Mortality (often determined by measured toxicity on mice) is a commonly used indicator of the danger of any given venomous snake, but important too are efficiency of venom delivery, venom yield, and behavior upon encountering humans. Given these additional, practical concerns, many snake experts have cited the black mamba and the coastal taipan as the world's most dangerous snakes – even though their venoms, drop for drop, are not the most lethal. Both species are
elapids, and in several aspects of morphology, ecology and behavior, the coastal taipan is strongly convergent with the black mamba.
Black mamba The
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 4.3 to 5.4 metres per second (16–20 km/h, 10–12 mph). The black mamba is the most feared snake in Africa because of its size, aggression, venom toxicity and speed of onset of symptoms following envenomation, and is classified as a snake of medical importance by the
World Health Organization. This species of snake shows tenacity, fearlessness, and aggression when cornered or threatened, during breeding season, or when defending its territory. They are also known to have up to 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 rapidly within the bitten tissue. The venom is the most rapid-acting venom of any snake species and consists mainly of highly potent
neurotoxins; it also contains
cardiotoxins,
fasciculins, 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, • (IP)
intraperitoneal: 0.30 mg/kg (average), 0.941 mg/kg. Black mambas possess the longest fangs of any elapid, which average around , but may grow as long as . The proteins in black mamba venom are of low molecular weight, low
viscosity, and the venom's 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 is 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 effects, 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, and
cardiovascular 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 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 kidney injury has been reported in a few cases of black mamba bites in humans as well as in animal models. Untreated black mamba bites have a mortality rate of 100%.
Antivenom therapy 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. In addition to antivenom treatment,
endotracheal intubation and
mechanical ventilation are required for supportive therapy.
Coastal taipan The
coastal taipan (
Oxyuranus scutellatus) is a large, highly venomous elapid, whose range includes the southern parts of the island of
New Guinea and extends 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. This snake can be highly aggressive when cornered and will actively defend itself. 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 an 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. 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.
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 the
Indian cobra (
Naja naja),
common krait (
Bungarus caeruleus),
Russell's viper (
Daboia russelii) and the
Saw-scaled viper (
Echis carinatus).
Indian cobra The
Indian cobra (
Naja naja) is a moderately venomous species, but has a rapid-acting venom. In
mice, the
SC 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. The mortality rate for untreated bite victims can vary from case to case, depending upon the quantity of venom delivered and 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%.
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 pre
synaptic and postsynaptic neurotoxins. The lethal adult human dose is 2.5 mg. The Russell's viper, although usually slow and sluggish and shunning humans in general, may resort to striking at a lightning speed when provoked beyond a certain limit. This species is responsible for more human fatalities in India than any other snake species, causing an estimated 25,000 fatalities annually. is believed to cause more human fatalities every year than any other snake species. In drier regions of the
African continent, such as the
Sahel 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
epistaxis also 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 kidney injury, 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. usually opting to flee from danger, but can suddenly reverse direction to vigorously defend themselves. and an in mice of 2.844 mg/kg
IP. The mean value of subcutaneous of five wild-caught king cobras in
Southeast Asia was determined to be 1.93 mg/kg. Between 350 and 500 mg (dry weight) of venom can be injected at once (Minton, 1974). In another study by Broad et al. (1979), the average venom quantity was 421 mg (dry weight of milked venom). In most of the local encounters with live, wild king cobras, the snakes appear to be of rather placid disposition, and they usually end up being killed or subdued with hardly any histrionics. These support the view that wild king cobras generally have a mild temperament, and despite their frequent occurrence in disturbed and built-up areas, are adept at avoiding humans. Naturalist Michael Wilmer Forbes Tweedie felt that "this notion is based on the general tendency to dramatise all attributes of snakes with little regard for the truth about them. A moment's reflection shows that this must be so, for the species is not uncommon, even in populated areas, and consciously or unconsciously, people must encounter king cobras quite frequently. If the snake were really habitually aggressive records of its bite would be frequent; as it is they are extremely rare." Mortality rates vary sharply depending on many factors. In cases where envenomation is severe, death can be rapid. The average venom yield from specimens kept on snake farms was between 4.6 and 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 values of 0.09 mg/kg 0.113 mg/kg
IV and 0.08 mg/kg
IP on
mice.
Malayan krait The
Malayan krait (
Bungarus candidus) is another dangerously venomous species of krait. In
mice, the
IV 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%.
