A Guide to the Snakes of Liberia

Transcription

Nimba Western Range Iron Ore Project,
Liberia
Environmental and Social Studies,
2008-2015
A Guide to the
Snakes of Liberia
Smith’s Water Snake: one of many harmless snakes in Liberia
VERSION DATE: 19 SEPTEMBER 2013
ArcelorMittal Liberia Limited
P.O. Box 1275
Tubman Boulevard at 15th Street
Sinkor, Monrovia
Liberia
T +231 77 018 056
www.arcelormittal.com
Nimba Western Range Iron Ore Project, Liberia
Environmental and Social Studies, 2008-2015: Project Phase 2 – Concentrator
Contents
SNAKE BITES: EMERGENCY GUIDE ................................................................................................. 3
If you have been bitten by a snake: ................................................................................................................. 3
PREVENTING SNAKE BITES .............................................................................................................. 4
1.
INTRODUCTION...................................................................................................................... 5
2.
SNAKES .................................................................................................................................. 6
2.1
2.2
Identification of snakes .......................................................................................................................... 6
What makes a snake dangerous? .......................................................................................................... 6
3.1
3.2
3.3
3.3
Potentially life-threatening snakes ......................................................................................................... 7
Potentially harmful snakes ..................................................................................................................... 8
Harmless snakes ................................................................................................................................. 11
Other dangerous snakes which probably do not occur in Liberia .......................................................... 13
4.1
4.2
4.3
4.4
4.5
4.6
General information about snake bites ................................................................................................. 14
Factors affecting the outcome of a snake bite ...................................................................................... 14
First aid in the event of a snake bite..................................................................................................... 15
Spitting snakes .................................................................................................................................... 17
Standard safety measures ................................................................................................................... 17
Removal of snakes .............................................................................................................................. 18
3.
PHOTOGRAPHIC GUIDE TO LIBERIAN SNAKES ................................................................. 7
4.
SNAKE BITES........................................................................................................................ 14
5.
CHECKLIST OF SNAKES OF NIMBA COUNTY, LIBERIA.................................................... 19
6.
REFERENCES....................................................................................................................... 21
6.1
6.2
Recommended reading ....................................................................................................................... 21
Photo sources ..................................................................................................................................... 21
Acknowledgements
This guide was adapted from a report produced by URS for ArcelorMittal Liberia Limited. The original
guide was written by Johannes Penner, with contributions from William Branch, Ben Phalan, Tanya
Romanenko and Gareth Hearn.
Version: 19 September 2013
Page 2 of 22
SNAKE BITES: EMERGENCY GUIDE
If you have been bitten by a snake:

Don’t panic. Over 90% of Liberian snake species cannot kill you. Most bites are not
life-threatening.

Stay calm and move around as little as possible. Don‟t try to run or walk to
hospital.

Call for help. Get others to organise transport to hospital.

Remove all tight objects from the bitten limb: rings, bracelets, watches,
clothes, shoes.

Let the bite bleed freely for some minutes (but do not suck the wound).

Apply a Pressure-Immobilization bandage.

Drink water. This will help you to stay calm and reduce the likelihood of shock.

Do NOT try to catch or kill the snake. This needs to be done by someone who has
been properly trained, with special tools. If possible, take a photograph of the
snake from a safe distance.

Do NOT drink alcohol, coffee or tea or any other liquid which stimulates blood
circulation.

Do NOT take any medication such as painkillers, other than 1g Paracetamol.

Do NOT cut or suck the bite.

Do NOT rely on a traditional healer. A bite from a venomous snake needs medical
treatment.

Unless you have medical knowledge:

Do NOT give antivenin. Incorrect administration of antivenin can kill.

Do NOT apply a tourniquet (a very tight bandage that stops blood flow).
If you get venom in your eyes from a spitting snake:

Wash your eyes with plenty of clean water or another safe, neutral liquid (e.g. milk or
vegetable oil) for at least 30 minutes.

Go straight to hospital.
If you are with someone who has been bitten by a snake:

Don't panic! Help the victim stay calm.

Arrange transport to hospital as quickly and safely as possible. Try to contact the hospital and
ensure they are informed of the incident.

Be prepared to apply resuscitation measures.

Do NOT try to catch the snake.
Who to contact:
Paramedic:
Yekepa: 077 767203
Buchanan: 077 767196
Environmental Officer:
Yekepa: 077 926989
Buchanan: 077827308
Page 3 of 22
PREVENTING SNAKE BITES
Nearly every snake can bite and will do so if it feels threatened. However, snake bites are
easy to prevent with proper procedures:

Do not molest or harm snakes.

Watch where you step and what you grab hold of.

Use a torch at night.

Do not put your hand underneath objects (e.g. logs, metal plates), or in holes
without checking them first from a safe distance and by using tools such as a
torch, indirect means (e.g. stick). When turning objects on the ground, always make
sure that the opening gap points away from you and not towards you or other people.
Check shoes, clothes, beds, sleeping bags, etc. before using them.

