snakes

SNAKES ARE REPTILES more than 2,700 species of snakes in the world of which about four fifths are non-venomous, are distributed throughout the temperate and tropical zones of the world About two thirds of all snake species belong to the family Colubridae; most of these are non-venomous.

Anatomical characterisitcs Snakes constitute the suborder Serpentes (or Ophidia). The skin, which is covered with scales, is shed, usually several times a year. The extremely long, narrow body is associated with distinctive internal features.

Jaws, teeth, sound perception. The jaws of snakes are loosely jointed and extremely flexible. The pointed, backward-curved teeth are fused to the supporting bones of the head. There are no ears or movable eyelids. They do not hear airborne sound waves, but can perceive low-frequency vibrations (100–700 Hz) transmitted from the ground to the bones of the skull.

CLASSIFICATION Snakes are classified into two groups. i. Poisonous ii. Non-Poisonous The Poisonous snakes are further classified into 3 main groups on the basis of poisons (Venom) secreted by them. 1. Elapids (Neurotoxic venom) 2. Vipers (Vasculotoxic Venom) 3. Sea Snakes (Myotoxic Venom)

DIFFERENCES OF POISONOUS & NON POISONOUS SNAKES 1. Body scales (By turning Belly upward) They are large & cover the entire breadth of belly Small or moderately large & don’t cover the entire breadth of the belly 2. Head Scales Usually small but some poisonous snakes have large head scales. Usually large but some poisonous. Snake have large scales. 3. Fangs Long & canalized like hypodermic needle Shot & solid 4. Tail Compressed Not markedly compressed 5. Habits Generally Nocturnal Not so 6. Bite Two fang marks with or without small marks of other teeth. A number of small teeth marks in a row.

VENOM highly modified saliva that is produced by special glands of certain species of snakes. It is provided with large alveoli in which the venom is stored before being conveyed by a duct to the base of the channeled or tubular fang through which it is ejected. Snake venom is a combination of many different proteins and enzymes. Many of these proteins are harmless to humans, but some are toxins.

CHARACTERISTICS OF SNAKE VENOM IN FRESH STATE Clear Transparent Amber tinted fluid DRIED UP VENOM Dries into a yellow granular mass Retains its activity for many years Contains toxalbumins

VENOM There are approximately 20 types of toxic enzymes found in snake poisons most snakes employ between six to twelve of these enzymes in their venom. Each of these enzymes has its own special function. Some aid in the digestive process, while others specialize in paralyzing the prey.

Chemical composition of snake venom Fibrinolysins Proteolysins Neurotoxins Cholinesterase (predominant in elapid venom) Haemolyins (predominant in viper venom) Thromboplastins Agglutinins Cardiotoxins Coagulase Hyaluronidase lecithinase

adenosine triphosphatase VENOM CHEMISTRY Scientists have identified the following chemicals from snake venom and the specific purpose of each as follows: cholinesterase attacks the nervous system, relaxing muscles to the point where the victim has very little control. amino acid oxidase plays a part in digestion and the triggering of other enzymes (is responsible for venom's characteristic light yellowish coloring.) hyaluronidase causes other enzymes to be absorbed more rapidly by the victim. proteinase plays a large part in the digestive process, breaking down tissues at an accelerated rate. (causes extensive tissue damage in human victims) adenosine triphosphatase believed to be one of the central agents resulting in the shock of the victim and immobilizing smaller prey. (present in most snakes.) phosphodiesterase accounts for the negative cardiac reactions in victims, most notably a rapid drop in blood pressure.

VENOM EFFECTS Hemotoxic venom acts on the heart and cardiovascular system. Neurotoxic venom acts on the nervous system and brain. Cytotoxic venom has a localized action at the site of the bite. myotoxic venom The most important symptoms are rhabdomyolysis (rapid breakdown of skeletal muscle tissue) and paralysis. Many snakes incorporate both neurotoxic and hemotoxic venom in their bites so when telling them apart one goes by which type is more predominant.

ELAPIDS

ELAPIDS Found in tropical and subtropical regions , including the Indian Ocean and the Pacific. Characterized by possessing a set of hollow, short and grooved fangs through which they inject venom These include Cobra King cobra Common krait Banded krait Coral.

ELAPID ENVENOMATION Pain is minor Clinically there is unimpressive local reaction There is more severe systemic manifestations The effect of the venom of elapid snakes is mainly on the nervous system.