Inland taipan The
inland taipan (
Oxyuranus microlepidotus) is considered the most venomous snake in the world with a
murine 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. Maximum venom yield for this species is 155 mg.
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. 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.
Tiger snake The
tiger snake (
Notechis scutatus) is highly venomous. Its venom possesses 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%. It is a major cause of snakebites and occasional snakebite deaths in Australia. The African tiger snake (
Telescopus semiannulatus), 60–70 cm long, on the other hand, is
rear-fanged and only mildly venomous and not dangerous to humans.
Green mambas Green mambas (western, eastern, and Jameson's) are all highly venomous snakes that can be highly aggressive and unpredictable in disposition. They can suddenly go from a state of relative calm to an extremely agitated and dangerous state. All three species have a tendency to strike repeatedly with little provocation, although they are generally much less aggressive than their larger cousin, the black mamba. All three species of green mamba are highly arboreal, alert, extremely quick, and agile. Although the potency of their venom is similar to the more venomous
cobra species, mamba venom is much more rapid-acting and the dendrotoxins contained in mamba venom is generally more devastating in nature to the central nervous system, causing more severe neurotoxicity in more rapid fashion. The
subcutaneous for this species ranges from 0.40 mg/kg to 3.05 mg/kg depending on different toxicology studies, authority figures and estimates. The mortality rate of untreated bites is unknown but is thought to be very high (70–75%). Generally the calmest and most shy of the green mamba species, the Eastern green will still strike repeatedly if cornered or agitated.
Jameson's mamba (
Dendroaspis jamesoni) is known to be quite aggressive and defensive. The average venom yield per bite for this species is 80 mg, but some specimens may yield as much as 120 mg in a single bite. The
SC for this species according to Brown (1973) is 1.0 mg/kg, while the
IV is 0.8 mg/kg. Envenomation by Jameson's mamba can be deadly in as little as 30 to 120 minutes after being bitten, if proper medical treatment is not attained. The mortality rate of untreated bites is not exactly known, but it's said to be very high (>80%).
True cobras The
cobras (
Naja spp.) are a medically important group of snakes due to the number of bites and fatalities they cause across their geographical range. The genus
Naja consists of 20 to 22
species, but has undergone several
taxonomic revisions in recent years, so sources vary greatly. They range throughout
Africa (including some parts of the Sahara where
Naja haje can be found),
Southwest Asia,
Central Asia,
South Asia,
East Asia, and
Southeast Asia. The most recent revision, listed 28 species after the synonymisation of
Boulengerina and
Paranaja with
Naja. But unlike some other members of the family
Elapidae (the species of the genus
Bungarus, genus
Oxyuranus, genus
Pseudohaje, and especially genus
Dendroaspis), half of the bites by many species of both African and Asian origin of the genus
Naja are "
dry bites" (a dry bite is a bite by a venomous snake in which no venom is released). Roughly 45–50% of bites by most cobra species are dry bites and thus don't cause envenomation. Some of the species that are known and documented to deliver dry bites in a majority of cases include
Naja naja,
Naja kaouthia,
Naja sputatrix,
Naja siamensis,
Naja haje,
Naja annulifera,
Naja anchietae, and
Naja nigricollis. Some species will inject venom in the majority of their bites, but still deliver high number of dry bites (40–45%) include:
Naja sumatrana,
Naja melanoleuca,
Naja atra,
Naja mossambica and
Naja katiensis. Within this
genus, there are a few species in which dry bites are very rare. Envenoming occurs in at least 75–80% of bite cases involving these species. The species that typically cause envenomation in the majority of their bites include some of the more dangerous and venomous species of this genus:
Naja oxiana,
Naja philippinensis,
Naja nivea, and
Naja samarensis. There are many more species within the genus that have not yet been subject to much research and studies, and as a result, very little is known about their behaviour, venom, diet, habitat, and general temperaments. Some of these species include
Naja sagittifera,
Naja annulata,
Naja christyi, and many others.
