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Family: Colubridae
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Subfamily: Colubrinae
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Genus: Thelotornis
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Species: capensis
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Subspecies: capensis , oatesii
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Common Names
Bird Snake , Twig Snake , Vine Snake , Cape Twig Snake , Southern Bird Snake , Southern Savanna Vine Snake or Savannah Vine Snake ( T. c. capensis ) , Oate's Twig Snake , Oate's Bird Snake , Oate's Vine Snake , Oate's Savanna Vine Snake ( T. c. oatesii )
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Local Names
Gewone Voelslang , Kotikoti
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Region
Sub-Saharan Africa
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Countries
Angola, Botswana, Democratic Republic of Congo, Kenya, Malawi, Mozambique, Namibia, South Africa, Swaziland, Zambia, Zimbabwe, Somalia
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Taxonomy and Biology
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Adult Length: 1.00 m
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General Shape
Medium in length, cylindrical, exceptionally slender bodied snake with an extremely long and slender tail. The tail is somewhat delicate and many specimens have truncated tails. Can grow to a maximum of about 1.68 metres. Head is elongate, flattened, lance shaped when viewed from above and distinct from slender neck. Snout is long with a distinct and projecting canthus which forms a shallow groove below it on the side of the snout. Eyes are large in size with horizontally elliptical pupils ( keyhole shaped ). Dorsal scales feebly keeled with apical pits. Dorsal scale count usually 19 - 19 ( 17 ) - 11 ( 13 ).
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Habitat
Savanna ( moist miombo woodlands, riparian forest as well as dry savanna forest ) and coastal bush / forest.
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Habits
Arboreal and diurnal. It will inflate its neck and protrude its red and black tongue if disturbed and can move swiftly if threatened. They often rely on camouflage by hanging motionless from a branch awaiting prey for extended periods. Prey is held tightly and chewed briefly to inject the venom until the prey succumbs. Prey is swallowed while the snake hangs downwards. Males engage in combat during mating season.
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Prey
Rely on their colouration ( camouflage ) and slow movement to ambush mainly lizards ( particularly chameleons ) and birds and occasionally frogs and other snakes.
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Venom
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Average Venom Qty
2.25 mg ( dry weight ), Weinstein and Smith (1993) ( Ref : R000609 ).
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General: Venom Neurotoxins
Not present
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General: Venom Myotoxins
Not present
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General: Venom Procoagulants
Present but not defined
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General: Venom Anticoagulants
Possibly present
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General: Venom Haemorrhagins
Possibly present
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General: Venom Nephrotoxins
Secondary nephrotoxicity only
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General: Venom Cardiotoxins
Not present
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General: Venom Necrotoxins
Not present
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General: Venom Other
Not present or not significant
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Clinical Effects
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General: Dangerousness
Moderate envenoming possible and potentially lethal
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General: Rate of Envenoming: Unknown
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General: Untreated Lethality Rate: Unknown
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General: Local Effects
Local pain only
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General: Local Necrosis
Not likely to occur
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General: General Systemic Effects
Variable non-specific effects which may include headache, nausea, vomiting, abdominal pain, diarrhoea, dizziness, collapse or convulsions
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General: Neurotoxic Paralysis
Insufficient clinical reports to know
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General: Myotoxicity
Not likely to occur
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General: Coagulopathy & Haemorrhages
Uncommon to rare, but may be moderate to severe coagulopathy
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General: Renal Damage
Recognised complication, usually secondary to coagulopathy
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General: Cardiotoxicity
Unlikely to occur
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General: Other
Not likely to occur
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First Aid
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Description: First aid for potentially dangerous non-front-fanged colubroid snakes (see listing in Comments section).
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Details
1. After ensuring the patient and onlookers have moved out of range of further strikes by the snake, the bitten person should be reassured and persuaded to lie down and remain still. Many will be terrified, fearing sudden death and, in this mood, they may behave irrationally or even hysterically. The basis for reassurance is the fact that many venomous bites do not result in envenoming, the relatively slow progression to severe envenoming (hours following elapid bites, days following viper bites) and the effectiveness of modern medical treatment.
2. The bite wound should not be tampered with in any way. Wiping it once with a damp cloth to remove surface venom is unlikely to do much harm (or good) but the wound must not be massaged.
3. All rings or other jewellery on the bitten limb, especially on fingers, should be removed, as they may act as tourniquets if oedema develops.
4. If the bite is on a limb, a broad bandage (even torn strips of clothing or pantyhose) should be applied over the bitten area at moderate pressure (as for a sprain; not so tight circulation is impaired), then extended to cover as much of the bitten limb as possible, including fingers or toes, going over the top of clothing rather than risking excessive limb movement by removing clothing. The bitten limb should then be immobilised as effectively as possible using an extemporised splint or sling.
5. If there is any impairment of vital functions, such as problems with respiration, airway, circulation, heart function, these must be supported as a priority. In particular, for bites causing flaccid paralysis, including respiratory paralysis, both airway and respiration may be impaired, requiring urgent and prolonged treatment, which may include the mouth to mask (mouth to mouth) technique of expired air transfer. Seek urgent medical attention.
6. Do not use Tourniquets, cut, suck or scarify the wound or apply chemicals or electric shock.
7. Avoid peroral intake, absolutely no alcohol. No sedatives outside hospital. If there will be considerable delay before reaching medical aid, measured in several hours to days, then give clear fluids by mouth to prevent dehydration.
8. If the offending snake has been killed it should be brought with the patient for identification (only relevant in areas where there are more than one naturally occurring venomous snake species), but be careful to avoid touching the head, as even a dead snake can envenom. No attempt should be made to pursue the snake into the undergrowth as this will risk further bites. In Australia and parts of New Guinea, Snake Venom Detection Kits are available to identify the snake from venom left on the skin.
9. The snakebite victim should be transported as quickly and as passively as possible to the nearest place where they can be seen by a medically-trained person (health station, dispensary, clinic or hospital). The bitten limb must not be exercised as muscular contraction will promote systemic absorption of venom. If no motor vehicle or boat is available, the patient can be carried on a stretcher or hurdle, on the pillion or crossbar of a bicycle or on someone's back.
10. Most traditional, and many of the more recently fashionable, first aid measures are useless and potentially dangerous. These include local cauterization, incision, excision, amputation, suction by mouth, vacuum pump or syringe, combined incision and suction ("venom-ex" apparatus), injection or instillation of compounds such as potassium permanganate, phenol (carbolic soap) and trypsin, application of electric shocks or ice (cryotherapy), use of traditional herbal, folk and other remedies including the ingestion of emetic plant products and parts of the snake, multiple incisions, tattooing and so on.
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Treatment
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Treatment Summary
Bites cause potentially severe, even lethal coagulopathy and require urgent assessment & treatment. Antivenom, though often difficult to obtain, is the most effective treatment for the coagulopathy by the related boomslang, but effectiveness for Thelotornis envenoming is not established and it should be used only with great caution, in severe cases.
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Key Diagnostic Features
Local pain, swelling + coagulopathy & haemorrhage
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General Approach to Management
All cases should be treated as urgent & potentially lethal. Rapid assessment & commencement of treatment including appropriate antivenom (if indicated & available) is mandatory. Admit all cases.
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Antivenom Therapy
Only antivenoms available are for related species, but should be considered for significant envenoming, if more conservative treatment is unsuccessful. There is no guarantee SAVP Boomslang Antivenom will have any beneficial effect for Thelotornis bites, but it remains the only product raised against even a vaguely related species. In considering whether to use this product, carefully weigh up the risks versus uncertain benefit. This is not an approved use for this antivenom, based on the producers guidelines.
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