How Not To Die In Australia Part 3: Sea Creatures

So, like a sensible tourist you’ve started taking every precaution to avoid a toxic death: you’re wearing unfashionably sensible footwear, you’ve starting obsessively checking your shoes and bedsheets for spiders and you’re making a concerted effort not to punch, kick or otherwise annoy funnel-webs or deadly snakes. To celebrate, you decide to take a lovely trip down to the beach, thinking that surely no horrors can await you there. Oh, how wrong you are…

Stonefish

Stonefish (image from Oceanpro Aquatics)

Personality: stonefish are rather unpleasant-looking fish up to 50cm in length. They are found in shallow waters around coral reefs, where they camouflage themselves as ugly bits of rock or old coral, or bury themselves in the sand. They can survive for up to 24 hours out of water and are sometimes found on beaches. These locations are unfortunately perfect for guaranteeing they will occasionally be trodden on by unsuspecting beachgoers, swimmers and divers. They feed on small fish and crustaceans, and are in turn eaten by rays, sharks, sea snakes and possibly Aboriginal folks.

Venom: the stonefish is the most venomous fish in the world. Its venom has an LD50 of 0.36mg/kg and contains many toxic compounds:

• Hyaluronidase – an enzyme which degrades connective tissue.
• Stonustoxin – causes nitric oxide-mediated vasodilation and profound, irreversible hypotension; increases vascular permeability to cause oedema; and forms pores in cell membranes, resulting in cytolysis, haemolytic anaemia and neurotoxicity.
• Verrucotoxin – interferes with cardiac calcium and potassium channels, putting the patient at risk of lethal arrythmias.
• Trachynilysin – an excitatory neurotoxin with haemolytic effects.

Weapons: they keep their venom glands in a series of thirteen sharp erectile spines running down their backs, which they raise if they feel threatened – they’re not the sort to run and hide. These spines can easily penetrate human skin if the stonefish is stepped on or handled by curious divers, and subsequently inject venom into muscle tissue.

Clinical features: the main feature of a stonefish sting is absolute agony. This starts immediately and radiates centripetally from the puncture wounds, which become tender and swollen with bruising or bluish discolouration. Symptoms of significant envenomation include dizziness, delirium, nausea, hypotension, collapse, cyanosis, pulmonary oedema, weakness and paralysis: these require urgent medical attention as massive envenomation can kill in 2 hours.

Management: get the patient out of the water and remove any broken fragments of spine using tweezers or forceps. DO NOT APPLY A TOURNIQUET OR PRESSURE BANDAGE. Some sources say that immersing the affected limb in HOT WATER (>45°C) may help to reduce the pain. IV analgesia or local/regional anaesthesia are often required. Tetanus prophylaxis may be appropriate depending on the patient’s vaccination status. Antivenom should be given intramuscularly if there are any signs of significant envenomation. Stonefish antivenom is the second most commonly used antivenom in Australia, and since its introduction in 1959 has successfully prevented any deaths.

Box Jellyfish

Box Jellyfish

Personality: box jellyfish (also known as sea wasps) are large, with cube-shaped bodies and about 15 tentacles, each up to 3 metres long. They are one of the few types of jellyfish to possess proper eyes – which are grouped in clusters around their bodies – but scientists are unsure how they actually manage to process visual information, as they don’t have brains! They are mainly found in the tropical waters of northern Australia and the South Pacific, particularly drifting around shallow waters or washed up on beaches. They tend to avoid contact with humans, so stings usually only occur if humans accidentally brush up against jellyfish in the water (they are practically invisible) or step on them.

Venom: good samples are very difficult to obtain, so our understanding of the toxins involved is rather sketchy. It contains a potent and fast-acting primary cardiotoxin, some myotoxic components, and probably some necrotoxins as well.

Weapons: box jellyfish tentacles contain millions of individual stinging cells called nematocysts, which use a tiny needle-like shaft to inject venom directly into capillaries under the skin. Nematocysts also help the jellyfish to cling tightly to its prey and restrain it while venom is injected.

Clinical features: the first feature of a sting is excruciating pain – victims are at risk of drowning before they are able to get back to land. The nematocysts adhere tightly to the skin, and any attempts to remove them only make the pain worse by causing even more venom to be released. Horrific red welts appear almost instantly on all affected areas – these can later become blistered, necrotic and scarred. If significant envenomation occurs (generally >10% of skin surface) the patient will progress within 4-6 minutes from agonised delirium to respiratory collapse, serious arrhythmias and cardiac arrest.

Management: get the patient out of the water. DO NOT TOUCH THE STING. Douse the entire affected area with as much VINEGAR as possible for at least 30 seconds – this inactivates the nematocysts, allowing them to be removed safely with a gloved hand. Give oxygen if available. Monitor closely for any deterioration in cardiac function, and commence CPR in the event of cardiac arrest. Cold ice packs may be applied to relieve pain. Significant envenomations should be treated with IV or IM  antivenom as soon as possible, to reduce pain and the potential for skin necrosis. The value of antivenom in correcting cardiotoxicity is less certain, and patients may require prolonged cardiopulmonary resuscitation in hospital before they begin to stabilise.

Irukandji Jellyfish

Irukandji Jellyfish (image from VUV14)

Personality: Irukandji jellyfish have absolutely tiny bodies 3-10mm long and virtually invisible to the naked eye, but their four tentacles can measure over a metre in length! Very little is understood about their life cycle and behaviour, as they are difficult to see, difficult to catch and extremely fragile. They mainly inhabit the deeper waters around northern Australia, but have been found as far afield as Japan, Britain and Florida.

