toxicity due to snake venom

1. Snake

2. Epidemiology
• There are more than 2000 species of snakes in the world.
• Global estimates suggest that 30,000–40,000 persons die each year from
venomous snake bite, but this range is likely anunder-estimate because of
incomplete reporting.

3. Morphology of snakes
• Elongated body, a proportionately short tail and no limbs.
• An opening, vent, is present in the rear part of the body as a common orifice for
the intestinal as well as genito-urinary system.
• The body is covered with scales.
• On the head there are two eyes, two nostrils and no external ear.
• The eye is covered by a transparent scale, has a round or vertical pupil but no
eyelid.
• The lower jaw consists of two bones in front joined by an elastic ligament which
is not properly articulated with the upper jaw so that the mouth of the snake is
widely distensible. This is an adaptation for the mode of feeding because a snake
may swallow creatures as a whole.
• The upper marginal teeth are modified to form fangs.

4. Morphology of snake
• The fangs are solid in nonpoisonous snakes, whereas they bear a groove or
channel in the poisonous ones. They are connected to the poison gland by means
of a duct.
• The parotid salivary gland is modified as venom gland in poisonous snakes to
secrete Venom.
• The tongue of the snake is forked at the outer end and often projects out of the
mouth even when it is closed.
• It is primarily a sense organ to help the snake in its search for food, opposite sex
and helping to detect the enemies.
• As soon as a snake comes into the world, it moults its skin and continues to do so
several times a year throughout life. Such moultings keep the snake active.

5. Difference between poisonous and non-poisonous snakes
Poisonous Non-Poisonous

6. • 1. Neurotoxic (all elapids, i.e. cobra, krait, etc.)
• 2. Vasculotoxic (vipers)
• 3. Myotoxic (sea snakes)

7. • 90%- Protein in the form of enzymes, non-enzymatic polypeptide toxins and
nontoxic proteins as venom procoagulants.
• Phospholipase A2 (lecithinase)
presynaptic β-neurotoxins,
 β-bungarotoxin,
 crotoxin
 taipoxin
• Hyaluronidase
• L-Amino acid
• Postsynaptic neurotoxins
• α-bungarotoxin
• cobrotoxin
contain about 60 short-chain or 60–70 long-chain amino-acid residues

8. Mechanism of toxicity
histamine, 5-
hydroxytryptamine, kinin,
proteases, phospholipases,
membrane damaging
polypeptide toxins
Incrrease vascular permeability
Swelling and bruising of bitten
area
Mycotoxic and cytolytic
factors
Tissue necrosis
Procoagulants
haemostatic defects
activation of blood clotting
cascade
fibrogenase
degrade
fibrinogen
haemorrhagin
damage vascular
endothelium
s
vessel damage
massive and incontinent
bleeding
death
Venom

9. sign and symptoms
• The presence of fang marks, usually two but only one may be evident in venomous snake biting.
• The presence of U-shaped set of teeth in non-venomous snake biting.
• repeated vomiting, colicky abdominal pain and widespread systemic bleeding including extensive
ecchymoses, incoagulable blood, intravascular haemolysis and renal failure.
• Local effects include pain, swelling, blistering, necrosis and enlargement of local lymph nodes.
• Gastrointestinal symptoms include nausea, vomiting and diarrhoea.
• Anaphylaxis (dyspnoea, respiratory failure) and ECG change.
• Neurotoxic effects
• vomiting, hypersalivation, headache, heaviness of the eyelids, blurred vision, paraesthesiae around the mouth, hyperacusis, dizziness,
vertigo and ‘gooseflesh’.
• Paralysis is first detectable as ptosis and external ophthalmoplegia appearing as early as a few minutes after the bite, but sometimes
may be delayed for some hours.
• Later, the face, palate, jaws, tongue, neck muscles and muscles of deglutition may become paralysed.
• Respiratory failure after paralysis of intercostal muscles and diaphragm.
• There occurs intense pain in the eye, blepharospasm, palpebral oedema and leucorrhoea.
• Rarely, venom is absorbed into anterior chamber causing hypopyon and anterior uveitis.

10. Sign and symptoms
• Thirst, sweating and vomiting.
• Generalised aching, stiffness and tenderness of the muscles
• Trismus is common.
• Generalized flaccid paralysis as in elapid neurotoxicity.
• Myoglobinuria
• Myoglobin and potassium released from damaged skeletal muscles can cause renal failure, while
hyperkalaemia may precipitate cardiac arrest.
• Haemostatic abnormalities are characteristic of bite by Viperidae.
• Persistent bleeding from fang punctures, venepuncture or injection sites, etc. suggests that blood is
incoagulable.
• Spontaneous systemic haemorrhage is most often detected in the gingival sulci.
• Epistaxis, haematemesis, haemoptysis, subconjunctival, retroperitoneal and intracranial haemorrhages
• Victims of Russell’s viper may become oliguric within a few hours of the bite and have loin pain suggesting
renal ischaemia.

11. treatment
• Local mechanical suction
• bitten extremity should be splinted and kept at approximately heart level.