The Big Four
The Big Four are the four venomous snake species responsible for causing the most snake bite cases in India. India has the Highest Number of Recorded Venomous Snake Bites and Fatalities in the World
There are a reported 2,50,000 estimated venomous snake bites per year in India. Of that number, it is estimated that there are at least 50,000 fatalities, or approximately 20% of the snake bite victims.
The “Big Four” of venomous snakes in India Include the following:
1). Common Krait
2). Saw Scaled Viper
3). Indian Spectacled Cobra
4). Russell’s Viper
These snakes are numerous and aggressive in the areas of India where they are found and are the most likely to bite. They tend to be attracted to agricultural areas, such as rice paddies, where they can find abundant food sources, such as rodents. The search for rodents also brings them into populated areas and on occasion into houses. These snakes are also big killers in other parts of South East Asia and pose a significant threat to agricultural workers, in particular.
India and other Asian countries now have much better medical treatment and antivenom available, but continue to suffer a high percentage of fatalities, due to continued reliance on folk medicine remedies and the length of time needed to get to a proper medical treatment center. Snakebites from these 4 snakes are so prevalent, that a common antivenom has been developed to treat the bites for all 4.
The common krait (Bungarus caeruleus, also known as Indian krait or Blue krait) is a species of genus Bungarus found in the jungles of the Indian subcontinent.It is a member of the “big four”, species inflicting the most snakebites in India.
The average length is 0.9 meters (2 ft 11 in) but they can grow to 1.75 meters (5 ft 9 in). Males are longer with proportionately longer tails. The head is flat. Neck hardly evident. The body is cylindrical, tapering towards the tail. The tail is short and rounded. The eyes are rather small, with rounded pupils, indistinguishable in life. The head shields are normal, no loreals; four shields along the margin of the lower lip; 3rd and 4th supraoculars touching the eye. Scales are highly polished, in 15-17 rows; the vertebral row is distinctly enlarged and hexagonal. Ventrals 185-225. Caudals 37-50, entire.
Colouration is generally black or bluish black, with about 40 thin, white crossbars which may be indistinct or absent anteriorly. The pattern however, is complete and well defined in the young which are marked with conspicuous crossbars even anteriorly; in old individuals the narrow white lines may be found as a series of connected spots, with a prominent spot on the vertebral region. A white preocular spot may be present: upper lips and the belly are white.
- Hindi – Karait.
- Bengali – Kalach, Domnachiti (North Bengal), Shiyar Chanda (South Bengal).
- Kannada – Kattige haavu.
- Telugu – Katla paamu.
- Gujarati – Kalo taro.
- Marathi – Manyar, kanadar.
- Oriya – Chitti.
- Tamil – Kattu viriyan, Yennai viriyan, Yettadi viriyan.
- Malayalam – Velli Kattan (Malabar and Cochin), Ettadi veeran (Travancore).
- Sinhala – Thel Karawala.
- Tulu – Katta Kadambale.
- Sri Lankan – Karawalaya.
Peninsular India from Sindh (Pakistan), to the West Bengal plains. It occurs throughout South India and Sri Lanka at elevations up to about 1600 metres.
Inhabits a wide variety of habitat in its range. It is found in fields, low scrub jungle as well as inhabited areas. They are known to take up residence in termite mounds, brick piles, rat holes and also inside houses. It is fond of water and is frequently found in it or within proximity to a water source.
These snakes prey on other snakes, lizards, frogs, rats, and mice. They will devour their young being cannibalistic in nature. Young are known to eat arthropods. As per Daniels, the common krait feeds primarily on other snakes, including “blind worms” (snakes of the genus Typhlops) and other kraits, and also feeds on frogs and lizards and small mammals. This snake is nocturnal. It is very active and agile at night. It often hides in rodent holes, loose soil or beneath debris, so it is rarely seen during day.
Behavioral differences during day and nighttime have been reported in Bungarus caeruleus. During the day it is sluggish and rolls its body into a loose coiled ball, keeping its head well-concealed. In balled condition, the snake allows considerable handling, however, over handling often instigates bites. At night the snake is very active, escapes by hissing loudly, or keeping still, occasionally biting the source of the annoyance.