Venom: most probably contains excitatory neurotoxins which affect the closure of voltage-gated sodium channels, resulting in continuous acetylcholine release and massive overstimulation of motor and autonomic nerves. Excessive catecholamine release is a key feature.

Weapons: unlike most jellyfish, Irukandji have nematocysts on their bodies as well as their tentacles, allowing them to sting their victims more effectively on contact. They also differ in that after being deposited their nematocysts only release venom from their tips, rather than from their whole surface. This explains the delay in development of pain.

Clinical features: Irukandji syndrome has a characteristic progression of symptoms. The sting itself is only mildly irritating with no obvious marks, except for some goosebumps on affected areas. Development of major symptoms is delayed by about 30 minutes. Patients will then begin to experience severe discomfort in the form of headaches, backache, myalgia, chest and abdominal pain. Other features include nausea and vomiting, sweating, a profound sense of impending doom, arrhythmias, malignant hypertension, heart failure and pulmonary oedema. The pain is so unbearable, and the overwhelming belief they are going to die is so great, that patients have been known to ask their doctors to kill them just to get it over with. Symptoms begin to wind down after about 24 hours, but can take up to two weeks to resolve completely.

Management: get the patient out of the water. DO NOT TOUCH THE STING. The entire affected area should be doused with as much VINEGAR as possible for at least 30 seconds, and inactivated nematocysts subsequently removed with a gloved hand. Monitor for deteriorations in cardiorespiratory function and provide appropriate first aid. There is no antidote to Irukandji venom, so treatment is mainly supportive and consists of effective analgesia with IV opioids, control of hypertension with short-acting drugs like magnesium sulphate, and early detection and management of pulmonary oedema. There have been 2 recorded deaths from Irukandji syndrome, both occurring before its aetiology, symptoms and management were properly understood.

Sea Snakes

Beaked Sea Snake and Belcher’s Sea Snake

Personality: yes, that’s right, even in the oceans you can’t escape Australia’s deadly snakes! Sea snakes are almost totally adapted to living underwater – most of them cannot even move on land – but they do not have gills and must therefore surface regularly to breathe. Some can respire to some extent through their skin, allowing longer and deeper dives. There are 31 different species of sea snake in Australia, all of which are potentially dangerous to humans. However, while they may be inquisitive they are not normally aggressive unless frightened or caught. Bites to humans are rare and there have been no recorded deaths.

Venom: contains postsynaptic neurotoxins and myotoxins. Depending on the species, the LD50 may be as low as 0.04mg/kg. The neurotoxin competitively binds to nicotinic acetylcholine receptors at the neuromuscular junction to induce neuromuscular blockade and flaccid paralysis. The myotoxins cause severe rhabdomyolysis, which ultimately leads to acute renal failure, hyperkalaemia and cardiac arrest.

Weapons: sea snake fangs are small (<4mm) and fragile, often breaking off and remaining stuck in their victim’s flesh. However, localised pain is absent or minimal. Close examination will reveal small, distinct puncture marks at the bite site with little or no surrounding swelling. Significant envenomation occurs in less than 20% of cases.

Clinical features: after experiencing early symptoms of systemic envenoming, patients progress within 1-3 hours to generalised myalgia and stiffness as their muscle tissue begins to break down. Trismus may also be a feature. Neurotoxic effects take slightly longer to appear (5-6 hours) and include ptosis, ophthalmoplegia, muscle weakness and paralysis. Within 12 hours of the bite you can expect to see frank myoglobinuria, acute renal impairment and hyperkalaemia.

Management: as for snake bites. Get the patient out of the water and immobilise them before identifying the bite wound and dressing it with a pressure bandage. DO NOT APPLY A TOURNIQUET. Monitor closely for signs of airway compromise or respiratory paralysis and provide artificial respiration if required. If there are any signs of significant envenomation (i.e. paralysis or myolysis) sea snake antivenom should be given intravenously. If sea snake antivenom is not available, tiger snake or polyvalent antivenoms can be used instead.

Blue-Ringed Octopus

Personality: the blue-ringed octopus is undeniably a pretty little beastie. However, before you rejoice at seeing one looking lovely in the wild just remember that it only turns its blue rings on when it feels angry or threatened! When the octopus feels peaceful or happy it is a rather boring browny-yellow colour. They are only small – starting life the size of a pea and growing to the size of a golf ball – and live in tidal rock pools and shallow waters, where they tend to get trodden on, poked or handled by children and excitable tourists. Males die immediately after mating, leaving females to incubate their eggs in their arms for six solid months without food or rest and die once their offspring have hatched.

Venom: each tiny octopus carries enough venom to kill 10 men, which is produced by bacteria living symbiotically in its salivary glands. The toxin was originally known as maculotoxin, but was more recently discovered to be identical to tetrodotoxin – the deadly substance found in blowfish venom. Tetrodotoxin is a potent presynaptic neurotoxin with an LD50 of 0.3mg/kg. It acts by binding to fast voltage-gated sodium channels, thereby blocking the propagation and conduction of peripheral nerve impulses. This results in rapidly progressive flaccid paralysis.

Weapons: its beak may be small, but it is sharp and powerful enough to penetrate a wetsuit. Bites are usually painless, so patients often have no idea they have been bitten until terrifying paralysis starts to set in.

Clinical features: early symptoms may include weakness, numbness, perioral tingling and paraesthesiae. Complete paralysis can occur within minutes of a bite, with no impairment of  conscious level or awareness. Pupils become fixed and dilated. If respiratory paralysis is allowed to progress, it results in cyanosis, hypotension, cerebral hypoxia and cardiac arrest. There may also be symptoms of systemic envenomation, including nausea and vomiting, diarrhoea, epigastric pain and headache.