Wear rubber boots or other strong boots which cover the ankle. Wear long
trousers, especially in environments with dense vegetation.

Wear leather gloves when gathering products from the forest floor and during
agricultural work.

Keep areas where humans live or work clear: cut grass regularly, trim bushes, and
avoid piles of rubbish and litter.

Store food and rubbish in sealed containers to avoid attracting rodents, which in
turn attract snakes.

Do not sleep at ground level, use raised beds and mosquito nets. This will also
reduce the likelihood of being bitten by other animals and insects, and will reduce the
transmission risk of diseases such as Malaria.

Do not keep livestock in the house.

Exercise first aid measures and conduct regular snake bite emergency drills as
part of the health and safety programme before a bite occurs.
If you encounter a snake:

Do not try to chase it away.

Do not attempt to kill or catch any snake. Snakes should only be removed by
trained and properly equipped personnel.

Do not behave aggressively as if you are trying to harm it.

Back away slowly, without sudden movements that may startle the snake,
especially if you are very close to the snake.

Use common sense!
Page 4 of 22
1.
INTRODUCTION
Snakes are an integral part of many ecosystems. Currently, nearly 3500 species are known
worldwide. They range from tiny blind-snakes, feeding on ant and termite eggs, to large species
reaching several metres in length – some can reach more than 7m. Although snakes are shy,
secretive creatures and mostly poorly studied, an amazing diversity of forms, colours and lifestyles is
known. Snakes have adapted to life on land, in fresh water, in the seas, on trees (even gliding from
tree to tree), and are found at a range of latitudes and altitudes. In Liberia 11 families (broad groups)
of snakes can be found. The role of each within their ecosystem varies widely. In many ecosystems
snakes are important predators of potential pest species such as rodents (mice, rats, etc.) which
means that they control rodent numbers and keep them at bay. Rodents can pose problems to
humans by severely decimating harvests or stored food, and also transmit a number of serious
diseases (e.g. Huntington disease, Lassa fever).
Snakes orientate themselves very well in their environment. Although only a few species of snake
have excellent vision, all are very sensitive to vibrations and can sense walking humans often well
before being spotted. Their most important sense is that of smell, and snakes “see” their environment
through smell. They smell through their nostrils, but more importantly odour molecules are picked up
by the tongue tips, which are forked to detect a gradient in the odour trace. In this way snakes are
able to establish, for example, in which direction prey is moving by following the stronger odour trail.
After picking up the molecules, the tongue is retracted into a sheath on the floor of the mouth where
the odour molecules are deposited on two “traps” which are then pushed upwards into the roof of the
mouth. There the odour is analysed by the „Jacobson‟s Organ‟, which is far more sensitive than the
nostrils. This is why snakes flick their tongue, which they do most when they become excited.
It is not known exactly how many different species of snake occur in Liberia, but it is currently
estimated that at least 70 species are highly likely to be found in Liberia. Another 8 are also listed in
the literature but are very unlikely to occur. Around 57 species can be found in the Nimba region,
which harbours probably the highest snake diversity known for any site on the African continent. This
underlines the importance of the Nimba region as a habitat for snakes. A full list of the species known
from Nimba County is given at the end of this booklet. No study on snakes has been conducted at
Greenhill and Buchanan but it is probable that they overall contain less species than the Nimba
region. All species either observed or reported to have been sighted at Greenhill and Buchanan are
also found in Nimba. Of the 70 Liberian species, 53 (approximately 75%) are considered harmless to
humans. The most commonly encountered snakes in Liberia are harmless colubrids, for example the
African Water Snake, the larger Smith‟s Water Snake, the herald snakes, the Striped and Green
Keeled Snakes, and other green snakes and file snakes. The large size of the latter is noteworthy
because they feed also on other snakes, including venomous species. Blind snakes are small
burrowing, worm-like snakes. They have poor vision, with eyes covered by scales, and most feed on
ant and termite eggs. They are completely harmless to humans. The larger Calabar Ground Boa is
also non-venomous. Of the remaining 25% snakes found in Liberia, approximately 16% can be
dangerous to humans and a further 9% carry venoms that can be life threatening.
Venom is an important part of snake ecology. Snakes do not have limbs and thus cannot hold mobile
prey. In addition snake teeth are fragile, break off easily and cannot be used for chewing. All snakes
swallow their prey whole. The vast majority of them either swallow defenceless prey (e.g. frogs or
insects) while they are still alive or they constrict them. The other method is to immobilise prey with
venom. This helps reduce the risk of injury to the snake. The venom either works rapidly or the snake
releases its prey after biting it. It then retrieves its prey once it dies, by following its odour trail. The
venom also aids with digestion of prey, and in evolutionary terms the venom gland is a development
