Basics :: Spiders :: Snakes :: Marine :: Others
AUSTRALIAN SNAKES
Brown Snake :: Tiger Snake :: Black Snake :: Death Adder :: Taipan
Introduction
Australia is home to 7 of the top 10 most venomous snakes in the world. Unlike snakes commonly found in North America, all Australian venomous snakes are Elapids (cobra type) having small to medium sized paired, hollow (syringe like) fangs at the front of the mouth. As the fangs become blunt or damaged by wear and tear, they are replaced with a new set of razor sharp ones. The elapid snakes have capacity to control venom injection resulting in the phenomenon of a definite bite without envenomation (dry bite)
It is estimated that there are about 3000 snake bites a year reported in Australia with antivenom administration required in approximately 10% of all cases. Despite all of this there have only been 38 reported snake bite deaths in Australia since 1980.
Although much variability exists between venom composition even within individual species, each group of snake has distinctive venom resulting in predictable local and general effects.
Antivenom is available for Brown snakes, Black snakes, Death Adders, Taipans, Tiger snakes and Sea snakes. The antivenom is produced by The Commonwealth Serum Laboratory (CSL) in Melbourne (Australia) by injection of processed venom into special Percheron horses and then extraction of the Immunoglobulin from the horse. When injected into humans, the antivenom neutralizes the venom effects.
First Aid
Following any snakebite General First Aid principles should be applied. The key intervention for all Australian snakebites is the pressure immobilisation technique. There have been no reported snake bite deaths following correct initiation of pressure immobilisation first aid.
Medical assistance should be sought immediately and wherever possible the patient should be transported to the location of medical care by vehicle or stretcher. Unnecessary walking or movement of the affected limb should be avoided.
Snake Venom Toxins
Neurotoxin
These toxins act on nerves supplying skeletal muscles causing progressive paralysis. It takes time for the venom to reach the nerves and the onset of paralysis is usually delayed for 1-2 hours after envenomation.
Muscles of the face and eyes are particularly susceptible to snake neurotoxin and early signs of neurotoxin effects include drooping of the eyelids (ptosis), double vision (diploplia) and loss of facial expression (ie. unable to smile). Over time the effects spread to involve other muscles in the body, eventually causing weakness of muscles required for breathing and full paralysis
Neurotoxins are typically found in venom of Tiger snakes, Death Adders, Taipans, Copperhead snakes and Rough-Scaled snakes.
Antivenom is effective against post-synaptic neurotoxins (Death Adder) but does not reverse pre-synaptic neurotoxins (Tiger snakes, Taipan)
Myolysin Toxin
These toxins attack muscle cells causing muscle damage resulting in pain in the muscle and weakness. It takes some hours for this to occur and by the time the pain and tenderness is noticed, the damage is irreversible. As muscle damage occurs, the products of muscle damage clog up the kidneys and can cause kidney failure.
Myolysins are typically found in venom of Tiger snakes, Taipans and Sea snakes.
Antivenom has proven effective in reducing muscle pain and reducing muscle cell damage and may protect against kidney damage.
Procoagulant Toxin
These toxins activate blood clotting processes in the blood stream resulting in a rapid consumption and deficiency in essential blood clotting products leading to an uncontrolled bleeding tendency. Bleeding may be observed from the gums or from scratches or cuts in the skin. Blood may also be noticed (and can be tested for) in the urine or faeces. Bleeding may occur anywhere in the body with bleeding in the brain or abdomen frequently responsible for deaths.
Procoagulants are typically found in venom of Brown snakes, Tiger snakes and Taipans.
Antivenom (often many ampoules) is essential for reversal of the clotting abnormality caused by Brown snakes and Tiger snakes however the clotting abnormalities caused by the Taipanis often self limiting and will resolve within 12 to 18 without treatment.
Anticoagulant Toxin
Unlike the procoagulant toxins that cause bleeding by consumption of clotting factors, anticoagulant toxins act directly to cause excessive bleeding tendency. The effect of the toxin is however identical with bleeding from the gums, skin, urine and faeces.
Anticoagulants are typically found in venom of Mulga snakes.
Nephrotoxin
There are no specific kidney directed toxins isolated from Australian elapid snakes however kidney damage is not rare following significant envenomations. The proposed mechanisms include direct toxic effect of venom on the kidneys as well as secondary damage from poor blood flow, accumulation of damaged muscle proteins or clotting abnormalities affecting the kidneys.
Kidney damage is most frequently seen following envenomation by Brown snakes, Tiger snakes and Taipans.
