|Common Name(s)||Saxitoxin; Paralytic Shellfish Poisoning (PSP)|
|Physical Attributes||Paralytic shellfish toxin produced or elaborated by planktonic algae (dinoflagellates, in most cases) upon which the shellfish fee|
|Mode(s) of Transmission||Ingestion|
|Likely BW Form(s)||Inhalation or toxic projectiles|
|Pathology||Numbness or tingling of the lips, tongue and fingertips, followed by numbness of the neck and extremities; parasthesias, a floating sensation, muscle weakness, vertigo, and cranial nerve dysfunction; death results in less than 24 hours from respiratory collapse|
|Vector/Dormant Form||Carried in marine dinoflagellates: blue-green algae, crabs, the blue-ringed octopus, and bivalve molluscs|
|Incubation Period||~30 minutes (10-60 minutes)|
|Fatality||Fatal dose: 0.2 miligrams|
|Treatment||No antidote avaliable; strong alkalis; supportive care (breathing support)|
Saxitoxin is the parent compound of a family of chemically related neurotoxins. In nature they are predominantly produced by marine dinoflagellates, although they have also been identified in association with such diverse organisms as blue-green algae, crabs, and the blue-ringed octopus. Human intoxications are principally due to ingestion of bivalve molluscs which have accumulated dinoflagellates during filter feeding. The resulting intoxication, known as paralytic shellfish poisoning (PSP), is known throughout the world as a severe, life-threatening illness requiring immediate medical intervention. In a BW scenario, the most likely route of delivery is by inhalation or toxic projectile. In addition, saxitoxin could be used in a confined area to contaminate water supplies.
The 20 toxins responsible for paralytic shellfish poisonings (PSP) are all derivatives of saxitoxin. Diarrheic shellfish poisoning (DSP) is presumably caused by a group of high molecular weight polyethers, including okadaic acid, the dinophysis toxins, the pectenotoxins, and yessotoxin. Neurotoxic shellfish poisoning (NSP) is the result of exposure to a group of polyethers called brevetoxins. Amnesic shellfish poisoning (ASP) is caused by the unusual amino acid, domoic acid, as the contaminant of shellfish.
After oral exposure, absorption of toxins from the gastrointestinal tract is rapid. Onset of symptoms typically begins 10-60 minutes after exposure, but may be delayed several hours depending upon the dose and individual idiosyncrasy. Initial symptoms are numbness or tingling of the lips, tongue and fingertips, followed by numbness of the neck and extremities and general muscular incoordination. Nausea and vomiting may be present, but typically occur in a minority of cases. Respiratory distress and flaccid muscular paralysis are the terminal stages and can occur 2-12 hours after intoxication. Death results from respiratory paralysis. Clearance of the toxin is rapid and survivors for 12-24 hours will usually recover. There are no known cases of inhalation exposure to saxitoxin in the medical literature, but data from animal experiments suggest the entire syndrome is compressed and death may occur in minutes.
Routine laboratory evaluation is not particularly helpful. Cardiac conduction defects may develop. Differential diagnosis may require toxin detection. Diagnosis is confirmed by detection of toxin in the food, water, stomach contents or environmental samples.
Management is supportive and standard management of poison ingestion should be employed if intoxication is by the oral route. Toxins are rapidly cleared and excreted in the urine, so diuresis may increase elimination. Incubation and mechanical respiratory support may be required in severe intoxication. Timely resuscitation would be imperative, albeit very difficult, after inhalation exposure on the battlefield.
No vaccine against saxitoxin exposure has been developed for human use.
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