of the salivary gland.
In virtually all encounters with humans a snake will either try to flee or will remain motionless, relying
on its camouflage. However, if cornered or attacked they will defend themselves e.g. by biting and
injecting venom if they are venomous. A few species of cobra (although only one is found in Liberia)
have evolved mechanisms to “spit” or rather spray venom to defend themselves against attackers,
although they can also bite and inject venom. The venom is sprayed towards the eyes and blinds the
attacker, giving the snake the chance to flee. This „spitting‟ is possible with the mouth nearly closed.
Page 5 of 22
2.
SNAKES
2.1
Identification of snakes
Identification of snakes can be difficult. To do this properly it is necessary to determine the presence
and number of certain scales on the snake‟s body. This requires the snake to be handled, and this is
not recommended. In addition, some snakes can feign death, lying on their back, opening their mouth
with their tongue out, and even by excreting small drops of blood, making handling of supposedly
dead snakes a risk as well. Other identifying features, besides scales, include internal organs, male
sexual organs (hemipenis), bones and teeth. To identify all these indicators with the available keys
(see Recommended Reading) it is necessary to undergo training, and therefore the non-specialist will
not be able to carry out effective identification. There are no general rules as to how to distinguish
between dangerous and harmless snakes, and every snake should therefore be considered
potentially dangerous and should not be approached or handled, other than by a specialist.
Most people will recognise a snake immediately. However, there are other limbless vertebrates such
as worm lizards (amphisbaenians), caecilians (snake-like amphibians) and lizards without legs. In
addition many blind snakes (families Typhlopidae or Leptotyphlopidae) are probably identified as
worms by most people.
2.2
What makes a snake dangerous?
Venom. Snake venoms are generally classified into two broad categories: cyto-hemotoxic and
neurotoxic. Many snake species possess mixtures of both categories but usually have larger
quantities of one than the other. Venom composition can change with age and the state of the snake.
Cyto-hemotoxic venom destroys cells and tissue and may also disable blood clotting. In the snake‟s
normal animal prey the venom causes fatal internal bleeding and systemic shock, whilst in human
victims it may lead to necrosis (tissue damage) and sometimes even death. Neurotoxic venom blocks
signal transmission of nerve cells, usually by blocking synapses. Thus snake bite victims die of
suffocation because their respiratory musculature ceases to work.
Venom delivery. Venomous snakes possess specially modified teeth (fangs) to deliver venom. Three
families found in Liberia have venom delivery systems that make their bites of particular medical
concern: the burrowing asps; the mambas, cobras and allies; and the vipers. Snakes in these three
families have hollow, syringe-like teeth (fangs) in the front of the mouth to inject venom into their prey.
Burrowing asps fold their teeth in when the mouth is closed. They unfold them sideways without
opening their mouth. This is an adaptive feature to their hunting behaviour. They hunt in narrow
rodent burrows where there is no space to open the mouth widely for biting. Thus, they erect a single
tooth with the mouth partially open and strike sideways, stabbing their prey. Mambas, cobras and
allies have small fixed fangs in the front of the mouth. Vipers have long front fangs which are hinged
and folded inwards. The largest group of snakes in Liberia, the colubrids (represented by four
families) are mostly harmless. Some colubrids are non-venomous and do not possess special teeth to
inject venom. Others have special teeth with simple grooves, located in the back of their mouth; these
are known as rear-fanged (or opistoglyph) snakes, and are often considered less dangerous to
humans because efficient venom delivery is impossible or at least difficult. In general they cannot
open the mouth far enough to inject venom directly into the blood stream of the victim, and in many
cases the venom itself does not cause much harm. However, some species of colubrids are
dangerous to humans, because they are larger and able to inject venom into the bloodstream, or
because they have stronger venom, or both. Five of these dangerous colubrids occur in Liberia, but
only two have caused recorded death.
Spitting. In Liberia one species of cobra can „spit‟ its venom. This is used as a defence mechanism
and is aimed at the victim‟s eyes.
Infection. Although it is non-venomous, the Rock Python can reach a sufficient size to pose a danger
to humans. It will bite readily when threatened, and bites can become seriously infected. This and
other non-venomous snakes can inflict deep bite wounds which can lead to severe infections,
especially if teeth break off in the skin.
Page 6 of 22
3.
PHOTOGRAPHIC GUIDE TO LIBERIAN SNAKES
The most commonly encountered snakes in Liberia are harmless colubrids, for example the African
Water Snake, the larger Smith‟s Water Snake, the herald snakes, the Striped and Green Keeled
Snakes, and other green snakes and file snakes. The large size of the latter is noteworthy because
they feed also on other snakes, including venomous species.
Blind snakes are small burrowing, worm-like snakes. They have poor vision, with eyes covered by
scales, and most feed on ant and termite eggs. They are completely harmless to humans. The larger
