Snake bites are a neglected tropical disease prevalent in Nepal, caused by venomous species like cobras, kraits, and vipers, transmitted via fangs injecting toxins. Globally, WHO estimates 5.4 million bites annually, with 1.8-2.7 million envenomings, leading to 81,410-137,880 deaths and triple the number of disabilities. In Nepal, ~20,000 bites occur yearly, causing >1,000 deaths, mostly pre-hospital due to delayed care. Of 89 snake species, 17 are highly venomous (front-fanged). Risk peaks in rural areas, monsoon season, and agricultural fields.
Fig: Common Venomous Snakes in Nepal (e.g., Common Cobra in forests/grasslands; Common Krait in houses/burrows; Russell’s Viper in forests, agricultural lands).
Venomous vs. Non-Venomous Snakes
| Characteristic | Venomous Snakes | Non-Venomous Snakes |
|---|---|---|
| Head Shape | Triangular/wedge-shaped, wider at back | Round/oval-shaped |
| Pupil Shape | Slit-like, elliptical | Round |
| Coloration/Patterns | Brightly colored with distinct patterns (e.g., red, yellow, black) | Muted colors or solid shades |
| Tail Characteristics | Rattles or bright in young | No rattles, uniform |
| Body Size/Shape | Stockier, robust | Varies; some large resemble venomous |
| Defensive Behavior | Rattling, hooding, aggressive | Flattening, non-confrontational |
| Feeding Behavior | Ambush predators, camouflaged | Active foragers, moving |
Source: https://news.wildlifesos.org/world-snake-day-know-the-big-four/
Symptoms
Symptoms emerge post-bite (30 min-24 hrs for neurotoxic; rapid for hematotoxic):
- Early Signs: Local pain/swelling, nausea, vomiting, abdominal pain, malaise, weakness, drowsiness, excessive salivation.
- Neurotoxic (Elapids: Cobra/Krait): 5 Ds (dyspnea, dysphonia, dysarthria, diplopia, dysphagia) + 2 Ps (ptosis, paralysis); progresses to respiratory failure.
- Hematotoxic (Vipers): Bleeding (gums, nose, urine), swelling/necrosis, shock, AKI.
- Myotoxic (Sea snakes): Muscle aches/swelling, dark urine, hyperkalemia, AKI. Occult (Krait): Morning paralysis/abdominal pain without local signs.
Clinical Syndromes of Snakebite Envenoming in Nepal
| Syndrome | Features |
|---|---|
| Syndrome 1 | Local swelling/other local envenoming with paralysis, no bleeding/clotting disturbances. COBRA or KING COBRA |
| Syndrome 2 | Nocturnal bite while sleeping on ground and paralysis with no/minimal local sign of envenoming. KRAIT |
| Syndrome 3 | Neurotoxicity with dark brown urine, severe muscle pain, without local swelling/bleeding/clotting disturbances and with/without renal failure. Bitten on land while sleeping indoors. KRAIT (B. niger) |
| Syndrome 4 | Marked swelling (sometimes with blisters/necrosis) with incoagulable blood and/or spontaneous systemic bleeding. RUSSELL’S VIPER (Daboia russelii) |
| Syndrome 5 | Marked swelling on bitten limb/part often with blisters (sometimes with severe pain) without bleeding/clotting disturbances. PITVIPERS (Ovophis monticola, Trimeresurus sp.: T. albolabris, and T. popeiorum). |
Clinical Features of Snakebite Envenoming by Species
| Feature | Cobras | Kraits | Russell’s Viper | Saw Scaled Viper |
|---|---|---|---|---|
| Local Damage (Pain/ Tissue) | YES | NO | YES | YES |
| Ptosis/Neurological Signs | YES | YES | YES! | NO |
| Haemostatic abnormalities | NO | NO! | YES | YES |
| Renal Complications | NO | NO | YES | NO |
| Response to Neostigmine | YES | NO? | NO? | NO |
| Response to ASV | YES | YES | YES | YES |
Venom Types and Effects
- Neurotoxins (Pre-synaptic: Destroy nerve endings; Post-synaptic: Block receptors) – Cause curare-like paralysis (cobras: rapid; kraits: delayed).
