| Bungarus | |
|---|---|
| Bungarus fasciatus (the largest species of krait) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Vertebrata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Elapidae |
| Genus: | Bungarus Daudin, 1803 |
| Synonyms | |
|
Pseudoboa Oppel, 1811 |
|
Bungarus, commonly referred to as kraits (pronounced "crates"), is a genus of venomous elapid snakes found in South and South-East Asia. There are 12 species and 5 subspecies recognized.
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Kraits are found in the Indian subcontinent (including Sri Lanka and eastern Pakistan) and southeast Asia (including Indonesia and Borneo).[1]
Kraits usually range between 1 to 1.5 meters (3 ft 3 in to 4 ft 10 in) in length, although specimens as large as 2 m have been observed. The Banded Krait (B. fasciatus) may grow as large as 2.125 meters (6 ft 11.7 in).[2] Most species of krait are covered in smooth glossy scales that are arranged in bold striped patterns of alternating black and light-colored areas. This gives the snake camouflage in its habitat of grassland and scrub jungle. The scales along the dorsal ridge of the back are hexagonal. The head is slender and the eyes have round pupils. Kraits have a pronounced dorsolateral flattening, and are triangular in cross section. The tail tapers to a thin point.
Kraits are ophiophagous, preying primarily upon other snakes (including venomous varieties) and are cannibalistic, feeding on other kraits. They will also eat mice and small lizards.[3]
All kraits are nocturnal. They are more docile during the daylight hours; at night they become very active, but are not very aggressive even when provoked. They are actually rather timid, and will often hide their heads within their coiled bodies for protection. When in this posture, they will sometimes whip their tail around as a type of distraction.[4]
Kraits are oviparous, and the female will lay a clutch of 12 to 14 eggs in piles of leaf litter and stay with them until they hatch.
Bungarus species have highly potent neurotoxic venom which can induce muscle paralysis. Clinically, their venom contains mostly pre-synaptic neurotoxins. These affect the ability of neuron endings to properly release the chemical that sends the message to the next neuron. Following envenomation with bungarotoxins, transmitter release is initially blocked (leading to a brief paralysis), followed by a period of massive overexcitation (cramps, tremors, spasms), which finally tails off to paralysis. These phases may not be seen in all parts of the body at the same time. Since kraits are nocturnal they seldom encounter humans during daylight hours, so bites are rare and they may prefer to deliver non-fatal bites,[5] but a bite from a krait is potentially life-threatening, and should be regarded as a medical emergency.
Typically, victims start to complain later of severe abdominal cramps accompanied by progressive muscular paralysis, frequently starting with ptosis. As there are no local symptoms, a patient should be carefully observed for tell-tale signs of paralysis (e.g. the onset of ptosis, diplopia and dysphagia) and treated urgently with antivenom. There is frequently little or no pain at the site of a krait bite, which can provide false reassurance to the victim. The major medical difficulty of patients envenomated are the lack of medical resources (especially intubation supplies and mechanical ventilators in rural hospitals) and the ineffectiveness of the antivenom. Definitive care may also be delayed as patients may first visit the local mantrik or tantrik, a holy person and traditional healer who may attempt to rid the body of the venom with spells or herbal remedies, which are ineffective interventions.
Once at a healthcare facility support must be provided until the venom is metabolised and the victim can breathe unaided, especially if there is no species-specific antivenom available. Given that the toxins alter acetylcholine transmission which causes the paralysis, some patients have been successfully treated with cholinesterase inhibitors such as physostigmine or neostigmine, but success is variable and may be species dependent as well. If death occurs it typically takes place approximately 6 to 12 hours after the krait bite, but can be significantly delayed. Cause of death is usually respiratory failure i.e. suffocation via complete paralysis of the diaphragm. Even if patients make it to a hospital subsequent permanent coma and even brain death from hypoxia may occur given potentially long transport times to get medical care.
The mortality rates caused by the members of this genus vary among different species:a bite from the banded krait has an untreated mortality rate of 1—10% [6] while that of the common krait is 70—80%.[7] Several websites state that there is a mortality rate of 50% even with treatment, but no specific species is given and there is no original source in the medical literature for this statement.
