Snakes: Difference between Poisonous and Non-Poisonous

Have you seen in movies the sucking of venom by mouth? And you wonder if that’s suicide, right? Well, medically, that’s POSSIBLE! Let us find out what this blog has got about snakes.

This blog will explain everything about snakes, that is, Types of snakes, Common snakes in India, How to find if a snake is poisonous, General management for snake bites, and the Treatment.

Almost everyone faces a snake, at least once in their lifetime, so why not just get some basics of snakes in short? A simple read can save someone’s life someday, and worth value for the doctors.

Snakes – An overview

Snakes are cylindrical, long, limbless, cold-blooded reptiles. There are about 3500 species of snakes known among which about 350 species are venomous. In India, about 216 species are found and among them, about 52 are poisonous.

The body of the snake is divided into:

  1. Head
  2. Trunk
  3. Tail

Types of Poisonous snakes

Poisonous snakes are divided into 5 families:

  1. Colubridae: e.g. African boomslang snake, twig snakes.
  2. Alractaspididae: e.g. mole vipers or adders.
  3. Elapidae: e.g. cobra, krait, coral snake.
  4. Viperidae: e.g. Russell’s viper, saw-scaled viper.
  5. Hydrophidae: e.g. Sea snakes.

Difference between Poisonous and Non-Poisonous Snakes

The following image will just clear out all doubts as to how you are going to quickly find out if the snake is venomous:

Common Non-Poisonous Snakes in India

  1. Rat snake (Dhaman Snake)
  2. Vine snake
  3. Bronze back tree snake
  4. Banded kukri
  5. Sand boa

Dhaman Snake is the most common non-poisonous snake found in India and is also known as Rat Snake. Non-poisonous snakes, at times, may resemble poisonous snakes and create confusion.

Features of Common Poisonous Snakes in India

Common cobra

Zoological name: Naja naja
Common names: Common cobra, nag


  • Common cobras are usually brown or black in color
  • The head is covered with shields. The third supra-labial shield touches the eye and nose
  • A small wedge-shaped scale called a cuneate is present between the 4th and 5th infra-labials
  • Pupils are round
  • The hood is present. The dorsal aspect of the hood may have a monocellate (monocele) or binocellate (spectacle) mark. The ventral surface of the hood has two dark spots
  • Fangs are short, grooved, and situated anteriorly
  • The tail is cylindrical. Caudal scales (scales on the undersurface of the tail) are divided and double
  • Venom — neurotoxic

Common Krait

Zoological name: Bungarus caeruleus
Common name: Indian krait, common krait, Maniyar, Kawadya


  • Usually, steel blue or black in color with single or paired white bands on the back. The bands are more distinct toward the tail
  • Pupils are round
  • Large hexagonal scale present over the back
  • The 4th infra-labial scale is the largest scale of other infra-labial scales
  • The subcaudal (ventral scales distal to vent) are undivided and entire
  • Fangs are short, grooved, and situated anteriorly
  • Venom — neurotoxic

Banded Krait

Zoological name: Bungarus fasciatus
Common name: Banded krait


  • Inverted “V” shaped mark on the head
  • Broad black and yellow glistening bands encircle the body. On cross-section, the bands are triangular in shape
  • As per habitat, the snake is shy in nature and often seen basking near water bodies usually in the morning hours
  • Venom — neurotoxic

Saw Scaled Viper

Zoological name: Echis carinatus
Common names: Carpet viper, phoorsa, afai


  • Aggressive snake
  • Viviparous
  • Usually brown in color and grows up to 1.5 to 2 feet
  • Head triangular with small scale. White “arrow mark” or “spear mark” may be present on the head
  • Pupils are vertical
  • A wavy white line (zig-zag pattern) may present on each flank
  • Diamond-shaped markings over the back
  • Belly scales are broad and cover the entire width
  • The scales of the viper are serrated, saw-like thus named saw scale viper
  • Fangs are long, curved, hollow, channelized, and hinged
  • Venom — vasculotoxic and hemotoxic
  •  (Can also be remembered as 5 V’s; V= viper, V=viviparous, V=vertical pupil, V=v shaped head (triangular), V=vasculotoxic venom)