When agitated, it will coil up with head concealed, body flattened, and make jerky movements. May also lift its tail. Reluctant to bite, but when it does bite, it typically bites and holds on for awhile, which enables it to inject considerable amounts of venom. Generally docile and unaggressive during the day, it may become aggressive at night if threatened.
The Indian krait’s venom consists mostly of powerful neurotoxins which induce muscle paralysis. Clinically, its venom contains pre-synaptic and post-synaptic neurotoxins. These neurotoxins generally affect the nerve endings near the synaptic cleft of the brain.
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. while the average venom yield is 10 mg (dry weight).
Kraits are nocturnal and seldom encounter humans during daylight hours, so incidents are rare. There is frequently little or no pain from a krait bite and this can provide false reassurance to the victim. Typically, victims complain of severe abdominal cramps, accompanied by progressive paralysis. Once bitten, the absorption of the venom into the victim can be considerably delayed by applying a pressure bandage to the bite site (using about the same tension as one uses for a sprained ankle) and immobilising the area. This allow for gentle transport to medical facilities, where the venom can be treated when the bandage is removed. As there are no local symptoms, a patient should be carefully observed for signs of paralysis (e.g., the onset of ptosis) and treated urgently with antivenom. It is also possible to support bite victims via mechanical ventilation, using equipment of the type generally available at hospitals. Such support should be provided until the venom is metabolised and the victim can breathe unaided. If death occurs it takes place approximately 6–8 hours after the krait bite. Cause of death is general respiratory failure, i.e. suffocation.
Often in rainy season the snakes come out of their hiding places and find refuge on dry places inside a house. If bitten by it in sleep the victim seldom comes to know as the bite feels more like an ant bite or a mosquito bite. The victim may be dead before he even wakes up.
One such case was recently reported in Indore, an accent instructor of English language was bitten by it inside his house, and was declared dead on arrival at the hospital.
A clinical toxicology study gives an untreated mortality rate of 70–80%
Saw Scaled Viper
Echis is a genus of venomous vipers found in the dry regions of Africa, the Middle East, Pakistan, India and Sri Lanka. They have a characteristic threat display, rubbing sections of their body together to produce a “sizzling” warning sound. The name Echis is a Greek word that means “viper.” Their common name is “saw-scaled vipers” and they include some of the species responsible for causing the most snakebite cases and deaths in the world. Eight species are currently recognized. It perhaps has the the fastest strike from the big four and it strikes to bite.
Relatively small in size with adults never larger than about 90 cm (35 in.) in length.
The head is short, wide, pear-shaped and distinct from the neck. The snout is short and rounded, while the eyes are relatively large and set well forward. The crown is covered with small, irregular, imbricate scales, which may be either smooth or keeled.
The body is moderately slender and cylindrical. The dorsal scales are mostly keeled. However, the scales on the lower flanks stick out at a distinct 45-degree angle and have a central ridge, or keel, that is serrated (hence the common name). The tail is short and the subcaudals single.
Found in India, Pakistan and Sri Lanka, parts of the Middle East and Africa north of the equator.
All members of this genus have a distinctive threat display, which involves forming a series of parallel C-shaped coils and rubbing them together to produce a sizzling sound, rather like water on a hot plate. The proper term for this is stridulation. As they become more agitated, this stridulating behavior becomes faster and louder. It is postulated that this display evolved as a means of limiting water loss, such as might occur when hissing. However, some authors describe this display as being accompanied by loud hissing.
These snakes can be fierce and will strike from the position described above. When doing so, they may overbalance and end up moving towards their aggressor as a result; most unusual behavior for a snake.
Little is known about the eating habits of some Echis species. For others the diet is reported to be extremely varied, and may include items such as locusts, beetles, worms, slugs, spiders, scorpions, centipedes, solifugids, frogs, toads, reptiles (including other snakes), small mammals and birds.
Most Echis species, such as those found in Africa, are oviparous, while others, such as those in India, are viviparous.
