Free Medical Courses

Master Medical Topics with free online courses for beginners. Learn how to approach a topic and understand critical topics easily.

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.
TRAIT COBRA VIPER
Body Long and also Cylindrical Short and also narrow neck
Head Small; Seldom broader than body; covered by large scales or shields of special forms. Large; broader than body; triangular and covered by numerous small scales.
Pupil Round Vertical
Maxillary bone Carries poison fangs and also other teeth Carries only poison fangs
Fangs Grooved , short and fine Canalised, long
Venom Neurotoxic Haemotoxic
Tail Round Tapering
Eggs Lay eggs Give birth to young ones

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
Poisonous snake
Common Krait

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.
Poisonous snake
Cobra

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.
Non-poisonous snake
Trait Venomous snakes Non-Venomous snakes
Head scales Small – Vipers
Large and (a)if there is an opening or pit between the eye and nostril (Pit viper)
(b) Third labial touches the eye and nasal shields
(c) No pit and third labial does not touch the nose and eye and central row of scales on back enlarged; undersurface of the surface of the mouth has only four infralabials, the fourth being the largest (kraits)
Large with the exceptions as mentioned, under the poisonous snakes.
Belly scales Large and cover entire breadth Small, like those on the back or moderately large, but do not cover the entire breadth
Fangs Hollow like hypodermic needles Short and solid
Teeth Two long fangs Several small teeth
Tail Compressed Not much compressed
Habits Usually nocturnal Not so.
Poisonous snake
Saw – Scaled Viper

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
Trait Colubrine bite Viperine bite
Area bitten Reddish wheal; tender with slight burning pain; oozing bloodstained fluid – less Pain and oozing of bloostained fluid – more
Swelling Minimal or absent in the bitten area Involves limb and spreads up to trunk
Symptoms Neurotoxic. Appear after 30 mins or more Haemotoxic. Appear immediately to 15 mins
Speech and Deglutition Difficult Normal
Paralysis Of lower imbs spreading to trunk and head Not present
Salivation Present Absent
Pupils Normal Dilated; do not react to light
Blood pressure Normal Hypotension
Bleeding and Clotting time Normal Prolonged
Haemorrhagic manifestations Not present Prominent feature
Cause of death Respiratory failure Circulatory failure due to haemolysis and haemorrhage

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.

© Medicinewithyugandhi | All Rights Reserved