The Herald (Harare)
8 September 2007
Posted to the web 10 September 2007
Only certain colubrids are venomous, and, because they are backfanged, cannot inject nearly as much venom as viperine (the puff adder family) or elapid (the cobra/mamba family) venomous snakes.
In fact, only two species are dangerous to humans. Even those rarely cause life-threatening symptoms, and these occur after several days as a complication -- usually shutdown of the kidney function.
The two snakes, as previously indicated, are the boomslang and the vine snake, and, unlike the adders, they hang on and chew, rather than strike and recoil.
Also, the anti-venom, if obtainable from South Africa, is different from the polyvalent antiserum given for puff adder or cobra bites.
It is always better to leave the decision as to whether or not to give antiserum to an expert, and some non-medical people, such as veterinarians or snake experts (herpetologists, I think they're called), know more about treating venomous snake bite than ordinary doctors do.
Colubrid venoms seem to be of two main types:
1. Fibrinolysins, which cause a bleeding tendency which cannot be stopped by routine methods,
2. Haemorrhagins, which produce spontaneous bruising or even generalised blood blisters (haematomas or ecchymoses). The most striking feature of this poison, which I have observed, is "yellow vision" -- caused by bleeding behind the retina of the eye, and, of course, the patient subsequently becomes blind in that eye. The vine snake has this as its "speciality".
Now I'll describe the two important venomous colubrids in Zimbabwe because they are most often left out of the overcrowded medical students' syllabus.
There are a whole variety of colubrids in Zimbabwe (22 venomous and 18 or 19 non-venomous) but most of them are entirely beneficial to man and his environment. (I suppose, in these modern days, I should indicate that "man embraces woman", in other words, it's the genus I'm talking about, not the gender).
Boomslang (Danhamakatu,Korakundu or iNdlondlo) literally translated from its original Afrikaans name, boomslang simply means tree snake, and that's where it spends most of its time, hunting, eating, and sleeping.
It likes bird's eggs, and their young - especially weaver birds, and that is why the weaver is at pains to ensure that the tree branch where it builds its nest is stripped of foliage -- and chameleons, so a game of camouflage is played.
When disturbed, it usually runs away, and because of its excellent eyesight it's likely to see you before you see it. But, if it's cornered, it puffs itself up by inflating its spare lung, and the neck, then the whole body, and then it'll strike and hang on.
Tradition has it that this is the type of snake, which bit St Paul on the island of Malta. When it does bite, the venom is very potent, and, although there isn't much local pain or inflammation, within an hour a splitting, vertical headache develops which lasts, usually, all day. First, the fang punctures, then any abrasions or cuts start to bleed, usually at least several hours after the event. Diagnosis, by this time, should be straightforward, but it is surprising how often the snake is assumed to be a "cobra", even by those who should know better.
Tourniquets, or other constrictive bandages should never be used, because, although blood-borne, the venom also acts outside the circulatory system.
Untreated, the victim of a major venomous bite dies a lingering death from low blood pressure (due to blood loss) unconsciousness, convulsions and vomiting of blood. Fortunately, I've never had that experience, but one of my Guernsey cows (in about 1988) died, and retrospectively we concluded that she had been bitten in the nose by a boomslang.
Boomslangs are prone to be mistaken for a leafy branch, as especially the males are bright green, with or without black scale edgings. Many bites from colubrids produce little in the way of systemic effects, but a bite from a boomslang should never be dismissed lightly.
Vine Snake (savanna vine snake, Kumtumuti, Rukukutwe or uKotikoti) I call this the sneakiest snake we've got in Zimbabwe, because, although long (one and a half metres), it's very slender, with a long, lance-shaped head and a distinctive pupil shaped a bit like an old-fashioned keyhole.
It has very sharp vision, and that's probably essential, because, like the boomslang, it lives in small trees and dead shrubs, where the sense of vibration possessed by all the snakes will not be much use. To me, it is the best camouflaged snake we've got, and the slenderness of its body belies the sometimes lethal, bite it can inflict on an unsuspecting victim.
It can stay in a dead tree or bush for hours, looking just like a dead branch.
It is common throughout Zimbabwe up to about 1 500 metres, and the bite is similar to the boomslang, though less severe. So for symptoms and treatment, look under "boomslang"!
