Envenomation by coral snake (micrurus fulvius) is a highly venomous elapid native to the southeastern United States. While its bite is rare due to its reclusive nature, envenomation can cause severe neurotoxic effects, requiring immediate medical intervention. This article provides a comprehensive overview of coral snake envenomation, including symptoms, diagnosis, treatment, and preventive measures.
Identification of Micrurus fulvius
Proper identification of the Eastern coral snake is crucial to differentiate it from non-venomous mimics such as the scarlet kingsnake (Lampropeltis elapsoides). Key features of Micrurus fulvius include:
- Distinct red, yellow, and black banding with red and yellow touching
- A black head without a distinct neck
- A slender body, averaging 50–80 cm in length
A common rhyme to distinguish it from lookalikes is: “Red touches yellow, kill a fellow; red touches black, venom lack.”
Venom Composition and Mechanism of Action
Coral snake venom is primarily neurotoxic, affecting the nervous system rather than causing local tissue damage. The venom contains:
- Phospholipase A2 – Disrupts cell membranes, leading to neurotoxicity
- Three-finger toxins – Block neuromuscular transmission, causing paralysis
- Other neurotoxic peptides – Impair respiratory and autonomic function
Unlike pit viper venom, coral snake venom does not induce significant swelling or pain at the bite site. However, systemic effects can be life-threatening.
Symptoms of Coral Snake Envenomation
Symptoms of Micrurus fulvius envenomation often present within a few hours but may be delayed up to 12 hours. They include:
- Initial Symptoms: Minimal local pain, numbness, or tingling
- Neurological Effects: Progressive muscle weakness, ptosis (drooping eyelids), slurred speech, difficulty swallowing
- Respiratory Complications: Paralysis of respiratory muscles leading to respiratory failure
- Autonomic Dysfunction: Hypotension, excessive salivation, sweating
Without prompt treatment, symptoms can rapidly progress to respiratory arrest and death.
Diagnosis of Coral Snake Envenomation
Diagnosis is primarily clinical, based on:
- History of snakebite with Micrurus fulvius identification
- Neurological examination showing progressive paralysis
- Absence of significant local swelling or tissue necrosis (unlike pit viper bites)
- Laboratory tests such as arterial blood gas (ABG) analysis and electromyography (EMG) to assess respiratory compromise
Treatment and Management of Coral Snake Envenomation
Immediate First Aid
- Keep the victim calm and immobilized to slow venom spread.
- Avoid cutting the wound, using tourniquets, or attempting to suck out venom.
- Transport the victim to a medical facility as soon as possible.
Medical Treatment
Administration of Coral Snake Antivenom
- Coral Snake Antivenin (North American Coral Snake Antivenin, Wyeth/Pfizer) is the only FDA-approved treatment.
- Given intravenously to neutralize venom and prevent symptom progression.
- Most effective when administered early before respiratory failure.
Supportive Care
- Mechanical ventilation may be required in severe cases due to respiratory paralysis.
- Intravenous fluids and vasopressors for hypotension management.
- Monitoring for delayed symptoms since venom effects may persist for days.
Prognosis and Recovery
With timely antivenom administration and supportive care, full recovery is expected. However, untreated envenomation can lead to fatal respiratory failure. Patients require observation for at least 24–48 hours in case of delayed symptom onset.
Prevention of Coral Snake Bites
Avoiding High-Risk Areas
- Exercise caution in wooded, swampy, or sandy regions where coral snakes inhabit.
- Avoid reaching into hollow logs or under debris where snakes may be hiding.
Protective Clothing
- Wear boots and long pants when hiking in snake-prone areas.
Safe Handling Practices
- Never attempt to handle or kill a coral snake.
- Educate children on snake safety and identification.
Emergency Preparedness
- Carry a mobile phone and know the location of the nearest medical facility.
- Learn basic first aid for snakebites.
