms of species dispersal (currents and tides) to a host of human-related phenomena such as nutrient enrichment (agricultural run-off), climate shifts, or transport of algae species via ship ballast water.

In popular culture

In the TV series ''

Elementary Elementary may refer to: Arts, entertainment, and media Music * ''Elementary'' (Cindy Morgan album), 2001 * ''Elementary'' (The End album), 2007 * ''Elementary'', a Melvin "Wah-Wah Watson" Ragin album, 1977 Other uses in arts, entertainment, a ...

'' episode "The Red Team" (original air date January 31, 2013), a witness is intentionally poisoned with domoic acid. In the " Bad Fish" episode of '' Get a Life'' (original air date: February 2, 1992), Sharon and Gus get amnesia after eating bad shellfish, and Chris seizes the opportunity to convince them that they are his best friends. Domoic acid poisoning may have caused an August 18, 1961, invasion of thousands of frantic seabirds in Capitola and

Santa Cruz, California Santa Cruz ( Spanish for "Holy Cross") is the county seat and largest city of Santa Cruz County, in Northern California. As of the 2020 census, the city population was 62,956. Situated on the northern edge of Monterey Bay, Santa Cruz is a po ...

. Director

Alfred Hitchcock Sir Alfred Joseph Hitchcock (13 August 1899 – 29 April 1980) was an English filmmaker. He is widely regarded as one of the most influential figures in the history of cinema. In a career spanning six decades, he directed over 50 featur ...

heard about this invasion while working on his adaptation of the

Daphne du Maurier Dame Daphne du Maurier, Lady Browning, (; 13 May 1907 – 19 April 1989) was an English novelist, biographer and playwright. Her parents were actor-manager Sir Gerald du Maurier and his wife, actress Muriel Beaumont. Her grandfather was Geo ...

novelette " The Birds" for his feature film '' The Birds'' (1963), and asked the ''

Santa Cruz Sentinel The ''Santa Cruz Sentinel'' is a daily newspaper published in Santa Cruz, California, covering Santa Cruz County, California, and owned by Media News Group. Ottaway Community Newspapers, a division of Dow Jones & Company bought the paper in 19 ...

'' for any further news copy as "research for his new thriller."

References

External links

Amnesic Shellfish Poisoning
at

Woods Hole Oceanographic Institution The Woods Hole Oceanographic Institution (WHOI, acronym pronounced ) is a private, nonprofit research and higher education facility dedicated to the study of marine science and engineering. Established in 1930 in Woods Hole, Massachusetts, i ...

Domoic acid and ''Pseudo-nitzschia'' references
at

Fisheries and Oceans Canada Fisheries and Oceans Canada (DFO; french: Pêches et Océans Canada, MPO), is a department of the Government of Canada that is responsible for developing and implementing policies and programs in support of Canada's economic, ecological and sci ...

Amnesic Shellfish Poisoning, Domoic Acid, and ''Pseudo-nitzschia'' links
at th
ISSHA
website

at International Programme on Chemical Safety
DOMOIC ACID — A MAJOR CONCERN TO WASHINGTON STATE’S SHELLFISH LOVERS
at

Washington Department of Fish and Wildlife The Washington Department of Fish and Wildlife (WDFW) is a department of the government of the state of Washington, United States of America. The WDFW manages over a million acres of land, the bulk of which is generally open to the public, and m ...