- Hemotoxins – Activate coagulation factors, cause consumptive coagulopathy/hemorrhage.
- Cytotoxins – Enzymes (phospholipase A2, etc.) cause local swelling, blistering, necrosis.
Diagnosis
Suspected: History of bite + symptoms (fever, pain, swelling, paralysis) or travel to endemic areas. Confirmation:
- Clinical: Fang marks (single/dual punctures/scratch/none); local/systemic signs.
- Bedside: 20-minute Whole Blood Clotting Test (20WBCT) – Positive if incoagulable (hematotoxic).
- Labs: Prolonged BT/CT/PT/INR; raised urea/creatinine (AKI); CBC (high WBC, low platelets/hemoglobin). No specific lab for neurotoxicity in Nepal.
Treatment
Stages of Snake Bite Management
- First aid treatment and transport to the hospital
- Rapid clinical assessment and resuscitation
- Antivenom treatment
- Supportive/ancillary treatment
- Treatment of the bitten part
- Follow-up/Rehabilitation
Fig : Management of Snake Bite
Note: ASV – Anti-snake Venom and AN- Atropine followed by Neostigmine
1. First Aid
Aims: Retard venom absorption, preserve life, prevent complications.
- Reassurance: Calm victim; most bites non-venomous/treatable.
- Immobilization: Splint/sling bitten limb; avoid movement to reduce venom spread. Remove rings/jewelry/tight clothing.
- Rapid Transport: To facility with ASV; avoid walking.
- Precautions: No tight arterial tourniquets (delay release if applied); no cutting/sucking/incision; no herbs/chemicals/ice/electricity/cow dung/snake stones.
- Monitoring: Vital signs; if shock, lay flat, elevate feet, cover with blanket.
2. Rapid Clinical Assessment and Resuscitation
ABCDE: Airway, Breathing, Circulation, Disability, Exposure. Urgent if: Hypotension/shock, respiratory failure, tourniquet release effects, hyperkalemia/cardiac arrest, late complications (AKI/septicaemia).
3. Antivenom (ASV) Treatment
Polyvalent ASV (India-imported): Effective vs. Cobra, Krait, Russell’s Viper, Saw-Scaled Viper; not pit vipers.
- Preparation: Lyophilized; reconstitute 1 vial in 10ml sterile water.
- Indications: Neurotoxicity (ptosis, etc.); coagulopathy (20WBCT positive, bleeding); rapid swelling (>half limb); shock/AKI (Russell’s viper).
- Route/Dosage:
- Initial Dose: 10 vials (100 ml) are diluted in isotonic saline (e.g., 250-500 ml for adults) and given as an IV infusion @2ml/min for adults/children (same dose).
- Neurotoxic: Repeat 5 vials IV push @2ml/min if deterioration.
- Hematotoxic: Repeat 5 vials after 6hrs if 20WBCT abnormal.
- Max: 20 vials total.
- Prophylaxis: Prophylactic Adrenaline preparation before ASV to treat possible anaphylactic reaction
- Monitoring: Vitals every 15-30min; observe for reactions.
- Reactions:
- Early Anaphylactic (within 3hrs): Itching, urticaria, cough, nausea; life-threatening: Airway obstruction, wheezing, hypotension.
- Pyrogenic (1-2hrs).
- Late (Serum Sickness: 1-12 days, mean 7).
- Note: ASV neutralizes free venom; won’t reverse necrosis/swelling/renal failure/coagulopathy (liver does)/pre-synaptic damage.
4. Supportive/Ancillary Treatment
- Respiratory Paralysis: Artificial ventilation if distress; avoid asphyxiation.
- Hypotension/Shock: Fluids, vasopressors.
- Airway: Protection/management.
- AKI (Russell’s viper): Dialysis if needed.
- Other: Pain relief, antibiotics for infection.
5. Treatment of Bitten Part
- Comfortable position, elevate limb.
- Wash with antiseptic (chlorhexidine/povidone-iodine).
- Antibiotics if infected.
