Medically Important Poisonous Snakes of Malaysia
Tan, Nget Hong
of Molecular Medicine
of Medicine, University of Malaya
is a serious public health problem in Malaysia. Approximately 55000
snakebite cases were admitted to the hospitals in Malaysia during the
period 1958 to 1980. (Lim and Ibrahim, 1970; Lim, 1982a). While the
mortality rate of snakebite in Malaysia is very low (0.3 per 100000
population), the venoms can cause prolonged morbidity. The symptomatology
and treatment of snakebites in Malaysia have been well documented (Reid,
1986). The systematics and zoogeography of the Malaysian poisonous
snakes have been described (Lim, 1982b, Tweedie, 1983). The present paper
is only a brief account of the medically important poisonous snakes of
Poisonous Snakes of Malaysia
Poisonous snakes are usually
classified into 3 families: Colubridae, Viperidae and Elapidae (Underwood,
1979). Only the front fanged poisonous snakes, the Viperidae and Elapidae
are medically important. Viperidae
is subdivided into three subfamilies: Azemiopinae,
Viperinae (viper) and Crotalinae (pit viper), while Elapidae
consists of five subfamilies: Elapinae,
Ephalophiini and Hydrophiini.
In Malaysia and its coastal waters, there are at least 40 species of front fanged poisonous snakes, of which 18 are land snakes and more than 22 are sea snakes (Tweedie, 1983). The land snakes include the two subfamilies Crotalinae (represented by the two genera Calloselasma and Trimeresurus) and Elapinae (represented by the five genera Naja, Bungarus, Ophiophagus, Maticora and Calliophis); whereas the sea snakes include three subfamilies: Laticaudinae, (represented by the genus Laticauda); Hydrophiini (represented by the six genera Enhydrina, Kerilia, Hydrophis, Thalassophis, Pelamis and Kolpophis) and Ephalophiini (represented by the only genus Aipysurus). However, only a few of the Malaysian poisonous snakes can be regarded as of medical importance. The studies by Reid et al (1963) and Sawai et al (1972) both indicated that snakebites in Malaysia were mainly due to four species of land snake, i.e., Calloselasma rhodostoma (Malayan pit viper), Naja naja (Asian common cobra), Trimeresurus purpureomaculatus (shore pit viper) and Trimeresurus wagleri (Wagler's pit viper). Other potentially dangerous poisonous snakes are Bungarus candidus (Malayan krait), Bungarus fasciatus (banded krait), Ophiophagus hannah (king cobra), Trimeresurus albolabris (White-lipped tree viper), Trimeresurus sumatranus (Sumatran pit viper) and the sea snakes.
Composition of snake venoms
Snake venom contains mainly proteins (70-90%) and small amounts of metals, amino acids, peptides, nucleotides, carbohydrates, lipids and amines (Tu, 1977). The protein components include enzymes and non-enzymatic proteins. Venoms of many elapid snakes (cobra, krait and sea snakes etc) produce flaccid paralysis and respiratory failure in animals. These effects have been attributed to the polypeptide postsnayptic neurotoxins of the venoms (Lee, 1972). Some krait and sea snake venoms also contain phospholipase A2 that exhibit presynaptic neurotoxic action. Another major toxic component in cobra venoms is polypeptide cardiotoxin. On the other hand, venoms of many crotalid snakes contain thrombin-like enzymes and proteolytic enzymes that exhibit hemorrhagic activities and other enzymes that affect blood coagulation system.
The Malayan cobra (Naja naja
sputatrix) and monocellate cobra (Naja
There are two subspecies of Asian
cobra (Naja naja) in Peninsular Malaysia: Malayan cobra (Naja
naja sputatrix) and monocellate cobra (Naja
The Malayan cobra: Notice the white mark on the throat
|A ‘baby’ Malayan cobra captured in the forest near the Faculty of Medicine, University of Malaya. It has to be kept in a bottle. Never closely inspect a spitting cobra confined behind wire netting! Injury to the eyes by the venom of a spitting cobra is extremely painful and an unpleasant experience|
the northern states, the common species found is monocellate cobra (Naja
naja kaouthia). It is grey brown or black with throat almost white. On
the back of the hood there is a centrally placed white circle.
The cobra is not an aggressive snake
and will always do its best to avoid encounters with humans. If cornered
it will give its warning display (with its hood ‘spread’) and possibly
attack. Young cobras are said to be more aggressive. The cobra is a common
snake throughout Malaysia. In 1984, a baby Malayan cobra was captured in
the forest adjacent to the Faculty of Medicine (see above picture),
University of Malaya, right in the centre of a modern urban area!
Venoms of N.n.sputatrix and N.n.kaouthia are immunologically different: the monospecific antivenom raised against N.n.sputatrix venom was ineffective against N.n.kaouthia venom (Theakston and Reid, 1983), suggesting that there are important differences in the toxin composition of the two cobra venoms (Tan and Tan, 1988). Both venoms contain substantial amounts of polypeptide neurotoxins and cardiotoxins.
The monocellate cobra (Naja naja.kaouthia)
The King cobra (Ophiophagus hannah)
King cobra is olive brown or
greenish yellow and its great size is an important recognition feature.
