Tiger snake

Tiger snake

Tiger snakes (Notechis spp) are highly venomous. Their venoms possess potent neurotoxins, coagulants, haemolysins and myotoxins and the venom is quick-acting with rapid onset of breathing difficulties and paralysis. The untreated mortality rate from tiger snake bites is reported to be between 40 and 60%. They are a major cause of snakebites and occasional snakebite deaths in Australia.

Common death adder

Common death adder

The Common death adder (Acanthophis antarcticus) is a highly venomous snake species with a 50-60% untreated mortality rate. It is also the fastest striking venomous snake in the world. A death adder can go from a strike position, to strike and envenoming their prey, and back to strike position again, in less than 0.15 seconds. The SC LD₅₀ value is 0.4 mg/kg and the venom yield per bite can range anywhere from 70–236 mg. Unlike other snakes that flee from approaching humans crashing through the undergrowth, common death adders are more likely to sit tight and risk being stepped on, making them more dangerous to the unwary bushwalker. They are said to be reluctant to bite unless actually touched.

Eastern brown snake

Eastern brown snake

The Eastern brown snake (Pseudonaja textilis) has a venom LD₅₀ value of 0.053 mg SC according to (Brown, 1973) and a value of 0.0365 mg SC according to (Ernst and Zug et al. 1996). According to both studies, it is the second most venomous snake in the world. Average venom yield is 2–6 mg according to (Meier and White, 1995). According to (Minton, 1974) average venom yield (dry weight) is between 5–10 mg. Maximum venom yield for this species is 155 mg. This species is legendary for its bad temper, aggression, and for its speed. This species is responsible for more deaths every year in Australia than any other group of snakes.

Inland taipan

Inland taipan

The Inland taipan (Oxyuranus microlepidotus) is considered the most venomous snake in the world with a murine LD₅₀ value of 0.025 mg/kg SC. Ernst and Zug et al. 1996 list a value of 0.01 mg/kg SC, which makes it the most venomous snake in the world in their study too. They have an average venom yield of 44 mg. Bites from this species have a mortality rate of 80% if left untreated, although it is very rare for this species to bite. This species is known to be a very shy, reclusive and a laid-back snake that will nearly always slither away from disturbance. It is not an aggressive species and rarely strikes.

Malayan krait

Malayan krait

The Malayan krait (Bungarus candidus) is another dangerously venomous species of krait. In mice, the IV LD₅₀ for this species is 0.1 mg/kg. Envenomation rate among this species is very high and the untreated mortality is 70%, although even with antivenom and mechanical ventilation the mortality rate is at 50%.

Many-banded krait

Many-banded krait

The Many-banded krait (Bungarus multicinctus) is the most venomous krait species known based on toxinological studies conducted on mice. The venom of the many-banded krait consists of both pre- and postsynaptic neurotoxins (known as α-bungarotoxins and β-bungarotoxins, among others). Due to poor response to antivenom therapy, mortality rates are very high in cases of envenomation - up to 50% of cases that receive antivenom are fatal. Case fatality rates of the many-banded krait envenoming reach up to 77%–100% without treatment. The average venom yield from specimens kept on snake farms was between 4.6—18.4 mg per bite. In another study, the average venom yield was 11 mg (Sawai, 1976). The venom is possibly the most toxic of any Bungarus (krait) species and possibly the most toxic of any snake species in Asia, with LD₅₀ values of 0.09 mg/kg—0.108 mg/kg SC, 0.113 mg/kg IV and 0.08 mg/kg IP on mice. Based on several LD₅₀ studies, the many-banded krait is among the most venomous land snake in the world. The Taiwan National Poison Control Center reports that the chief cause of deaths from snakebites during the decade (2002-2012) was respiratory failure, 80% of which was caused by bites from the many-banded krait.