Caspian cobra The most medically important species of snake bites in
Central Asia is the
Caspian cobra (
Naja oxiana). It is the most venomous species of
cobra in the world, slightly ahead of the Philippine cobra based on a
toxinological study from 1992 found in the
Indian Journal of Experimental Biology, in which this species produced the highest potency venom among cobras. The venom of this species has the most potent composition of toxins found among any
cobra species known. It is made up of primarily highly potent
neurotoxins but it also has
cytotoxic activity (tissue-death, necrosis) and
cardiotoxins. Two forms of "cytotoxin II" (
cardiotoxin) were found in the venom of this species. The crude venom of this species produced the lowest known lethal dose (LCLo) of 0.005 mg/kg, the lowest among all cobra species, derived from an individual case of poisoning by
intracerebroventricular injection. According to Brown (1973), the
subcutaneous LD99–100 value is 0.4 mg/kg, Average venom yield per bite for this species is between 75 and 125 mg (dry weight), but it may yield up to 590 mg (dry weight) in a single bite. The bite of this species may cause severe pain and swelling, along with severe
neurotoxicity. Weakness, drowsiness,
ataxia, hypotension, and paralysis of throat and limbs may appear in less than one hour after the bite. Without medical treatment, symptoms rapidly worsen and death can occur rapidly after a bite due to respiratory failure. An adult woman bitten by this species in northwestern Pakistan suffered severe neurotoxicity and died while en route to the closest hospital nearly 50 minutes after envenomation. Between 1979 and 1987, 136 confirmed bites were attributed to this species in the former
Soviet Union. Of the 136, 121 received antivenom, and only four died. Of the 15 who did not receive antivenom, 11 died. This species is an abundant snake in northeastern Iran and is responsible for a very large number of snakebite mortalities. Antivenom is not as effective for envenomation by this species as it is for other Asiatic cobras within the same region, like the Indian cobra (
Naja naja) and due to the dangerous toxicity of this species' venom, massive amounts of antivenom are often required for patients. As a result, a monovalent antivenom serum is being developed by the
Razi Vaccine and Serum Research Institute in Iran.
Forest cobra The
forest cobra (
Naja melanoleuca) is the largest true cobra of the genus
Naja and is a bad-tempered and irritable snake when cornered or molested as handled in captivity. The venom yield per bite ranges drastically among sources: a maximal dose of 500 mg has been recorded while another venom yield project on two individuals obtained an average dose of 571 mg (dry venom) with a maximum of 1102 mg from 59 times of milking. The forest cobra is one of the least frequent causes of snake bite among the African cobras. This is largely due to its forest-dwelling habits. It is the largest of the
Naja cobras and the venom is considered highly toxic. If the snake becomes cornered or is agitated, it can quickly attack the aggressor, and if a large amount of venom is injected, a rapidly fatal outcome is possible. Clinical experience with forest cobras has been very sparse, and few recorded bites have been documented. However, in 2008, around the area of
Friguiagbé in
Guinea, there were 375 bites attributed to the forest cobra and of those 79 were fatal. Most of the fatal bites were patients who received no medical treatment. Deaths from respiratory failure have been reported, but most victims will survive if prompt administration of antivenom is undertaken as soon as clinical signs of envenomation have been noted.
Philippine cobra The
Philippine cobra (
Naja philippinensis) is one of the most venomous cobra species in the world based on
murine studies. The average
subcutaneous for this species is 0.20 mg/kg. and the average venom yield per bite is 90–100 mg.
Cape cobra The
Cape cobra (
Naja nivea) is regarded as one of the most dangerous species of cobra in Africa, by virtue of its potent venom and frequent occurrence around houses. The venom of this snake tends to be thick and syrupy in consistency and dries into shiny pale flakes, not unlike yellow sugar. The Cape cobras venom is made up of potent postsynaptic
neurotoxins and might also contain
cardiotoxins, that affect the
respiratory system,
nervous system, and the
heart. The mouse
SC for this species' venom is 0.72,
Jararaca The
jararaca (
Bothrops jararaca) is a species that is often abundant within its range, where it is an important cause of snakebite. The lethal dose for a 60 kg adult human is 70 mg.