Management: get the patient out of the water. Treat as a snake bite: immobilise the patient and apply a pressure bandage to the wound if it is identifiable. DO NOT APPLY A TOURNIQUET. Protect the airway (there is significant risk of aspiration of vomitus) and provide mouth-to-mouth or bag-and-mask respiration as required. Remember that the patient is AWAKE and can see and hear everything that is going on around them. Blue-ringed octopus venom has no known antidote, so the only way to tackle its effects is to provide supportive treatment and mechanical ventilation until it wears off – this takes about 24 hours.

Stingray

Stingrays

Personality: stingrays can be over a metre long, and they live buried in the sand on the sea bed to conceal themselves from prey. They are extremely placid and usually allow snorkellers and scuba divers to swim alongside them. Attacks involving humans are rare – usually occurring when an unsuspecting stingray is stepped on – with only 2 deaths ever reported in Australia. It’s horribly ironic that Steve Irwin, a man who spent his life annoying Australia’s most vicious and deadly creatures, ended up being killed by something as innocuous and friendly as a stingray!

Venom: not particularly deadly. It contains a mixture of hyaluronidase, proteases, cardiotoxins, respiratory depressants and convulsants.

Weapons: stingrays have one or more barbed stings on their tails, which are sharp, serrated and coated with venom. These stingers can be up to 35cm long, and when wielded with a slicing or stabbing motion they can cause serious injuries to skin and underlying structures, especially if internal organs or major blood vessels are penetrated.

Clinical features: the main problem is usually the result of mechanical injury by the stinger; lacerations and stab wounds may cause profuse bleeding and, depending on their location, damage to internal structures such as bowel, liver, heart, lungs and vasculature. The sting itself causes intense pain with local swelling, erythema and itch. Systemic symptoms include nausea, vomiting, abdominal pain, palpitations, collapse, headache, muscle cramps and fasciculations. Massive envenomations may result in hypotension, arrythmias, paralysis and convulsions, but even if these do occur, death is virtually always due to coexisting trauma.

Management: get the patient out of the water and remove any broken stinger fragments. STINGS TO THE NECK, CHEST OR ABDOMEN SHOULD BE LEFT UNTOUCHED. Staunch any bleeding with local pressure, bandaging and tourniquets (if severe). Again, immersion in HOT WATER (>45°C) may help control pain. Don’t forget to check the patient’s tetanus vaccination status. Surgical interventions may be required to control bleeding, repair damage to anatomical structures or remove deeply embedded stinger fragments. The injury may be complicated by wound infections, ulceration or tissue necrosis.

Great White Shark

Great White Shark

Personality: these legendary creatures have been terrorising the oceans since the dinosaurs were around. They can grow to 5m in length and weigh over a ton, although every now and again there are reports of monster sharks that are much larger still. They are apex predators (i.e. the top of the food chain) with little to no fear of any creature they come into contact with. They are curious animals, and like to explore anything new or unusual they encounter in their territories: unfortunately without hands or feet the only way they can investigate new things is by taking “exploratory bites” with their teeth! Their sense of smell is so keen it can famously detect the presence of a single drop of blood in an Olympic swimming pool. Additionally, like all sharks, they have sensory organs – known as the Ampullae of Lorenzini – which allow them to detect the electromagnetic field generated by the heartbeats and movements of living animals: these are sensitive enough to detect half a billionth of a volt of electricity. This “sixth sense” is known as electroreception.

Venom: does it look like it needs any?

Weapons: great white sharks have hundreds of serrated triangular teeth arranged in several rows. Contrary to their depiction in the media as frenzied killing machines, they are actually subtle, cautious hunters which prefer to strategically stalk their prey from below before striking with devastating speed and force. After inflicting one or two swift bites, they retreat and wait for blood loss to weaken their victims before coming back to feed. Attacks on humans may be provoked or unprovoked: there are several patterns of unprovoked attack including “hit and run” and “bump and bite“, which are two ways of curious sharks giving humans an exploratory bite to see what they taste like; and “sneak“, where sharks mistake humans for prey and move in for the kill – this is the most vicious and the most commonly fatal. In most cases the victim does not see the shark coming.

Clinical features: a shark attack can result in several characteristic injuries: a ragged crescent-shaped bite mark from being enclosed in its jaws, a series of deep parallel cuts from the teeth raking through skin, the removal of small to large chunks of flesh, and traumatic amputations of limbs. If the victim was involved in a “bump and bite” attack they may also have abrasions caused by the shark’s sandpapery skin rubbing against them. The violence and force of attacks can fracture bones. Blood loss and exsanguination is the most common cause of death.

Management: get the patient out of the water as soon as it is safe to do so. Try to keep them warm. Manage bleeding as an absolute priority: if injuries are severe, death from haemorrhagic shock can occur within minutes. Lost limbs should be retrieved if possible and brought with the patient to hospital for assessment of viability. The main objectives of hospital management are control of bleeding, reattachment of tissue that remains viable, and prevention of wound infections with wash-outs and antibiotic prophylaxis. There are 10-20 shark attacks every year in Australia, and at least one of these is fatal.

Saltwater Crocodile

Saltwater Crocodile (image from Northern Territory News)

Personality: the saltwater crocodile is the world’s largest reptile, growing to lengths of 6 metres and weighing in at up to 1300kg. It is not technically a sea creature as it is most commonly found living in swamps, rivers and estuaries across northern Australia – swimming in these places is definitely not worth the risk! Another apex predator, it can eat virtually any animal that strays into its territory, including things like cows, horses and water buffalo (which can weigh over a ton), and various species of shark. It can go for months without eating anything at all. It is generally very lazy and spends most of its time sunbathing and sleeping, but is easily galvanised into action if intruders blunder into its territory.

