Arthropods—including insects and arachnids—are responsible for a large number of bites and stings worldwide. While many cause only mild local reactions, some species inject potent venom that may result in systemic toxicity, allergic reactions, or life-threatening anaphylaxis. Understanding the clinical presentation and management of common arthropod envenomations is essential for effective toxicology practice.
Common Arthropods Involved in Envenomation
- Scorpions
- Spiders
- Bees
- Wasps
- Ants (fire ants)
1. Scorpion Stings
Scorpion venom contains neurotoxins that stimulate autonomic nervous system activity.
Mechanism
- Activates sodium channels
- Excess acetylcholine and catecholamine release
- Sympathetic and parasympathetic overactivity
Clinical Features
- Local: burning pain, redness
- Systemic: sweating, salivation, hypertension
- Muscle twitching
- Arrhythmias and pulmonary edema in severe cases
Management
- Analgesics for pain
- Local ice application
- Benzodiazepines for muscle twitching
- Monitor cardiac and respiratory functions
- Scorpion antivenom (region-specific)
2. Spider Bites
a. Black Widow Spider
Venom contains alpha-latrotoxin.
Symptoms
- Severe muscle cramps
- Abdominal rigidity
- Hypertension and tachycardia
Management
- Analgesics and benzodiazepines
- Calcium gluconate (for muscle spasms)
- Antivenom for severe cases
b. Brown Recluse Spider
Venom contains sphingomyelinase D, causing necrotic lesions.
Symptoms
- Pain and itching
- Bull’s-eye lesion
- Progressive ulcer or necrosis
Management
- Cold compresses
- Wound care
- Antibiotics only for secondary infection
- Surgical debridement in advanced necrosis
3. Bee and Wasp Stings
These stings cause both toxic and allergic reactions. Bees leave a barbed stinger; wasps do not.
Local Reaction
- Pain, swelling, redness
- Warmth and itching
Systemic Toxicity (Multiple Stings)
- Nausea and vomiting
- Hemolysis and rhabdomyolysis
- Acute kidney injury
Anaphylaxis (Medical Emergency)
- Urticaria
- Wheezing and bronchospasm
- Hypotension and shock
Management
- Remove stinger (scrape, do not squeeze)
- Cold compresses and antihistamines
- Epinephrine IM for anaphylaxis
- IV fluids and oxygen
- Corticosteroids and bronchodilators if needed
4. Fire Ant Stings
Fire ants inject venom containing alkaloids and proteins causing painful, sterile pustules.
Symptoms
- Intense burning pain
- Pustule formation within hours
- Occasional allergic reactions
Management
- Wash area with soap and water
- Hydrocortisone cream for inflammation
- Oral antihistamines for itching
- Epinephrine for anaphylaxis
General Principles of Management
- Assess airway, breathing, circulation
- Treat anaphylaxis immediately
- Monitor vital signs
- Provide supportive therapy depending on the species involved
- Educate patients about preventing future stings
Complications
- Anaphylactic shock
- Secondary bacterial infections
- Tissue necrosis (spiders)
- Cardiotoxicity (scorpions)
- Renal injury (multiple bee stings)
Detailed Notes:
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PATH: PHARMD/ PHARMD NOTES/ PHARMD FOURTH YEAR NOTES/ CLINICAL TOXICOLOGY/ ENVENOMATIONS – ARTHROPOD BITES AND STINGS.