The venom of snakes is produced in modified salivary glands and has the purpose of immobilizing prey, digestion of prey and possibly defence against predators.

The venoms are a mixture of various toxins which often work synergistically and can end up being very potent because of the combinations. We broadly categorise the toxins into Neurotoxins which cause flaccid paralysis and are further divided into Presynaptic, Postsynaptic and Anticholinasterase effects, Haemotoxins that interfere with normal haemostasis by causing either bleeding or thrombosis, Cytotoxins (also called necrotoxins) which cause direct cell deaths at the site of the bite and surrounding area, Myotoxins which destroy skeletal muscles and then Cardiotoxins which means it has a negative effect on the action of the heart, due to poisoning of the cardiac muscle or of its conducting system.

In South Africa we group the snakes into the first three main categories as these are usually the effects that we monitor and ensure that they if treated correctly then death should not be the outcome. As I have already stated some snakes have combinations of these toxins but we have managed to divide them into just three for these purposes.

Neurotoxins include:
The Mambas (Dendroaspis spp), the Rinkhals H. haemachatus (which also has a reasonable cytotoxic effect), the Cobras (Naja spp) excluding the Spitting cobras N. mossambica and Naja nigricinta.

Cytotoxins include:
Spitting cobras (Naja mossambica and N. nigricinta) which also have a reasonable neurotoxic effect, large adders (Bitis arietans and B. gabonica) which both also have a significant haemotoxic effect.

Haemotoxins include:
Boomslang (D. typus) and the Vine snake (Thelotornis spp) which also have nephrotoxic component.

The South African Vaccine Producers (SAVP) produce a polyvalent which is effective for the treatment of the first two groups (Neurotoxins and Cytotoxins) and they also make a monovalent for the Boomslang (D. typus) which is not effective for bites of the Vine snake also known as the Twig snake or the Bird snake (Thelotornis species).