Terciopelo

Terciopelo

The Terciopelo (Bothrops asper) has been described as excitable and unpredictable when disturbed. They can, and often will, move very quickly, usually opting to flee from danger, but are capable of suddenly reversing direction to vigorously defend themselves. Adult specimens, when cornered and fully alert, should be considered dangerous. In a review of bites from this species suffered by field biologists, Hardy (1994) referred to it as the "ultimate pit viper". Venom yield (dry weight) averages 458 mg, with a maximum of 1530 mg (Bolaños, 1984) and an LD₅₀ in mice of 2.844 mg/kg IP. This species is an important cause of snakebite within its range. It is considered the most dangerous snake in Costa Rica, responsible for 46% of all bites and 30% of all hospitalized cases; before 1947, the fatality rate was 7%, but this has since declined to almost 0% (Bolaños, 1984), mostly due to the Clodomiro Picado Research Institute, responsible for the production of antivenom. In the Colombian states of Antioquia andChocó, it causes 50-70% of all snakebites, with a sequelae rate of 6% and a fatality rate of 5% (Otero et al., 1992). In the state of Lara, Venezuela, it is responsible for 78% of all envenomations and all snakebite fatalities (Dao-L., 1971). One of the reasons so many people are bitten is because of its association with human habitation and many bites actually occur indoors (Sasa & Vázquez, 2003).

Saw-scaled viper

Saw-scaled viper

The Saw-scaled viper (Echis carinatus) is small, but its ill-temper, irritability, extremely aggressive nature, and lethal venom potency make it very dangerous. This species is one of the fastest striking snakes in the world, and mortality rates for those bitten are very high. In India alone, the saw-scaled viper is responsible for an estimated 5,000 human fatalities annually. However, because it ranges from Pakistan, India (in rocky regions of Maharashtra, Rajasthan, Uttar Pradesh and Punjab), Sri Lanka, parts of the Middle Eastand Africa north of the equator, is believed to cause more human fatalities every year than any other snake species. In drier regions of the African continent, such as sahels and savannas, the saw-scaled vipers inflict up to 90% of all bites. The rate of envenomation is over 80%. The saw-scaled viper also produces a particularly painful bite. This species produces on the average of about 18 mg of dry venom by weight, with a recorded maximum of 72 mg. It may inject as much as 12 mg, whereas the lethal dose for an adult human is estimated to be only 5 mg. Envenomation results in local symptoms as well as severe systemic symptoms that may prove fatal. Local symptoms include swelling and intense pain, which appear within minutes of a bite. In very bad cases the swelling may extend up the entire affected limb within 12–24 hours and blisters form on the skin. Of the more dangerous systemic symptoms, hemorrhage and coagulation defects are the most striking. Hematemesis, melena, hemoptysis, hematuria and epistaxisalso occur and may lead to hypovolemic shock. Almost all patients develop oliguria or anuria within a few hours to as late as 6 days post bite. In some cases, kidney dialysis is necessary due to acute renal failure (ARF), but this is not often caused by hypotension. It is more often the result of intravascular hemolysis, which occurs in about half of all cases. In other cases, ARF is often caused by disseminated intravascular coagulation.

Russell's viper

Russell's viper

Russell's viper (Daboia russelii) produces one of the most excruciatingly painful bites of all venomous snakes. Internal bleeding is common. Bruising, blistering and necrosis may appear relatively quickly as well. The Russell's viper is irritable, short-tempered and a very aggressive snake by nature and when it gets irritated it coils tightly, hisses, and strikes with a lightning speed. This species is responsible for more human fatalities in India than any other snakes species, causing an estimated 25,000 fatalities annually. TheLD₅₀ in mice, which is used as a possible indicator of snake venom toxicity, is as follows: 0.133 mg/kg intravenous, 0.40 mg/kg intraperitoneal, and about 0.75 mg/kg subcutaneous. For most humans, a lethal dose is approximately 40–70 mg. However, the quantity of venom produced by individual specimens is considerable. Reported venom yields for adult specimens range from 130–250 mg to 150–250 mg to 21–268 mg. For 13 juveniles with an average length of 79 cm, the average venom yield was 8–79 mg (mean 45 mg).

