Monday, December 14, 2009

TEN Interesting Facts About Venomous Snakes in Malaysia That You May Not Know

While researching for facts for a First aid book manuscript by my colleauges and I, I have stumbled upon many interesting facts about venomous snake bites in Malaysia. I have compiled them and placed them in this blog post. Free reference resources that I have used are found at the end of this blog post.

1. Most snakes in Malaysia are harmless to human
17 out of the 105 strictly land snakes are venomous
Even bites of venomous snakes are not life threatening in humans unless sufficient venom is injected at the time of bite. In fact, most are dry bites. The problem, however, is the accurate identification by the witnesses. Because we are not sure whether the snake is venomous or not, coupled with the fact that there is no simple physical features criteria to differentiate venomous from non-venomous snakes, the victim should be treated with vigilant medical care for the benefit of doubt.

2. All sea snakes in Malaysia are venomous, they are powerful and dangerous to human.
All 14 species of fresh water snakes are harmless but all 22 species of sea snakes are venomous

Most sea snakes live along shallow coastal water and therefore, fishermen is the group of people most at risk to be bitten by sea snake.
Enhydrina schistosa

Enhydrina schistosa is the most common and dangerous sea snakes along the coast and in river mouths of Peninsular Malaysia. This may surprise some people, but the venom of this snake is rated four to eight times as toxic as cobra venom.

3. Unfortunately, sea snake bites have little or no pain, and no edema (or only with a mild local reaction) at the site of bite. (On the contrary, fish stings are painful).

4. According to many studies, most (about 2/3rd) of the snake bites in Malaysia are due to the Malaysian pit viper bites.
And about 75% of these cases are confined to the northern states of Perlis, Kedah and Penang.
Snake bites are twice as common in males as in females, and it commonly affects the age group of 10 - 19 years old.

5. A peculiar characteristic of the Malayan pit viper is that it will not easily move away, but rather will stay on at the same spot despite several hours after the attack, and therefore, it can be easily found!!

This earn the Malayan pit viper the Malay name "ULAR KAPAK BODOH" (translated as "the dumb pit viper") [click here to read the article "The Medically Important Poisonous Snakes In Malaysia" by Prof Tan Nget Hong]

Triangular head of the Malayan pit viper

Contrary to what many people believe, the King Cobra is actually not an aggressive snake. In fact, it keeps out of people's way.
It only attack when provoked, or accidentally stepped on. And
if cornered, the king cobra can be extremely dangerous because of the large amount of venom it is capable of delivering in a bite.

7. On the other hand, the Malayan pit viper, although a "dumb" snake, it is a bad tempered snake, quick to strike if disturbed.

8. One should not assume that bites from the young, small or baby snakes are less harmful.
Quite the contrary! According to the WHO management guidelines for snake bites in South East Asia region (see link below for free download of this excellent manual), although large snakes tend to inject more venom than smaller specimens of the same species, the venom of smaller, younger vipers may be richer in some dangerous components, such as those affecting haemostasis. Therefore, bites by small snakes should not be ignored or dismissed. They should be taken just as seriously as bites by large snakes of the same species.

In fact, there is a legend that says that the young snakes have not yet learned how to control the amount of venom they inject. They are therefore more dangerous than adult snakes, which will restrict the amount of venom that accompanies a bite. It’s repeated so often that it’s become a sort of mantra among laypeople and biologists alike!

Whether this legend is true or not is beyond the scope of this medically focused post as this is more of a herpetology question (for a more extensive discussion of this questionable nature of baby snake, click here for this blog post). But suffice to summarily say here (to borrow the argument from that blog post), that for this legend to be true, the follow four assumptions must also be answered:

  1. this means that snakes are able to control the amount of venom they inject?
  2. this means that there is some disadvantage to a snake when it injects all of its venom in every bite? (otherwise why not inject all of their venom all of the time?)
  3. and as a result, as the snake mature, the snake learns of the disadvantages of injecting all venoms and therefore, change its behavior?
  4. a full envenomation from a young snake maybe more dangerous than a partial envenomation from an adult snake?

