This toxin is produced naturally by marine diatoms belonging to the genus Pseudo-nitzschia and the species Nitzschia navis-varingica.[2] 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.[3][4][5][6][7][8][9][10]
Although human illness due to domoic acid has only been associated with shellfish, the toxin can bioaccumulate in many marine organisms that consume phytoplankton, such as anchovies and sardines. Intoxication by domoic acid in nonhuman organisms is frequently referred to as domoic acid poisoning.
In the brain, domoic acid especially damages the hippocampus and amygdaloid nucleus.[1] It damages the neurons by activating AMPA and kainate receptors, causing an influx of calcium. Although calcium flowing into cells is a normal event, the uncontrolled increase of calcium causes the cell to degenerate.[11][12]
Gastrointestinal symptoms can appear 24 hours after ingestion of affected molluscs. They may include vomiting, nausea, diarrhea, 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, dizziness, disorientation, vision disturbances, loss of short-term memory, motor weakness, seizures, profuse respiratory secretions, hiccups, unstable blood pressure, abnormal heart rhythms, and coma.[citation needed]
People poisoned with very high doses of the toxin or displaying risk factors, such as old age and kidney failure, can die. Death has occurred in four of 107 confirmed cases. In a few cases, permanent sequelae included short-term memory loss and peripheral polyneuropathy.[citation needed]
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.[citation needed]
ASP was first discovered in humans late in 1987, when a serious outbreak of food poisoning occurred in eastern Canada.[1][13] 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.[14]
Epidemiologists from Health Canada quickly linked the illnesses to restaurant meals of cultured mussels harvested from one area in Prince Edward Island, 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 laboratory in Halifax, Nova Scotia. 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.[15][16]
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.[citation needed]
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.[18]
In the TV series Elementary episode "The Red Team" (original air date January 31, 2013), a witness is intentionally poisoned with domoic acid.[citation needed]
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.[citation needed]
^ abcClark, R. F.; Williams, S. R.; Nordt, S. P.; Manoguerra, A. S. (1999). "A Review of Selected Seafood Poisonings". Undersea and Hyperbaric Medicine. 26 (3): 175–184. PMID10485519. Archived from the original on 2011-08-11. Retrieved 2008-08-13.{{cite journal}}: CS1 maint: unfit URL (link)
^Bates, S. S.; Trainer, V. L. (2006). "The Ecology of Harmful Diatoms". In Granéli, E.; Turner, J. (eds.). Ecology of Harmful Algae. Ecological Studies. Vol. 189. Heidelberg: Springer-Verlag. pp. 81–93. doi:10.1007/978-3-540-32210-8_7. ISBN978-3-540-74009-4.
^Trainer, V. L.; Hickey, B. M.; Bates, S. S. (2008). "Toxic Diatoms". In Walsh, P. J.; Smith, S. L.; Fleming, L. E.; Solo-Gabriele, H.; Gerwick, W. H. (eds.). Oceans and Human Health: Risks and Remedies from the Sea. New York: Elsevier Science. pp. 219–237. ISBN978-0-12-372584-4.
^Bargu, S.; Smith, E.; Ozhan, K. (2011). "Toxic Diatom Pseudo-nitzschia and its Primary Consumers (Vectors)". In Seckbach, J.; Kociolek, P. (eds.). The Diatom World. Springer. pp. 493–512. ISBN978-9400713260.
^Bargu, S.; Goldstein, T.; Roberts, K.; Li, C.; Gulland, F. (2012). "Pseudo-nitzschia Blooms, Domoic Acid, and Related California Sea Lion Strandings in Monterey Bay, California". Marine Mammal Science. 28 (2): 237–253. doi:10.1111/j.1748-7692.2011.00480.x.
^Lelong, A.; Hégaret, H.; Soudant, P.; Bates, S. S. (2012). "Pseudo-nitzschia (Bacillariophyceae) Species, Domoic Acid and Amnesic Shellfish Poisoning: Revisiting Previous Paradigms". Phycologia. 51 (2): 168–216. doi:10.2216/11-37.1. S2CID55094773.
^Trainer, V. L.; Bates, S. S.; Lundholm, N.; Thessen, A. E.; Cochlan, W. P.; Adams, N. G.; Trick, C. G. (2012). "Pseudo-nitzschia Physiological Ecology, Phylogeny, Toxicity, Monitoring and Impacts on Ecosystem Health". Harmful Algae. 14: 271–300. doi:10.1016/j.hal.2011.10.025. hdl:1912/5118.
^Ramsdell, J. S. (2007). "The Molecular and Integrative Basis to Domoic Acid Toxicity". In Botana, L. (ed.). Phycotoxins: Chemistry and Biochemistry. Cambridge, MA: Wiley-Blackwell. pp. 223–250. doi:10.1002/9780470277874.ch13. ISBN978-0-8138-2700-1.
^Bates, S. S.; et al. (1989). "Pennate diatom Nitzschia pungens as the primary source of domoic acid, a toxin in shellfish from eastern Prince Edward Island, Canada". Canadian Journal of Fisheries and Aquatic Sciences. 46 (7): 1203–1215. doi:10.1139/f89-156.