Venom: see Great White Shark.

Bite: crocodiles attack with extraordinary speed and their bites carry enormous pressures of up to 5000 pounds per square inch. A large crocodile’s bite can easily crush a water buffalo’s skull, so something as puny as a human really doesn’t stand a chance. After trapping prey between their jaws, crocodiles perform a “death roll” to throw it off balance and drag it into the water, where it either drowns or dies from its injuries (or both). They then tear their victim into bitesized pieces by shaking it violently from side to side.

Clinical features: bites and “death roll” trauma result in deep and often catastrophic lacerations to skin and underlying structures. Limbs and other body pieces may be missing: these can usually be found scattered around the area of the attack or in the crocodile’s stomach.

Management: as for shark attacks. Specialist limb reattachment services may be required. Wound infections with Pseudomonas and Clostridia are a major problem, and can progress to osteomyelitis (which may necessitate amputation) and severe sepsis. Crocodile attacks kill one or two people every year in Australia and leave several more with horrific and debilitating injuries.

Some reassuring facts

• Between 2000 and 2006 in Australia, horses killed 40 people, cattle 20 and dogs 12. In comparison, sharks killed 11 people, crocodiles 4, and stingrays 1. There were probably a couple of jellyfish-related deaths too. In the same time period, thousands of people will have been killed in car crashes, hundreds will have drowned or died after falling down the stairs, and dozens will have died in lightning strikes or scuba-diving accidents. Just to give you a bit of perspective 🙂

• Australia is very proactive about preventing and treating animal incidents on its beaches. Most beaches have safety nets to keep out most of the nasties and are closed if there are risks to the public. Lifeguards and first-aiders are fully trained in recognising and treating stings, bites and other injuries – and most of the locals will probably know what to do too! And of course, antivenoms are available for the three most deadly sea creatures: stonefish, box jellyfish and sea snakes.

• If you’re really desperately worried about these animals, they’re pretty easy to avoid: just don’t go in the water!

• Research into the venoms of marine animals doesn’t just help to protect humans from dying if they are envenomed. The fact that the venoms often act very quickly to elicit very specific effects on various body systems is also guiding the development of new and better drugs for a whole variety of conditions. For example, the cardiotoxic effects of box jellyfish venom may actually be used to treat heart problems in the future. Experiments with various deadly neurotoxins have found that they can be effective in the treatment of epilepsy, Parkinson’s disease, dementia and pain. Ziconotide, an antinociceptive analgesic derived from cone snail venom, was introduced in 2004 for the treatment of severe chronic pain. It is up to 1000 times more powerful than morphine, and is non-addictive. So, these animals may actually help humans in the future!

Of course, no epic foray into the dangers of Australian wildlife would be complete without a bit of Steve Irwin – what an absolute legend that man was 🙂 I get a tear in my eye whenever I watch that second video!

How Not To Die In Australia Part 2: Spiders

Australia’s snakes may be scary, but I think its spiders are definitely worse: these guys are much more likely creep into your bedroom and get you when you’re sleeping, or hide somewhere in your house just waiting to bite you if you inadvertently disturb them…

Sydney Funnel-Web Spider

Funnel-Web Spider (image from ScenicReflections)

The Sydney funnel web spider has an LD50 of 0.16mg/kg – making it more deadly than most snakes – and is regarded by many authorities to be the most dangerous spider in the world.

Personality: funnel-webs are scary-looking things, with a body length of up to 7cm. They can be extremely aggressive if they feel threatened. Females spend most of their long lives hiding in their silky burrows, only emerging to grab passing prey, and therefore rarely cause any problems. Males, however, spend most of their time wandering around trying to find females to mate with. This means they regularly end up in houses, cars, shoes, clothes and many other places where unsuspecting humans might disturb them. They are attracted to water and often fall into swimming pools, where they can survive underwater for up to 24 hours and subsequently bite anyone who tries to remove them. They are most commonly found within a 100km radius of Sydney.

Venom: contains an excitatory neurotoxin known as delta-atracotoxin or robustoxin. Robustoxin acts by slowing the inactivation of voltage-gated sodium channels and stopping them from closing properly. This results in continuous acetylcholine release, overstimulation of the neuromuscular junction, widespread overexcitation of the nervous system and ultimately weakness and paralysis resulting from depletion of neurotransmitter reserves.

Bite: funnel-web fangs are large (5-7mm long) and powerful – they can penetrate soft shoes and even toenails. Bites are usually extremely painful due to the large puncture marks and the acidic nature of the venom. Each bite delivers only a small amount of venom (about 0.14mg), but funnel-webs tend to cling tightly to their victim and inflict multiple bites. Despite this, the rate of significant envenomation is only 10-20%.

Clinical features: the venom can take effect extremely rapidly, causing death in under an hour. There may be symptoms of systemic envenomation as described previously. Excitatory neurotoxicity manifests itself as muscle fasciculations (characteristically affecting the tongue in early stages) and autonomic symptoms such as perioral tingling, sweating, salivation, lacrimation, piloerection, tachycardia, malignant hypertension and pulmonary oedema. Severe envenomation may progress to involve convulsions, fixed dilatation of the pupils, confusion, loss of consciousness, raised intracranial pressure and death.

Redback Spider

Redback Spider (image from DryadMusings)

Redback spiders are close relatives of the infamous Black Widow. This deadly heritage is reflected by their extremely potent venom, with its LD50 of 0.90mg/kg.

