Bungarus

Bungarus is a genus of venomous elapid snakes, the kraits ("krait" is pronounced /kraɪt/, rhyming with "kite"),[1][2] found in South and Southeast Asia. The genus Bungarus has 15 species.

"Krait" redirects here. For the ship, see MV Krait. For the CPU, see Krait (CPU).

Bungarus
Bungarus fasciatus (the largest species of krait)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Bungarus
Daudin, 1803
Synonyms

Distribution

Kraits are found in tropical Asia, from near Iran, through the Indian subcontinent (including Sri Lanka and Bangladesh) and on to Southeast Asia (including Indonesia and Borneo).[3]

Description

Kraits usually range between 1.0 and 1.5 m (3 ft 3 in and 4 ft 11 in) in total length (including tail), although specimens as large as 2.0 m (6 ft 7 in) have been observed. The banded krait (B. fasciatus) may grow as large as 2.125 m (6 ft 11.7 in).[4] Most species of kraits are covered in smooth, glossy scales arranged in bold, striped patterns of alternating black and light-colored areas. This may serve as aposematic colouration 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 pronounced dorsolateral flattening, which causes them to be triangular in cross section.

Diet and behavior

Kraits are ophiophagous, preying primarily upon other snakes (including venomous varieties) and are cannibalistic, feeding on other kraits. They also eat mice and small lizards.[5]

All kraits are nocturnal. They are more docile during the daylight; at night, they become very active, but are not very aggressive even when provoked. They are actually rather timid, and often hide their heads within their coiled bodies for protection. When in this posture, they sometimes whip their tails around as a type of distraction.[6]

Reproduction

Kraits are oviparous. The female lays a clutch of 12 to 14 eggs in piles of leaf litter, and stays with them until they hatch.

Venom

Bungarus contains some species which are among the most venomous land snakes in the world to mice based on their LD50.[7] They have highly potent neurotoxic venom which can induce muscle paralysis. Clinically, their venom contains mostly presynaptic 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, 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 of severe abdominal cramps accompanied by progressive muscular paralysis, frequently starting with ptosis. As no local symptoms are seen, a patient should be carefully observed for tell-tale signs of paralysis (e.g. the onset of bilateral ptosis, diplopia, and dysphagia), and treated urgently with antivenom. Frequently, little or no pain occurs at the site of a krait bite, which can provide false reassurance to the victim. The major medical difficulty of envenomated patients is 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 no species-specific antivenom is 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 about 6-12 hours after the krait bite, but can be significantly delayed. Cause of death is usually respiratory failure—suffocation by 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 the potential for long transport times to get medical care.

Mortality rates caused by bites from the members of this genus vary by species; according to University of Adelaide Department of Toxicology, bites from the banded krait have an untreated mortality rate of 1–10%,[8] while those of the common krait are 70–80%.[9] Several websites state the mortality rate is 50% even with treatment, but no specific species is mentioned and no original source in the medical literature for this statement is given. In common with those of all other venomous snakes, the death time and fatality rate resulting from bites of kraits depend on numerous factors, such as the venom yield and the health status of the victim.

Polyvalent elapid antivenom is effective in neutralizing of the venoms of B. candidus and B. flaviceps and rather effective for B. fasciatus. In this last case, the monovalent B. fasciatus antivenom is also moderately effective.[10]

