Clinical Toxicology: Venomous Animals

Study Notes

Acute poisoning by venomous animals is common in tropical and subtropical climates.
The precise chemical composition and pathophysiology of animal venoms are incompletely known, thus limiting specific treatment options.
General principles of intensive supportive therapy should be followed in managing these poisonings.

Over 3,000 snake species exist globally, though only around 250 are venomous.
Venomous snakes are classified into two types based on fang structure:
- Viperids (foldable fangs)
- Elapids (fixed fangs)
Common examples include rattlesnakes, saw-scaled vipers, cobras, mambas, and sea snakes.
Snake bites are common in children and men due to accidental encounters.
Snake venom contains enzymes, non-enzymatic proteins, and other substances like acetylcholine and 5-hydroxytryptamine that provoke further inflammatory responses.
Severity depends on venom type and quantity, with nocturnal bites often being more venomous than daytime bites.
Venomous snakes leave two (occasionally one) fang marks, while non-venomous snakes produce a semi-circular tooth mark.
Local effects can range from mild inflammation to severe tissue necrosis (especially in Viperidae and Crotalidae bites), often preceded by pain and swelling.
Systemic effects can include nausea, vomiting, hypotension, drowsiness, muscular weakness (including diplopia, speech and swallowing issues), respiratory paralysis, coma, or convulsions.
Severe systemic reactions may result in clotting and bleeding issues, polymyositis (muscle inflammation), elevation of muscle enzymes/plasma potassium, and potential myoglobinuria and renal failure (especially in sea snake bites).
There are popular misconceptions about snake bite management; bandaging and incision/suction are not effective and can be harmful.

Stings from ants, bees, wasps, and hornets usually cause local pain and swelling, but may cause respiratory distress if on the mouth/tongue.
Systemic effects of insect stings are uncommon though can be fatal.
Bee stings are alkaline, while wasp and hornet stings are acidic.
Allergic reactions can be severe and require immediate medical intervention (SC adrenaline and hydrocortisone).

Poisonous spiders, such as the black widow and funnel-web spiders, live in warmer climates.
Children and laborers are particularly vulnerable.
Initial bite may be unnoticed, followed by generalized muscular pain, burning sensation, gastrointestinal problems, abdominal rigidity (suspected acute abdomen), salivation, pyrexia, sweating, leucocytosis, mild hypertension and macular rash.
Effective treatments include cleaning the bite, analgesic for pain, and supportive therapy.

Nocturnal creatures of the tropics and subtropics.
Typically, stings result in intense local pain, sweating, numbness, and hyperesthesia (sensory sensitivity) and in severe cases, respiratory and cardiac depression.
Treatment focuses on cleaning the sting, managing pain, and providing intensive supportive therapy.

Marine creatures present in warm seas.
Venom contains a thermolabile toxin.
Bites cause a sharp wound and severe local pain.
Systemic effects can include hypotension, oculogyric crises (eyes turning upwards), and convulsions.
Careful cleansing, surgical examination, and hot water immersion are vital (to try and destroy toxin).
Systemic/local pain relief, intensive supportive therapy in severe cases are needed.

Local pain is the primary effect, which may be severe.
Physalia in particular can cause extensive and generalised muscle pains, colic, nausea and breathlessness with cyanosis, which may be rapidly fatal.
Medical care should focus on promptly removing any residual tentacles and supportive care.

Large spiders, sometimes mistaken for large centipedes due their leg design.
Non-venomous, but can inflict a significant bite due to their powerful jaws, and may cause minor to significant human skin injuries with potential for infection/swelling and/or bleeding.

General: Careful cleansing of the affected wound is essential (often with sterile saline).
Snake Bites: Intensive supportive therapy is usually required. Specific antivenin should be administered if available, especially if severe systemic reactions are present.
Insect Bites: Analgesic medications and supportive care may be needed, including treatment for allergic reactions.
Spider Bites: Cleaning and pain management are critical. Anti-infective treatment may be necessary.
Scorpion Stings: Analgesics and intensive supportive care are important, especially in severe reactions.
Stingrays/Jellyfish: Removal of any residual tentacles, supportive care, and possible hot water therapy, or local anaesthetics are key.