THE HERALD (Harare, Zimbabwe) 20 August 07 Snakes And Snakebite (Dr T Stamps is the Health Advisor in The Office of The President and Cabinet)

The good news is that most of the snakes in Zimbabwe are harmless to man, although some may attack if teased. Bites are more commonly experienced by snake collectors, who often know more about the incident and its consequences than the doctor does.

It's useful to talk to the patient, if possible, and the culprit snake should be identified, preferably by seeing the (dead) snake oneself.

Snake bites are commonest in summer, so the timing of this article is not accidental, especially as we hope for an influx of tourists this rain season.

Nearly 90 percent of snake bites are on the lower limb, and 80 percent of the rest are on the hand or wrist. Other parts of the body are more dangerous (for example you can't use a tourniquet for a cobra bite on the head!), but they are also very uncommon (less than 2 percent).

The commonest age group is the 16 to 20 year olds, and much more frequently males, though, with the passing of the 17th Amendment to the Constitution equalising women, I expect that to become more equal, too.

Only about 12 of the 74 or so varieties of snake we have here in Zimbabwe are dangerous to man, and a survey carried out by the late Professor Levy revealed that over a 5-year period an average of five people a year died of snake bite in Zimbabwe.

I hope that even this small number can be further reduced. Death from snake bite is eminently preventable by simple measures. Snakes do not make unprovoked attacks on human beings.

But, remember, nothing is more infectious than panic, and there seems to be an unrealistic fear of snakes. After all, motor vehicles cause 100 times the number of deaths, yearly, in Zimbabwe and nobody is pathologically afraid of motor cars!

To keep this resume manageable, I shall confine my remarks about the hazards to man to just four types - three are venomous, and one, the African python, has no venom but holds on by biting and then constricting the victim.

(Personally, I've only heard of one such case in Zimbabwe, and this was a herpetologist's son who was severely maimed by a python in captivity.)

Killing a python is a punishable offence.

The other three groups are:

The viperine group - puff adders, Gaboon vipers and various other types of adders. The venom is injected by long, erectile, front fangs. This type of venom is called "cytotoxic", because it cases mainly localized, tissue related, damage, and results in a large scar or even gangrene of the extremity (usually the calf and foot)

The elapids - cobras, mambas and garter snakes. The venom here is injected through relatively short, fixed, front fangs. The venom more or less rapidly involves the nervous system, and is intended to paralyse the prey. This type of venom is called "neurotoxic".

The colubrids, or back-fanged snakes, such the Boomslang and the Tree snakes. This type of venom is injected by short, back fangs, and acts by coagulating the blood. The venom is called "haemotoxic", and often causes kidney symptoms (renal shutdown) or fits.

Adders and vipers

The puff adder (Bvumbi,Chiva,iBululu or Piri) is the cause of at least 75 percent of the serious snake-bites in Zimbabwe, because of its habit of lying on paths used by humans, and its very good camouflage.

Because the whole weight of the snake, which is quite bulky and is about 1 metre in length when fully grown is launched into the action of biting, the fangs are likely to penetrate quite deeply, even biting through shoes.

The bite is usually at ankle level and is typical of a viperine snake bite, causing immediate shock and, within a short time, swelling, heat, and pain, rapidly becoming severe as the venom is what is termed "cytotoxic" (or cytolytic) causing local cell destruction, visually making the wound site turn blackish.

In some cases the poison enters the blood stream, and being cytolytic, causes generalised haemorrhages throughout the skin, mucous membranes, kidneys, eyes and even the brain. Untreated, death often supervenes in 4 to 6 days.

Tourniquets or constrictive bandages must NEVER be used as emergency treatment, because this will slow the blood flow and natural healing process, and may even cause gangrene and sloughing of the toe or foot.

The correct treatment is immobilisation of the affected limb, and the appropriate anti-venom when the patient is in hospital. The use of anti-venom is not urgent, and may be unnecessary, because puff adder bites are not always venomous.

Cold compresses and painkillers, such as paracetamol or aspirin will ease the pain, and these, coupled with rest and reassurance will mitigate the shock.

The Gaboon viper, mostly found in the Eastern districts, especially Rusitu valley and Mount Chirinda, and the Honde and Pungwe area, is a snake which likes evergreen forests, mainly rainforests below 1 500 m.

As a result, it is often half hidden by being buried in fallen leaves, but it does give warning of its presence by hissing if trodden on. It hunts for its prey - mostly rats and other rodents, but it has also been known to catch and eat monkeys and hares - at dusk.

It can bite very deeply - its fangs can be as much as 25 cm long - and injects much more venom than a puff adder, and its venom also contains fraction of haemorrhagic toxin so the urgency of specific anti-viper venom is much greater than with other adders or vipers.

Very severe shock and collapse occurs with Gaboon viper bites. I noted that during Cyclone Eline and its aftermath a lot more Gaboon viper bites occurred because its natural habitat was destroyed, and the sad thing at that time (2000) was that no hospital, in Manicaland, had anti-venom, which has to be administered promptly and in a large (100ml) volume preferably in a vein (intravenously).

For the Berg Adder no suitable anti-venom is available, and, as its name suggests, it frequents Chimanimani mountains, and less often, Inyangani and the other mountains of the Eastern Highlands, and the most frequent victims are mountain climbers.

The venom is also neurotoxic as well as the normal viper poison, but, again, a tourniquet should NEVER be used. As the snake is much smaller than the puff adder (about 300 to 400 mm), and its habitat really confined to the mountains, its bites are not so often encountered, but, although smaller, its fangs can inflict a serious bite.

Since there is no anti-serum, sucking out the venom limits the poisoning, and there used to be an expert employed by the Duke of Edinburgh Outward Bound camp in Chimanimani, who was able to do this effectively.

The other adders, including the Horned Adder (which inhabits the south of Matebeleland only) and the three Night adders do produce bites, but they all give rise to less serious symptoms, and in Zimbabwe they are treated symptomatically.

Remember NEVER to use a tourniquet in treating adder bites.
Snakes And Snakebite

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