CHEMICAL CAUSES : MOLLUSCA
 
  • Bivalvia (bivalves)
  • => nondiarrhetic toxins : => diarrhea-causing toxins : ... enters the food chain when the mussels fed on Dinophysis acuminata
    Routes of intoxication : consumption of shellfish
    Symptoms & signs (diarrhetic shellfish poisoning (DSP)) : diarrhea

    => saxitoxins / PSP toxins (PSTs) enters the food chain when the mussels fed on Gonyaulacaceae. Softshell clams (Mya arenaria) from areas exposed to 'red tides' are more resistant to PSTs, as demonstrated by whole-nerve assays, and accumulate toxins at greater rates than sensitive clams from unexposed areas. PSTs lead to selective mortality of sensitive clams. Resistance is caused by natural mutation of a single amino acid residue, which causes a 1,000-fold decrease in affinity at the saxitoxin-binding site in the sodium channel pore of resistant, but not sensitive, clams. Thus PSTs might act as potent natural selection agents, leading to greater toxin resistance in clam populations and increased risk of PSP in humans. Furthermore, global expansion of PSP to previously unaffected coastal areas might result in long-term changes to communities and ecosystemsref.
    Routes of intoxication : human LD50 for ...

    Saxitoxin is 1,000 times more toxic than the potent nerve gas sarin.
    Symptoms & signs (paralytic shellfish poisons (PSPs)) : occur between 10' and 4 hours after ingestion, depending on the dose. Inhalation of the toxin will produce a more rapid onset of symptoms, and, injection of saxitoxin may cause death in < 15'. The clinical signs of PSP include paresthesias of the lips, tongue, and gums, rapidly progressing to involve the distal extremities. Headaches, ataxia, muscle weakness, paralysis, and cranial nerve dysfunction have also been reported; the moderate to severe hypotension in puffer fish is not usually seen in PSP (Kao CY. Paralytic shellfish poisoning. In: Algal Toxins in Seafood and Drinking Water. Falconer IR (ed). NY: Academic Press, 1993: pp 75-86). Gastrointestinal signs such as nausea, vomiting, abdominal pain and diarrhea are less common. Generally, fatalities occur within the 1st 12 hours of clinical signs, and death is usually from respiratory failure. PSP usually lasts 3 days, but muscle weakness may persist for weeks. Cardiac arrest is not generally associated with PSP.  If a victim survives for 12 hours, he has a good chance of recovering as the toxin is rapidly removed from the body. There is no specific antidote therapy, only symptomatic treatment; mechanical ventilation has been used successfully in some cases. Identification of saxitoxin as a cause of intoxication by virtue of clinical symptoms is not simple but is very importrant for military medicine, because faulty identification of this toxin as nerve gas poisoning may be fatal and administration of atropine would increase fatalities. PSP has been known to have a death rate of 1-12%

    => domoic acid / amnesic shellfish toxin enters the food chain when the mussels fed on a toxic algal bloom of the pennate diatom Pseudo-nitzschia pungens forma multiseries and Pseudo-nitzschia delicatissima
    Epidemiology : in 1987, 150 reported cases, 19 hospitalisations and 4 deaths following the consumption of blue mussels caught off Prince Edward Island, Canada
    Routes of intoxication : consumption of shellfish
    Symptoms & signs (amnesic shellfish poisoning (ASP)) : gastrointestinal disturbances and neurotoxic effects such as hallucinations, memory loss and coma

    => brevetoxins enters the food chain when the mussels fed on Karenia brevis
    Epidemiology : a long history of toxic microalgal blooms exists in the Gulf of Mexico, blooms that have caused massive fish kills and respiratory irritation in humans. It was later realized that BVX in these blooms could also be passed to humans via shellfish to cause a syndrome named
    Symptoms & signs (neurotoxic shellfish poisoning (NSP)) : tingling in the face, throat and digits, dizziness, fever, chills, myalgia, abdominal pain, nausea and vomiting, diarrhea, headache, bradycardia and mydriasis. There have been no reported fatalities from NSP, although BVX kills test mammals when administered by various routes, including orally
     

  • Cephalopoda
  • Gastropoda

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