x Abu Dhabi, UAESunday 23 July 2017

Waiting to unleash their venom

There are four species of viper recorded in the UAE and each one is capable of delivering a fatal dose of venom.

AD200810705948239AR
AD200810705948239AR

On a recent visit to Qarn Nazwa, a rocky outcrop in the sand sea near Dubai, I made what could have been a dangerous move. Climbing the rough limestone rock in the moonlight, I reached for a hold to pull myself up and was startled by a loud sizzling hiss. There, in a small hollow, was a baby saw-scaled viper, coiled in its defensive position. The loud and distinctive warning hiss says, "Move away now or risk a nasty bite". No need to say who won that dispute. Saw-scaled vipers, even baby ones, are not to be trifled with.

Vipers can generally be recognised by their rough appearance, small scales on top of the head and relatively short bodies. And if you spend any time in the great outdoors, they are well worth recognising; there are four species of viper recorded in the UAE and each one is capable of delivering a fatal dose of venom. Of the 10 other species of land snakes in the country, some, such as the hooded malpolon, have a mild venom. However none can be considered dangerous to humans. As a general rule, if you see a long, thin and fast-moving snake, it is not a viper.

Of the four types of viper known in the UAE, the most frequently encountered are the saw-scaled vipers of the genus Echis. Two species of these small, but very dangerous, snakes are found here - the Sind saw-scaled viper (Echis carinatus sochureki), common in firmer sand and gravel desert areas, and its close relative, the Oman saw-scaled viper (Echis omanensis), usually found in wadis and rocky areas in the mountains.

Both use a distinctive threat display, forming C-shaped coils with the body, rubbing their scales together to make a hissing or sizzling sound, like water falling on a hot plate, and striking vigorously if provoked further. This type of warning is believed to be an adaptation to life in the desert; the more common snake hiss, which involves the lung being inflated and exhaled, results in some loss of water.

Saw-scaled vipers of various species are also found across the Indian subcontinent and much of Africa and are believed to kill more people there than any other species of snake, thanks largely to their abundance in remote agricultural areas. They do not hesitate to bite when they feel threatened and, with poor medical care or inappropriate treatment, death frequently results. Although viper venoms are usually of relatively low toxicity, they may be produced in large volumes. Symptoms include swelling, localised tissue death and blood complications. The destruction of blood cells may in turn lead to kidney damage which, in the case of an untreated bite from a saw-scaled viper, may be permanent. The venom affects the blood's ability to clot which, potentially, may cause severe internal bleeding, even some days after the bite.

However, if you are unlucky enough to be bitten by one, all is not lost. The first thing to do is to resist any attempts by well-meaning passersby to emulate Hollywood's enthusiasm for tourniquets or, worse, opening the flesh with a knife and sucking out the venom. Cutting around the bite site can sever medium or major arteries and, because of the venom's anti-clotting effect, can result in excessive blood loss and infection. Besides, it is not possible to suck out significant amounts of venom.

Because tourniquets cut off the blood supply, they may cause massive tissue death, resulting in loss of the limb. They also serve no purpose; the venom, normally injected into tissue, does not travel through the blood but spreads via the lymphatic system. Because this is driven by muscle movement, the correct first response is to apply a light-pressure bandage and limit movement of the bitten limb by strapping, splinting or the use of a sling.

The good news is that, with prompt medical treatment, the bite is unlikely to be fatal. Because the venom is not a nerve toxin, there is plenty of time to get to hospital and untreated victims are very unlikely to become incapacitated or die within 24 hours. However, death may occur through stroke or kidney failure days after the bite. Therefore, get to a hospital and, if necessary, get antivenom treatment.

An antivenom effective against the major Arabian venomous snakes is produced in Saudi Arabia by the National Antivenom and Vaccine Production Centre and is available in the better hospitals in the UAE. (The centre, in Riyadh, also produces antidotes for major systemic scorpion and spider venoms.) There is, however, a 50-50 chance it will not be necessary; despite the presence of fang marks, half of all viper bites are likely to be "blanks", with no venom being injected, so a hospital should check that there has been envenomation before embarking on antivenom treatment. They should also have adrenalin at the ready in case of anaphylactic shock brought on by the antivenom itself.

The best protection, of course, is commonsense prevention. Because vipers are nocturnal, and much prefer warm nights to chilly ones, most bites occur during the summer months. Bites usually result from walking on, or very close to, a snake in the dark and the foot or ankle is the most common target. Wearing boots or stout shoes is therefore a sensible precaution for campers walking around at night.