South American bushmaster The
South American bushmaster (
Lachesis muta muta) is the longest species of venomous snake in the
Western Hemisphere and the longest
pit viper in the world. It is native to parts of
South America, especially the equatorial forests east of the
Andes. They are active at dusk or after dark and they are very secretive and elusive. This species is large, fast and has a reputation for being particularly aggressive when cornered. Some reports suggest that this species produces a large amount of venom that is weak compared to some other vipers. Others, however, suggest that such conclusions may not be accurate. These animals are badly affected by stress and rarely live long in captivity. This makes it difficult to obtain venom in useful quantities and good condition for study purposes. For example, Bolaños (1972) observed that venom yield from his specimens fell from 233 mg to 64 mg while they remained in his care. As the stress of being milked regularly has this effect on venom yield, it is reasoned that it may also affect venom toxicity. This may explain the disparity described by Hardy and Haad (1998) between the low laboratory toxicity of the venom and the high mortality rate of bite victims. However, wild specimens have an average venom yield per bite of 280–450 mg (dry weight) (U.S. Dept. Navy, 1968). According to (Sanchez et al., 1992), who used wild specimens from
Pará, Brazil, the average venom yield per bite was 324 mg, with a range of 168–552 mg (dry weight). Brown (1973) gives the following values for mice: 1.5 mg/kg
IV, 1.6–6.2 mg/kg
IP, 6.0 mg/kg
SC. He also notes a venom yield of 200–411 mg.
Gaboon viper The
Gaboon viper (
Bitis gabonica), although generally docile and sluggish, has the longest fangs of any venomous snake. Their venom glands are enormous; each bite produces the largest quantities of venom of any
venomous snake. Yield is probably related to body weight, as opposed to milking interval. Brown (1973) gives a venom yield range of 200–1000 mg (of dried venom), Based on how sensitive
monkeys were to the venom, Whaler (1971) estimated 14 mg of venom would be enough to kill a human being: equivalent to 0.06 ml of venom, or 1/50 to 1/1000 of what can be obtained in a single milking. Marsh and Whaler (1984) wrote that 35 mg (1/30 of the average venom yield) would be enough to kill a man of . Local tissue damage may require surgical
excision and possibly
amputation. The values of its venom in
mice are 0.29 mg/kg
IV, The average venom yield from a snake of this species kept at a snake farm was about 250.8 mg (80 mg dry weight). Brown listed a venom yield of 184 mg (dry weight). The neurotoxins of this particular species are weak. The venom of this species also contains
myotoxins and
cardiotoxins. The median lethal dose () is 0.28–0.33 mg per gram of mouse body weight. In case of
IV the is 0.373 mg/kg, and 0.225 mg/kg in case of
IP. The average venom yield per bite is approximately 263 mg (dry weight).
Envenomation usually presents predominantly with extensive local
necrosis and systemic manifestations to a lesser degree. Drowsiness, neurological and neuromuscular symptoms will usually manifest earliest;
hypotension, flushing of the face, warm skin, and pain around bite site typically manifest within one to four hours following the bite;
paralysis, ventilatory failure or death could ensue rapidly, possibly as early as 60 minutes in very severe cases of envenomation. However, the presence of fang marks does not always imply that envenomation actually occurred.
Egyptian cobra The
Egyptian cobra (
Naja haje) is another species of cobra that causes a significant number of bites and human fatalities throughout its range. The venom of the Egyptian cobra consists mainly of
neurotoxins and
cytotoxins. The average venom yield is 175 to 300 mg in a single bite, and the
murine subcutaneous value is 1.15 mg/kg. This species has large fangs and can produce large quantities of venom. Envenomation by this snake is a very serious medical emergency. Brown (1973) listed the intravenous LD50 for
N. a. annulata at 0.2 mg/kg.
Black cobra The
black desert cobra (
Walterinnesia aegyptia) is a highly venomous snake species found in the
Middle East. The subcutaneous for the venom of this species is 0.40 mg/kg. For comparison, the
Indian cobra's (
naja naja) subcutaneous is 0.80 mg/kg, while the
Cape cobra's (
naja nivea) subcutaneous is 0.72 mg/kg. This makes the black desert cobra a more venomous species than both.
Spitting cobras Spitting cobras are another group of cobras that belong to the genus
Naja. Spitting cobras can be found in both Africa and Asia. These cobras have the ability to eject venom from their fangs when defending themselves against predators. The sprayed venom is harmless to intact skin. However, it can cause permanent blindness if introduced to the eye and left untreated (causing chemosis and corneal swelling). The venom sprays out in distinctive geometric patterns, using muscular contractions upon the venom glands. These muscles squeeze the glands and force the venom out through forward-facing holes at the tips of the fangs. The explanation that a large gust of air is expelled from the lung to propel the venom forward has been proven wrong. According to Ernst & Zug et al. the murine
SC value is 0.21 mg/kg,
Indochinese spitting cobra The
Indochinese spitting cobra (
Naja siamensis) is a venomous spitting cobra whose venom consists of postsynaptic neurotoxins, metalloproteinases, powerful cardiotoxins, with cytolytic activity, and Phospholipase A2 with a diversity of activities. The of its venom is 1.07–1.42 mg/gram of
mouse body weight.