Calabar Ground Boa is also non-venomous.
The sections below illustrate and describe the main snakes that may be found.
3.1
Potentially life-threatening snakes
Western Green Mamba
(Dendroaspis viridis)
A large (1.8-2.2m long), snake with very large, blackedged green body scales and a golden tail, It is a fast
and shy snake often common in agricultural areas.
Lives high up in trees and palms, and is often mistaken
for other harmless, green coloured snakes
(Philothamnus, Hapsidophrys and Dipsadoboa). Bites
are rare. [neurotoxic].
Forest Cobra
(Naja melanoleuca)
A large (1.5-2.5m long) cobra with a stout head, thick
body and glossy body scale. It lives in forested areas
including regrown clearings. Spreads a narrow hood as
warning. [neurotoxic]
Spitting Cobra
(Naja nigricollis)
A large (1.5-2.1m long) dark cobra with glossy scales. It
occurs commonly in drier areas and agricultural areas,
but is absent from mature forest. Spreads hood as
warning before bite, and bites readily. Can spit its
venom over large distances (up to 2m) without
spreading hood. [cyto-hemotoxic]
Page 7 of 22
Black Tree Cobra
(Pseudohaje nigra)
A large (1.5-2.2m long) snake; head short with yellow
sides and black-barred lips; body black with white belly.
A true forest species, living in trees and so rarely
encountered. [no known bites but venom is probably
neurotoxic]
[No suitable picture was found, so this image shows
Gold‟s Tree Cobra (Pseudohaje goldii) which looks very
similar in colouration and scaling]
Nose-horned Viper or Rhinoceros Viper
(Bitis nasicornis)
Usually smaller (60-90cm long) than the West African
Gaboon Viper, but also has paired horns on snout;
head narrower with dark arrow shape on crown; body
with geometric pattern, but bolder and bluer. Only found
in forest, preferring humid to wet areas, often along
rivers. Relies on camouflage and does not flee
immediately. Generally a very calm snake which rarely
bites. [cyto-hemotoxic]
West African Gaboon Viper or Rhinoceros Viper
(Bitis rhinoceros)
A large (1.0-1.6m long), heavy bodied snake with a
broad, cream-topped head and paired horns on the tip
of snout; body scales have an attractive geometric
pattern. Frequently encountered in Liberia. Occurs in
secondary vegetation, agricultural areas and forests.
Relies on camouflage and does not flee immediately.
Generally a very calm snake which rarely bites.
However, has large venom fangs and can inject large
amounts of venom. [cyto-hemotoxic]
3.2
Potentially harmful snakes
Green Bush Viper
(Atheris chlorechis)
Small (30-50cm long) arboreal viper with a plump body
and triangular head covered with small scales; common
in forests and agricultural areas, and regularly
encountered. Bites can cause severe necrosis (tissue
damage). [cyto-hemotoxic]
Page 8 of 22
Forest Night Adder
(Causus lichtensteini)
Small (30-55cm long) ground living viper with a plump
green body and slightly triangular head covered on top
with large scales. Looks superficially like a greenish
colubrid snake. Occurs only in forested areas thus
rarely encountered. [cyto-hemotoxic]
Spotted Night Adder
(Causus maculatus)
Common small snake (40-60cm long) with a plump
brown body and slightly triangular head covered on top
with large scales in agricultural areas and in villages.
Has V-shaped mark on top of head. [cyto-hemotoxic]
Fat Burrowing Asp
(Atractaspis corpulenta)
Small (30-50cm long) burrowing asp; head short with
no obvious neck, grey to black body with a white tail tip.
Can be found in forested areas. Sometimes detected
while crossing roads or emerging after rains. [cytohemotoxic]
Variable Burrowing Asp
(Atractaspis irregularis)
Small (30-50cm long) burrowing asp, head short with
no obvious neck and with a uniform grey body.
Regularly encountered in agricultural areas. Sometimes
detected while crossing roads or emerging after rains.
[cyto-hemotoxic]
Page 9 of 22
Boomslang
(Dispholidus typus)
A large (up to 2m long), slender, strictly arboreal snake.
Head roundish with very big eyes, keeled scales to
body (i.e. with a ridge down the centre of each scale);
can be confused with other tree snakes (see below),
but body usually olive to green. In general, a fast, docile
snake but with a potent venom. [cyto-hemotoxic]
Forest Vine Snake
(Thelotornis kirtlandii)
Large (90-130cm long), very slender and fast snake,
with long, thin, green-topped head and large eyes.
Inflates its neck and displays tongue when threatened.
Has horizontal pupils and excellent 3D vision. [cytohemotoxic]
Black Tree Snake
(Thrasops occidentalis)
Large (1.0-1.5m long) snake with large eyes; adults all
black, juveniles with brown, yellow pattern. Arboreal
and rarely encountered.
Blanding’s Tree Snake
(Boiga blandingii)
Very large (2.2.4m long) snake, with brown, darkbanded body and velvety scales; gapes readily when
threatened. [neurotoxic]
Page 10 of 22
Powdery Tree Snake
(Boiga pulverulenta)
A large (80-120cm long), thin snake, with velvety body
scales; very similar to previous species but with light
brown body and dark brown, sometimes white-centred
bands. A very common and regularly encountered
snake in Liberia. Also gapes readily when threatened.
[probably neurotoxic]
Rock Python
(Python sebae)
A very large snake (up to 7 m long) with triangular head
and heavy body with small scales. It often lives along
water courses. Non-venomous, but may be dangerous
to humans because of its size. Bites readily when
threatened. Now rarely encountered because, like the
large vipers, it is commonly hunted for food by people.
[not venomous, but bite site can become seriously
infected]
3.3
Harmless snakes

