17.Animal irritants

Ophitoxemia

• Poisoning by snake bite is referred to as ophitoxemia.

• Snakes are among the most feared creatures in the animal kingdom, yet many religions venerate them.

Overview of Snakes

• Approximately 2000 species of snakes exist worldwide, with less than 10% being poisonous.

• In India, a significant number of poisonous snakes are identified.

Common Poisonous Snakes in India

• Elapidae

  • Common Cobra (Naja naja)

  • King Cobra

  • Common Krait (Bungarus caeruleus)

  • Banded Krait

  • Coral Snakes

• Viperidae

  • Russell's Viper

  • Saw-Scaled Viper

  • Pit Vipers

• Hydrophidae

  • Sea Snakes

Snake Bite Statistics

• Annual snake bites may reach up to 5 million, with 2.8 million resulting in poisoning.

• Fatalities from snake bites can range from 1.2 to 1.4 lakh deaths annually worldwide.

• In India, approximately 45,000 snakebite fatalities are estimated each year, though accurate records are lacking.

Identifying Poisonous vs. Non-Poisonous Snakes

Identification of Poisonous Snakes

General Guidelines

• Belly Scales:

  • Divided scales indicate non-poisonous snakes.

  • Single scales may indicate poisonous or non-poisonous.

Head Characteristics

• Triangular Head:

  • Covered with small scales may indicate poisonous (viper).

  • Look for a pit between the eye and nostrils (pit viper).

  • An arrow mark or bird foot mark on the head center indicates poisonous (saw-scaled viper).

• Large Head Scales:

  • May indicate poisonous or non-poisonous.

  • Check the 3rd supra labial:

    • If touching the eye and nasal shield, it is poisonous (cobra or coral snake).

    • If not touching, check the ventral aspect of the head.

• Infra Labial:

  • If the 4th infra labial is larger than others, it is poisonous (krait).

• Uniform Body Color:

  • Black head with uniform body color (without dots) indicates poisonous (coral snake).

    

Cobra

Common Cobra (Naja naja)

• Characterized by a hood and a spectacle or monocle mark on the dorsal side.

• Sometimes has 3 bands on the underside of the mark.

• White band at the separation between the hood and body.

• Length: 1.5 to 2 metres.

• Belly scales: single up to genital pore and double thereafter.

• Poisonous fangs on the upper jaw, grooved, followed by one or two small teeth.

• Predominantly neurotoxic, slightly hemotoxic.

• Head Structure:

  • Large scales on head

• 3rd Supra-labial Shield:

  • Larger and touching the eye and nasal shield.

  • Pupils are circular.

King Cobra (Opheophagus hannah)

• Hood present, but lacks a spectacle or monocle mark.

• Length: Typically 3 to 4 meters.

• Yellow, brown, or black, often with yellow or white cross bands.

• Habitat: Forest areas of the Himalayas, Bengal, Assam, Western Ghats; rarely in human habitats.

• Belly scales are undivided; caudal scales are divided.

• Venom: Predominantly neurotoxic with slight cardiotoxic effects; fangs are grooved.

Vipers

• Three main categories:

  1. Russell's viper

  2. Saw-scaled viper

  3. Pit viper

Russell's Viper (Daboia russelli)

• Also known as "kinder" in northern states.

• Length: 1 to 1.5 meters.

• Characteristic flat triangular head with a distinct 'V' mark.

• Back features three rows of diamond-shaped brown or dark brown marks with black rings; outer rows have white edges.

• Belly has broad undivided scales; caudal scales divided into two rows.

• Small scales on the head; makes a hissing sound when disturbed.

• Fangs are canalized; pupils are vertical.

• Reproduction: Viviparous, giving birth to 20 to 25 young at a time.

Saw-scaled Viper (Echis carinatus)

• Length: Usually 40 to 80 cm.

• Body covered with highly keeled, dry, and pointed scales that create a rustling sound.

• Color: Brown, dark brown, or mixed with yellow.

• Back has a wavy white line on both sides with brown spots in between.

• Triangular head with arrow or bird's foot mark.

• Has small scales on the head.

• Abdomen: Broad single row of scales.

• Tail Shields: Not divided.

Pit Vipers (Family: Crotalinae)

• Identification: A noticeable pit located between the nostril and the eye, allows them to sense temperature difference, environment, objects moving nearby.

• Belly scales not divided

• Short tails with divided ventral scales.

• Types of Pit Vipers in India:

  • Bamboo Pit Viper (Trimeresurus gramineus)

    • Habitat: Forest areas of the Western Ghats.