Black-necked spitting cobra The
black-necked spitting cobra (
Naja nigricollis) is a species of spitting cobra found mostly in
Sub-Saharan Africa. They possess medically significant
venom, although the mortality rate for untreated bites on humans is relatively low (~5–10%). Like other
spitting cobras, this species is known for its ability to project
venom at a potential threat. The venom is an irritant to the skin and eyes. If it enters the eyes, symptoms include extreme burning pain, loss of coordination, partial loss of vision and permanent blindness.
N. nigricollis is known for its tendency to liberally spit venom with only the slightest provocation. However, this aggressiveness is counterbalanced by it being less prone to bite than other related species. but with other components also. It retains the typical
elapid neurotoxic properties while combining these with highly potent
cytotoxins (
necrotic agents) and
cardiotoxins. Bite symptoms include severe external
hemorrhaging and tissue
necrosis around the bite area and difficulty breathing. Although mortality rate in untreated cases is low (~5–10%), when death occurs it is usually due to asphyxiation by paralysis of the
diaphragm. The of this species is 2 mg/kg
SC and 1.15 mg/kg
IV. The average venom yield per bite of this species is 200 to 350 mg (dry weight) according to Minton (1974).
Mali cobra The
Mali cobra (
Naja katiensis) is a venomous species of spitting cobra native to western Africa. The venom of this species consists of postsynaptic
neurotoxins and
cardiotoxins with
cytotoxic (necrotizing) activity. The West African spitting cobra is one of the most common causes of snakebite in
Senegal. Over 24 years, from 1976 to 1999, a prospective study was conducted of overall and cause-specific mortality among the population of 42 villages of southeastern Senegal. Of 4228 deaths registered during this period, 26 were caused by snakebite, four by invertebrate stings and eight by other wild or domestic animals. The average annual mortality rate from snakebite was 14 deaths per 100,000 population. Among persons aged one year or over, 0.9% (26/2880) of deaths were caused by snakebite and this cause represented 28% (26/94) of total deaths by accidents. Of 1280 snakes belonging to 34 species collected, one-third were dangerous, and the proportions of Viperidae, Elapidae and Atractaspidae were 23%, 11% and 0.6%, respectively. This species was third, responsible for 5.5% of the snakebites.
Rinkhals The
rinkhals (
Hemachatus haemachatus) is not a true cobra in that it does not belong to the genus
Naja. However, it is closely related to the true
cobras and is considered to be one of the true
spitting cobras. The venom of this species is less viscous than that of other African elapids, naturally, as thinner fluid is easier to spit. However, the venom of the rinkhals is produced in copious amounts. Average venom yield is 80–120 mg and the murine is 1.1–1.6 mg/kg
SC with an estimated lethal dose for humans of 50–60 mg. Actual bites from this species are fairly rare, and deaths in modern times are so far unheard of. Local symptoms of swelling and bruising is reported in about 25% of cases. General symptoms of drowsiness, nausea, vomiting, violent abdominal pain and vertigo often occur, as does a mild pyrexial reaction. Neurotoxic symptoms are however rare and have only included diplopia and dyspnoea. Ophthalmia has been reported, but has not caused as severe complications as in some of the spitters in the genus
Naja (especially
N. nigricollis and
N. mossambica).
Puff adder The
puff adder (
Bitis arietans) is responsible for more fatalities than any other African snake. This is due to a combination of factors, including its wide distribution, common occurrence, large size, potent venom that is produced in large amounts, long fangs, their habit of basking by footpaths and sitting quietly when approached. and is one of the most
toxic of any vipers based on LD50 studies. Serious bites cause limbs to become immovably flexed as a result of significant
hemorrhage or
coagulation in the affected muscles. Residual induration, however, is rare and usually these areas completely resolve. Most fatalities are associated with bad clinical management and neglect. At least one antivenom protects specifically against bites from this species: India Antiserum Africa Polyvalent.