The venom of Echis species consists mostly of haemotoxin. The genus is recognized as medically significant in many tropical rural areas. They are widespread and live in areas that lack modern medical facilities. Most victims are bitten after dark when these snakes are active.
Most of these species have venom that contains factors that can cause a consumption coagulopathy and defibrination which may persist for days to weeks. This may result in bleeding anywhere in the body, including the possibility of an intracranial hemorrhage. The latter classically occurs a few days following the bite.
Venom toxicity varies among the different species, geographic locations, individual specimens, sexes, over the seasons, different milkings, and of course the method of injection (SC, IM, IP, IV). Consequently, the LD50 values for Echis venom differ significantly. In mice the intravenous LD50 ranges from 2.3 mg/kg (U.S. Navy, 1991) to 24.1 mg/kg (Christensen, 1955) to 0.44-0.48 mg/kg (Cloudsley-Thompson, 1988). In humans, the lethal dose is estimated to be 3–5 mg (Minton, 1967). Latifi (1991) notes that venom from females was more than twice as toxic on average than venom from males.
The amount of venom produced also varies. Reported yields include 20–35 mg of dried venom from specimens 41–56 cm in length (Minton 1974, U.S. Navy, 1991), 6–48 mg (16 mg average) from Iranian specimens (Latifi, 1991) and 13–35 mg of dried venom from animals from various other localities (Boquet, 1967). Yield varies seasonally, as well as between the sexes: the most venom is produced during the summer months and males produce more than females.
Indian Spectacled Cobra
Indian Cobra (Naja naja) or Spectacled Cobra is a species of the genus Naja found in the Indian subcontinent and a member of the “big four”, the four species which inflict the most snakebites in India. This snake is revered in Indian mythology and culture, and is often seen with snake charmers. It is now protected in India under the Indian Wildlife Protection Act (1972).
On the rear of the snake’s hood are two circular ocelli patterns connected by a curved line, evoking the image of spectacles. Hindus believe them to be the footmarks of Krishna, who danced on Kaliya, the hundred and ten hooded snake’s head. An average cobra is about 1.9 meters (6 feet) in length and rarely as long as 2.4 meters (nearly 8 feet). The most distinctive and impressive characteristic of the Indian cobra is the hood, which it forms by raising the anterior portion of the body and spreading some of the ribs in its neck region when it is threatened. The spectacle pattern on the hood varies greatly, as does the overall colour of the snake.
The genus name Naja comes from Indian Languages. The Indian Cobra or Spectacled Cobra, being common in South Asia, is referred to by a number of local names deriving from the root of Naag (Hindi, Sanskrit, Oriya, Marathi), Moorkan (Malayalam), Naya (Singhalese), Naagu Pamu (Telugu), Nagara Haavu (Kannada), Naaga Pambu or Nalla pambu (Tamil) and Gokhra (Bengali).
The Oriental Ratsnake Ptyas mucosus is often mistaken for the cobra; however this snake is much longer and can easily be distinguished by the more prominent ridged appearance of its body. Other snakes that resemble Naja naja are the Banded Racer Argyrogena fasciolata and the Indian Smooth Snake Coronella brachyura.
Distribution, habitat and ecology
The Indian cobra is native to the Indian subcontinent which includes present day Nepal, India, Pakistan, Bangladesh, and Sri Lanka. It can be found in plains, jungles, open fields and the regions heavily populated by people. Its distribution ranges from sea-level up to 2,000 metres (6,600 ft) above sea-level. This species normally feed on rodents, toads, frogs, birds and other snakes. Its diet of rats leads it to areas inhabited by humans including farms and outskirts of urban areas.
Indian cobras are oviparous and lay their eggs between the months of April and July. The female snake usually lays between 10 to 30 eggs in rat holes or termite mounds and the eggs hatch 48 to 69 days later. The hatchlings measure between 20 and 30 centimetres (7.9 and 12 in) in length. The hatchlings are independent from birth and have fully functional venom glands.
The Indian cobra’s venom mainly contains a powerful post-synaptic neurotoxin and cardiotoxin. The venom acts on the synaptic gaps of the nerves, thereby paralyzing muscles, and in severe bites leading to respiratory failure or cardiac arrest. The venom components include enzymes such as hyaluronidase that cause lysis and increase the spread of the venom. Envenomation symptoms may manifest between 15 minutes to 2 hours following the bite.