African Water Snake
(Afronatrix anoscopus)
Smith’s Water Snake
(Grayia smithii)
Page 11 of 22
Herald Snake
(Crotaphopeltis hotamboeia)
Green Keeled Snake
(Hapsidophrys smaragdinus)
Striped Keeled Snake
(Hapsidophrys lineatus)
Green Snake
(Philothamnus irregularis)
Page 12 of 22
Savannah File Snake
(Gonionotophis crossi)
Plain Cat Snake
(Dipsadoboa unicolor)
3.3
Other dangerous snakes which probably do not occur in Liberia
There is some uncertainty about whether some species occur in Liberia or not. The list below names
the dangerous species that, according to some existing literature, do occur in Liberia, though there
are no scientifically confirmed sightings.
Potentially life threatening species:
Black Mamba (Elapidae Dendroaspis polylepis)
A large (2.0-2.5m long), dull grey snake with a flat-sided head and black inner mouth, gapes when
threatened. Restricted to dry savannah and few West African records exist [neurotoxic]
Senegal Cobra (Elapidae Naja senegalensis)
(Previously confused with the Egyptian cobra, Naja haje) A large (1.1-1.4m long) cobra with broad
head and suboculars (small scales between eye and lip scales); body a uniform grey-brown, with
black bands below neck. It occurs in dry savannahs. [neurotoxic]
Puff Adder (Viperidae Bitis arietans)
A large (70-100cm long), heavy bodied viper that lacks horns on the snout; body brown with chevron
pattern. Found in drier, savannah regions. Hisses and puffs loudly as a warning when threatened.
Relies on camouflage and does not flee immediately. [cyto-hemotoxic]
Potentially harmful species:
Garter Snake (Elapidae Elapsoidea semiannulata)
Small (40-70cm long) burrowing snake with banded body. Restricted to drier regions. [neurotoxic]
Rhombic Night Adder (Viperidae Causus rhombeatus) – similar to Causus maculatus.
[cytohemotoxic]
Yellow-throated Bold-eyed Tree Snake (Colubridae Thrasops flavigularis) – similar in
appearance to the other Thrasops species, colour yellow and green.
Page 13 of 22
4.
SNAKE BITES
4.1
General information about snake bites
Do not molest or harm snakes. Nearly every snake can bite and will do so if it feels threatened. Even
harmless snakes can inflict deep wounds, and teeth that break off in the skin can lead to severe
infections. Most snakes bite faster than a human can pull its hand away.
In general, snakes are shy and secretive. Incidents with humans are uncommon and happen usually
accidentally, such as when stepping on a snake or by uncovering a snake when moving objects, such
as household rubbish bins. In some cases snake bites result from the victim trying to catch or kill a
snake. The vast majority of bites occur in rural areas during agricultural activities (40-54%) or during
travelling on foot in rural areas (19-24%). In rural areas people also rarely wear gloves or appropriate
footwear. Around 87% of all bites happen below the knee and around 67% below the ankle. Other
bites are often on hands and wrists (8%), and are rarely on other parts of the body. Snake bites vary
between eco-regions, landscapes and seasons.
A study of snakebites at the Firestone Rubber Plantation in Liberia gives some perspective (Stahel
1980). The number of snakebites per 1000 people in one year was 1.5 overall, and 4.2 for field
employees working in the plantation. In 93% of cases, patients were bitten on the feet. In over a
quarter of cases, there were no symptoms of poisoning. In a further two-thirds of cases, there was
only local swelling and pain. Most of these bites were from Spotted Night Adders (see image in
Section 3.2). Fewer than 5% of snakebite victims (four out of 95 reported bites) had serious medical
complications, and none of these resulted in death. These more serious bites were caused by the
Forest Cobra and West African Gaboon Viper (see images in Section 3.1).
The seriousness of the outcome of a snake bite is closely linked to the quality and access to health
care, which is often poor in rural areas. In addition, inappropriate first aid measures are often applied.
Unfortunately, antivenin when available is very expensive, and in serious cases can amount to
thousands of US dollars where large quantities of antivenin are required.
With good health care and suitable first aid measures snake bites are treatable. Most snake bites can
easily be prevented with proper procedures (see „Preventing Snake Bites‟).
4.2
Factors affecting the outcome of a snake bite
Every snake bite is unique. The outcome of a snake bite depends on:
 The location on the body of the bite (e.g. a bite to the neck is worse than a bite on the finger).
 The general state of health of the victim (e.g. sick and old people or children will experience
more problems after a snake bite than healthy, fit adults).
 Whether the victim has been bitten previously (as with other substances, many people either
are directly or can become allergic to snake venom. Thus, a snake bite could sensitise a
person, triggering an allergic reaction, thereby resulting in a much worse outcome the second
time).
The outcome also depends on the snake:
 The health or age of the snake.
 When it last fed.