- Necrosis/Gangrene: Surgical debridement, skin grafting.
- Tetanus Toxoid: IM (postpone if coagulopathy).
6. Follow-Up/Rehabilitation
Monitor for long-term: Ulceration, infection, CKD, hypopituitarism, psychological issues (depression/PTSD).
Do’s and Don’ts after snake bite
| Do’s | Don’ts |
|---|---|
| Reassure the victim that most snakebites are from non-venomous snakes and are treatable. | Do not use tight arterial tourniquets; if already applied, delay release until medical help is available. |
| Immobilize the bitten limb with a splint or sling to reduce venom spread. | Do not cut, suck, or incise the bite site, as it increases risk of infection and bleeding. |
| Remove rings, jewelry, tight clothing, or fittings to prevent complications from swelling. | Do not apply snake stones (Jharmauro). |
| Arrange rapid transport to a medical facility equipped with anti-snake venom. | Do not apply electric current to the bite area. |
| Monitor vital signs; if in shock, lay the patient flat, elevate feet, and cover with a blanket. | Do not apply chemicals, herbs, cow dung, ice, or other traditional remedies. |
| Clean the wound gently with antiseptic if possible, but avoid interference that could increase absorption or bleeding. | Do not allow the victim to walk or move unnecessarily, as it promotes venom spread. |
| Seek immediate medical care for assessment and possible antivenom administration. | Do not give the victim food, alcohol, or stimulants. |
Prevention
- Avoid high-risk times/places: Monsoon, night, fields; wear boots/long pants.
- Sleep under nets/elevated; clear debris.
- Don’t disturb snakes; use lights at night.
Case Investigation Form – Snakebite Envenoming
| Section | Key Fields/Details |
|---|---|
| Health Facility | Name; Address |
| Patient’s Details | Name; Age/Sex; Address; Occupation |
| Details of Snakebite | Date of bite; Time of bite; Location (Field/Road/Others/Garden/Forest); Site of bite (Diagram: Front/Back); Saw snake? (Yes/No; Type: Krait/Cobra/Viper/Unknown; Local name); Tourniquet (Yes/No; Number); Local treatment (Soap & water/Incision/Draining/Sucking/Others); Visited other place? (Yes/No; Where: Faith healer/Private Hosp/Govt hospital); Past history of snake bite (Yes/No); Mode of transportation (Ambulance/Jeep/Van/Car/Motorcycle/Bicycle/Others); Time between snakebite and symptoms development |
| Clinical Feature – At Arrival | BP (mm Hg); Temp; Pulse (/min); Fang mark (Definite/Scratch/No); RR (/min) |
| Clinical Feature – During Hospital Stay | Local symptoms (Pain/Bleeding/Swelling (>half/<half limb)/Blister/Cellulitis/Necrosis/Scalding/Compartment syndrome/Burning/Neuritis); Neurotoxicity (Inability to frown/Ptosis/Diplopia/Blurred vision/Hypersalivation/Dysphonia/Difficult swallowing/Neck muscle weakness/Respiratory muscle weakness/Altered sensorium); Bleeding symptoms (Continuous from bite site/Gingival/Petechiae/Hematuria); Other symptoms |
| Investigation | 20-minute Whole Blood Clotting Test (WBCT) normal (Yes/No/Not done) |
| Treatment and Management | Describe; Anti-snake venom (Number of vials given; Date & time of initiation; List any other drugs given; Discharge date & time (dd/mm/yyyy at am/pm); Outcome (Improved/Referred/Died during treatment/Brought dead/LAMA); If referred, Hospital name |
| Health Care Provider | Name/Position; Signature |
Conclusion
Snake bites in Nepal demand prompt first aid, ASV, and supportive care for survival. Prevention and early treatment are key; access to care saves lives.
References
- National Guidelines for Snakebite Management in Nepal.
- WHO Snakebite Reports.
- https://iris.who.int/bitstream/handle/10665/204464/B4508.pdf
- https://animalia.bio/lists/country/snakes-of-nepal?page=1
- https://news.wildlifesos.org/world-snake-day-know-the-big-four/