In mice, the SC LD50 range for this species is 0.57 mg/kg – 0.80 mg/kg. The average venom yield per bite is between 169 —250 mg. Though it is responsible for many bites, only a small percentage are fatal if proper medical treatment and anti-venom are given. Mortality rate for untreated bite victims can vary tremendously, but according to one study it is approximately 15-20%. Another study with 1,224 bite cases the mortality rate was only 6.5%. Mortality rate without anti-venom is estimated to be at 30%.
The Indian cobra is one of the Big four snakes of South Asia (mostly India) which are responsible for the majority of human deaths by snakebite in Asia. Polyvalent serum is available for treating snakebites caused by this species. Zedoary, a local spice with a reputation for being effective against snakebite, has shown promise in experiments testing its activity against cobra venom.
The venom of young cobras has been used as a substance of abuse in India, with cases of snake charmers being paid for providing bites from their snakes. Though this practice is now seen as outdated, symptoms of such abuse include loss of consciousness, euphoria, and sedation.
The spectacled cobra is greatly respected and feared, and even has its own place in Hindu mythology as a powerful deity. The Hindu god Shiva is often depicted with a protective cobra coiled around his neck. Vishnu, the preserver of the universe, is usually portrayed as reclining on the coiled body of Sheshnag, the Preeminent Serpent, a giant snake deity with multiple cobra heads. Cobras are also worshipped during the Hindu festival of Nag Panchami.
There are numerous myths about cobras in India, including the idea that they mate with ratsnakes.
The Indian cobra’s celebrity comes from its popularity as a snake of choice for snake charmers. The cobra’s dramatic threat posture makes for a unique spectacle as it appears to sway to the tune of a snake charmer’s flute. Snake charmers with their cobras in a wicker basket are a common sight in many parts of India only during the Nag Panchami festival. The cobra is deaf to the snake charmer’s pipe, but follows the visual cue of the moving pipe and it can sense the ground vibrations from the snake charmer’s tapping. For safety, all the venoms in Cobra’s teeth are removed. The snake-charmers sell the venom at a very high price. In the past Indian snake charmers also conducted cobra and mongoose fights. These gory fight shows, in which the snake was usually killed, are now illegal.
Daboia is a monotypic genus of venomous Old World viper. The single species, D. russelii, is found in Asia throughout the Indian subcontinent, much of Southeast Asia, southern China and Taiwan. The species was named in honor of Patrick Russell (1726–1805), a Scottish herpetologist who first described many of India’s snakes; and the genus is after the Hindi name meaning “that lies hid”, or “the lurker.” Apart from being a member of the big four snakes in India, Daboia is also one of the species responsible for causing the most snakebite incidents and deaths among all venomous snakes on account of many factors, such as their wide distribution and frequent occurrence in highly-populated areas. Two subspecies are currently recognized, including the nominate subspecies described here.
Daboia are commonly known as Russell’s viper and chain viper, among other names.
This snake can grow to a maximum length of 166 cm (5.5 ft) and averages about 120 cm (4 ft) on mainland Asian populations, although island populations do not attain this size. It is more slenderly built than most other vipers.
The head is flattened, triangular and distinct from the neck. The snout is blunt, rounded and raised. The nostrils are large, in the middle of a large, single nasal scale. The lower edge of the nasal touches the nasorostral. The supranasal has a strong crescent shape and separates the nasal from the nasorostral anteriorly. The rostral is as broad as it is high.
The crown of the head is covered with irregular, strongly fragmented scales. The supraocular scales are narrow, single, and separated by 6–9 scales across the head. The eyes are large, flecked with yellow or gold, and each is surrounded by 10–15 circumorbital scales. There are 10–12 supralabials, the 4th and 5th of which are significantly larger. The eye is separated from the supralabials by 3–4 rows of suboculars. There are two pairs of chin shields, the front pair of which are notably enlarged. The two maxillary bones support at least two and at the most five or six pairs of fangs at a time: the first are active and the rest replacements. The fangs attain a length of 16 mm in the average specimen.