 The state of its teeth (fangs), i.e. whether they are functional or broken.
 Whether venom is injected and in what quantity.
Snake venom changes with the age and health of the snake. Even venom from the same snake can
differ between the right and left venom glands. As mentioned above, snakes can control the amount
of venom they inject. Thus not every bite necessarily delivers venom – it may be what is called a „dry
bite‟ – and even if venom is injected, the amount differs. This is an important medical consideration
because it means that not every snake bite, even by a venomous snake, leads to envenomation.
Page 14 of 22
4.3
First aid in the event of a snake bite
In the event of a snake bite the following behaviour and measures should be adopted.
Action by the victim
a) Do not panic.
Many people suffer severe shock when bitten by a snake. This alone may present risks, including
heart attacks. Remember that nearly 50% of all snake bites result in no symptoms at all, and that
even venomous snakes give „dry bites‟ (with no venom).
b) Remove all tight objects from the bitten limb.
These include rings, bracelets, watches, clothes, shoes which might cause problems during swelling.
c) Let the bite bleed freely for some minutes (but do NOT suck the wound).
d) Apply a Pressure-Immobilisation (PI) bandage.
Carry a PI bandage at all times. It will also be useful for ankle sprains, should they occur. Following a
snake bite, apply the bandage properly (see Figure 4). The aim is to prevent the flow of the lymph and
NOT to restrict blood flow. Be aware that this is mainly recommended for species which possess
neurotoxic venom (most elapids, see 2.5) and it should not be used for bites from snakes with venoms
that lead to swelling and necrosis (cyto-hemotoxic venom; this includes most vipers: see Sections 3.1
and 3.2). However, snake venoms are often a mixture of both, and in remote areas if bitten by a cytohemotoxic venomous snake, the question of „life or limb‟ could arise. Applying a PI to a cytohemotoxic (viper) bite elevates the risk of limb loss; but not applying one might increase the chance of
death.
The bandage should be semi-elastic, applied firmly but not with too much pressure. Use a splint if
possible to stabilise the limb and avoid unnecessary exhaustion, keep the limb immobile after
application, monitor that blood is still flowing in and out of the affected limb, e.g. by checking the
colour of the skin (this should remain “normal” and not become purple); and temperature of the
affected digits to ensure that swelling does not make the PI too tight, such that it becomes a
tourniquet. Upon arrival at hospital the release of the PI bandage should be slow and monitored, in
case a surge of venom enters the blood stream.
e) Stay calm.
Do not move around and especially do not run around excitedly. Do not run or undertake physical
exercise (carry heavy loads, walk long distances or climb, etc.). Ask others for help, both in terms of
alerting medical assistance and in applying the PI. The repetition is important: Do not panic! Stay
calm!
f) Get transport to hospital.
Stay where you are. Call for assistance if you possibly can. Ask others to organise transport to
hospital. Do not walk or drive yourself unless there is no option. Ask those with you to carry you to a
vehicle and then drive you to a hospital or medical facility.
g) Drink water.
Drinking water helps the victim to stay calm and reduces the likelihood of shock.
h) Pain relief.
For pain relief, 1g Paracetamol can be taken. Other pain killers should not be taken without medical
supervision.
Page 15 of 22
Correct application of pressure immobilization (PI) technique. The aim is to allow blood to flow but to
prevent flow of lymphatic liquid (flows underneath the skin).
Action by the helpers
a) All measures should be taken to calm the victim.
These might include harmless measures associated with superstition, such as “black stones” or other
snake stones. While they do not have any effect on the venom, if their application reassures the victim
and prevents shock, then they can be considered as useful, as long as the first aid measures listed
above are adhered to.
b) Be prepared to apply resuscitation measures.
Neurotoxic venoms block nerve signal transmission and therefore cause respiratory failure. The best
and most effective counter measure is mouth-to-mouth breathing, either unaided or aided e.g. via bag
valve masks. Monitor breathing very closely throughout transport of the victim, and check for signs
that may indicate the onset of neurological symptoms, such as limb weakness. In case of respiratory
failure or difficulties, clear respiratory pathways, and keep artificial breathing in progress until hospital
is reached and medical staff take over.
c) Try to ensure that the hospital and paramedics are informed of the incident before
transport to hospital starts. Arrange transport to hospital as quickly and as safely as
possible.
d) The victim should stay in hospital under close surveillance, and be checked at least every
hour, for a minimum of 24 hours.
The onset of snake bite symptoms can be delayed, depending on how quickly the venom enters the
