Anti-venoms were first produced over a century ago. It was discovered that it was possible to “hyper-immunize” an animal against snakebite by gradually increasing the dosage of venom on a regular basis. It was also discovered that an envenomed animal could be saved if the serum of the immunized creature was injected into the envenomed animal.
The principle of modern antivenom production is to this day conducted in basically the same way, although certain modifications have been implemented such as neutralizing the venom with formaldehyde prior to using it on animals which reduces the suffering of immunized animals.
The animal used in the production of antivenom in SA is the horse. Increased dosage of venom is injected into the horse until the horse becomes ‘hyper immunized” upon which the blood is drawn and the serum removed. The rest of the blood is transfused back into the horse. The serum obtained then passes through various testing and refinement until it is able to be used in humans with the same results.
The basis of the serum contains immunoglobulins, and these are digested by pepsin to isolate the antigen that in turn neutralizes the venom.
Initially in South Africa the antivenom production was limited to the venoms of the Puff Adder and the Cape Cobra. A bivalent antivenom was later produced for the venoms of both snake. A trivalent antivenom was also produced for the three Mamba species found in southern Africa. During the 1970’s all the antivenoms (Bivalent, trivalent and monovalent) were integrated to form one polyvalent antivenom which is effective against most venoms with the exception of the Boomslang, and the Saw-scaled Viper.
These antivenoms are very safe, but being an animal protein derivative a small percentage of people may display dangerous allergic reactions to the antivenom. This hyper-allergic reaction may lead to what is known as anaphylactic shock which can be more serious than the venom itself and possibly lead to death.
There are two types of antivenom available:
– Polyvalent : This contains antibodies from several snake species and is effective against most venoms. Polyvalent antivenom can be used for all our South African venomous snakes with the exception of Boomslang (Dispholidus typus), Vine snake (Thelotornis capensis) and Yellow bellied sea snake (Pelamis plantura).
– Monovalent : This contains the antibodies from one strain of a single species. In South Africa this is the Boomslang (Dispholidus typus).