The body is stout, the cross-section of which is rounded to cylindrical. The dorsal scales are strongly keeled; only the lower row is smooth. Mid-body, the dorsal scales number 27–33. The ventral scales number 153–180. The anal plate is not divided. The tail is short — about 14% of the total body length — with the paired subcaudals numbering 41–68.
The color pattern consists of a deep yellow, tan or brown ground color, with three series of dark brown spots that run the length of its body. Each of these spots has a black ring around it, the outer border of which is intensified with a rim of white or yellow. The dorsal spots, which usually number 23–30, may grow together, while the side spots may break apart. The head has a pair of distinct dark patches, one on each temple, together with a pinkish, salmon or brownish V or X pattern that forms an apex towards the snout. Behind the eye, there is a dark streak, outlined in white, pink or buff. The venter is white, whitish, yellowish or pinkish, often with an irregular scattering of dark spots.
- English – Russell’s viper, chain viper, Indian Russell’s viper, common Russell’s viper, seven pacer, chain snake, scissors snake. Previously, another common name was used to described a subspecies that is now part of the synonymy of this form: Sri Lankan Russell’s viper for D. r. pulchella.
- Urdu, Hindi, Hindustani, Punjabi – daboia.
- Kashmiri – gunas.
- Oriya – Chandan Boda
- Sindhi – koraile.
- Bengali – bora, chandra bora, uloo bora.
- Gujarati – chitalo, khadchitalo.
- Marathi – ghonas.
- Telugu – katuka rekula paamu. or raktha penjara/penjari.
- Thai – ngu maew sao
- Kannada – mandaladha haavu or mandalata havu, kolakumandala.
- Tamil – retha aunali, kannadi virian or kannadi viriyan.
- Malayalam – mandali, ruthamandali,chenathandan, manchatti, shanguvarayan, “Rakta Anali”
- Sinhala – thith polonga.
- Burmese – mwe lewe.
- Tulu – PILI kandhodi
Found in Pakistan, India, Sri Lanka, Bangladesh, Nepal, Myanmar, Thailand, Cambodia, China (Guangxi, Guangdong), Taiwan and Indonesia (Endeh, Flores, east Java, Komodo, Lomblen Islands). The type locality is listed as “India”. More specifically, this would be the Coromandel Coast, by inference of Russell (1796).
Brown (1973) mentions that it can also found in Vietnam, Laos and on the Indonesian island of Sumatra. Ditmars (1937) reportedly received a specimen from Sumatra as well.However, the distribution of this species in the Indonesian archipelago is still being elucidated.
Within its range it can be very common in some areas, but scarce in others. In India, is abundant in Punjab, very common along the West Coast and its hills, in southern India and up to Bengal. It is uncommon to rare in the Ganges valley, northern Bengal and Assam. It is prevalent in Myanmar.
It is not restricted to any particular habitat, but does tend to avoid dense forests. The snake is mostly found in open, grassy or bushy areas, but may also be found in second growth forests (scrub jungles), on forested plantations and farmland. They are most common in plains, coastal lowlands and hills of suitable habitat. Generally not found at altitude, but has been reported as far up as 2300–3000 m. Humid environments, such as marshes, swamps and rain forests, are avoided.
This species is often found in highly urbanized areas and settlements in the countryside, the attraction being the rodents commensal with man. As a result, those working outside in these areas are most at risk of being bitten. It should be noted, however, that D. russelii does not associate as closely with human habitation as Naja and Bungarus (cobras and kraits).
Terrestrial and active primarily as a nocturnal forager. However, during cool weather it will alter its behavior and become more active during the day.
Adults are reported to be persistently slow and sluggish unless pushed beyond a certain limit, after which they become aggressive. Juveniles, on the other hand, are generally more nervous.
When threatened they form a series of S-loops, raise the first third of the body and produce a hiss that is supposedly louder than that of any other snake. When striking from this position, they can exert so much force that even a large individual can lift most of its body off the ground in the process.These snakes are strong and may react violently to being picked up. The bite may be a snap, or they may hang on for many seconds.
