Lethal microcystin

As mentioned before, microcystins are lethal to a diverse group of animals including dogs, livestock, wild mammals, birds and fish, and intoxications in humans were reported. In rats and mice death occurs approximately 1-3 hr after i.p. injection of the lethal dose of microcystin-LR (37,58,59) and nodularin (56) (LD50 of 50-100 pg/kg). The toxin causes disruption of the liver leading to death possibly due to liver failure and hemorrhagic shock (59). 

Marine toxins may be developed from marine organisms. Examples include saxitoxin, tetrodotoxin, palytoxin, brevetoxins, and microcystin. Saxitoxin is a sodium-channel blocker and is most toxic by inhalation compared to the other routes of exposure. Saxitoxin and tetrodotoxin are similar in mechanical action, toxicity, and physical attributes. They can be lethal within a few minutes when inhaled. It has not yet been chemically synthesized efficiently, or easily created in large quantities from natural sources. Palytoxin is produced from soft coral and is highly toxic. It is, however, difficult to produce or harvest from nature. 

Microcystis, Nostoc, and Oscillatoria (Planktothrix). Cyanobacteria toxins (cyanotoxins) include cytotoxins and biotoxins (neurotoxins anatoxin-a, anatoxin-a(s) and saxitoxins, and the hepatotoxins microcystins MCs, and nodularins), with biotoxins being responsible for acute lethal, acute chronic, and subchronic poisonings of wild/domestic animals and humans. In most of the reported cases, afflicted animals consumed water from water bodies where there was an obvious presence of cyano-bacterial scum on the water surface. More recent measurements of cyanobacterial toxins using sensitive modem analytical methods have often revealed high frequencies of toxic blooms even when animal poisonings have not been reported. 

Microcystin. An example of this type of toxin is microcystin (produced by blue-green algae), which binds covalently to a phosphatase inside liver cells this toxin does not damage other cells of the body. Unless uptake of the toxin by the liver is blocked, irreversible damage to the organ occurs within 15 to 60 minutes after exposure to a lethal dose. When this happens, the tissue damage to the liver is so severe that therapy may have little or no value. For microcystin, unlike most toxins, the toxicity is the same, no matter what the route of exposure. 

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