    • Physical Traits: Triangular head, greenish color, length around 60-100 cm.

  • Malabar Pit Viper (Trimeresurus malabaricus)

    • Color Variations: Brown, green, yellow, or red.

    • Habitat: Found in green forests of the Western Ghats, particularly near streams.

    • Local Name (Kerala): Paramandali or cholamandali.

    • Length: 30 to 80 cm.

  • Hump Nosed Pit Viper (Hypnale hypnale)

    • Known for its hump-nosed triangular head shape.

    • May have dark spots on either side of the back.

    • Length: 40 to 80 cm.

    • Hemotoxic Properties: All vipers, including the hump-nosed pit viper, are predominantly hemotoxic.

Krait

Common Krait

• Scientific Name: Bangarus caeruleus

• Local Names: Known as 'karayat' in the northern states and 'vellikettan' in Kerala.

• Length: 1 to 1.5 meters.

• Coloration: Steel blue or black with single/double white bands on the back and a creamy-white belly.

• Physical Features:

  • Head covered with large scales.

  • 4 infra-labial shields (the 4th one is the largest).

  • Central row of large hexagonal scales on the back.

Banded Krait

• Scientific Name: Bangarus fasciatus

• Length: Usually 2 meters.

• Description: Blunt tail end; predominantly black with wide yellow or white bands.

• Physical Features:

  • Black mark on the neck that extends to the eyes.

  • 4 infra-labials (4th one is largest).

  • Caudal and belly shields are not divided.

• Geographical Range: Commonly found in the north-eastern regions.

Coral Snakes (Colliophis)

• Description:

  • Slightly venomous snakes, rarely bite

  • Brown body with a black head

  • Typically found in forest areas of South India

  • Average length: approximately 0.5 meters

• Anatomy:

  • Caudal scales are usually divided

  • The 3rd supralabial scale touches the eye and the nasal shield

• Venom:

  • Neurotoxic venom

• Species Examples:

  • Slender coral snake (Colliophis melanurus)

  • Striped coral snake (Colliophis nigrescens)

  • Bibron’s coral snake

Sea Snakes (Hydrophidae)

• Overview:

  • 70 species of sea snakes worldwide, 22 species documented in the Indian Ocean

  • All sea snakes are poisonous

• Characteristics:

  • Small eyes and prominent nostrils on top of the head

  • Paddle-shaped flat tails

  • Coloration: black, bluish-black, or yellowish, with or without bands

• Beaked sea snake (Enhydrina schistosa)

  • Most common variety in Kerala coast (called 'valakadian kadal pambu')

  • Rarely bites but highly venomous; myotoxic and neurotoxic

• Other common species include annulated sea snake, bar bellied sea snake, and yellow sea snake

• Sea snakes are all poisonous.

• Their venom is both myotoxic (affecting muscles) and neurotoxic (affecting the nervous system).

Fangs and Venom

• Fangs: Two curved teeth on the upper jaw connected to the venom gland via a venom duct.

• The venom gland is a type of salivary gland in poisonous snakes.

• Types of fangs:

  • Viper: Canalized fangs.

  • Cobra: Grooved fangs.

• Fang replacement takes 4-6 weeks.

• When a snake prepares to bite, fangs become erect and point forward.

• Bite marks: Two distinct impressions from the fangs.

• The distance between the marks indicates the size of the snake's mouth.

• Only one mark may be seen if the bite is weak or if a fang is broken.

Constituents of Snake Venom

• Color: Pale yellow, amber, or colorless.

Cobra Venom

• Predominantly neurotoxic, containing:

  1. Neurotoxin: Polypeptides causing paralysis and affecting cardiac and respiratory centers.

  2. Cardiotoxin: Direct action on the heart.

  3. Cholinesterase: Impairs neuromuscular transmission.

  4. Phospholipase-A: Destroys phospholipids in nervous tissue, aiding neurotoxin penetration.

  5. Hyaluronidase: Facilitates venom spreading by breaking down tissue barriers.

  6. Protease: Enzymatic action.

  7. Histamine: Involved in inflammatory response.

Viper Venom

• Predominantly hemotoxic, containing:

  1. Phospholipase-A, B, C, D : Catalyzes the hydrolysis of lipids, causing lysis of red blood cells.

  2. Hyaluronidase

  3. Lecithinase

     • Acts on endothelial cell lipid layers.

     • Produces lysolecithin.