Common krait

Common krait

The common krait (Bungarus caeruleus) is often considered to be the most dangerous snake species in India. Its venom consists mostly of powerful neurotoxins which induce muscle paralysis. Clinically, its venom contains presynaptic and postsynaptic neurotoxins, which generally affect the nerve endings near the synaptic cleft of the brain. Due to the fact that krait venom contains many presynaptic neurotoxins, patients bitten will often not respond to antivenom because once paralysis has developed it is not reversible. This species causes an estimated 10,000 fatalities per year in India alone. There is a 70-80% mortality rate in cases where there is no possible or poor and ineffective treatment (e.g., no use of mechanical ventilation, low quantities of antivenom, poor management of possible infection). Average venom yield per bite is 10 mg (Brown, 1973), 8 to 20 mg (dry weight) (U.S. Dept. Navy, 1968), and 8 to 12 mg (dry weight) (Minton, 1974). The lethal adult human dose is 2.5 mg. In mice, the LD₅₀ values of its venom are 0.365 mg/kg SC, 0.169 mg/kg IV and 0.089 mg/kg IP.

Indian cobra

Indian cobra

The Indian cobra is a moderately venomous species, but has a rapid-acting venom. In mice, the SC LD₅₀ for this species is 0.80 mg/kg and the average venom yield per bite is between 169 and 250 mg. Though it is responsible for many bites, only a small percentage are fatal if proper medical treatment and antivenom are given. Mortality rate for untreated bite victims can vary from case to case, depending upon the quantity of venom delivered by the individual involved. According to one study, it is approximately 15–20%. but in another study, with 1,224 bite cases, the mortality rate was only 6.5%. Estimated fatalities as a result of this species is approximately 15,000 per year, but they are responsible for an estimated 100,000-150,000 non-fatal bites per year. 

The Big Four

The Big Four are the four venomous snake species responsible for causing the most snake bite cases in South Asia (mostly in India). The Big Four snakes cause far more snakebites because they are much more abundant in highly populated areas. They are theIndian cobra (Naja naja), common krait (Bungarus caeruleus), Russell's viper (Daboia russelii) and the Saw-scaled viper (Echis carinatus).