blood circulation. If no symptoms develop after 24 hours and all medical parameters are normal the
victim can be discharged. In this case the bite was either from a harmless snake or the victim luckily
received a „dry bite‟ (see above).
What not to do
Many supposed snake bite treatments are useless and may even do more harm. The following should
not be undertaken.
a) Do not drink alcohol or any other liquids which stimulate blood circulation (e.g. coffee or
tea).
So-called snake bite remedies to be taken orally do not work and should not be taken.
b) Do not take any other medication (e.g. painkillers).
Page 16 of 22
c) Do not incise or suck the bite.
Generally the venom is injected by the snake too deeply and spreads too quickly for such methods to
remove any significant amounts of venom. This includes the numerous snake bite kits sold with
cutting blades and suction caps. All are ineffective and by cutting and creating open wounds they
increase the risk of infection.
d) Do not cool or heat the bite.
e) Do not use electric voltage.
Electric shocks do not affect the venom and only make conditions more painful and uncomfortable for
the victim.
f) Do not go to a traditional healer.
Traditional healers are an important part of culture throughout the world, including Liberia, and many
possess valuable knowledge that allows them to cure many ailments. However, all tested remedies by
traditional healers for snake bites have been shown to have either no effect or negative effect.
Because the vast majority of snake bites are harmless, the impression is given that traditional
remedies work, when in fact they are unnecessary.
g) Do not administer antivenin without a doctor unless the snake bite is life threatening.
Antivenin regularly causes severe allergic reactions (anaphylactic shock). This alone can kill a patient,
even when bitten by a harmless snake. Thus antivenin must be used very carefully under medical
supervision with the proper countermeasures at hand. Medical staff have to monitor life functions
regularly (various blood parameters, breathing, kidney function, etc.) and only apply antivenin if the
thresholds are reached which indicate an acute life threatening situation.
h) Do not apply a tourniquet.
A proper tourniquet will stop blood flow and will cause additional damage to the limb. Its use should
only to be considered in very remote places, where medical help is more than half a day away. While
the use of a tourniquet in this situation may damage the limb, it may also save the victim‟s life.
i) Do not try to catch the snake.
The majority of medical staff are untrained in identifying snakes. Do not therefore risk further snake
bites by trying to kill the snake for later identification. Instead take a photograph if possible, from a
safe distance. Most antivenins are polyvalent, and therefore react with venom from different snake
species. Medical treatment should always be guided by the onset and type of symptoms that occur.
4.4
Spitting snakes
Venom in the eye is very painful and if untreated can seriously damage the cornea, causing
permanent blindness. First aid measures include washing the eyes with large quantities of neutral
liquid (preferably clean water) but where there is no clean water available use any safe liquid (e.g.
milk, vegetable oil, etc). Do not use acid or alkaline liquids, or other dangerous liquids such as petrol
or kerosene. Wash the eyes for at least 30 minutes. Go immediately to a hospital or clinic to have the
eyes checked and receive further treatment (washings) if necessary.
Venom on the skin or on clothing does no harm, unless it can enter the blood stream via scratches or
other injuries.
4.5
Standard safety measures
Personnel working outside the office should be supplied with proper footwear, gloves and safety
goggles. The health and safety induction and drills should cover snake encounter situations, how to
behave when encountering a snake, and how to respond to a snake bite from the perspective of a
victim, helper and first aider, as outlined in the sections above.
Page 17 of 22
It is important that special “snake courses” are given regularly to all site staff by appropriately qualified
trainers to raise awareness of snakes and human behaviour that will help to avoid or minimise snake
bites, as well as appropriate first aid measures. Special courses should also be given to medical and
environmental staff to develop or enhance snake identification skills and the treatment of snake bites.
4.6
Removal of snakes
Snakes should only be removed by trained and properly equipped personnel. All snakes should be
treated as if they are dangerous, even though most are not.
There are two regularly observed methods of catching snakes. Both are dangerous and should be
avoided. Either the snake is grabbed by the tail or at the neck, directly behind the head. Besides the
stress to person and snake, as well as the high likelihood of injuring the snake, both methods have
serious disadvantages. Grabbing the tail is dangerous because the snake can twist around and bite a
holding hand. The snake can also turn and bite towards the feet and body of the person holding it.
