SNAKES Ophidia Poisonous l NonPoisonous l l Classified

SNAKES (Ophidia)

Poisonous l Non-Poisonous l l. Classified into

Five families of poisonous snakes Viperidae Ø Elapidae Ø Hydrophidae Ø Colubridae Ø Ataspididae Ø

In India l Common krait. (Bengarus caerulus) l Common Cobra (Naja naja) l Saw scaled Viper(Echis carinatus) l Russels viper (Viper russelli) l King cobra

Families of snakes.

Sense organs of snakes Vision Eyes without eyelids For moving objects l Touch Quite effective l Hearing No external ear So doubtful l Smell Strong smell sensation l

Sense organs of snakes l Vibration Jacobson’s sense organs l Special sensitive cells in the palate l l Temperature variation Pit vipers have pits l On each side of the head l Sensitive to temperature variation l Pythons-on the lips l

Poison glands l. Salivary glands of snakes l. Situated behind the eyes l. Above the upper jaw

Fangs l All poisonous snakes have two fangs l Curved teeth l Situated on the maxillary bones l Lie along the jaws l Covered by a flaps of mucous membrane

DIFFERENCES BETWEEN POISONOUS & NON- POISONOUS SNAKES Trait Poisonous snakes General Stout, dull coloured, abruptly tapering tail Non-poisonous snakes Slender, bright coloured, gradually tapering tail Tail Rounded or flattened Always rounded Belly scales Head Broad Usually triangular in shape Small, does not extend across entire width Usually rounded or oval

Trait Poisonous snakes Non-poisonous snakes Fangs Present; Grooved All teeth uniform , not grooved or or channellised Saliva Contains toxic (Venom) peptides and enzymes Saliva is nontoxic

COBRA&VIPER Trait Cobra Viper Body Long and cylindrical Short, narrow neck Head Small, seldom broader Larger, than the body covered triangular. and with large scales covered mostly with smaller scales Pupils Circular Vertical, slit-like Neck Not prominent Narrow, prominent

COBRA&VIPER Trait Cobra Viper Tail Less tapering More tapering Fangs Longer and channellised Absent Reproductions Shorter and grooved Present in the upper jaw Oviparous Venom Neurotoxic Haemolytic Other teeth Viviparous

Snake Venom Clear amber coloured l Proteinous in nature l Most are glycopeptides l Enzymatic in action l

Constituents of snake venom l Neurotoxin l Haemolysin l Proteolysin l Fibrinolysin l Cholinesterase l Coagulase l l Cardiotoxin Nucleotidase l Hyaluronidase l RNA ase l DNAase l Histamines l Serotonin l Phospholipidase-A etc

Common krait. (Bengarus caerulus) l l l l l 3 to 4 to 5 feet in length Shining steel black colour Narrow single or double bands across the back Belly creamy white Head is covered with large shields Four shields on either side of lower lip Scales on the central row on back are hexagonal Tail is round Plates under belly undivided Venom is NEUROTOXIC

Common Cobra (Naja naja) 5 -6 feet variable colour-usually black Well marked hood Double or single spectacle markon the dorsal side Area surrounding spectacle mark is speckled Hood cannot be seen in dead cobra A tiny triangular shield –wedge shield-between 4 and 5 l Infralabials l Caudal scales are double l Venom is NEUROTOXIC l l l l

Common Cobra (Naja naja)

Russels viper l l l Buff or ljght brown colour 4 -51/2 feet in length stouter than other poisonous snakes Narrows towards tail Head flat heavy triangular White V shaped mark with apex pointing forwards Nostrils bigger Three rows of brown or black spots along its back Outer 2 rows-spots ringed with white Entire broad plates on the belly Small scales on head Shields beneath tail divided into two rows

Saw scaled viper (echis carinata) l l l l l Length of 1 1 /2 feet Brown or brownish grey Head triangular Upper surface of head-small white mark resembling bird’s foot print Diamond shaped areas of darker colourbetwwen the upper curves of two wavy lines Back covered with rough scales Ridge on the middle of each scale dented like a saw Broad plates on the belly Small scales on head Entire shields beneath tail

Saw scaled viper (echis carinata)

SEA SNAKE

RAT SNAKE

Symptomatology of snake bite Cobra and krait Locall Burning or tingling pain l Redness l Irritation l Swelling l Inflammation

Constitutional 15 mins-1 to 2 hrs l l l l l giddiness lethargy Muscular weakness Drowsiness Intoxicated feeling Nausea and vomiting Weakness of muscles Develops into paralysis of lower limbs Staggers or falls on attempt to stand Paralysis spreads to trunks

l l l l l Ptosis Dysphagia and difficulty in talking Breathing-laboured Death due to respiratory paralysis Conscious till end Krait-convulsions and violent abdominal pain sometimes Drowsiness more Pain –lesser Albumin in urine

RUSSELS VIPER AND ECHIS CARINATE l 50% symptomless as little or no venom is injected l spot develops severe pain l area around bite is red and painful l swelling starts within 15 minutes l blood stained discharge from wound

In moderate poisoning l l l Marked feeling of intense pain Vomiting Giddiness Sweating Abdominal pain Dialatation of pupils-get insensitive to light Marked collapse Complete loss of consciousness Skin temperature-raised Tingling and numbness of tongue mouth or scalp Paraesthesia around wound Local extravasation of blood

In severe cases l Main feature is persisting shock l Blood –early haemoconcentration l -then decrease in RBC and platelets l Urine contains blood, sugar, proteins l Bleeding and clotting time-prolonged l Hges from gum, rectum, site of bite l Haemoptysis l Haemoglobinuria and renal failure

In systemic poisoning l Blood becomes defibrinated l Will not clot l Increasing respiratory depression l Giddiness l Headache l Weakness l Towards the end-extensive suppuration and sloughing l Malignant oedema of bitten area l DEATH due to SHOCK and HAEMORRHAGE

l Bites SEA SNAKES cause little or no local reaction ½ to 1 hrl pain l stiffness and l weakness of skeletal muscles l polymyositis with limb girdle distribution l muscle enzymes increased l plasma potassium increased l Myoglobinuria with renal failure l weakness of skeletal muscles persist for months

l FATAL DOSE : - Cobra-12 mg Russel’s viper 15 mg Echis-8 mg Krait-6 mg l FATAL PERIOD –cobra and krait-1/2 -6 hrs -viper-1 -2 days

First aid l Reassure the patient l apply firm pressure over bitten area l Sutherland wrap l Immobilise the bitten limb l Make parallel incisions through fang marks l Clean the wound with sterile saline or water

Treatment l Polyvalent anti snake venom serum l 20 ml given IV l Repeated 1 hr l Furthur doses every 6 hrs l If not available-antivenin l In viper bite-inject around site also l Neostigmine if there is neuroparalysis l In severe poisoning-normal saline or transfusion of blood and plasma l Haemodialysis or peritoneal dialysis

PM APPEARENCES l One or two fang marks l Colubrine bite-site-haemolysed l Viperine-discolouration l swelling l cellulitis l hges l Hges into bowel l Purpuric spots on pericardium l Hges into lungs l Kidneys inflamed l Internal organs-congested blood

CIRCUMSTANCES OF POISONING l Accidental l Occasionally murder l Occasionally cattle poison