Introduction :

• In the whole world there are more than 3500 species of snakes.
• Of that only about 216 snakes are found in India.
• In that only 52 snakes are venomous.
• According to WHO, there are more than 2.5 million venomous snake bites in the world-wide in each year.
• The snake bites each year reports with more than 1,25,000 deaths.
• In India only five snakes remains dangerously poisonous to man.
• They are King cobra, Common cobra, Common krait, Russell’s viper and Saw – scaled viper.
• Of the five the most common poisonous snake is common Krait.

Classification of snakes :

• Venomous snakes are classified into five families. They are
  • Viperidae
  • Crotalidae
  • Elapidae
  • Hydrphidae
  • Colubridae
  • Atractaspididae
• Viperidae :
  • Russel’s viper, Gaboon viper, Saw sclaed viper and also Puff adder comes under the classification Viperidae.
  • They reside in all parts of the world except Americas.
• Crotalidae :
  • Rattlesnakes, Pigmy rattlesnakes, Copperheads, Cottonmouths ( Water moccasins ), pit viper, the massasaugas and also bushmaster comes under the classification Crotalidae.
  • They are reside in Asia and America.
  • And also the Water Moccasins are found in swampy areas or along the banks of the streams.
  • Moreover it is a strong swimmer and also can bite underwater.
• Elapidae :
  • Cobras, Kraits, Mambas, Tiger snake, Taipan, Death adder, Copperhead snakes and also Coral snakes comes under the classification of Elapidae.
  • They also reside in all parts of the world except in the Europe.
• Hydrphidae or Sea snakes :
  • All snakes are poisonous but they sledom bite.
• Colubridae :
  • Boomslangs and also Bird snakes of the African continent fall under the classification Colubridae.
• Atractaspidiae :
  • African and Middle Eastern burrowing asps or stilleto snakes also known as burrowing or mole vipers or adders or false vipers.

Common venomous snakes :

• The cobra
• The King Cobra
• The common Krait
• The Banded Krait
• Russel’s Viper or Doboia
• The Saw – Scaled viper
• And also Pit vipers

The Cobra :

• The Cobra contains a Hood.
• On the dorsal side it often bears a double or single spectacle mark.
• But sometimes it has an oval spot surrounded by an ellipse.
• Head scales are usually large and also the third labial touches the eye and also the nasal field.
• The portion of the neck surrounding the spectacle mark is usually darker than the rest of the back.
• And also the back is usually speckled with the golden spots.
• Moreover in a dead cobra it is difficult to notice the hood.
• The reason is that the Joints and neck becomes stiff.
• There are two blacks spots, and three black bands beneath the hood.
• And also the caudal scales are double.
• Moreover there is a white band in the region where the hood touches the body region.
• The colour is usually brown or black.
• The length of the snake is usually two meters in length.
• Moreover the neck is dilatable.

Sea snakes :

• Twenty types of Sea snakes are seen in Indian waters, all of them being venomous.
• The features of the sea snakes are
  • Small eyes
  • Prominent nostrils on the top of the head
  • Broad ventrals
  • Small tuberculated dorsal scales
  • Paddle-shaped flat tails
  • Moreover Black, Greenish – black or Bluish – black in colour.
  • They may be present with or without black bands.
  • They are mostly found in the rivers estuaries and also even in fresh water lakes.

Poisonous Venom Glands :

• The poisonous glands are the salivary glands of the snake.
• They are situated behind the eyes.
• Location : One on each side of the head above the upper jaw.

Fangs :

• All venomous snakes have two fangs.
• The teeth becomes erect when the snake is about to bite.
• Moreover the teeth become straight forward when the snake is about to bite.
• When a poisonous snake bites, it leaves a two deep faint impressions.
• The distance between two points is about 8mm to 4cm.
• A side sweep may produce a single puncture.
• Moreover non-venomous snake bites leave a number of small impressions in a row.
• Eventhough if the venomous snakes like the viper leave the bite marks, most of the time patients do not present with the symptoms.
• Moreover the discharge orifice of the viper fang is usually well above its tip.
• The fangs can penetrate deeply.
• But the truth is that a part or most of the venom may be ejected superficially or externally without entering the wound.
• In such cases even a thin layer of clothing may provide a greater protection.

Snake venom :

• The saliva of the snake is called the venom.
• The venom of the cobra is faint transparent yello and viscous.
• Whenever it gets exposed to the sun it turns slightly turbid.
• Russel’s viper venom is white or yellow.
• The venom is usually a mixture of toxalbumins and enzymes in varying proportions.
• The enzymatic components cause local and systemic effects.
• Whereas the non-enzymatic parts provide lethality.
• Moreover the venom is water and alcohol soluble.

Constituents :

• Proteolytic
• Fibrin ferments
• Neurotoxins
• Cholinesterase
• Haemolysins
• Cardiotoxin
• Cytolysins
• Agglutinins
• Lecithinases
• Phospholipase
• Phosphotidases
• Proteinases
• Hyaluronidase
• Ribonuclease
• Ophioxidase
• Protease
• Enzymes
• Peptides and Polypeptides

• The concentration of the venom shows diurnal and seasonal variation.
• Bites inflicted at the nights are the most dangerous.
• Moreover the bites inflicted after the hibernation period of the snakes is also most dangerous.
• Venom travels in the body through the lymphatics and superficial veins and spreads rapidly through the subcutaneous areolar space.
• Most importantly the hyaluronidase enzyme is present in every snake venom.

Types of Venom in snake bite:

• Neurotoxic – Colubrine and Elapidae venom
• Haemolytic – Viperine venom and also
• Myotoxic – Sea snake venom

Sea snake bites :

• They may cause a little or no local reaction.
• After half to one hour, the patient develops pain, stiffness and weakness of the skeletal muscles.
• Sea snake bites result in marked polymyositis with a limb – girdle distribution.
• Early stage – Trismus
• Late stage – Flaccid paralysis begins with ptosis
• Death occurs due to the cardiac arrest or the failure of the respiratory muscles.

Fatal Dose :

• Cobra 12 mg; Russel’s viper – 15mg; echis – 8mg; krait – 6mg of dried venom.
• The approximate yield in one bite – interms of dry weight of lyophilised venom is : Cobra – 170 to 325mg; Russel’s viper 130 to 250 mg; krait 20mg; and echis 20 to 35 mg.

Fatal period of snake bite :

• Cobra – Half to six hours
• Viper – One to two days

Diagnosis :

• Snake specific venom antigens to be detected in the wound swabs, aspirates, or biopsies, serum, CSF, urine and other body fluids.
• Specimens to be collected – skin and underlying tissue surrounding the fang punctures, wound and blister aspirates, serum and urine should be collected.
• Bitten area to be preserved in the normal saline.
• Urine venom – still remains detectable even after giving antivenom.
• Radioimmunoassay
• Enzyme immunoassay
• Cholinesterase and thromboplastin may be detectable in the bitten area.
• ELISA

First AID to be done in snake bite :

• Assure the patient
• Pressure immobilization for elapid and sea-snake bites but not for the viper bites because it may cause local necrosis.
• Try to occlude the superfcial lymphatics as much as possible.
• Should not occlude tightly so as the blood flow is stopped.
• Immobilise the limb.
• Local incision or suction of the venom should not be done.
• Do not suck venom out of the wound and do not use chemicals over it.
• The wound should not be cauterized.