The polyvalent Elapid Antivenom is effective in neutralizing of the venoms of Bungarus candidus and Bungarus flaviceps and rather effective in the neutralization of the venom of Bungarus fasciatus. In this last case, the monovalent Bungarus fasciatus antivenom is also moderately effective.[5]
| Species | Authority | Subsp.* | Common name | Geographic range |
|---|---|---|---|---|
| B. andamanensis | Biswas & Sanyal, 1978 | 0 | South Andaman krait | India (Andaman Island) |
| B. bungaroides | (Cantor, 1839) | 0 | Northeastern hill krait | Myanmar, India (Assam, Cachar, Sikkim), Nepal, Vietnam |
| B. caeruleus | (Schneider, 1801) | 0 | common krait | Afghanistan, Pakistan, India (Bengal,Maharashtra, Karnataka), Sri Lanka, Bangladesh, Nepal |
| B. candidus | (Linnaeus, 1758) | 0 | Malayan krait, blue krait | Cambodia, Indonesia (Java, Sumatra, Bali, Sulawesi), Malaysia (Malaya), Singapore, Thailand, Vietnam |
| B. ceylonicus | Günther, 1864 | 1 | Sri Lankan krait | Sri Lanka |
| B. fasciatus | (Schneider, 1801) | 0 | banded krait | Bangladesh, Brunei, Myanmar, Cambodia, south China (incl. Hong Kong, Hainan), north-east India, Bhutan, Nepal, Indonesia (Sumatra, Java, Borneo), Laos, Macau; Malaysia (Malaya and East Malaysia), Singapore, Thailand, Vietnam |
| B. flaviceps | (Reinhardt, 1843) | 1 | red-headed krait | South Thailand, South Myanmar, Cambodia, Vietnam, Malaysian Peninsula, Pulau Tioman, Indonesia (Bangka, Sumatra, Java, Billiton, Borneo) |
| B. lividus | Cantor, 1839 | 0 | lesser black krait | India, Bangladesh, Nepal |
| B. magnimaculatus | Wall and Evans, 1901 | 0 | Burmese krait | Myanmar |
| B. multicinctus | Blyth, 1861 | 1 | many-banded krait | Taiwan, south China (incl. Hong Kong, Hainan), Myanmar, Laos, north Vietnam, Thailand |
| B. niger | Wall, 1908 | 0 | greater black krait | India (Assam, Sikkim), Nepal, Bangladesh, Bhutan |
| B. sindanus | Boulenger, 1897 | 2 | Sind krait | South-east Pakistan, India |
*) Not including the nominate subspecies (typical form).
Kraits have a reputation as deadly snakes and have figured in fiction as such. Rudyard Kipling used a small, sand colored krait as one of the three main villains in his short story "Rikki-Tikki-Tavi". (The other two villains being a pair of black cobras). In another Kipling short story, "The Return of Imray," a servant arrested for murder cheats the rope by stepping on a karait.
Roald Dahl uses the krait as a device in his short story "Poison". A version of "Poison" is shown in Alfred Hitchcock Presents (TV series) October 5, 1958 and remade in Tales of the Unexpected (TV series) March 29, 1980. The krait also appears in Frederick Forsyth's short story "There Are No Snakes in Ireland" (referencing Kipling's Rikki-Tikki-Tavi, with the assumption that Kipling may actually have meant the Saw-scaled viper; included in his collection No Comebacks).
It has been argued that the deadly snake in the Sherlock Holmes story "The Adventure of the Speckled Band" may have been a krait, although it is described in that work as an "Indian swamp adder." (The Russell's Viper has also been considered as a possible culprit.)[8]
In a slightly more oblique reference, the motion picture Snakes on a Plane features a villainous snake smuggler named "Kraitler." [9]
In Dean Koontz's The Good Guy, the hitman assigned to murder one of the protagonists calls himself Krait.
In the Guild Wars expansion Eye Of the North there is a race of snake-like creatures called Krait.
In Mercedes Lackey's The Serpent's Shadow, Maya's father was killed by a krait while living in India.
In the Star Wars: Legacy comic book series, the leader of the New Sith Order is known as Darth Krayt. Though named after the fictional Krayt Dragon, it is possible that the venomous dragon was named after the krait.
In the early computer game Elite, Krait is the model name of a pirate starship. An homage to it is presented in the later game Escape Velocity Override, where a similar type of renegade fighter craft is also named the Krait.
In Ben Bova's book The Precipice: The Asteroid Wars, vol.1, the character Pancho Lane has a 35 cm Metallic blue Krait, named Elly.
In Mohammed Hanif's book A Case of Exploding Mangoes, Ali Shigri sees them and Blind Zainab kills one.
In James Patterson's The 8th Confession kraits are the murder weapons used by a serial killer.
In Philip Caputo's "In the Forest of the Laughing Elephant" krait venom is on the arrow that kills the main character, Lincoln Coombes.
In the Alfred Hitchcock Presents episode "Poison", a man discovers there is a krait lying on his stomach.