Russell’s Viper

Zoological name: Vipera russelli
Common name: Kander, ghonas


  • The head is large, flat, and triangular with small scales. A White V-shaped mark is present on the head
  • Pupils are vertical
  • Large nostrils
  • The body is stout and fatty with a brown or yellowish color
  • Body scales are semi-elliptical
  • Three rows of chained dark spots present on the back
  • Tail is narrow and short. Scales are divided into two rows
  • Fang are long, curved, hollow, channelized and hinged
  • When disturbed, makes a loud and hissing sound
  • Venom — Vasculotoxic and hemotoxic

Sea Snakes

  • Sea snakes are usually bluish, grayish or greenish in color. They have prominent nostrils and are situated on the top of snout
  • Body is flat and belly scales are not broad
  • Tail is flattened and paddle shaped
  • Venom — myotoxic


Basically snake venom are of three types, namely neurotoxic, haemotoxic and myotoxic venom.

Types of venom are:

Neurotoxic Venom

  • Origin—Common in Elapidae snakes, e.g. krait, cobra, etc.
  • Action—Acts like Curare, mainly on the motor nerve cells and results in muscular paralysis, the muscles are affected in following order:
  • >Firstly—Muscles of the mouth
  • >Secondly—Muscles of the throat
  • >Finally—Muscles of respiration
  • Symptoms at bite site—Local manifestations are least with neurotoxic venom snake bite
  • Other symptoms—Convulsions may be seen with Cobra venom (Krait venom produces only paralysis)

Haemotoxic Venom

  • Origin—Common in Viperidae snakes, e.g. Pit viper (Crotalidae); Pit-less viper (Russell’s viper, Saw scaled viper/Phoorsa/Echis/Echis Carinata), and Bamboo snake (Common green pit viper)
  • Action—Acts by cytolysis of endothelium of blood vessels, lysis of red cells and other tissue cells, and coagulation disorders. All of these can lead to:
  • >Severe swelling with oozing of blood and spreading cellulitis at the bite site. Blood from such patients fails to clot even on adding thrombin, because of very low levels of fibrin.
  • >Necrosis of renal tubules, and
  • >Functional disturbances like convulsions, due to intracerebral hemorrhage.

Myotoxic Venom

  • Origin—Common in hydrophidae or sea snakes
  • Action—Produces generalized muscular pain, followed by:
  • >Myoglobinuria within 3 to 5 hours
  • >Death usually occurs due to respiratory failure

Fatal Dosage for Venom?

Depending upon snake type, some common snake venoms with dosage toxicity are:

Clinical Features

The signs and symptoms of snake bite vary depending on the snake that bites:

Non-Poisonous Snake

  1. Fear and apprehension
  2. Sweating
  3. The patient may be in a state of shock with a feeble pulse, hypotension, syncope, rapid and shallow breathing
  4. Bite area — may show multiple teeth marks

Poisonous snake

Elapid Bite

Local Features:

  • Fang marks
  • Burning pain
  • Swelling and discoloration are sometimes associated with some blisters
  • Serosanguinous discharge from bite site
  • In comparison with viper bite, local manifestations are milder in elapid bite

Systemic features:

  • Pre-paralytic stage — characterized by vomiting, headache, giddiness, weakness, lethargy
  • Paralytic stage — characterized by spreading paralytic features with ptosis, ophthalmoplegia, drowsiness, dysarthria, convulsions, bulbar paralysis, respiratory failure, and death

Viperid bite

Local features:

  • Rapid swelling of the bite site
  • Discoloration
  • Blister formation — may extend to the entire limb and even spread to the trunk
  • Bleeding from the bite site
  • Pain