Pre paralytic stage Paralytic stage Bulbar paralysis Respiratory failure Death

MECHANISM OF ACTION OF NEUROTOXIC VENOM Injection of elapid venom Acetylcholine receptor are blocked by cobra venom. A similar effect can be achieved by high doses of curare or nicotine

SYSTEMIC EFFECTS SIGN/SYMPTOMS OF ELAPID ENVENOMATION LOCAL SYMPTOMS Mild in reaction Fang marks Burning pain Swelling and discoloration Blood tinged fluid

SYSTEMIC EFFECTS SIGN/SYMPTOMS OF ELAPID ENVENOMATION PRE PARALYTIC nausea salivation vomiting euphoria weakness giddiness dizziness

SYSTEMIC EFFECTS SIGN/SYMPTOMS OF ELAPID ENVENOMATION PARALYTIC Spreading paralysis Ptosis Ophthalmoplegia diplopia dyspnea drowsiness muscle tenderness convulsions Respiratory paralysis Death

IN COBRAS FEW MINUTES TO FEW HOURS FATAL DOSE FATAL PERIOD 15 MG OF DRIED COBRA VENOM AMOUNT OF DRIED COBRA VENOM IN A BITE = 200 – 350 MG IN COBRAS FEW MINUTES TO FEW HOURS

VIPERS

THESE ARE FURTHER CLASSIFIED INTO VIPERS THESE ARE FURTHER CLASSIFIED INTO PIT VIPERS e.g. bamboo snake. PITLESS VIPERS Russell viper Saw scaled viper

PIT VIPERS triangular head, wider than the neck. Pupils are vertical. Tail is tapering. FANGS . These are long movable and canalized So a viper can bite through the clothes and give a complete dose.

The ‘pit’ is a special organ in between the eyes and the nostrils. PIT VIPERS The ‘pit’ is a special organ in between the eyes and the nostrils. The pit senses body heat from animals and gives the snake a ‘picture’ of that animal. This helps these snakes to find prey in the dark, which is when most snakes like to hunt.

THIS INCLUDES RUSSELL’S VIPER SAW SCALED VIPER PITLESS VIPERS THIS INCLUDES RUSSELL’S VIPER SAW SCALED VIPER

NEUMEROUS UNIDENTFIED VIPER VENOM VARIOUS PROTEINS PEPTIDES LIPIDS CARBOHYDRATES ENZYMES NEUMEROUS UNIDENTFIED PROTEOLYTIC ENZYMES PROCOAGULANTS ANTICOAGULANTS CARDIOTOXINS HEMOTOXINS

LOCAL REACTION Severe local symptoms include Intense local pain Rapid swelling Severe oozing of hemolytic blood Blisters appear on entire limb even trunk Which may be Serous serosanguinous

SYSTEMIC SIGNS When the venom is injected subcutaneously It travels by Lymphatics Superficial venous channels And spreads rather slowly to reach the general circulation.

INTRAVASCULAR ENVONOMATION This produces significant systemic symptoms in a matter of minutes including NON-SPECIFIC WEAKNESS MALAISE NAUSEA RESTLESSNESS

INTRAVASCULAR ENVONOMATION Specific Petechial haemorrhages Bleeding from gums Hemoptysis Bleeding from mucus membrane of rectum and other orifices of the body

FINALLY IN VIPER ENVENOMATION COLLAPSE SETS IN WITH Cold clammy skin Rapid feeble pulse Dilated pupils insensitive to light THIS IS FOLLOWED BY COMA DEATH IN EVENT OF RECOVERY Local lesion suppurates Undergoes superficial necrosis

RARELY PATIENT MAY EXHIBIT Disseminated Intravascular Coagulation [DIC] Along with spontaneous bleeding Significant hypotension Multi organ system failure

FATAL DOSE FATAL PERIOD 20 MG VIPER VENOM 6 MG KRAIT VENOM 8 MG SAW-SCALED VIPER AMOUNT OF DRIED VIPER VENOM IN SINGLE BITE YIELDED IS 150-200 MG VIPER VENOM 20 MG KRAIT VENOM 25 MG SAW-SCALED VIPER VENOM IN VIPERS A FEW DAYS

DIFFERENCES BETWEEN ELAPIDS & VIPERS Body Long & cylindrical Short Head Nearly of the same width as neck Triangular & wider than neck Pupils Round Vertical Maxillary bones Carries fangs + other teeth Only fangs Fangs Short, fixed & grooved Long, movable & canalized Tail Tapering Venom Neurotoxic Vasculotoxic Other Characteristics Oviparous Ovi-viviparous

SEA SNAKES

ANATOMY Head is small. Belly plates are not broad. Back has dull, tuberculated scales. Fangs are delicate very short fixed situated posteriorly nostrils are situated dorsally on the top of the snout. have valves that consist of a specialized spongy tissue to keep water out. The windpipe can be drawn up to where the short nasal passage opens into the roof of the mouth. an important adaptation for an animal that must still come to the surface to breathe air, but may have its head partially submerged when doing so.