Adults can attain a length of 4.8-5.4 m.
A unique feature of the species is the presence of large occipital
shields. It is found throughout the whole of Malaysia in forest and in
populated areas. The snake is not aggressive. Tweedie (1983) reported:
‘The only hamadryad (king cobra) I have ever encountered in the wild was
crawling along in a dry ditch by a forest path in Kelantan. I bent down
until I could clearly see the occipital shields and then, I admit, stepped
smartly backwards. It took no notice of me, not even raising its head.”
If cornered, however, the king cobra
can be extremely dangerous because of the large amount of venom it is
capable of delivering in a bite. When angry they give a deep resonant hiss
similar to the growl of a small dog. King cobra bite in man appears to be
infrequent. The main systemic effect of king cobra venom bite appears to
be neurotoxic poisoning (Ganthavorn, 1971).
Note the characteristics two occipital shields (shaded)
Handling the king
cobra with care
The King Cobra
The Banded krait (Bungarus fasciatus)
Banded krait is a common krait
throughout Southeast Asia. It has a pattern of alternating light (usually
yellow) and dark bands encircling the body. Its average length is 1.2-2.1
m. It is a quiet snake and
inoffensive in disposition, flinching convulsively and hiding its head in
its coils if molested. If you encounter one, do not trifle with it, just
leave it alone. Bites by banded krait are very rare. It causes neurotoxic
The Malayan krait (Bungarus candidus)
Malayan krait is black above with about thirty white cross-bands in body and tail. This snake is 1-1.5 m in length. It is wide distribute but rare. Malayan krait bite may cause severe neurotoxic envenomation in man (Warrell et al., 1983)
The Red-headed Krait (Bungarus flaviceps)
Red-headed krait is a rare snake, mostly found in mountain or foothill forest. It is a snake with very striking and distinctive coloring: it is blue black above with the head, neck and tail bright red. The venom exhibited neurotoxic activity.
The Beaked Sea Snake (Enhydrina schistosa)
The beaked sea snake is uniformly dull
olive green above or pale greenish grey with dark cross-bands that tend to
fuse anteriorly; cream on sides and belly. Average adult length 1-1.3 m.
It is a shallow sea snake. The nostril in front gives a characteristic
beak-like appearance. The venom exhibited both neurotoxic and myotoxic
Notice the nostril with beak-like appearance.
The Malayan Pit Viper (Calloselasma rhodostoma)
Malayan pit viper (Calloselasma rhodostoma) was previously known as Agkistrodon rhodostoma or Ancistrodon rhodostoma. The snake is reddish or purplish brown with series of dark brown crossbands. Head triangular, snout pointed with facial pit. It is the only Asian pit viper with large scales on the crown (see picture). The average length of the snake is 0.6-0.8 m
Comparing the heads of Calloselasma
rhodostoma (left) and Trimerresurus (right).
Note the large scale on the crown of the Calloselasma
Notice the loreal pit between the eye and the nostril. It is a thermosensitive organ
The Malayan pit viper is a bad tempered snake, quick to strike if
disturbed. In Malaysia, it is confined only to the northern states of
Kedah, Perlis and Penang but is the commonest cause of snakebite in
Peninsular Malaysia. The snake is remarkably sedentary, and not unusual to
be found at the site of an attack after several hours. It is known in
Malaysia as ‘Ular Kapak Bodor; --the ‘stupid viper’. It earned the
reputation of being ‘stupid’ because the snake usually remains at the
site of biting and hence usually killed.
The principal characteristics of systemic Malayan pit viper venom poisoning is systemic bleeding characterized by defibrination and thrombocytopenia (Reid et al. 1963b).
Speckled pit viper (Trimeresurus
The adult Speckled pit viper (below,
left) is black with scattered green spots above, crossed by numerous croo-bars,
green above, yellow on the sides. Young (below, right) is green with
regularly spaced spots. Brattstrom (1964) argued that Trimeresurus
wagleri has many morphological characteristics that distinguish it
from other species of Trimeresurus
and as such he puts this species in the subgenus Tropidolaemus.
The Speckled Pit Viper (adult)
A young Speckled Pit Viper
Shore pit viper (Trimeresurus purpureomaculatus)
Shore pit viper (also known as
mangrove pit viper) is a lowland snake and is very numerous in the
mangrove and swamp forests.The colour of shore pit viper is variable. One
common variety is purplish brown. Average length is 0.7-0.9 m. It is a
fairly common cause of snakebite in costal region but fatalities were
rare. The venom exhibits moderate procoagulant activity.
White-lipped tree viper (Trimeresurus
White-lipped tree viper occurs in East Malaysia. The upper lip is pale green,yellow or white. The body is greenish with an average length of 0.4-1 m. In severe white-lipped tree viper venom poisoning, hemorrhage, defibrination and thrombocytopenia.
Sumatran pit viper (Trimeresurus sumatranus)
The Sumatran pit viper is found in forest in inland localities. It is green with dark cross-bands and grows to over one meter. The venom contains procoagulant activity.
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