8 September 2007
Posted to the web 10 September 2007
Only certain colubrids are venomous, and, because they are backfanged, cannot inject nearly as much venom as viperine (the puff adder family) or elapid (the cobra/mamba family) venomous snakes.
In fact, only two species are dangerous to humans. Even those rarely cause life-threatening symptoms, and these occur after several days as a complication -- usually shutdown of the kidney function.
The two snakes, as previously indicated, are the boomslang and the vine snake, and, unlike the adders, they hang on and chew, rather than strike and recoil.
Also, the anti-venom, if obtainable from South Africa, is different from the polyvalent antiserum given for puff adder or cobra bites.
It is always better to leave the decision as to whether or not to give antiserum to an expert, and some non-medical people, such as veterinarians or snake experts (herpetologists, I think they're called), know more about treating venomous snake bite than ordinary doctors do.
Colubrid venoms seem to be of two main types:
1. Fibrinolysins, which cause a bleeding tendency which cannot be stopped by routine methods,
2. Haemorrhagins, which produce spontaneous bruising or even generalised blood blisters (haematomas or ecchymoses). The most striking feature of this poison, which I have observed, is "yellow vision" -- caused by bleeding behind the retina of the eye, and, of course, the patient subsequently becomes blind in that eye. The vine snake has this as its "speciality".
Now I'll describe the two important venomous colubrids in Zimbabwe because they are most often left out of the overcrowded medical students' syllabus.
There are a whole variety of colubrids in Zimbabwe (22 venomous and 18 or 19 non-venomous) but most of them are entirely beneficial to man and his environment. (I suppose, in these modern days, I should indicate that "man embraces woman", in other words, it's the genus I'm talking about, not the gender).
Boomslang (Danhamakatu,Korakundu or iNdlondlo) literally translated from its original Afrikaans name, boomslang simply means tree snake, and that's where it spends most of its time, hunting, eating, and sleeping.
It likes bird's eggs, and their young - especially weaver birds, and that is why the weaver is at pains to ensure that the tree branch where it builds its nest is stripped of foliage -- and chameleons, so a game of camouflage is played.
When disturbed, it usually runs away, and because of its excellent eyesight it's likely to see you before you see it. But, if it's cornered, it puffs itself up by inflating its spare lung, and the neck, then the whole body, and then it'll strike and hang on.
Tradition has it that this is the type of snake, which bit St Paul on the island of Malta. When it does bite, the venom is very potent, and, although there isn't much local pain or inflammation, within an hour a splitting, vertical headache develops which lasts, usually, all day. First, the fang punctures, then any abrasions or cuts start to bleed, usually at least several hours after the event. Diagnosis, by this time, should be straightforward, but it is surprising how often the snake is assumed to be a "cobra", even by those who should know better.
Tourniquets, or other constrictive bandages should never be used, because, although blood-borne, the venom also acts outside the circulatory system.
Untreated, the victim of a major venomous bite dies a lingering death from low blood pressure (due to blood loss) unconsciousness, convulsions and vomiting of blood. Fortunately, I've never had that experience, but one of my Guernsey cows (in about 1988) died, and retrospectively we concluded that she had been bitten in the nose by a boomslang.
Boomslangs are prone to be mistaken for a leafy branch, as especially the males are bright green, with or without black scale edgings. Many bites from colubrids produce little in the way of systemic effects, but a bite from a boomslang should never be dismissed lightly.
Vine Snake (savanna vine snake, Kumtumuti, Rukukutwe or uKotikoti) I call this the sneakiest snake we've got in Zimbabwe, because, although long (one and a half metres), it's very slender, with a long, lance-shaped head and a distinctive pupil shaped a bit like an old-fashioned keyhole.
It has very sharp vision, and that's probably essential, because, like the boomslang, it lives in small trees and dead shrubs, where the sense of vibration possessed by all the snakes will not be much use. To me, it is the best camouflaged snake we've got, and the slenderness of its body belies the sometimes lethal, bite it can inflict on an unsuspecting victim.
It can stay in a dead tree or bush for hours, looking just like a dead branch.
It is common throughout Zimbabwe up to about 1 500 metres, and the bite is similar to the boomslang, though less severe. So for symptoms and treatment, look under "boomslang"!