The other two viper species found in the UAE are the Persian horned viper (Pseudocerastes persicus) and the Arabian horned viper (Cerastes gasperettii). The Arabian horned, which often, but not always, has horns above the eyes - each formed from a single scale - is a denizen of the sand seas. The Persian - which has a stubby horn above each eye, formed from a cluster of small scales - restricts itself to mountain tops, where it is sometimes to be seen sunning on rocks beside a path. Not desert-adapted, it hisses its warning by inflating the body rather than with writhing coils.

Snakes are not the only venomous animals that the UAE has to offer. A variety of scorpions, spiders, centipedes, ants, bees and wasps are all to be found here. Next to snakes, scorpions are probably the next most feared animals, and not without good reason. After bees, scorpions are responsible for more human deaths each year than any other group of non-parasitic animals. According to a recent estimate of 100,000 scorpion stings each year worldwide, perhaps 800 are lethal.

Most scorpions, however, are not deadly. Of the more than 1,500 species worldwide, fewer than 25 are known to be potential killers and the sting of many species is no more painful or dangerous than that of a bee. The venom is produced by a pair of glands in the telson, the stinging organ at the end of the tail, and is injected through the sharp hollow sting. Scorpion venom is a complex mixture of nerve poisons. In dangerous species, some of these toxins have similar potency to snake venoms and the toxins from arrow-poison frogs, some 10,000 times more poisonous than cyanide.

Most of the scorpions with toxins dangerous to mammals are in the family Buthidae, which unfortunately also happens to be the most widespread scorpion family in the UAE. The stings of buthids cause severe pain because the venom directly affects the nerves. Although there have not been any published studies of scorpion envenomation in the UAE, there are species that are known to have severe stings elsewhere in the Middle East. There are probably about 25 species of scorpion here, of which two are dangerous. The most notorious is Leiurus quinquestriatus, found in North Africa, Turkey and Arabia. It is a pale yellow scorpion with a black tail segment just behind the white telson and narrow claws.

Another potentially dangerous species is the large black Androctonus crassicauda - a living refutation of another Hollywood myth, promulgated by Indiana Jones, that only small scorpions are dangerous. This one is found over much of the UAE, including urban areas, and can be recognised by its thick and heavily armoured tail segments. In most cases of scorpion stings, the victim will experience a burning pain at the sting site that may last several hours. The severity will depend on the species, the amount of venom injected and the site of the sting, among many other factors.

The symptoms may be relieved with painkillers such as paracetamol and the application of ice. Generally this is all that is required, though in severe cases a local anaesthetic administered by a doctor may help. In rarer cases with systemic symptoms, the victim should seek hospital treatment. Such symptoms, which may be delayed by several hours, include sweating, pallor, slow pulse and breathing and high blood pressure, followed by frothy saliva, wheezing, blurred vision and extreme restlessness. Remember that the sting may be much more serious for infants and children than for healthy adults.

To avoid scorpions, be careful where you put your fingers and, again, wear shoes after dark. During the day scorpions can be found under rocks or wood, but they come out at night to feed on insects and other prey. Despite all spiders having venom, which they use for killing their prey, most species in the UAE are harmless to people. An exception is the red-back or black widow. These are generally medium-size glossy black spiders, which have a round abdomen, sometimes with a bright red marking. They make untidy webs that can sometimes be found around piles of rubbish, such as old logs or concrete blocks.

A few years ago in Dubai there was quite a scare when some of these spiders were found in the gardens in many of the newly developed suburbs. At the time, the assumption was that they were an introduced pest from Australia or elsewhere. However, there are several native Arabian species of these spiders, which have a wide distribution in the UAE. Fortunately they are much less venomous than their Australian cousins. They can still give a painful bite, however, and medical help should be sought if pain does not subside or systemic symptoms appear.

For all our instinctive fear of snakes, spiders and scorpions, far more deaths and illness are caused by the bees, wasps and ants in the region. While generally these do not have dangerously toxic venom, they may cause severe allergic reactions in sensitised people. One to watch out for in particular in the UAE is the samsum ant. These are not uncommon and often live in lawns, where they can be a painful nuisance. Anyone experiencing severe allergies to insect stings, and at risk of anaphylactic shock, should consider carrying an EpiPen or similar device at all times, to give a life-saving injection of adrenalin.

Most people who live here will rarely, if ever, encounter a snake or scorpion. While it makes sense to be aware of the dangers and have a healthy regard for the animals with which we share the environment, all these creatures are a fascinating part of the UAE's natural heritage. We should appreciate them, learn to live alongside them and not allow fear of them to spoil our enjoyment of the outdoors during the months when the weather abates sufficiently to allow us to explore our fascinating landscape.

Drew Gardner is associate professor in biology in the Department of Natural Science and Public Health at Zayed University, Abu Dhabi. drew.gardner@zu.ac.ae