ENVENOMATION The majority of sea snakes are highly venomous. Bites in which envenomation does occur are usually painless and may not even be noticed when contact is made. Teeth may be left in the wound. There is usually little or no swelling involved and it is rare for any nearby lymph nodes to be affected.

BITE FROM A SEA SNAKE This is felt as a sharp initial prick which becomes painless later. Early symptoms include headache, a thick-feeling tongue, thirst, sweating, vomiting. Symptoms that can occur after 30 minutes to several hours post bite include generalized aching, stiffness, tenderness of muscles .

SYMPTOMS OF ENVENOMATION After 3-8 hours myoglobin as a result of muscle breakdown may start to show up in the blood plasma, which can cause the urine to turn a dark reddish, brown, or black color, eventually lead to acute renal failure. After 6-12 hours Serum transaminase becomes elevated Severe hyperkalemia, also the result of muscle breakdown, can lead to cardiac arrest.

MYOTOXIC PHOSPHOLIPASE A2 (PLA2-H1) A toxic phospholipase A2 (PLA2-H1), isolated from the venom of the sea snake induces myonecrosis. Induction of myonecrosis occurs by the ability of phospholipase to release creatine kinase (CK) from damaged muscle fibers.

FATAL DOSE FATAL PERIOD 1.5 milligrams. Most Sea Snakes produce an average of 10-15 mg of venom so they should always be approached with caution as this venom is 10x more lethal than the venom of the land based Rattlesnake or Africa's deadly Black Mamba. 24- 48 HOURS

MANAGEMENT OF SNAKE BITE

EXTENT OF ENVENOMATION CLINICAL OBSERVATION ANTIVENOM RECOMMENDATION OTHER TREATMENT DISPOSITION NONE [DRY BITE] FANG MARKS MAY BE SEEN, BUT NO LOCAL OR SYSTEMIC SYMPTOMS AFTER 8-12 HOURS. NONE LOCAL WOUND CARE TETANUS PROPHYLAXIS DISCHARGE AFTER 8-12 HOURS OF OBSERVATION MINIMAL MINOR LOCAL SWELLING DISCOMFORT ONLY WITH NO SYSTEMIC SYMPTOMS NO HEMATOLOGIC ABNORMALITIES ADMIT TO MONITORED UNIT FOR 24 HOUR OBSERVATION MODERATE PROGRESSION OF SWELLING BEYOND AREA OF BITE LOCAL TISSUE DESTRUCTION HEMATOLOGIC ABNORMALITIES SYSTEMIC SYMPTOMS YES INTRAVENOUS FLUIDS CARDIAC MONITORING ANALGESICS FOLLOW LABORATORY VALUES ADMIT TO ICU SEVERE MARKED PROGRESSIVE SWELLING AND PAIN BLISTER FORMATION NECROSIS SYSTEMIC SYMPTOMS INCLUDING VOMITING FASCICULATIONS WEAKNESS TACHYCARDIA HYPOTENSION SEVERE COAGULOPATHY OXYGEN VASOPRESSOR

MANAGEMENT OF SNAKE BITE INITIAL OBJECTIVE DETERMINE THE PRESENCE OR ABSENCE OF ENVENOMATION. TO PROVIDE BASIC SUPPORTIVE THERAPY. TO TREAT THE LOCAL AND SYSTEMIC EFFECTS OF ENVENOMATION. TO LIMIT OR REPAIR TISSUE LOSS AND OR FUNCTIONAL DISABILITY. MEDICAL THERAPY SUPPORTIVE CARE ANTIVENOM WHEN WARRENTED CONSERVATIVE SURGICAL TREATMENT DEBRIDEMENT OF DEVITALIZED TISSUE WHEN INDICATED AS INDIVIUALIZED FOR EACH PATIENT HENCE AS A RULE THE FASTER THE TREATMENT IS INSTITUTED THE BETTER IS THE FINAL OUTCOME.

