The Big Four

The Big Four are the venomous snake species considered to be India's and Pakistan's most dangerous, as together they account for nearly all Indian and Pakistani snakebite fatalities.

The Big Four are:

1. Indian cobra
2. Common krait
3. Russell's viper
4. Saw-scaled viper

The members of the Big Four 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.

Polyvalent serum has been developed in India specifically for treatment of snake bite by any of the Big Four cases.

Common Cobra (Naja naja)


The cobra is the most common poisonous snake in the India.

The venom of cobras is highly neurotoxic and dangerous. Early symptoms of a bite include ptosis, diplopia , dysphagia, and dizziness, followed by progress ive respiratory muscle weakness, ultimately requiring endotracheal intubation. Cobra venom is a postsynaptic neurotoxin. It works by stopping the acetylcholine molecules in the diaphragm muscle from interacting. Without treatment death from respiratory failure may occur as early as 30 minutes after being bitten.

Standard treatment involves the use of antivenin. Additionally, it is possible to support bite victims via mechanical ventilation, using equipment of the type generally available at hospitals. If too far away from a hospital, doctors prefer the "suck and spit" formation. Such support should be provided until the venom is metabolised and the victim can breathe unaided. If death occurs it takes place approximately 6 to 12 hours after the cobra bite. Cause of death is respiratory failure or suffocation caused by complete paralysis of the diaphragm.

Russell's Viper (Daboia russelli)
Tamil - retha aunali, kannadi virian or kannadi viriyan
It is a thick set, ground dwelling snake, with a small conical head and large nostrils. Dorsum brown, with three rows of spots along the body, the belly is cream in colour. It lives in grasslands or scrub forests. They are aggressive once threatened or disturbed. The smaller ones are much more aggressive than adults. Once agitated, they produce a high pitched hissing sound which is audible from even a few meters away.

It should be noted, however, that D. russelii does not associate as closely with human habitation as Naja and Bungarus (cobras and kraits).

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.

Severe pain may last for 2-4 weeks. Locally, it may persist depending on the level of tissue damage. Often, local swelling peaks within 48-72 hours, involving both the affected limb and the trunk. If swelling up to the trunk occurs within 1-2 hours, massive envenomation is likely. Discoloration may occur throughout the swollen area as red blood cells and plasma leak into muscle tissue. Death from septicaemia, respiratory or cardiac failure may occur 1 to 14 days post-bite or even later.

Saw scaled Viper (Echis carinatus)
Tamil - surattai pambu.viriyan pamboo, surutai vireyan

A small viper which is distributed across the Indian sub-continent. Even the slightest disturbance will make this snake react aggressively. The snake makes noise by rubbing its scales together. Its venom is hemo-toxic.

Its inconspicuousness nature, the speed of its strike, and its readiness to bite at the smallest provocation make this one of the most dangerous reptiles of India.

Of the more dangerous systemic symptoms, hemorrhage and coagulation defects are the most striking. Hematemesis, melena, hemoptysis, hematuria and epistaxis also occur and may lead to hypovolemic shock. Almost all patients develop oliguria or anuria within a few hours to as late as 6 days post bite. In some cases, kidney dialysis is necessary due to acute renal failure (ARF), but this is not often caused by hypotension. It is more often the result of intravascular hemolysis, which occurs in about half of all cases. In other cases, ARF is often caused by disseminated intravascular coagulation.

In any case, antivenin therapy and intravenous hydration within hours of the bite are vital for survival.At least eight different polyvalent and monovalent antivenins are available against bites from this species.

Common Krait (Bungarus caeruleus)
Tamil - Kattu viriyan, Yennai viriyan, Yettadi viriyan.

The krait is largely nocturnal in nature. While it stays hidden & dormant during the day, it becomes very alert at night. Its body is glossy black with paired bands on the body. Widely spread over the Indian subcontinent . Studies indicate the venom is more toxic than that of a cobra. The snake often enters people’s houses in its quest to find a cool place. People get bitten when they step on the snake accidentally.