(I) Venomous snakes of India (VSofI): WHO categories

To clarify concepts: 

Venom is something that goes directly into your bloodstream, as a result of a wound, punction, bite...

Poison is something you take, eat or drink. 

That is the reason why we should use "SNAKEBITE ENVENOMATION" and not poisoning, even if this term is quite popular.


CLASSIFICATION OF VENOMOUS SNAKES:
There are three families of venomous snakes in South-East Asia,

• Elapidae, 
• Viperidae and 
• Colubridae. 

ELAPIDAE
This family includes:

• Cobras, king cobra, 
• Kraits, 
• Sea snakes. 

Elapidae are relatively long, thin, uniformly-coloured snakes with large smooth symmetrical scales (plates) on the top (dorsum) of the head. There is no loreal scale between the preocular and nasal scales. Some, notably cobras, raise the front part of their body off the ground and spread and flatten the neck to form a hood. Several species of cobra can spit their venom for one meter or more towards the eyes of perceived enemies. Venomous sea snakes have flattened paddle-like tails and their ventral scales are greatly reduced in size or lost. Envenomation by an elapide snake is typically neurotoxic. Sea snakes produce myonecrosis (muscle destruction).

VIPERIDAE 
Viperidae have relatively long fangs (solenoglyph) which are normally folded flat against the upper jaw but, when the snake strikes, they are erected.
There are two subfamilies:

• Typical vipers (Viperinae) and 
  
• Pit vipers (Crotalinae). 

The Crotalinae have a special sense organ, the loreal pit organ, to detect their warm-blooded prey. This is situated between the nostril and the eye.

Viperidae are relatively short, thick-bodied snakes with many small rough scales on the top (dorsum) of the head and characteristic patterns of colored markings on the dorsal surface of the body.
Envenomation by a viperide snake is typically hemotoxic


COLUBRIDAE
This snakes are mildly or non-venomous and usually are not considered as medically important snakes but, some of the can be easily confused with venomous snakes.

MEDICALLY IMPORTANT VENOMOUS SNAKES IN SOUTH-EAST ASIA REGION 

(WHO 2010)

India has around 275 species of snakes, out of which fifty are venomous plus another forty five mildly venomous. Of this fifty, not all are lethal, and some of them are distributed in very restricted areas.Based on current herpetological and medical literature, it is possible to partially prioritize the species of snakes that are of greatest medical importance in different regions.

Detailed statistics on the species of snakes responsible for envenoming and fatalities throughout the world are lacking, except for a few epidemiological studies which include rigorous identification of the biting snake in a few scattered localities.

Venomous snakes of highest medical importance can be classified into two categories according to the following criteria:

Definitions of Category 1 and Category 2 are:

Russell's viper fangs

CATEGORY 1: Highest medical importance
Definition: Highly venomous snakes which are common or widespread and cause numerous snakebites, resulting in high levels of morbidity, disability or mortality.

CATEGORY 2: Secondary medical importance
Definition: Highly venomous snakes capable of causing morbidity, disability or death, for which exact epidemiological or clinical data may be lacking; and/or which are less frequently implicated (due to their activity cycles, behavior, habitat preferences or occurrence in areas remote to large human populations).


Category 1: The venoms of these species should be considered a starting point for establishing the most important targets for anti-venom production

• Elapidae: 
• Common Krati (Bungarus caeruleus)
• Monocled Cobra (Naja kaouthia) (east)
• Spectacled Cobra (Naja naja) (throughout)

• Viperidae: 
• Russell's Viper (Daboia russelii) 
• Saw Scaled Viper (Echis carinatus)
• Hump Nose Pit Viper (Hypnale hypnale) (south-west) 

Category 2: 

In many countries, territories and other areas there are species of snakes that rarely bite humans but are capable of causing severe or fatal envenoming. Their medical importance may not justify inclusion of their venoms in the immunizing mixture for production of poly-specific anti-venoms but the need to make anti-venoms against these species needs to be carefully analyzed. 

• Elapidae: 
• Northeastern hill krait (Bungarus bungaroides) 
• Banded Krait (Bungarus fasciatus)
• Lesser black Krait (Bungarus lividus) 
• Black Krait (Bungarus niger)
• Sind Krait (Bungarus sindanus)
• Wall's sind Krait (Bungarus walli)
• Caspian Cobra (Naja oxiana) (northwest), 
• Andaman Cobra (Naja sagittifera) (Andaman Islands); 
• King Cobra (Ophiophagus hannah) (south, north-east, Andaman Islands); 

• Viperidae: 
• White lipped pit viper (Cryptelytrops albolabris) 
• Red tail pit viper (Cryptelytrops erythrurus)
• Northern white lipped pit viper (Cryptelytrops septentrionalis)
• Himalayan pit viper (Gloydius himalayanus)
• Jerdon's pit viper (Protobothrops jerdonii)
• Kaulback's lance-head pit viper (Protobothrops kaulbackii)
• Brown spotted pit viper (Protobothrops mucrosquamatus)
• Bamboo pit viper (Trimeresurus gramineus) (south India), 
• Malalbar pit viper (Trimeresurus malabaricus) (south-west),

The forgotten Sea snakes!!!
"Although venomous marine sea snakes have not been included in the tables of medically important venomous snakes, it should be recognized that there are a number of species of marine snakes with potent venoms that can cause illness or death"

SOURCE: WHO guidelines for the production, control and regulation of Snake Anti-venom Immunoglobulins 2010 

http://www.who.int/bloodproducts/snake_antivenoms/snakeantivenomguideline.pdf




THE ANTI-VENOM

Nowadays, the only anti-venom available in India is a polyvalent anti-venom against four out of the six snakes listed in the category 1:

• Common krait (Bungarus caeruleus)
• Spectacled Cobra (Naja naja)
• Viper Russell's (Daboia russelii)
• Saw scaled viper (Echis carinatus)  

There is NO anti-venom for:

•  any of the two left snakes in category 
• Monocled Cobra (Naja kaoutia)
• Hump Nose pit viper (Hypnale Hypnale)
• or any of the snakes listed in category 2 and we should have in mind that 
• sea snakes also are not included in any list or category.

Furthermore, anti-venom activity has a high geographical variability.
Ideally, anti-venom should be produced from the same snakes common in a particular geographical area otherwise, less activity, waste of vials, increase of secondary effects include anaphylaxis are the consequence. We will see that in another post.
Next post about "the Big Four and much more".

ॐ लोकाः समस्ताः सुखिनो भवन्तु ॥

Om Lokah Samasthah Sukhino Bhavantu

May all beings everywhere be happy and peaceful.