9. There is no simple rule to differentiate a venomous snake from a non-venomous snake although certain features are notoriously seen in venomous snakes like a spreading hood in cobra, a triangular head and Loreal pits between the eyes and the nostril of a pit viper, the pair of sharp fangs as well as the more elliptical eyes as compared to the rounded eyes of non venomous snakes. Nevertheless, some harmless snakes have evolved to look almost identical to venomous ones.
The pair of fangs, spreading hood and elliptical eyes of a king cobra

The loreal pits colored red - an infrared sensor organ

10. Do not handle a dead snake as reflex envenomation by the decapitated head of the snake can still occurs up to several hours after its death!! In a website, it is quoted that reflex envenomation causes up to 3% of snake bites.

Free Resources:
1. FREE Download of "The Clinical Management of Snake Bites In The South East Asia Region" by the WHO. Click here.

2. FREE Download of "Ministry of Health Malaysia Clinical Protocol Management of Snake Bite". Click here.

3. Jamaiah I, Rohela M, Roshalina R et al. Prevalence of snake bites in Kangar District Hospital, Perlis, west Malaysia: a retrospective study (January 1999-December 2000). Southeast Asian J Trop Med Public Health 2004; 35 (4):962-5. Click here to download FREE pdf copy.

4. Jamaiah I, Rohela M, Ng TK et al. Retrospective prevalence of snakebites from Hospital Kuala Lumpur (HKL) (1999-2003). Southeast Asian J Trop Med Public Health 2006; 37 (1):200-5. Click here to download FREE pdf copy.

Free Web Resources
5. The Medically Important Poisonous Snakes of Malaysia by Prof Tan Nget Hong. Click here

6. The Management of Snakebites in Malaysia by Prof Tan Nget Hong. Click here.

All images in this blog post are linked, scaled images from the original sources. I do not own the copyright of any of them. They are linked here for non-commercial, educational purposes only. Clicking on the image will bring you back to the original source. If you are the copyright owner and want the image to be removed, please email me. Thanks.


zahirah ardy said...

I like this entry! :D However, just out of curiosity... reading the, "sea snake bites have little or no pain, and no edema ...", part... I watched a Discover Channel program, it showed a person who was bitten by a snake (but I can't remember the name of the snake) and he told that his hands swelled about twice their original size, as well as signs of tissue necrosis - the tissue appear black. Can you comment a little bit about that? Are the effects of land snakes' venom different?

cksheng74 said...

Hi Zahirah,
Thanks for your comments.

One of the important aspects that I did not include the post is the different types of toxins produced by the different venomous snakes.

The venomous snakes in Malaysia are basically three groups: the elapidae (which includes cobra or naja and the kraits), the viperidae (the vipers) and the sea snakes. Although the toxins in the venoms are a mixture of many things, the Elapidae produces venom that is predominantly NEUROTOXIN (causes paralysis including resp muscle paralysis), the Viperidae produces venom that is predominantly HEMOTOXIN (causes bleeding, coagulopathy) and the sea snakes produce venom that is predominantly MYOTOXIN plus neurotoxin. I usually memorize them like this: EN (Elapidae = neurotoxin), VH (Viperidae = hemotoxin), SM (sea snakes = myotoxin).

So, I suppose the person in the Discovery Channel program who got bitten in the sea had gangrenous area because of the MYOTOXIN causing myonecrosis, which can result in rhamdomyolysis, renal failure, etc.

In one of the articles, it is also mentioned that sea snake bite can also cause sleepiness, where the victim went to sleep, deteriorated into a comatose state, not waking up, and die. I am not sure exactly how to explain that sleepiness.

StorytellERdoc said...

Great post, although being in Pennsylvania, some of those snakes will never have to be my worry! Thanks for the information. Happy New Year to you and yours.

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Grace said...

Dr Chew, I stumbled on your blog while trying to identify and understand a snake i found in my house. I then wrote about what i read from several sites in my blog post.

I've cited your blog of course. Hope that's alright.


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