There is no single treatment for a snakebite. There are as many treatments as there are species of snakes. This month we take a look at the various anti-venoms on the market.
About 18 species and sub-species of the 171 different snakes in southern Africa are considered deadly and have caused human fatalities. Most of them – the cobras, mambas, two dangerous adders and the rinkhals – are covered by polyvalent anti-venom, manufactured by the South African Vaccine Producers (www.savp.co.za) in Johannesburg.
The boomslang (Dispholidus typus) is an extremely placid snake that spends most of its life in trees and seldom features in snakebite incidents. But some people do get bitten, usually when trying to catch or kill one, or when accidentally stepping on one.
The SAVP makes specific anti-venom for the boomslang but in small quantities and it is not freely available. It is usually supplied on demand and is highly effective. It is also used for domestic pets, but is expensive.
There are a number of venomous snakes that are not considered deadly but that have venom that is potent enough to cause serious damage or even death. The berg adder (Bitis atropos) comes to mind and there are unconfirmed reports of fatal bites. A number of patients have suffered particularly bad bites and even ended up on a ventilator for days. In other cases, patients have lost their vision for weeks. Unfortunately, the polyvalent anti-venom does not cover the venom of the berg adder.
Other snakes that are not covered by polyvalent anti-venom and that have caused at least one human fatality include the Kunene shield cobra (Aspidelaps lubricus cowlesi), the many-horned adder (Bitis cornuta) and the speckled shield cobra (Aspidelaps scutatus scutatus). Most of these bites, however, are not considered serious.
A number of lesser-venomous snakes are capable of inflicting extremely painful bites, some resulting in necrosis, and there is little that doctors can do other than treat symptoms. There is no evidence that the administration of cortisone, antihistamine or antibiotics is largely beneficial. Snakes in this category, and that are not covered by anti-venom, include the stiletto snake (Atractaspis bibronii), horned adder (Bitis caudalis), night adder (Causus rhombeatus) and the coral shield cobra (Aspidelaps lubricus lubricus).
Then there is the twig or vine snake (Thelotornis capensis), previously called the bird snake as it was incorrectly thought that it used its brightly-coloured tongue to lure birds closer to it for an easy meal. It actually feeds on other snakes and lizards and rarely eats birds. When it does, the victim will be a hatchling taken from a nest.
The twig snake lives in shrubs and low trees where it will freeze and watch the ground below for potential prey. It is perfectly camouflaged and can remain absolutely still for hours.
Like the boomslang, it is also a placid snake that is reluctant to bite, unless captured or threatened. When provoked, the twig snake will inflate its neck, displaying the bright interstitial skin, and will then strike out with meaning.
For many years the twig snake was considered harmless until a fatal bite was inflicted on FJ de R Lock in December 1953, near Mbeya in Tanzania. But the snake involved was probably the Tanzanian species, Thelotornis mossambicanus, and not “our” twig snake.
A famous herpetologist, Dr Robert Mertens, was bitten by his “pet” twig snake on 5 August 1975. That snake was probably the Namibian variety, the Thelotornis capensis oatesii.
The effects of the bite were serious, perhaps even fatal. Mertens started off with a headache, and this was followed by vomiting about 12 hours later. Another day later there was haemorrhaging from his stomach and urinary tract, and that led to unconsciousness. I’m not sure how long after the bite he died, as there are conflicting reports.
There is no anti-venom for twig snake. Boomslang anti-venom does not neutralise the venom of the twig snake. Like boomslang venom, the venom of the twig snake is potently haemotoxic, affecting the body’s blood clotting mechanism and causing uncontrolled bleeding. But it appears there has not been a fatal bite from a twig snake in SA.
A number of snake handlers get bitten every year, but with no or few symptoms. This is partially because the fangs of this snake are situated far back in the mouth and the venom glands are not as advanced as those of the cobras, mambas and adders. However, if the snake has the opportunity to hang on and chew for a few seconds, the effects could be severe.
The treatment would probably have to include blood transfusions, but whether a patient who has been severely “envenomed” can be saved is unknown.