Systemic features:

  • Generalized bleeding—epistaxis, hemoptysis, hematemesis, bleeding gums, hematuria, melaena, hemorrhagic areas over skin and mucosa
  • Shock
  • Renal failure

Hydrophid bite

Local features:

  • Local swelling
  • Pain

Systemic features:

  • Myalgia
  • Muscle stiffness
  • Myoglobinuria
  • Renal failure


Diagnosis depends on:

  1. Identification of fang marks
  2. Identification of snake—vide supra
  3. Laboratory methods

Fang marks

Usually, two fang marks in form of a puncture wound can be noticed. The puncture wounds are usually separated from each other by a distance varying from 8 mm to 4 cm depending on the type of poisonous snake.

At times, due to sideswiping, a single mark may be produced or if the area is bitten multiple times, it may result in more fang marks.

Laboratory methods

  • Complete blood count—leucocytosis may be evident with thrombocytopenia
  • Smear — hemolysed and fragmented RBCs
  • Increased prothrombin time and increased partial thromboplastin time
  • Immunodiagnosis — consists of:
  1. Immunodiffusion
  2. Counter-current immunoelectrophoresis
  3. ELISA
  4. Radioimmunoassay


General Measures

Non-poisonous snakebite:

  • Allay the anxiety and fear
  • Reassure the patients that all snakes are not poisonous
  • Avoid alcohol or morphine, for these, can increase the rate of absorption of venom

First aid and field management

  • Reassurance
  • Limit the systemic spread of venom by immobilizing the affected part (e.g. limb)
  • For Viperid bites, the bitten limb should be splinted if possible and kept at approximately heart level
  • For elapid or sea snakebites, the Australian pressure immobilization technique is beneficial. In this method, the entire bitten limb is wrapped with an elastic or crepe bandage and then splinted
  • Tourniquet—a proximal lymphatic-occlusion constriction band or tourniquet may limit the spread of venom if applied within 30 minutes. The tourniquet should be applied such that it does not prevent the arterial flow of blood and the distal pulsation should be appreciated

Hospital Management

  • Monitor vital signs, cardiac rhythm, oxygen saturation, and urine output
  • The level of local edema/swelling/erythema in the bitten limb should be marked and the circumference should be measured every 15 minutes until the swelling has stabilized
  • Intravenous access with fluid resuscitation. If needed, vasopressors (e.g. dopamine) should be administered
  • Blood and urine should be collected for laboratory evaluation
  • Care of bite site — apply dry sterile dressings. A splint may be applied
  • Tetanus immunization should be updated as appropriate
  • If the swelling in the affected limb continues and impending tissue perfusion causes muscle compartment syndrome, intra-compartmental pressure should be checked. If pressure is elevated prompt surgical consultation should be obtained while antivenin continues
  • Antivenin therapy—antivenin should be administered only when indicated. Antivenins are available as monovalent (i.e. species-specific) or polyvalent. In India, polyvalent antivenin is available that is effective against the common cobra, common krait, Russell’s viper, and saw-scaled viper. The antivenin should be administered with caution. Usually, the antivenins are of equine origin and carry the risk of anaphylaxis or delayed-hypersensitivity type of reactions. Prior to the administration of antivenin infusion, the patient should receive appropriate loading doses of intravenous antihistamines. The antivenin should be administered as an intravenous infusion. It should be dissolved in 500 ml of normal saline or Ringer’s lactate or 5% dextrose for adults and 20 ml/kg for children
  • Severe hemorrhage or bleeding may require blood or fresh frozen plasma
  • If there are features of neurotoxicity, neostigmine may be required. Every injection of neostigmine should be preceded with atropine
  • Oxygen, ventilatory support
  • Management of renal failure on the usual line

Adverse reactions to antivenin

  • Anaphylaxis
  • Delayed type of hypersensitivity reaction

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