Coastal taipan/Papuan taipan

Coastal taipan/Papuan taipan

The Coastal taipan (Oxyuranus scutellatus scutellatus) is a large, highly venomous Australian elapid that ranges in an arc along the east coast of Australia from northeastern New South Wales through Queensland and across the northern parts of the Northern Territory to northern Western Australia. It has one subspecies, the Papuan taipan (Oxyuranus scutellatus canni). The Papuan taipan is found throughout the southern parts of the island of New Guinea. This snake can be highly aggressive when cornered and will actively defend itself.^[61] They are extremely nervous and alert snakes, and any movement near them is likely to trigger an attack. When threatened, this species adopts a loose striking stance with its head and forebody raised. It inflates and compresses its body laterally (not dorso-ventrally like many other species) and may also spread the back of its jaws to give the head a broader, lance-shaped appearance. In this position the snake will strike without much provocation, inflicting multiple bites with extreme accuracy and efficiency. The muscular lightweight body of the Taipan allows it to hurl itself forwards or sideways and reach high off the ground, and such is the speed of the attack that a person may be bitten several times before realizing the snake is there. This snake is considered to be one of the most venomous in the world. Ernst and Zug et al. 1996 and the Australian venom and toxin database both list a LD₅₀ value of 0.106 mg/kg for subcutaneous injection. Engelmann and Obst (1981) list a value of 0.12 mg/kg SC, with an average venom yield of 120 mg per bite and a maximum record of 400 mg. To demonstrate just how deadly this species is, an estimate was made on the number of mice and adult human fatalities it is capable of causing in a single bite that yields the maximum dose of 400 mg. Based on the study by Ernst and Zug et al. 1996, which listed the LD₅₀ of the coastal taipan at 0.106 mg SC and a venom yield of 400 mg, this would be sufficient enough to kill 208,019 mice and 59 adult humans in a single bite that delivers 400 mg of venom. The venom apparatus of this species is well developed. The fangs are the longest of any Australian elapid snake, being up to 12 millimetres (1.2 cm; 0.47 in) long, and are able to be brought forward slightly when a strike is contemplated. Coastal taipans can inject large amounts of highly toxic venom deep into tissue. Its venom contains primarily taicatoxin, a highly potent neurotoxin known to cause hemolytic and coagulopathic reactions. The venom affects the nervous system and the blood’s ability to clot, and bite victims may experience headache, nausea and vomiting, collapse, convulsions (especially in children), paralysis, internal bleeding, myolysis (destruction of muscle tissue) and kidney damage. In a single study done in Papua New Guinea, 166 patients with enzyme immunoassay-proven bites by Papuan taipans (Oxyuranus scutellatus canni) were studied in Port Moresby, Papua New Guinea. Of the 166 bite victims, 139 (84%) showed clinical evidence of envenoming: local signs were trivial, but the majority developed hemostatic disorders and neurotoxicity. The blood of 77% of the patients was incoagulable and 35% bled spontaneously, usually from the gums. Microhematuria was observed in 51% of the patients. Neurotoxic symptoms (ptosis, ophthalmoplegia, bulbar paralysis, and peripheral muscular weakness) developed in 85%. Endotracheal intubation was required in 42% and mechanical ventilation in 37%. Electrocardiographic (ECG or EKG) abnormalities were found in 52% of a group of 69 unselected patients. Specific antivenom raised against Australian taipan venom was effective in stopping spontaneous systemic bleeding and restoring blood coagulability but, in most cases, it neither reversed nor prevented the evolution of paralysis even when given within a few hours of the bite. However, early antivenom treatment was associated statistically with decreased incidence and severity of neurotoxic signs. The low case fatality rate of 4.3% is attributable mainly to the use of mechanical ventilation, a technique rarely available in Papua New Guinea. Earlier use of increased doses of antivenoms of improved specificity might prove more effective. The onset of symptoms is often rapid, and a bite from this species is a life-threatening medical emergency. Prior to the introduction of specific antivenom by the Commonwealth Serum Laboratories in 1956, a coastal taipan bite was nearly always fatal. In case of severe envenomation, death can occur as early as 30 minutes after being bitten, but average death time after a bite is around 3–6 hours and it is variable, depending on various factors such as the nature of the bite and the health state of the victim. Envenomation rate is very high, over 80% of bites inject venom. The mortality rate among untreated bite victims is nearly 100%.

Black mamba

Black mamba

The African Black mamba (Dendroaspis polylepis) is a large and highly venomous snake species native to much of Sub-Saharan Africa. It is the second longest venomous snake species in the world and is the fastest moving land snake, capable of moving at 4.32 to 5.4 metres per second (16–20 km/h, 10–12 mph). It is by far the most feared and most dangerous snake species in Africa and it has a legendary reputation as a very fierce and territorial snake. When cornered or threatened, the black mamba can put up a fearsome display of defense and aggression. A black mamba will often mimic a cobra by spreading a neck-flap; exposing its black mouth, raising its body off the ground, and hissing. It can rear up around one-third of its body from the ground, which can put it at about four feet high. When warding off a threat, the black mamba delivers multiple strikes, injecting large amounts of virulently toxic venom with each strike, often landing bites on the body or head, unlike other snakes. Their strikes are very quick and extremely accurate and effective.If the attempt to scare away the threat fails, it will strike repeatedly.  This species of snake often shows an incredible amount of tenacity, fearlessness, and aggression when cornered or threatened, during breeding season, or when defending its territory. They are also known to have a 100% rate of envenomation. The probability of dry bites (no venom injected) in black mamba strikes is almost non-existent. The venom of the black mamba is a protein of low molecular weight and as a result is able to spread extraordinarily rapidly within the bitten tissue. The venom of this species is the most rapid-acting venom of any snake species and consists mainly of highly potent neurotoxins; it also contains cardiotoxins , fasciculins and calciseptine.

Based on the Median lethal dose (LD₅₀) values in mice, the black mamba LD₅₀ from all published sources is as follows:

·         (SC) subcutaneous (most applicable to real bites): 0.32 mg/kg, 0.28 mg/kg.

·         (IV) intravenous: 0.25 mg/kg, 0.011 mg/kg.