Species
Species Authority Subsp.* Common name Geographic range
Bungarus andamanensis Biswas & Sanyal, 1978 0 South Andaman krait India (Andaman Island)
Bungarus bungaroides (Cantor, 1839) 0 northeastern hill krait Myanmar, India (Assam, Cachar, Sikkim), Nepal, Vietnam
Bungarus caeruleusT (Schneider, 1801) 0 common krait, Indian krait Afghanistan, Pakistan, India (Bengal, Maharashtra, Karnataka), Sri Lanka, Bangladesh, Nepal
Bungarus candidus (Linnaeus, 1758) 0 blue krait, Malayan krait Cambodia, Indonesia (Java, Sumatra, Bali, Sulawesi), Malaysia (Malaya), Singapore, Thailand, Vietnam
Bungarus ceylonicus Günther, 1864 1 Ceylon krait, Sri Lankan krait Sri Lanka
Bungarus fasciatus (Schneider, 1801) 0 banded krait Bangladesh, Brunei, Myanmar, Cambodia, south China (incl. Hong Kong, Hainan), north-east India, Eturnagaram[Warangal[Telangana]India], Bhutan, Nepal, Indonesia (Sumatra, Java, Borneo), Laos, Macau; Malaysia (Malaya and East Malaysia), Singapore, Thailand, Vietnam and Philippines
Bungarus flaviceps (Reinhardt, 1843) 1 red-headed krait South Thailand, South Myanmar, Cambodia, Vietnam, Malaysian Peninsula, Pulau Tioman, Indonesia (Bangka, Sumatra, Java, Billiton, Borneo)
Bungarus lividus Cantor, 1839 0 lesser black krait India, Bangladesh, Nepal
Bungarus magnimaculatus Wall & Evans, 1901 0 Burmese krait Myanmar
Bungarus multicinctus Blyth, 1861 1 many-banded krait Taiwan, south China (Hong Kong, Hainan), Myanmar, Laos, northern Vietnam, Thailand and northern Philippines
Bungarus niger Wall, 1908 0 black krait, greater black krait India (Assam, Sikkim), Nepal, Bangladesh, Bhutan
Bungarus persicus Abtin, Nilson, Mobaraki, Hosseini & Dehgannejhad, 2014 0 none Iran
Bungarus sindanus Boulenger, 1897 2 Sind krait Southeast Pakistan, India
Bungarus slowinskii[11] Kuch, Kizirian, Q. Nguyen, Lawson, Donnelly & Mebs, 2005 0 Red River krait Northern Vietnam
Bungarus walli Wall, 1907 0 none India (Uttar Pradesh), Nepal, Bangladesh

*) Not including the nominate subspecies (typical form).
T) Type species

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See also

References
  1. "krait, n." Oxford English Dictionary Online. Oxford University Press (accessed June 30, 2014).
  2. "krait". American Heritage Dictionary. Accessed June 30, 2014.
  3. SurvivalIQ: Krait
  4. Smith, Malcolm A. (1943). The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-region. Reptilia and Amphibia. Vol. III.—Serpentes. London: Secretary of State for India. (Taylor and Francis, printers). xii + 583 pp. (Bungarus, genus and species, pp. 407-418).
  5. Richard Mastenbroek's Elapid Pages: Kraits (Bungarus ssp.)
  6. "Living in Indonesia:Banded Krait". Archived from the original on 2006-05-08. Retrieved 2006-06-01.
  7. Whitaker, Romulus; Captain, Ashok (2004). Snakes of India, The Field Guide. Chennai: Draco Books. 495 pp. ISBN 81-901873-0-9.
  8. "Bungarus fasciatus ". WCH Clinical Toxinology Resources.
  9. "Bungarus caeruleus ". WCH Clinical Toxinology Resources. Archived from the original on 2016-10-16. Retrieved 2011-11-10.
  10. Prof Tan, Nget Hong. "Antivenoms against Malaysian poisonous snakes". University of Malaya. Archived from the original on 2009-02-28. Retrieved 2009-09-23.
  11. Kuch, Ulrich; Kizirian, David; Nguyen, Quang Truong; Lawson, Robin; Donnelly, Maureen A.; Mebs, Dietrich (2005). "A new species of krait (Squamata: Elapidae) from the Red River System of Northern Vietnam". Copeia 2005 (4): 818-833. (Bungarus slowinskii, new species).

Further reading
  • Boulenger GA (1896). Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the Colubridæ (Opisthoglyphæ and Proteroglyphæ) ... London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiv + 727 pp. + Plates I-XXV. (Genus Bungarus, pp. 365-366, Figure 26, three views of skull).
  • Daudin FM (1803). Histoire Naturelle, Génerale et Particulière des Reptiles; Ouvrage faisant suite aux Œuvres de Leclerc de Buffon, et partie de Cours complete d'Histoire naturelle rédigé par C.S. Sonnini, membre de plusieurs Sociétés savantes. Tome cinquième [Volume 5]. Paris: F. Dufart. 365 pp. (Bungarus, new genus, p. 263). (in French).
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