Australian black snakes King brown snake The
king brown snake (
Pseudechis australis) or mulga snake is the largest species of venomous snake in Australia. The venom of this snake is relatively weak compared to many other Australian species. The
LD50 is 2.38 mg/kg
subcutaneous. However, these snakes can deliver large amounts of venom when they bite, compensating for the lower venom potency. Average venom yield is 180 mg and they have a maximum yield of 600 mg. The venom of this species contains potent
myotoxins and
anticoagulants, that can inhibit blood clotting. The neurotoxic components are weak. This snake can cause severe envenomation of humans. They are a moderately common cause of snakebites and uncommonly to rarely cause snakebite deaths in Australia at present. Envenomation can cause anticoagulation coagulopathy, kidney damage or kidney failure. They do not cause significant neurotoxic paralysis (muscle weakness, respiratory failure), though rarely they may cause ptosis (drooping of the upper eyelids). Bites can also cause myolysis (rhabdomyolysis, muscle damage) which can be very severe and is the major effect of bites. Rate of envenomation is 40–60%, while untreated mortality rate is 30–40%.
Red-bellied black snake The
red-bellied black snake (
Pseudechis porphyriacus) is a venomous species native to Australia. The venom of the red-bellied black snake consists of myotoxins, coagulants and also has haemolytic and cytotoxic properties. It also contains weak pre-synaptic neurotoxins. The murine is 2.52 mg/kg
SC. Average venom yield per bite is 37 mg and a maximum yield of 97 mg.
Australian brown snakes Dugite The
dugite (
Pseudonaja affinis) is a highly venomous Australian brown snake species. The venom of this species contains highly potent presynaptic and postsynaptic neurotoxins and procoagulants. The murine is 0.66 mg/kg
SC. The average venom yield per bite is 18 mg (dry weight of milked venom) according to Meier and White (1995). Rate of envenomation is 20–40% and the untreated mortality rate is 10–20% by cardiac arrest, kidney failure, or cerebral hemorrhage.
Western brown snake The
western brown snake (
Pseudonaja nuchalis) is a highly venomous species of brown snake common throughout Western Australia. Its venom contains powerful
neurotoxins,
nephrotoxins and a
procoagulant, although humans are not usually affected by the neurotoxins. The bite is usually painless and difficult to see due to their small fangs. Human symptoms of a Western Brown snake bite are headache, nausea/vomiting, abdominal pain, severe coagulopathy and sometimes, kidney damage. The in mice is 0.47 mg/kg and the average venom yield per bite is 18 mg (dry weight of milked venom) according to Meier and White (1995). The western brown snake can cause rapid death in humans by cardiac arrest, kidney failure, or cerebral hemorrhage. The envenomation rate is 20–40% and the untreated mortality rate is 10–20%.
Rattlesnakes Some
rattlesnake species can be quite dangerous to humans.
Tiger rattlesnake The
tiger rattlesnake (
Crotalus tigris) has a comparatively low
venom yield but is considered to have the most toxic of all rattlesnake venoms, and the highest venom toxicity of all snakes in the Western Hemisphere. Although reluctant to bite, tiger rattlesnakes are known to be cantankerous and aggressive. Because of their tendency to stand their ground and aggressively defend themselves, they pose a serious threat to humans. Tiger rattlesnake venom has a high
neurotoxic fraction that is
antigenically related to Mojave toxin (see
Crotalus scutulatus, venom A), and includes another component immunologically identical to crotamine, a
myotoxin also found in tropical rattlesnakes (see
Crotalus durissus). The venom has low but significant
protease activity, although there does not seem to be any hemolytic activity. Brown (1973) lists an average venom yield of 11 mg (dried venom) and values of 0.07 mg/kg
IP, 0.056 mg/kg
IV, and 0.21 mg/kg
SC. Minton and Weinstein (1984) list an average venom yield of 6.4 mg (based on two specimens). Weinstein and Smith (1990) list a venom yield of 10 mg. Humans are rarely bitten by the tiger rattlesnake, and literature available on bites by this snake is scarce. The several recorded human envenomations by tiger rattlesnakes produced little local pain, swelling, or other reaction following the bite and, despite the toxicity of its venom, no significant systemic symptoms have been recorded. The comparatively low venom yield (6.4–11 mg dried venom) and short to fangs of the tiger rattlesnake possibly prevent severe envenoming in adult humans. However, the clinical picture could be much more serious if the person bitten was a child or an individual with a slight build. The early therapeutic use of
antivenom is important if significant envenomation is suspected. Despite the low venom yield, a bite by this rattlesnake should be considered a life-threatening medical emergency. Untreated no known mortality rate or deaths. due to the presence of
neurotoxins (crotoxin and
crotamine) that cause progressive paralysis. While the lethal dose for a 60 kg adult human is 18 mg. The huge area of distribution, potent venom in fairly large quantities and a definite willingness to defend themselves are important factors in their dangerousness. In Brazil and probably also in other countries in their area of distribution, this species is probably the most dangerous rattlesnake. After the fer-de-lance (
Bothrops asper), it is the most common cause of snake envenoming. In the first half of the 20th century as well as in the 1950s and 1960s, 12% of treated cases ended fatally. Untreated cases apparently had a mortality rate of 72% in the same period, but this was due to the fact that there was no antivenom, poor medical care and neglect (Rosenfeld, 1971). In more recent times, an average of 20,000 snakebites are registered each year in Brazil, almost 10% of them caused by the neotropical rattlesnake. The mortality rate is estimated at 3.3% and is thus much lower than in the past (Ribeiro, 1990b). A study from southeastern Brazil documented only one fatality from 87 treated cases (Silveira and Nishioka, 1992).
