Snake and Insect Bites



  • Injury to the human skin and/or subcutaneous tissues caused by bite, envenomation, or sting, causing local but sometimes systemic effects
  • Snake bites
    • Crotalinae (pit vipers: cottonmouths, copperheads, and rattlesnakes)
    • Elapidae (coral snakes)
  • Spider bites
    • Black widow (Latrodectus mactans)
    • Brown recluse (Loxosceles reclusa)
  • Insect stings: Hymenoptera, fire ants (Solenopsis), wasps (including hornets and yellow jackets), bees


  • Snake bites
    • Only 15% of all snake bites are from poisonous snakes, and only ~2/3 of those involve true envenomation.
    • Crotaline snakes are the most common cause of venomous snake bites in the United States.
    • Between 2010 and 2013, approximately 1,300 snake bites per year were reported in children and adolescents and about half of those were venomous.
    • Coral snake bites constitute <1% of all snake bites.
  • Spider bites
    • The black widow spider is found in most areas of North America but especially in southern New England.
    • The brown recluse spider is found in southern and midwestern states.
  • Approximately 3% of the U.S. population is at risk for anaphylaxis from Hymenoptera stings.


  • Annually, ~8,000 people sustain a poisonous snake bite in the United States, 99% of which are from crotaline snakes; 5 to 6 fatalities occur annually.
  • The incidence of black widow and brown recluse spider bites are unknown.
  • 90 to 100 people die each year from sting anaphylaxis.


  • Snake bites
    • Snake venom consists of numerous enzymes and polypeptides that are neurotoxic, cytotoxic, and/or hemotoxic.
    • Pit viper venom produces significant local inflammation and injury to vascular endothelium and may lead to coagulopathy, thrombocytopenia, and shock.
    • The venom of the coral snake is primarily neurotoxic and may produce neuromuscular paralysis and respiratory depression.
  • Spider bites
    • Most of the 20,000 species of venomous spiders in the United States lack fangs capable of penetrating human skin or toxin strong enough to produce more than a mild reaction. However, the black widow and brown recluse spiders can cause significant harm.
    • The black widow venom, α-latrotoxin, is a neurotoxin that stimulates myoneural junctions and nerve terminals by increasing synaptic release of acetylcholine and by initiating a massive influx of calcium, causing severe skeletal muscle pain and cramping and autonomic disturbances such as hypertension, tachycardia, and diaphoresis. Pediatric patients are more severely inflicted given the ratio of milligram of venom to kilogram of body weight.
    • The brown recluse venom, mainly sphingomyelinase D and hyaluronidase, acts on erythrocyte membranes, platelets, endothelial cells, and other cells, resulting in tissue infarction and necrosis. Systemic symptoms are more likely to occur in children, presumably because of a smaller ratio of body weight to venom volume. Hemolysis, hemoglobinuria, renal failure, DIC, shock, seizures, and death may occur.
  • Insect stings
    • The fire ant bites with its jaws and then swings its head around to inflict multiple stings. The venom has a direct toxic effect on mast cell membranes, causing an immediate urticarial reaction at the bite site.
    • The venoms of the bee and wasp (hornet and yellow jacket) contain antigens that trigger an IgE antibody response, resulting in allergic reactions that vary in severity from mild local effects to anaphylaxis.
    • Cross-reaction between Hymenoptera species occurs. Those who react to fire ants may also react to bees and wasps.

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