Personality: female redbacks are much larger than males, but their bodies are still only about 1cm in diameter. Despite their small size they can easily prey upon lizards, mice and even small snakes. The females perform sexual cannibalism during mating. Unlike funnel-webs, it is the female redback which causes most problems with bites. Although they are common in urban areas they rarely stray from their messy webs, so humans are much less likely to encounter them unexpectedly unless the webs are located in frequently-visited places such as letterboxes, garages or garden furniture.

Venom: contains an excitatory neurotoxin called alpha-latrotoxin. It interacts with receptors on the membranes of presynaptic neurones and becomes inserted into the membrane, forming a pore which is permeable to calcium ions.  The subsequent calcium ion influx triggers massive neurotransmitter release, and neurotransmitters can also leak passively out of the pores in the membrane. This results in initial overstimulation of the nervous system, followed by muscle weakness or paralysis once neurotransmitter reserves become exhausted. The pores also leak water, causing nerve terminal swelling and oedema.

Bite: redbacks only have tiny fangs, so bites to humans are often quite ineffective. Even if the spider does manage to give you a decent bite, the rate of significant envenomation is less than 20%. Because the puncture marks are so small, pain is often delayed by up to half an hour.

Clinical features: redback bites progress very slowly and symptoms can persist for days. Once the venom begins to take effect, the pain around the bite can soon become excruciating. Pain then spreads proximally to involve the whole limb, regional lymph nodes and eventually the whole body, resulting in a variety of symptoms such as headache, aching joints, chest pain and abdominopelvic pain. Sweating, piloerection and swelling are also characteristic features and follow the same pattern, beginning around the area of the bite before becoming generalised and excessive. Other common features include muscle cramps, pyrexia, nausea, tachycardia, and hypertension. Severe cases may progress to muscle weakness and paralysis. These symptoms are virtually identical to those caused by black widow bites, and form the syndrome known as lactrodectism.

Mouse Spider

Mouse Spider (image from Biodiversity Snapshots)

Mouse spiders are often mistaken for funnel-webs: they are generally considered much less deadly, but their bites are nasty and can sometimes have serious consequences.

Personality: mouse spiders are pretty scary but not as big as funnel-webs; their bodies can be up to 3cm in length. Females are completely black, whereas males have impressive blue and red colouration. Females live in deep burrows covered with a trapdoor – which can be opened quickly to grab passing insects – and spend most of their time guarding their eggs or raising their little spiderlings. Males wander in search of females, and die after mating. Both can be aggressive and will bite if provoked, but they tend to avoid heavily populated areas so encounters with humans are less common.

Venom: the venom of the Eastern mouse spider has been found to contain compounds similar to robustoxin, the deadly excitatory neurotoxin found in funnel-web spider venom. Preliminary tests in mice have found that mouse spider venom may actually be more lethal than funnel-web venom!

Bite: they have large fangs which inflict a deep painful bite. The rate of significant envenomation is unknown but is likely to be very low: it is believed that most mouse spider bites are “dry” bites devoid of venom.

Clinical features: most people who are bitten will only suffer the distress of a vicious spider attack and the effects of a painful bite. However, in rare cases bites have been known to cause symptoms very similar to funnel-web bites, with rapid onset of excitatory neurotoxicity and autonomic dysfunction. As a result, it is vital that all patients seek medical attention as soon as possible. Medical staff should treat mouse spider bites as funnel-web bites until proven otherwise.

White-Tailed Spider

White-Tailed Spider (image from Morwell National Park)

White-tailed spiders are generally considered to be relatively harmless, but there is ongoing debate as to whether their bites can cause necrotising arachnidism (which is unfortunately just as nasty as it sounds).

Personality: female white-tailed spiders are larger than males, with a body length of about 2cm. They are hunting spiders and therefore do not build webs, but instead wander around at night looking for food. They like to eat other spiders (mainly house spiders, but redbacks too!) which can always be found in bountiful quantities in and around human dwellings. They will happily find shelter under almost anything in the home, especially bedsheets and things like shoes, towels and clothes that have been left on the floor. This habit of hiding in inconvenient places means that white-tailed bites are fairly common.

Venom: analysis of white-tailed spider venom has so far yielded no evidence of components that could cause major harm to humans. The venom of male spiders contains small amounts of histamine and noradrenaline, which explains the localised effects experienced after a bite. Importantly, there is no evidence that the venom contains any toxins that could cause skin necrosis.

Bite: white-tailed spider fangs are only small and often cannot penetrate human skin. When bites do occur they are usually painful. Their fangs have been found to carry Mycobacterium ulcerans, which could be a contributing factor in reported infections and skin ulcers following a bite.

Clinical features: immediate localised pain is followed by erythema, swelling and itch around the area of the bite. In rare cases patients may develop systemic features such as malaise, nausea, vomiting or headache. A number of cases have been reported of white-tailed spider bites causing necrotising arachnidism; this is characterised by blistering, ulceration and skin necrosis which can be severe and distressing. However, in many of these cases the bite was unwitnessed and the white-tailed spider could not be reliably identified as the culprit. In a prospective study of 130 confirmed white-tailed spider bites in Australia there were no cases of infection or ulceration, but another study of 15 cases of ulceration or necrosis following spider bites reported that white-tailed spiders were responsible in at least 3 cases. The presence of destructive M. ulcerans in their fangs provides a plausible explanation for the occasional case of skin ulceration, but generally white-tailed spider bites heal uneventfully with little need for medical attention.

Managing a spider bite

Generally it’s a good idea to try to catch the spider if possible, as there are no venom identification methods available for spider bites and it is important to know the species responsible so that interventions can be made quickly if required. If you cannot catch the spider, try to remember features such as size, shape, colour, and location so you can describe it to medical staff later. Appropriate first aid interventions vary depending on the type of spider and degree of risk: if the spider is definitely non-lethal (e.g. a white-tailed spider) they can usually be managed at home with simple wound care, but if there is ANY DOUBT as to the species responsible immediate medical attention should be sought.

