Sunday, March 13, 2011

poisonous snakes in malaysia

1. Poisonous Snakes of Malaysia
1.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, Laticaudinae, Hydrophiinae, 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.

2. 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.

3. The Malayan cobra (Naja naja sputatrix) and monocellate cobra (Naja naja kaouthia)
There are two subspecies of Asian cobra (Naja naja) in Peninsular Malaysia: Malayan cobra (Naja naja sputatrix) and monocellate cobra (Naja naja kaouthia).
The species found throughout most of Peninsular Malaysia is Malayan cobra. The snake is brown or black usually with some white marks on the throat. Average length 1-1.25 m, maximum about 1.5 m. This species of cobra has the habit of spraying or `spitting' venom. Batchelor (1958) reported: ‘I have known several instances of dogs being temporary blinded by venom but not one instance of one being killed.’
                     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

In 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)

4.  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
5. 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 poisoning.  

6. 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)

7.  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.

8.  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 actions.
      This is the commonest species of sea snake in Malaysian waters and also the most aggressive species (Reid, 1979). Other common Malaysian sea snakes include Hydrophis cyanocinctus, Hydrophis spiralis and Hydrophis klossi.      
                                                                                  Notice the nostril with beak-like appearance. 
9.  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 rhodostoma.  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).

10. Speckled pit viper (Trimeresurus wagleri)
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 snake is abundant in lowland, primary forest and secondary forest. It is often seen climbing in low bushes. During the day it is sluggish and docile, quite rough handling being needed to persuade it to bite! The bite can cause severe pain and local swelling. This is the species that is displayed at the Snake Temple at Penang, Malaysia.
The Speckled Pit Viper (adult)


                 A young Speckled Pit Viper

11.  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.

12. White-lipped tree viper (Trimeresurus albolabris)
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.

13.  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.
                                             with bright green colour with black stripes