     • Increases fragility and permeability of blood vessel walls, leading to leakage of blood cells and plasma into extracellular space.

  4. Proteases

     • Cause tissue damage.

     • Result in anticoagulant effects due to fibrinogen destruction.

     • Lead to disseminated intravascular coagulation (DIC).

     • Alter vascular permeability resulting in edema, bruising, blistering, and necrosis at bite sites.

  5. Cytolysin

  6. Proteinase

  7. Histamine: Platelet Lysis

  8. Thromboplastin

  9. 5-Hydroxytryptamine (serotonin): Increase vascular permeability; also linked to pain.

Krait Venom

• Neurotoxic, similar constituents to cobra venom.

Signs and Symptoms of Snake Bites

• Factors Influencing Symptoms:

  • Site, depth, and number of bites.

  • Amount of venom injected.

  • Species and size of the snake.

  • Individual’s reaction, age, and size.

• Site: Extremities most commonly bitten; bites to head, face, or chest are more dangerous.

• Severity of Symptoms:

  • Varies based on snake species and size.

  • Cobra bite: Primarily neurological symptoms.

  • Viper bite: Hemorrhagic tendencies and nepatorenal damage.

  • Sea snakes: Myotoxic effects.

• Dry Bites: Minimal or no symptoms if venom is not injected (e.g., biting over clothes).

• Individual Reaction: Anxiety and fright can escalate clinical conditions, leading to psychological shock or death.

• Faster absorption of the poison with exertion.

Cobra Bite

• Initial Reactions (10 minutes post-bite):

  • Reddish wheal around the bite mark.

  • Minimal local swelling; tenderness and slight radiating pain present.

• Progression:

  • Numbness due to nerve paralysis begins after 30 minutes.

  • Symptoms include sleepiness, intoxication-like feeling, weakness, reluctance to move.

  • Muscle weakness increases, leading to spastic paralysis in lower limbs.

  • Paralysis may spread to trunk and head.

  • Possible nausea, vomiting, excessive salivation.

  • Weakness in extra-ocular muscles, strabismus, ptosis, ataxia, incoordination.

  • Difficulty in speech and swallowing due to paralysis of the tongue, pharynx, and larynx.

• Complete Paralysis: Observed roughly 2 hours after the bite.

• Respiration and Heart Rate Changes:

  • Respiration becomes slower.

  • Heart rate increases.

  • Patient remains conscious but cannot speak.

  • Comatose state leads to eventual respiratory failure and heart stop.

    

• Fatal Dose:

  • 3 drops of cobra venom; 12 mg of dried venom.

• Fatal Period:

  • Death typically occurs 8 to 12 hours after bite.

  • Severe poisoning may lead to death within half an hour.

Krait Bite

• Symptoms resemble cobra bite but with no swelling or pain at the bite site.

• Drowsiness and intoxication are intensified.

• Mild convulsions occur only in terminal stages.

• Fatal Dose: 6 mg of dried venom.

• Fatal Period: 4 to 6 hours; severe cases may see death within half an hour.

Viper Bite (Viperine Snake Bite)

• Immediate Symptoms:

  • Severe pain at the bite site within minutes.

  • Tenderness, redness, and pain in the area surrounding the bite.

  • Swelling occurs within 15 minutes; blood-stained discharge develops from the wound.

• Additional Symptoms:

  • Nausea, giddiness, vomiting, sweating, dilated pupils, and abdominal pain.

  • Elevated body temperature.

  • Tingling and numbness of the tongue, mouth, and scalp.

  • Localized swelling; possible blood extravasation and blister formation.

• Hematological Effects:

  • Hemolysis, decreased red blood cell count, and platelet count.

  • Urine may contain blood; sputum may be blood-stained.

  • Prolonged bleeding time and clotting time.

  • Disseminated Intravascular Coagulation (DIC) results in bleeding from gums, rectum, and bite site.

• Renal Complications:

  • Signs of renal failure include oliguria, albuminuria, and hematuria.

  • Symptoms include blurring of vision, headache, dizziness, and weakness.

• Terminal Symptoms:

  • Severe suppuration at the wound site, circulatory collapse, and coma can result.

  • Violent convulsions may occur just before death.

  • Cause of Death: Typically due to hemorrhage and shock.

  • If survival occurs, necrosis and sloughing at the bite site may take months to heal.

    

• Russell's Viper: Fatal dose = 15 mg; Fatal period = 1 to 2 days.

• Saw-scaled Viper: Fatal dose = 8 mg.Fatal period = 1 to 2 days.