Grabbing behind the head is dangerous because snakes with mobile, erectile fangs can move parts of
their flexible jaws and bite the hand or fingers.
The best methods for removing snakes are those where no direct physical contact with the snake is
required. This includes the use of hooks, tongs, bags and tubes. However, a qualified specialist is
required to apply these methods safely, and even then a degree of risk is involved.
Page 18 of 22
5.
CHECKLIST OF SNAKES OF NIMBA COUNTY, LIBERIA
Species in bold are those which have been verified from Nimba County (34 species). Species not in
bold are speculated to occur based on what is known of their distribution and habitat requirements (23
species). Species with names in red are potentially life-threatening, while those in orange are
potentially harmful but not normally life-threatening.
Family
English name
(family or
group)
English name (species)
Afrotyphlops manni
Mann„s Blind Snake
Afrotyphlops punctatus
Spotted Blind Snake
Boids
Calabaria reinhardti
Calabar Ground Boa
Pythons
Python sebae
Rock Python
Aparallactus lineatus
Lined Centipede Eater
Aparallactus modestus
Giant Centipede Eater
Aparallactus niger
Black Centipede Eater
Atractaspis irregularis
Variable Burrowing Asp
Atractaspis corpulenta
Fat Burrowing Asp
Polemon acanthias
Reinhardt’s Snake-eater
Boiga blandingii
Blanding„s Tree Snake
Boiga pulverulenta
Powdery Tree Snake
Crotaphopeltis hippocrepis
Smooth-scaled Herald Snake
Crotaphopeltis hotamboeia
Herald Snake
Dasypeltis fasciata
Forest Egg-eater
Dasypeltis parascabra
West African Egg-eater
Dipsadoboa brevirostris
Green Cat Snake
Dipsadoboa underwoodi
Underwood‘s Cat Snake
Dipsadoboa unicolor
Plain Cat Snake
Dipsadoboa weileri
Weiler„s Cat Snake
Dispholidus typus
Boomslang
Grayia smithii
Smith’s Water Snake
Hapsidophrys smaragdinus
Green Keeled Snake
Hapsidrophys lineatus
Striped Keeled Snake
Meizodon regularis
Crowned Snake
Philothamnus heterodermus
Slender Green Snake
Philothamnus irregularis
Green Snake
Rhamphiophis aethiopissa
Beautiful Tree Snake
Thelotornis kirtlandii
Forest Vine Snake
Thrasops occidentalis
Black Tree Snake
Typhlopidae
Blind snakes
Boidae
Pythonidae
African
Atractaspididae Burrowing
Snakes
Colubridae
Scientific name
Colubrids
Page 19 of 22
Family
Lamprophidae
Natricitidae
English name
(family or
group)
Colubrids
Colubrids
Psammophidae Colubrids
Elapidae
Viperidae
Mambas,
cobras and
allies
Vipers
Scientific name
English name (species)
Bothrophthalmus lineatus
Red-black Striped Snake
Chamaelycus fasciatus
Forest Wolf Snake
Gonionotophis crossi
Savannah File Snake
Gonionotophis guirali
Mocquard„s File snake
Gonionotophis klingi
Slender File Snake
Gonionotophis poensis
Forest File Snake
Gonionotophis stenophthalmus
Small-eyed File Snake
Hormonotus modestus
Slender Night Snake
Boaedon fuliginosus
Black House Snake
Boaedon lineatus
Lined House Snake
Boaedon olivaceus
Olive House Snake
Boaedon virgatus
Forest House Snake
Lycophidion irroratum
Wolf Snake
Lycophidion nigromaculatum
Black-spotted Wolf Snake
Lycophidion semicinctum
Wolf Snake
Afronatrix anoscopus
African Water Snake
Natriciteres variegate
Variegated Marsh Snake
Psammophis philllipsi
Sand Snake
Dendroaspis viridis
Western Green Mamba
Naja melanoleuca
Forest Cobra
Naja nigricollis
Spitting Cobra
Pseudohaje nigra
Black Tree Cobra
Atheris chlorechis
Green Bush Viper
Bitis nasicornis
Nose-horned Viper /
Rhinoceros Viper
Bitis rhinoceros
West African Gaboon Viper
Causus lichtensteini
Forest Night Adder
Causus maculatus
Spotted Night Adder
Page 20 of 22
6.
REFERENCES
6.1
Recommended reading
Buys, P.J.C. (2003). Medical management of snakebite in Namibia. Gamsberg Macmillan Publishers,
37pp.
Chippaux, J.-P. (2002). Venins de serpent et envenimations. IRD Éditions, 288pp.
Chippaux, J.-P. (2006). Les serpents d‟Afrique occidentale et central. IRD Éditions, 311pp.
Meirte, D. (1992). Clés de détermination des serpents d‟Afrique. Annalen Zoologische
Wetenschappen 267: 1–152.
Stahel, E. (1980) Epidemiological aspects of snake bites on a Liberian rubber plantation. Acta Tropica
37: 367–374.
Uetz, P. & Hošek, J. (2013). (Eds.) The reptile database, www.reptiliaweb.org.
Villiers, A. (1975). Les serpents de l‟ouest Africain. Université de Dakar, Institut Fondamental
d‟Afrique Noire, Les Nouvelles Éditions Africains, 195pp.
United States Environmental Protection Agency. Lethal Dosage Values.
http://www.epa.gov/agriculture/ag101/pestlethal.html
6.2
Photo sources
All by Johannes Penner, apart from those labeled on the relevant photographs, and:
Figure 3 C - http://www.flickriver.com/photos/20644495@N05/3472281974/
Figure 3 D - http://www.megasphera.cz/africanvenomoussnakes/images/uvod_personal/
fotografie/foto_jed%20hadi%20Afr/Pseudohaje%20goldii_V.jpg
Figure 4 - http://emedicine.medscape.com/article/771918-treatment
Page 21 of 22
If you are bitten by a snake,
DON’T PANIC!
Very few snake bites actually
poison the victim
But you must seek medical
assistance just to be sure
Page 22 of 22

A Guide to the Snakes of Liberia

Transcription

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