The Big Four:
- Indian cobra, Symptoms of cobra envenomation can begin from 15 minutes to two hours after the bite, and can be fatal in less than an hour. It is the most dangerous of the Big Four.
- Common krait, Krait venom is extremely neurotoxic and quickly induces muscle paralysis. It is many times more venomous than that of the common cobras.If death occurs it takes place approximately 6-8 hours after the krait bite. Cause of death is general respiratory failure i.e. suffocation.
- Russell's viper, Envenomation symptoms begin with pain at the site of the bite, immediately followed by swelling of the affected extremity. Bleeding is a common symptom, especially from the gums, and sputum may show signs of blood within 20 minutes post-bite. There is a drop in blood pressure and the heart rate falls. Blistering occurs at the site of the bite, developing along the affected limb in severe cases. Necrosis is usually superficial and limited to the muscles near the bite, but may be severe in extreme cases. Vomiting and facial swelling occurs in about one-third of all cases.
- Saw-scaled viper, Local symptoms include swelling and pain, which appear within minutes of a bite. In very bad cases the swelling may extend up the entire affected limb within 12-24 hours and blisters form on the skin. The venom yield from individual specimens varies considerably, as does the quantity injected per bite. About 20% of all bites are fatal.
Another famous species, the king cobra, Ophiophagus hannah, is not a member of the Big Four. This species may have a potent venom of which it can inject enormous quantities and is deadlier when compared to the smaller species listed above, but it is actually rather shy, living mostly in dense jungle where it rarely comes into contact with humans. It also feeds only on other snakes not mice which may not be found in high population regions (hence its scientific name, which means "snake-eater king") and is even listed as a threatened species.
The members of the Big Four, on the other hand, are all quite common and bite readily. They are often found in proximity to human habitation, as they are attracted to the associated rodent populations on which they feed. These species are all primarily nocturnal and most victims are bitten at night when walking barefoot and accidentally stepping on them. Thus it is these snakes' feeding behavior, combined with their density in populated areas, which causes these snakes to account for the majority of snakebite incidents in India.
Polyvalent serum has been developed in India specifically for treatment of snake bite by any of the Big Four cases. The serum is widely available in India and is used to save the lives of people bitten by any of these snakes. Antivenin for the king cobra is not available in India, but is available in Thailand where, presumably, the likelihood of encounter with this snake is greater.