Two reassuring things to remember are that most spider bites do not result in significant envenomation, and effective antivenoms are readily available.

Funnel-webs & mouse spiders

1. NEUTRALISE THE SPIDER. Remove it if it is still attached to the patient, and ensure it is no longer a threat before continuing – try to catch it, but squish it if you have to. Put it in a jam jar or other container to take to the hospital for identification.
2. Get someone to call an ambulance (dial 000 in Australia).
3. Reassure the patient and persuade them to LIE DOWN AND REMAIN AS STILL AS POSSIBLE (muscle contractions hasten the absorption and spread of venom through the lymphatic system).
4. Do not interfere with the bite wound in any way.
5. Remove jewellery and other items from the bitten limb. This prevents a “tourniquet effect” from occurring if the limb becomes oedematous later.
   

   How to dress and immobilise a spider bite (image from Wikihow)

6. DO NOT APPLY A TOURNIQUET or attempt to cut/suck out the wound. The bitten limb should be dressed with a broad bandage applied over the wound area at moderate pressure – being careful not to disrupt blood flow to the extremities – and extended in both directions to cover as much of the rest of the limb as possible. This should be applied over clothing as the patient needs to be kept as still as possible. Bites to the head, neck and torso are slightly more tricky: apply firm local pressure if possible.
7. After dressing the wound, immobilise it as best you can using a splint or sling.
8. Be vigilant in monitoring the patient for any signs of deterioration, especially breathing difficulties, paralysis, loss of consciousness or cardiovascular collapse.
9. Avoid any oral intake – if transport to a hospital is likely to take several hours, clear fluids may be given to maintain hydration.
10. Await transport to the nearest medical facility. If you are in an isolated area or emergency service access is likely to be difficult, the patient should be conveyed or carried to a more convenient location whilst remaining as immobile as possible.

Redbacks & white-taileds

Generally as above, but with the following modifications:

• DO NOT USE A PRESSURE BANDAGE. The pain associated with bites from these spiders can be very severe, and will only be made significantly worse by the application of a pressure bandage. Also, the slow-spreading nature of their venom means that a pressure bandage is unlikely to be particularly helpful.
• APPLY A COLD ICE PACK to the wound to relieve pain and help keep the patient calm and still.
• If the spider was definitely non-lethal (e.g. a white-tailed spider) some sources say oral analgesics like paracetamol are also appropriate to help control pain. Oral antihistamines can also help relieve itch and swelling.

Antivenoms

Effective antivenoms are available to funnel-web and redback spider venoms, and should be given to any patient with signs of systemic envenomation. Funnel-web antivenom has also been effective in treating severe cases of mouse spider envenomation in the past. Although most antivenoms are administered intravenously, it is currently recommended that redback antivenom be given intramuscularly because the small amounts of venom involved do not necessitate an IV dose in most cases. It is important to remember that antivenoms are derived from powerfully immunogenic animal antibodies, so there is a risk of allergic reactions including anaphylaxis and delayed-onset serum sickness. For more on antivenoms, click here.

Some reassuring statistics

• The last recorded death from a venomous spider bite in Australia was in 1979: since then antivenoms have prevented any fatalities.
• In Australia up to 4000 people are bitten by venomous spiders each year, but only about 250 of these will require treatment with antivenom.
• Most spiders won’t bite you unless you provoke or frighten them. If you do accidentally manage to piss one off and need to defend yourself, just remember, in a battle of man versus spider, you’re much more likely to win.

How Not To Die In Australia Part 1: Snakes

One of the main things Australia is famous for is its legions of deadly animals – snakes, spiders and various sea creatures – waiting to bite, poison and generally cause misery. It’s definitely one of the things I spent time fretting about before I came here, especially seen as Queensland has almost all of them. I decided to “know my enemy”, and actually found it quite interesting, mainly because animals as exotic and exciting as these don’t exist in England!

Inland Taipan (Fierce Snake)

Inland Taipan (image from Idilium.com)

In terms of LD50 values in mice the Inland Taipan is the most venomous land snake in the world, with an LD50 of 0.025mg/kg. This makes its venom more deadly than arsenic and sodium cyanide. It is classed as a vulnerable species.

Personality: despite its deadly venom, the taipan is actually extremely shy and reclusive, and will always prefer to escape from conflict (the name fierce snake refers to the venom, not the snake itself!). As a result, there has never been a recorded death from a taipan bite in Australia, and the few people who have been bitten were mostly herpetologists who handle taipans on a regular basis. It varies in colour from golden to dark brown depending on the season. Its favourite food is the plague rat, and taipan populations vary year-on-year depending on the availability of these delicious rodents.

Venom: consists of Taipoxin and procoagulants. Taipoxin is a potent presynaptic neurotoxin which gradually reduces the victim’s release of acetylcholine from motor nerve terminals, resulting in neuromuscular blockade, muscle weakness and eventual asphyxia. The procoagulants in the venom are amongst the most potent known to man, and in large doses can cause defibrination and haemorrhage. Also present in smaller quantities are postsynaptic neurotoxins which bind to acetylcholine receptors, resulting in flaccid paralysis; myotoxins capable of causing rhabdomyolysis; and other components which have been noted to have a nephrotoxic effect.

Bite: taipan fangs are over a centimetre in length and can easily penetrate protective footwear. The area around the bite is often swollen and sore. On average a single bite delivers 44mg of venom, which is easily enough to kill hundreds of mice or several humans. As up to 90% of bites produce significant envenoming, rapid assessment and treatment is critical.

