Snake venom is a highly developed form of saliva, injected by the snake into its victim through hollow, modified fangs. Wear and tear are heavy on the fangs, which are soon blunted or wrenched out in the struggles of prey animals (or when being milked). But fresh fangs are always held in reserve; each poised to move into position when required.
The base of a functioning fang, and often the first reserve fang behind it as well , is penetrated by a duct that leads from a large gland behind the eye. These glands- one on either side of the head – are modified salivary glands surrounded by muscle which, when contracted, forces the clear or yellowish venom along the venom ducts and down through the fangs, squirting out under pressure as if from a pair of hypodermic syringes. Venom may be injected with each of a possible series of consecutive bites. Interestingly however, venom is not always injected.
Focused judgement and great dexterity are needed to obtain snake venom from the dangerous species of snakes found in Australia. Keepers position the snake’s fangs to penetrate a latex membrane stretched over a glass beaker. The beaker collects the venom, which is desiccated under vacuum or freeze-dried.
After drying, the venom crystals are carefully scraped from the beakers for weighing and packaging. Trained staff, who work with the venom in its various stages of processing, work extremely carefully with the venom to ensure it is not contaminated. Apart from the snakes, which take turns being’milked’ during the Australian Reptile Park’s public demonstrations, all snake venom extraction is done on a scheduled fortnightly basis.
An inventory of dried venoms from a wide assortment of native and non-native snake species is maintained at all times. The venom of each species is unique, consisting of a combination of complex proteins, which act on the prey or bite victim in various ways. In most dangerous Australian species, the most significant action of the venom lies in its effect upon the victim’s nervous system, hindering the operation of muscles and causing paralysis that can lead to death from heart failure.
Other components present in the venoms of certain species act to destroy blood cells, to cause blood clots or excessive bleeding, or to destroy tissue. Typical early symptoms of bites, where significant envenomation has occurred, include severe headache, nausea, vomiting, confusion, temporary loss of consciousness, fast pulse and tender lymph nodes. Later signs of envenomation may include drooping eyelids, voice change, double vision, difficulty in swallowing and intense abdominal pain, which may be followed by the vomiting of blood.
Anti-venoms are produced by BioCSL in Melbourne. Snake venom is forwarded from the Australian Reptile Park to the laboratories where, after being processed, it is injected into Percheron horses. Over 250 horses take part in the anti-venom program, all living the life of luxury. They undergo minimal stress during the inoculation and extraction processes. Inoculation is quite harmless, and extraction is as simple as donating blood for humans.
The horses are given increasing doses of venom over a period of time until they have built up sufficient antibodies to the venom. After this has occurred, antibodies are extracted from the blood, purified and reduced to a usable form – this becomes anti-venom.
The anti-venom taken from the horses are used to treat humans suffering from snake envenomation. Injected into the human bloodstream, the antibodies attack the venom, neutralising its effects. The dose of anti-venom given to a patient varies according to the species responsible for the bite and, when it can be ascertained, the amount of venom injected. The age and weight of the victim makes no difference to the dose of anti-venom required in the treatment.