What is a venom?
A venom is a chemical of biological origin (i.e. made by an animal) used by the animal for the purpose of attack or defence. Venoms are made by specialized apparatus such as modified salivary glands and delivered via specialized systems such as stinging cells or grooved or hollow fangs. Most venoms consist of a complex mixture of chemical substances, including proteins, peptides, sugars and other substances. Venoms may affect many systems of the body. Common venom effects include paralysis, interference with blood clotting, breakdown of muscle, pain, breakdown of tissues and effects on the cardiorespiratory system (the heart and lungs).
Snake venoms for example are a complex mixture of toxic and non-toxic substances, mostly proteins. Australian snake venoms display neurotoxic (paralysing), pro-coagulant (blood clotting) or anticoagulant (blood thinning) and usually weak cytotoxic (tissue damaging) properties. Some also contain potent myotoxic (muscle damaging) activity. The composition of particular venoms influences the clinical presentation of particular snakebites.
What is antivenom?
Antivenoms are purified antibodies against venoms or venom components. Antivenoms are produced from antibodies made by animals to injected venoms. Antivenom is the only definitive treatment for effective bites by venomous Australian snakes. Prior to the availability of antivenom, death ensued in approximately 45% of tiger snake envenomations and more than 90% of taipan envenomations. The decision to use antivenom should be based on the patient's history, examination and pathologic findings, and the type of antivenom used will depend on geographic, clinical and pathologic factors.
The most commonly used animal in the production of Australian antivenoms is the horse. Sheep, rabbits and dogs are also currently used in Australia.
How is antivenom made?
Venom is obtained from the various creatures in different ways. Snakes and funnel web spiders are milked for their venom. Stonefish, redback spider and box jellyfish antivenoms are made from venom extracted from the animal by dissection. This may be a dangerous process.
Small doses of venom or venom components are injected into the animal, and the dose gradually increased as the animal builds up a tolerance to the venom. In response to the introduction of the venom (a foreign substance), the animal produces antibodies to the venom. When the doses being injected are large, the amount of antibody produced is large.
(Photos K. Winkel)
These antibodies are harvested by taking blood from the animals and separating out the antibodies, which are then fragmented and purified by a series of digestion and processing steps.
When injected into a patient, the binding sites on the antibody fragments bind to the venoms or venom components in the circulation and neutralize the activity of the venoms in the patient. Antivenoms have been made since the 1890s.
Australia was one of the first countries in the world to experiment with snake antivenoms, in 1898, when Frank Tidswell commenced immunization of a former ambulance horse with tiger snake (N. scutatus) venom.
CSL Ltd is the sole manufacturer of antivenoms for human use in Australia. Australian antivenoms are amongst the best in the world, in terms of purity and adverse reaction rate.
Australian Snake Antivenoms
Other Australian Antivenoms
Tiger snake antivenom
Funnel web spider antivenom
Brown snake antivenom
Redback spider antivenom
Australian paralysis tick antivenom
Black snake antivenom
Box jellyfish antivenom
Death adder antivenom
Sea snake antivenom
Polyvalent snake antivenom
Choice of antivenom: Snake Identification
Identification of the offending snake will aid in the choice of the appropriate antivenom and alert clinicians to particular features characteristic of envenomation by that type of snake. In cases of snakebite involving zoo staff, herpetologists or other experienced snake handlers, the snake’s identity may be known (although this cannot always be relied upon, particularly in the case of enthusiastic amateurs). Identification of snakes by the general public or by hospital staff is frequently unreliable. Sometimes, the snake is not seen, or is only glimpsed in retreat.