Clinical features: defibrination coagulopathy tends to develop first (complete defibrination can happen in under an hour, resulting in an INR of infinity!) and poses a significant risk of major haemorrhage. This is followed by gradual onset of neurotoxic paralysis in the following 2-6 hours, starting in the cranial nerves and progressing to limbs and respiratory muscles. Myolysis and renal impairment are much less common. Other symptoms of systemic envenoming include headache, nausea and vomiting, abdominal pain, tender lymphadenopathy, confusion, collapse and convulsions (especially in children).

Australian Eastern Brown Snake

Eastern Brown Snake (image from TalismanCoins.com)

The Eastern Brown Snake is the second most venomous snake in the world according to LD50 values (0.0365mg/kg).

Personality: like the taipan, Eastern brown snakes are naturally timid animals which can be extremely aggressive if provoked. However, unlike the taipan they are comfortable living in urban areas, and as a result end up encountering humans on a much more regular basis. Snake management services remove hundreds of them from properties every year, and in more than 10% of cases the snake is found inside the house! Despite being much less venomous than the taipan, Eastern browns are responsible for at least half of deaths caused by snakebites in Australia.

Venom: contains a potent procoagulant, and both pre-synaptic and post-synaptic neurotoxins in the form of textilotoxin and pseudonajatoxin. It is directly nephrotoxic as well as possibly having cardiotoxic effects. The procoagulant is a complete prothrombin activator which can cause defibrination coagulopathy in high enough doses. Textilotoxin inhibits phospholipase A2 to block acetylcholine release from the presynaptic neurone. Pseudonajatoxin binds to acetylcholine receptors to block neuromuscular transmission.

Bite: their fangs are only tiny (about 2.8mm long) making bite marks difficult to spot at first and often painless. The rate of significant envenoming is lower than the taipan, at 20-40%, and the untreated mortality is as low as 10%. Eastern browns produce very little venom – a single bite may only carry 4.7mg – but have a tendency to inflict multiple bites if they feel threatened.

Clinical features: variable symptoms of systemic envenoming as described above. Coagulopathy is the main characteristic of significant envenoming: complete defibrination with catastrophic coagulopathy and haemorrhage can occur within 30 minutes of the bite. Sudden collapse with arrhythmia and cardiac arrest has been reported in cases of massive envenoming; this is believed to be secondary to occlusion of coronary blood flow by rapid formation of thrombi. Nephrotoxicity is a major problem, especially in adults and after alcohol consumption. Paralysis can occur but is uncommon.

Death Adder

Death Adder

Death adders are another common deadly snake found in Australia, with an LD50 of 0.5mg/kg. There are several species, all in the genus Acanthopis.

Personality: unlike most other snakes, death adders do not flee when approached. Instead they tend to hide and rely on their camouflage, which unfortunately makes them much more likely to be stepped on and angered by blundering humans. They are ambush hunters, and often wait hidden in the undergrowth for days until an unsuspecting meal walks past. They then wriggle their tails to give the impression of a small grub or worm on the ground, which entices the prey into within striking distance. The death adder has the quickest strike of any snake in the world: an attack literally takes “the blink of an eye”. Thankfully death adders appear to resent the company of humans, so their presence is rarely noted in urban areas and most bites are caused by captive specimens.

Venom: contains postsynaptic neurotoxins (acantoxins) and myotoxins (acanmyotoxins). There are several subtypes of acantoxins found in different species, but they all act by inhibiting nicotinic acetylcholine receptors on the postsynaptic membrane. The myotoxins in the venom have only been recently discovered, and explain why many patients develop rhabdomyolysis following a death adder bite.

Bite: a combination of their lightning speed and long fangs (6-8mm) have made death adder bites devastatingly effective. The bite itself is often painful and swollen. They can deliver 40-100mg of venom with each attack, and around 60% of bites result in significant envenoming requiring treatment with antivenoms.

Clinical features: symptoms of systemic envenoming often develop within minutes. This is followed by a gradual onset of flaccid paralysis and asphyxia, which often takes several hours to become clinically apparent. Myolysis can also occur. Death adder bites used to be amongst the most feared by the public and doctors alike – they were fatal in at least 50% of cases – but the advent of modern life support capabilities has made managing respiratory paralysis much easier.

Tiger Snake

Tiger Snake (image from PelionClimber)

Tiger snakes are a group of snakes of the genus Notechis. The mainland tiger snake is considerably deadly, with an LD50 of 0.214mg/kg.

Personality: another species which tends to avoid conflict unless excessively provoked. Tiger snakes used to be the commonest cause of snake bite fatalities in Australia, but this position has now been taken by the Eastern Brown Snake. This is because tiger snakes live in wet areas and mainly eat frogs, which are rapidly declining in numbers due to habitat destruction, disease and introduced predators. Tiger snake numbers are similarly declining as a result, but they are still the second most likely snake to kill you while you’re in Australia.

Venom: contains a potent mixture of presynaptic and postsynaptic neurotoxins, procoagulants and myotoxins. Nephrotoxicity can also occur but is likely to be secondary to the damaging effects of the venom on blood and muscle tissue.

Bite: Their fangs are quite short, so shoes and thick items of clothing like jeans stand a pretty good chance of deflecting a bite. Bites are painful and often become swollen and bruised. Each bite can carry 30-70mg of venom. Rate of significant envenomation is 40-60%, with an untreated mortality of around 60%.

