Bungarus, commonly referred to as kraits (pronounced "Kra-its"), is a genus of venomous elapid snakes found in South and South-East Asia. There are 13 species and 5 subspecies (excluding nominal) recognized.
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). 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.
Diet and behavior
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.
Bungarus contains some species which are among the most venomous land snakes in the world to mice based on their LD50. They 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, 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.
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.
Mortality rates caused by bites from the members of this genus vary from species to species: according to University of Adelaide Department of Toxicology, bites from the banded krait has an untreated mortality rate of 1—10% while that of the common krait is 70—80%. 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.In common with those of all other venomous snakes, the death time and fatality rate resulting from bites of kraits depend on numerous factors, like the venom yield and the health state of the victim.
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.
|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. caeruleusT||(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|
|B. slowinskii||Kuch et al., 2005||0||Red River krait||northern Vietnam|
*) Not including the nominate subspecies (typical form).
T) Type species
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.)
In Dean Koontz's The Good Guy, the hitman assigned to murder one of the protagonists calls himself 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 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.
- SurvivalIQ: Krait
- Smith, Malcolm A. Fauna of British India...Vol III - Serpentes, pages 411 to 413
- Richard Mastenbroek's Elapid Pages: Kraits (Bungarus ssp.)
- Living in Indonesia:Banded Krait
- Whitaker, Captain, Romulus, Ashok (2004). Snakes of India, The Field Guide. India: Draco Books. ISBN 81-901873-0-9.
- "Clinical Toxinology-Bungarus fasciatus". http://toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0018.
- "Clinical Toxinology-Bungarus caeruleus". http://toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0015.
- Prof Tan, Nget Hong. [monovalent B.fasciatus antivenom "Antivenoms against Malaysian poisonous snakes"]. University of Malaya. monovalent B.fasciatus antivenom. Retrieved 2009-09-23.
- Kuch, U., D: Kizirian, Q.T. Nguyen, R. Lawson, M.A. Donnelly, & D. Mebs (2005). A new species of krait (Squamata: Elapidae) from the Red River System of Nothern Vietnam. Copeia 2005(4): 818-833
- "Fauna in the Canon". strangemag.com. http://www.strangemag.com/rosenblatt.fauna.html.
- "Snakes on a Plane". IMDb. http://www.imdb.com/title/tt0417148/fullcredits#cast.