·         (IP) intraperitoneal: 0.30 mg/kg (average), 0.941 mg/kg. 0.05 mg/kg (the last quote doesn't make it clear if is either intravenous or intraperitoneal).

It is estimated that only 10 to 15 mg will kill a human adult; however, its bites deliver about 120 mg of venom on average, although they may deliver up to 400 mg of venom in a single bite. If bitten, severe neurotoxicity invariably ensues rapidly. This is due to several factors that include the high potency of their venom, the unique composition of synergistic toxins contained within the venom which bring on severe symptoms of envenomation and death much faster than any other venomous snake in the world. In addition, the species itself possesses the most advanced, evolved, and efficient venom delivery apparatus among all venomous snakes, and the most advanced and evolved dentition of all elapids. Black mambas possess the longest fangs of any elapid, averaging around 13.1 millimeters (0.52 in), but may grow as long as 22 millimeters (0.87 in). Another feature which distinguishes the dentition and the venom delivery apparatus of this species from all other elapids and other species of venomous snake, including those of the family Viperidae is the fact that the fangs are positioned very forward at the most-anterior position possible in its mouth - right up in the front of its upper jaw. The proteins in black mamba venom are of extremely low molecular weight, low viscosity, and the venom's very high activity in terms of hyaluronidases, which is also essential in facilitating dispersion of venom toxins throughout tissue (spreading the venom through the body) by catalyzing the hydrolysis of hyaluronan, a constituent of the extracellular matrix (ECM), hyaluronidase lowers the viscosity of hyaluronan, and Dendroaspin natriuretic peptide (DNP), a newly discovered component of mamba venom, is the most-potent natriuretic peptide and it's unique to the genus Dendroaspis, or mambas. It is a polypeptide analogous to the human atrial natriuretic peptide; it is responsible for causing diuresis through natriuresis and dilating the vessel bloodstream, which results in, among other things, acceleration of venom distribution in the body of the victim, thereby increasing tissue permeability. These advanced and highly evolved physical and biological features combined with this species' large size, explosive aggression, and quickness make the black mamba a terrifying adversary. Neurological, respiratory, andcardiovascular symptoms rapidly begin to manifest, usually within less than ten minutes. Common symptoms are rapid onset of dizziness, drowsiness, headache, coughing or difficulty breathing, convulsions, and an erratic heartbeat. Other common symptoms which come on rapidly include neuromuscular symptoms, shock, loss of consciousness, hypotension, pallor, ataxia, excessive salivation (oral secretions may become profuse and thick), limb paralysis, nausea and vomiting, ptosis, fever, and very severe abdominal pain. Local tissue damage appears to be relatively infrequent and of minor severity in most cases of black mamba envenomation. Edema is typically minimal. Acute renal failure has been reported in a few cases of black mamba bites in humans as well as in animal models. The venom of this species has been known to cause permanent paralysis in some cases. Death is due to suffocation resulting from paralysis of the respiratory muscles. Untreated black mamba bites have a mortality rate of 100%. Antivenomtherapy is the mainstay of treatment for black mamba envenomation. A polyvalent antivenom produced by the South African Institute for Medical Research (SAIMR) is used to treat all black mamba bites from different localities. Due to antivenom, a bite from a black mamba is no longer a certain death sentence. But in order for the antivenom therapy to be successful, vigorous treatment and large doses of antivenom must be administered very rapidly post-envenomation. In case studies of black mamba envenomation, respiratory paralysis has occurred in less than 15 minutes. Envenomation by this species invariably causes very severe neurotoxicity due to the fact that black mambas often strike repeatedly in a single lunge, biting the victim up to 12 times in extremely rapid succession. Such an attack is very fast, lasting less than one second and so it appears to be a single strike and single bite. With each bite the snake delivers anywhere from 100 to 400 mg of a rapid-acting and virulently toxic venom. As a result, the doses of antivenom required are often massive (10–30+ vials) for bites from this species. Although antivenom saves many lives, mortality due to black mamba envenomation is still at 14%, even with antivenom therapy. In addition to antivenom therapy, endotracheal intubation and mechanical ventilation are required for supportive therapy.