Clinical features: variable symptoms of significant envenoming. Defibrination coagulopathy with is common and can result in profound haemorrhagic complications, but unlike the coagulopathy inflicted by brown snake venom it resolves spontaneously within 15-18 hours. The likelihood of severe myolysis increases the longer adequate treatment is delayed: this can result in nephrotoxicity and hyperkalaemia. Progressive neurotoxic paralysis is also a common feature and it is important that this is identified early, as the presynaptic paralysis resulting from tiger snake venom is not reversible by antivenoms.

Red-Bellied Black Snake

Red-bellied black snake (image from AussiePythons.com)

The red-bellied black snake is a member of the Pseudechis family of black snakes. It’s venom is rarely fatal (with an LD50 of only 2mg/kg) but can cause significant morbidity.

Personality: a very pretty snake with a personality to match its looks, the red-bellied black is generally mild-mannered and docile. There exists only one recorded incidence of death from a red-bellied black snake bite, when a newborn baby was bitten in the 1800s. It prefers to live near water and enjoys eating frogs and toads. The species was nearly driven to extinction in the past following the ill-considered introduction of the poisonous cane toad into its environment, but thankfully they are now learning to avoid eating yummy-looking poisonous frogs. They are also renowned for chasing and killing Eastern Brown Snakes that stray into their territory!

Venom: predominantly myotoxic, with other less significant neurotoxic and anticoagulant effects.

Bite: often painful and swollen, with the potential for minor necrotic changes. Red-bellied blacks deliver around 37mg of venom with each bite – a small amount considering its relatively high LD50. Significant envenoming occurs in 40-60% of cases, but less than 1% of those who are significantly envenomed will actually die from an untreated bite.

Clinical features: variable symptoms of systemic envenoming. The main clinical feature is myolysis, which is rarely severe (peak CK <2000) but can be very distressing for the patient. A minor coagulopathy may occur if patients receive a large dose of venom. Neurotoxic paralysis and kidney damage are theoretically possible but extremely rare.

Managing a snake bite

There are two reassuring things to remember when dealing with a snake bite victim. Firstly, the envenoming process is slow, as venom is deposited subcutaneously and spreads slowly through the lymphatic circulation. It is extremely uncommon to die in the first 4 hours after a snake bite. This gives you a fairly decent time window in which to get a compression bandage on and get the patient to hospital. Secondly, effective antivenoms to almost every snake venom are readily available.

First aid

1. GET AWAY from the snake. Don’t try to chase it, catch it or exact revenge. If you are forced kill the snake, stay away from its head as a dead snake can still envenom.
2. Get someone to call an ambulance (dial 000 in Australia).
3. Reassure the patient and persuade them to LIE DOWN AND REMAIN AS STILL AS POSSIBLE (muscle contractions hasten the absorption and spread of venom through the lymphatic system).
4. DO NOT CLEAN THE WOUND. This will interfere with venom sampling for identification when the patient reaches hospital.
5. Remove jewellery and other items from the bitten limb. This prevents a “tourniquet effect” from occurring if the limb becomes oedematous later.
   

   How to dress and immobilise a bitten limb (image from WikiHow)

6. DO NOT APPLY A TOURNIQUET or attempt to cut/suck out the wound. The bitten limb should be dressed with a broad bandage applied over the wound area at moderate pressure – being careful not to disrupt blood flow to the extremities – and extended in both directions to cover as much of the rest of the limb as possible. This should be applied over clothing as the patient needs to be kept as still as possible. Bites to the head, neck and torso are slightly more tricky: apply firm local pressure if possible.
7. After dressing the wound, immobilise it as best you can using a splint or sling.
8. Be vigilant in monitoring the patient for any signs of deterioration, especially respiratory paralysis, bleeding or cardiovascular collapse.
9. Avoid any oral intake – if transport to a hospital is likely to take several hours, clear fluids may be given to maintain hydration.
10. Await transport to the nearest medical facility. If you are in an isolated area or emergency service access is likely to be difficult, the patient should be conveyed or carried to a more convenient location whilst remaining as immobile as possible.

Antivenoms

Patients with signs of systemic envenoming (about 1 in 20) will require treatment with an intravenous infusion of specific antivenoms, e.g. taipan antivenom, brown snake antivenom, death adder antivenom… Most antivenoms are monovalent and are produced by collecting horse antibodies to individual snake venoms. As a result, they are powerfully immunogenic and the administration of an antivenom carries a risk of allergy (4%), anaphylaxis (<1%) and delayed-onset type III hypersensitivity reactions like serum sickness (10%). Anaphylactic reactions should be anticipated – some hospitals give prophylactic adrenaline – and promptly managed. Patients should be advised to look out for symptoms of serum sickness in the first 14 days after the bite, and treated with oral steroids if it occurs. If patients have received several vials of antivenom, a course of prophylactic oral steroids is often useful.

If it is unclear which species of snake is responsible for the bite and venom identification tools are unavailable or would take too long, a polyvalent antivenom is also available which covers all dangerous Australian snakes.

Some reassuring statistics

• As many as 98% of snake bites are the result of people attempting to catch, chase, kill or otherwise provoke the snake. So in most cases you really have to be asking for it before they’ll attack you.
• Since 1980 there have only been 41 deaths from snake bites in Australia.
• Of the 128 animal-related deaths in Australia between 2000 and 2006, only 8 were due to snakes. Crocodiles and spiders caused even less. In comparison, horses caused 40 deaths, cattle 20, and dogs 12. One elderly lady died after tripping over her cat.
• Of the approximately 3000 snake bites which occur every year in Australia, only one or two will prove fatal. You are statistically much more likely to be struck by lightning (30-60 people per year) or die from a bee sting (10 people per year) in the comfort of the British countryside than die from a snake bite in Australia!