INGESTED TOXINS
Shell Fish
This derives from dinoflagellates contaminating shellfish (clams, scallops, oysters, etc.). The toxin, saxotoxin, is water soluble, heat and base stabile, and is therefore not affected by steaming or cooking. It inhibits sodium channels of excitable membranes, blocking propagation of nerve and muscle action potentials. Symptoms: These usually occur within 30 minutes, and include parasthesias of the lips, tongue, gums and face. This process proceeds to the trunk and may progress to paralysis and respiratory arrest. The gastrointestinal form may appear hours or days after ingestion with nausea, vomiting, diarrhea and abdominal pain. Treatment: No specific treatment. Stop eating if oral sensations are perceived. Empty stomach if systemic symptoms are noted, using emetic or lavage. Give respiratory support and monitoring if needed.
Scombroid Occurs in tuna, mackerel, skipjack and other members of the family scombridae. Fish left at room temperature undergo bacterial breakdown of tissue histidine to histamine and saurine. Spoiled fish have a sharp, peppery taste. Symptoms: Occur in the first hour, and a histamine-like intoxication is seen. There is headache, flushing, dizziness, palpitations and tachycardia. One may see hypotension, bronchospasm, urticaria and anaphylaxis. GI symptoms include nausea, vomiting, diarrhea, abdominal pain, thirst and dysphagia. Treatment: Gastric lavage, respiratory and circulatory support. Antihistamines appear to be helpful.
Toad, or pufferfish, common in tidal creeks and coastal waters are well-known for their amusing habit of inflating their bodies with water or air to balloon-like proportions when provoked. Along with their relatives the porcupine fish, cowfish, boxfish, tobies and sunfish, their bodies contain the same toxin as the saliva of the blue-ringed octopus with the same, potentially fatal effects. Easily caught on fishing lines, they must never be eaten. Derived from algae covered with bacteria Alteromonas sp.Being ingested by pufferfish The toxin concentrates in the liver and gonads. The toxin inhibits sodium transport, affects neuronal transmission in the CNS and periphery and also affects cardiac nerve conduction and contraction. Symptoms: Entirely dose dependent-can have oral paresthesias, muscular fasciculations then a flaccid type of paralysis occurs. (curare-like). Treatment: Gastric lavage and respiratory support, usually for 24 hours or more. Consider sedation because cognitive function intact. There will be spontaneous remission if the patient is otherwise supported.
A form of food poisoning which occurs occasionally in certain coral reef fish. It originates in a tiny organism (dinoflagellate) attached to algae growing usually on dead coral. It is eaten by plant-eating fish and then accumulates in large predatory fish such as mackerel, coral trout and cod. The tasteless and odourless toxin is not destroyed by cooking or freezing. All reef fish over 10kg should be treated with caution. Eat only a little and if symptoms develop discard the fish. Avoid internal organs of any reef fish. Symptoms, which begin 2-12 hours after fish are eaten, are varied and can include breathing difficulty requiring artificial respiration. If symptoms develop, induce vomiting.
INJECTED TOXINS
Happily for humans, the animals which inhabit the beautiful cone shells are nocturnal. Hunters by nature, many carry a toxic concoction which is capable of killing humans; in fact, the venom from one geographer cone (Conus geographus) is capable (in theory of course,) of killing 700 people. There are about 80 species of cone shells in Australia, mostly in tropical waters. Some feed on worms, some on molluscs (including other cone shells) and some on fish. It is the last two types which are most dangerous to humans. To stop a fish in its tracks a snail needs a formidably fast-acting venom. It is thought that the cone detects its prey from chemicals in the water drawn through its siphon. Some visual sense may also be involved. The cone then extends its proboscis, a hollow feeding tube, on the end of which is a hollow, barbed tooth. Attached to a poison sac, this tooth is driven harpoon-style into the hapless victim, poison being injected through the tooth. The force of the harpoon has been known to penetrate a periwinkle shell. Each tooth is used only once. The best way to avoid stings is not to touch live cone shells. The extendable harpoon-wielding proboscis is capable of reaching most parts of the shell so it is not safe to grip the wide end. Thick shoes should be worn for reef walking and cones should never be put in pockets or sleeves. Sting symptoms progress from numbness to breathing failure.
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