Although this genus does not have the heat-sensitive pit organs common to the Crotalinae, it is one of a number of viperines that are apparently able to react to thermal cues, further supporting the notion that they too possess a heat-sensitive organ. The identity of this sensor is not certain, but the nerve endings in the supranasal sac of these snakes resemble those found in other heat-sensitive organs.
This species is ovoviviparous. Mating generally occurs early in the year, although gravid females may be found at any time. The gestation period is more than six months. Young are produced from May to November, but mostly in June and July. It is a prolific breeder. Litters of 20–40 are common, although there may be fewer offspring and as little as one. The reported maximum is 65 in a single litter. At birth, juveniles are 215–260 mm in length. The minimum length for a gravid female is about 100 cm. It seems that sexual maturity is achieved in 2–3 years. In one case, it took a specimen nearly 4.5 hours to produce 11 young.
It feeds primarily on rodents, especially murid species. However, they will eat just about anything, including rats, mice, shrews, squirrels, land crabs, scorpions and other arthropods. Juveniles are crepuscular, feeding on lizards and foraging actively. As they grow and become adults, they begin to specialize in rodents. Indeed, the presence of rodents is the main reason they are attracted to human habitation.
Juveniles are known to be cannibalistic.
Some herpetologists believe that, because D. russelii is so successful as a species and has such a fearful reputation within its natural environment, another snake has even come to mimic its appearance. Superficially, the rough-scaled sand boa, Gongylophis conicus, has a color pattern that often looks a lot like that of D. russelii, even though it is completely harmless.
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).
The LD50 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, about 0.75 mg/kg subcutaneous. For most humans, a lethal dose is approximately 40–70 mg. In general, the toxicity depends on a combination of five different venom fractions, each of which is less toxic when tested separately. Venom toxicity and bite symptoms in humans vary within different populations and over time.
Envenomation symptoms begin with pain at the site of the bite, immediately followed by swelling of the affected extremity. Bleeding is a common symptom, especially from the gums and in the urine, and sputum may show signs of blood within 20 minutes post-bite. There is a drop in blood pressure, and the heart rate falls. Blistering occurs at the site of the bite, developing along the affected limb in severe cases. Necrosis is usually superficial and limited to the muscles near the bite, but may be severe in extreme cases. Vomiting and facial swelling occur in about one-third of all cases. Kidney failure (renal failure) also occurs in approximately 25-30 percent of untreated bites. Severe disseminated intravascular coagulation also can occur in severe envenomations. Early medical treatment and early access to antivenom can prevent and drastically reduce the chance of developing the severe/potentially lethal complications.
Severe pain may last for 2–4 weeks. Locally, it may persist depending on the level of tissue damage. Often, local swelling peaks within 48–72 hours, involving both the affected limb and the trunk. If swelling up to the trunk occurs within 1–2 hours, massive envenomation is likely. Discoloration may occur throughout the swollen area as red blood cells and plasma leak into muscle tissue. Death from septicaemia, kidney, respiratory or cardiac failure may occur 1 to 14 days post-bite or even later.
A study in The Lancet journal showed that out of a sample of people bitten by Daboia russelii who survived, 29% of them suffered severe damage to their pituitary glands, which later resulted in hypopituitarism. Other scientific studies support the hypothesis that D. russelii bites can cause hypopituitarism.
Because this venom is so effective at inducing thrombocytopenia, it has been incorporated into an in vitro diagnostic test for blood clotting that is widely used in hospital laboratories. This test is often referred to as Dilute Russell’s viper venom time (dRVVT). The coagulant in the venom directly activates factor X, which turns prothrombin into thrombin in the presence of factor V and phospholipid. The venom is diluted to give a clotting time of 23 to 27 seconds and the phospholipid is reduced to make the test extremely sensitive to phospholipid. The dRVVT test is more sensitive than the aPTT test for the detection of lupus anticoagulant (an autoimmune disorder), because it is not influenced by deficiencies in clotting factors VIII, IX or XI.
In India, the Haffkine Institute prepares a polyvalent antivenin that is used to treat bites from this species.
(More to come)