Mojave rattlesnake The
Mojave rattlesnake (
Crotalus scutulatus), also called Mojave green, is another species which is considered to be dangerous. Although they have a reputation for being aggressive towards people, such behavior is not described in the scientific literature. Like other rattlesnakes, they will defend themselves vigorously when disturbed. The
IP value is 0.18 mg/kg with an average venom yield between 50 and 150 mg per bite. The most common subspecies of Mojave rattlesnake (type A) has venom that is considered to be one of the most debilitating and potentially deadly of all North American snakes, although chances for survival are very good if medical attention is sought as soon as possible after a bite. Based on median LD50 values in lab mice, venom A from subspecies A Mojave rattlesnakes is more than ten times as toxic as venom B, from type B Mohave green rattlesnakes which lacks Mojave toxin. Medical treatment as soon as possible after a bite is critical to a positive outcome, dramatically increasing chances for survival. Risk to life and limb is still significant, as with all rattlesnakes, if not treated as soon as possible after a bite. All rattlesnake venoms are complex cocktails of enzymes and other proteins that vary greatly in composition and effects, not only between species, but also between geographic populations within the same species. The Mojave rattlesnake is widely regarded as producing one of the most toxic snake venoms in the New World, based on studies in laboratory mice. Their potent venom is the result of a
presynaptic neurotoxin composed of two distinct
peptide subunits. The basic subunit (a
phospholipase A2) is mildly toxic and apparently rather common in North American rattlesnake venoms. The less common acidic subunit is not toxic by itself, but in combination with the basic subunit, produces the potent neurotoxin called "Mojave toxin". Nearly identical neurotoxins have been discovered in five North American rattlesnake species besides the Mojave rattlesnake.
Pit vipers The
Crotalinae, commonly known as
pit vipers, crotaline snakes (named for the
krotalon castanet/rattle of a
rattlesnake's tail), or
pit adders, are a
subfamily of
venomous vipers found in
Eurasia and the
Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on both sides of the head. Currently, 22
genera and 151
species are recognized: These are also the only
viperids found in the Americas. The groups of snakes represented here include
rattlesnakes,
lanceheads, and
Asian pit vipers. The
type genus for this subfamily is
Crotalus, of which the
type species is the
timber rattlesnake,
C. horridus.
Timber rattlesnake The
timber rattlesnake, (
Crotalus horridus), is a
species of
venomous pit viper endemic to eastern North America. This is the only
rattlesnake species in most of the populous
northeastern United States and is second only to its cousins to the west, the
prairie rattlesnake, as the most northerly distributed venomous snake in
North America. No
subspecies are currently recognized.
Malayan pit viper The
Malayan pit viper (
Calloselasma rhodostoma) is an Asian species of pit viper that is reputed to be an ill-tempered snake that is quick to strike in defense. This species is one of the main causes of snakebite envenoming in Southeast Asia. However, mortality rate among untreated bite victims is very low (1–10%). Although bites are common, death is very rare. When a victim dies of a bite it is chiefly caused by haemorrhages and secondary infections. The intravenous for Malayan pit viper venom is 6.1 mg/kg mouse Brown (1973) mentions a venom yield of up to 214 mg (dried) and values of 0.04 mg/kg
IV, 4.0 mg/kg
IP and 9.2–10.0 mg/kg
SC. Antivenom is produced in China and Taiwan. thus, the
scientific name translates into "twisted hook-tooth". ==Notes==