INITIAL TREATMENT REASSURANCE IMMOBILIZATION OF THE AFFECTED AREA BITTEN PART SHOULD BE IMMOBILIZED AS ACTIVITY INCREASES SPREAD OF VENOM. CLEANSING OF THE WOUND SHOULD BE DONE WITH PLAIN WATER SALINE TOURNIQUET OR PRESSURE BANDAGE

TORNIQUET Application of torniquet is only possible when the bite is on the limbs. If the bite is on face, neck, or trunk firm pressure over bitten area may be applied. APPLICATION OF THE TORNIQUET. It should be applied 5 cm proximal to the bite It should be tight enough to exclude the Venous circulation lymphatic flow Without impeding the Arterial deep venous flow

TORNIQUET INSTRUCTIONS A CONSTRICTION BAND IS NOT A TRUE TORNIQUET. A broad firm constrictive wrap [elastic bandage] placed over the bitten area and encircling the entire immobilized limb will slow the systemic absorption of venom improve outcome of neurotoxic envenomations.

IMMEDIATE IN-HOSPITAL THERAPY PAIN AND ANXIETY ANALGESICS ANXIOLYTICS TETANUS PROPHYLAXIS IMMOBILIZE THE EXTREMITY IN A WELL-PADDED SPLINT IN NEAR FULL EXTENSION AND ELEVATED TO AVOID DEPENDENT EDEMA.

ANTIVENOM THERAPY THIS THERAPY IS GIVEN TO AMELIORATE THE EFFECT OF LOCAL BITE SYSTEMIC ENVENOMATION AND IT IS CONSIDERED TO BE LIFE SAVING HOWEVER PROPHYLACTIC ADMINISTRATION IS NOT RECOMMENDED

THE MAJOR INDICATIONS FOR ANTIVENOM THERAPY ARE Rapid progression of swelling Significant coagulopathy Thrombocytopenia Neuromuscular toxicity Hemodynamic compromise No dose adjustment is required as venom required for neutralization is not dependent on patient’s weight.

ANTIVENIN SPECIFIC ANTIVENIN. POLYVALENT ANTIVENIN. Is prepared by hyper immunizing horses against venom of a specific snake. POLYVALENT ANTIVENIN. Is prepared by hyper immunizing horses against venoms of four common snakes Cobra Common Krait Russell’s viper Saw scaled viper

POLYVALENT ANTIVENOM STRENGTH OF POLYVALENT ANTI-VENOM 1 ml of anti-venom will neutralize 0.6 mg of dried cobra venom 0.45 mg of dried krait venom 0.6 mg of dried Russell viper venom 0.45 mg of dried saw scaled viper venom

ADULT DOSE OF ANTI-VENOM Total dose 60 ml in adults 1/3rd S/C. or around the bite. 1/3rd 1/m. 1/3rd I/V. The intravenous dose can be repeated any time if collapse appears OR Every 6 hours till symptoms disappear.

IF THE PATIENT IS SENSITIVE TO SERUM Desensitization is achieved by injecting Multiple small doses under cover of Adrenaline Antihistamines corticosteroids

ACTION OF ANTI-VENOM Anti-venom can neutralize the circulating toxin only. The toxin action at the tissue level[ fixed in tissues] may be antagonized by IN ELAPID BITE Neostigmine-atropine therapy IN VIPER BITE Heparin along with supportive fibrinogen transfusion Sea snake anti-venom can be effective even when started several hours after onset of poisoning.

GENERAL MEASURES STIMULANTS in paralytic cases ARTIFICIAL RESPIRATION. TRANSFUSION OF WHOLE BLOOD OR FFP in hemorrhagic cases STEROIDS in allergic manifestations of anti-venom therapy FOR SECONDARY INFECTION antibiotic prophylaxis

POSTMORTEM APPEARANCE Marks of snake bite Swelling & cellulitis at the site NEUROTOXIC VENOM produces signs of asphyxia IN VIPER BITE Oozing of blood Blood is fluid & haemolysed causing early staining of blood vessels Haemorrhage in lungs, serous membranes & left ventricle

POSTMORTEM APPEARANCE Petechial Haemorrhage in kidney, pelvis and mucosa of urinary bladder, stomach and intestines. Arterioles & capillaries have blurred walls and swollen endothelial cells Necrosis of renal tubules Cloudy swelling and granular changes in cells of other organs

Usually accidental Rarely Homicidal Very rarely Suicidal MEDICOLEGAL ASPECT Usually accidental Rarely Homicidal Very rarely Suicidal