Spider Bite

Aka: Spider Bite, Spider, Arachnidism

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II. Definitions

  1. Arachnidism
    1. Toxic effect of venom of Spider (Spider Envenomation)

III. Pathophysiology

  1. Spiders are Arachnids (8 legged arthropods) along with mites and ticks

IV. Precautions

  1. "Spider Bites" are typically not due to Spiders, but rather other causes (e.g. MRSA Cellulitis)
  2. Most Spider Bites are benign (not black widow or brown recluse)
    1. Need only minimal local therapy (Wound Cleansing, cold therapy)
    2. Although all Spiders are venomous, very few Spiders have fangs long enough to penetrate human skin

V. Types: Most toxic Spiders (worldwide)

  1. Spiders in U.S.
    1. Black Widow Spider Bite (lactrodectism)
      1. Medium size black Spider (up to 4 cm) with a red or yellow hourglass on the Abdomen
      2. Typically found in outdoor spaces (or basements, garages, sheds)
    2. Brown Recluse Spider Bite (Loxoscelism)
      1. Small Spider (up to 2 cm) with a dark violin shaped pattern on the anterior thorax
      2. Typically found in indoor, quiet spaces (e.g. furniture, clothes, bedsheets)
    3. Wolf Spider
    4. Red Legged Widow Spider (Red Widow Spider, Lactrodectus bisophi)
      1. Rare relative to Black Widow Spider found in Florida
    5. Yellow sac Spider or Common Sac Spider (Cheiracanthium inclusum)
    6. Brown Widow Spider (Lactrodectus geometricus)
      1. Causes lactrodectism, similar to Black Widow Spider, red back Spider, katipo
      2. Originally found in Africa and South America, but have also been found in U.S. (e.g. California)
    7. Tarantula Bite
  2. Spiders outside U.S.
    1. Brazilian Wandering Spider (Phoneutria fera, Phoneutria nigriventer)
      1. Most neurologically active venom
    2. Siz-Eyed Sand Spider
      1. Southern Africa Spider (related to Brown Recluse Spider)
    3. Chilean Recluse Spider (arana de rincon, aranha-marrom, corner Spider)
      1. Most dangerous of the Recluse Spiders
    4. Redback Spider (Lactrodectus hasselti)
      1. Black widow relative, primarily found in Australia (and invasive to New Zealand, Belgium, Japan via Grapes)
    5. Northern Funnel Web Spider (Dipluridae family)
      1. Australian Spider
      2. Among the most poisonous Spiders worldwide
    6. Sydney Funnel Web Spider (Dipluridae family)
      1. Australian Spider
  3. References
    1. Encyclopedia Britannica (accessed online)
      1. https://www.britannica.com/list/9-of-the-worlds-deadliest-spiders

VI. Types: Spiders without significant bite reactions (U.S.)

  1. Orb Weaver (Araneus)
  2. Garden Spider (Argiope)
  3. Trap door Spider (Bothriocytum)
  4. Mouse Spider (Drassodes)
  5. Parson Spider (Herpyllus)
  6. Huntsman Spider (Heteropoda)
  7. Running Spider (Liocranoides)
  8. Wolf Spider (Lycosa)
  9. Crab Spider (Misumenoides)
  10. Barn Spider (Neoscona)
  11. Green lynx Spider (Peucetia)
  12. Jumping Spider (Phiddipus)
  13. False Black Widow Spider (Steatoda)
  14. Trap door Spider (Ummidia)

VII. History

  1. Circumstances of bite (e.g. garage, basement) and timing of bite
  2. Characteristics of biting Spider (coloration, size, markings)
  3. Anatomic location of bite
  4. Associated local and systemic symptoms

VIII. Findings

  1. See Black Widow Spider Bite (lactrodectism)
  2. See Brown Recluse Spider Bite (Loxoscelism)
  3. General
    1. Solitary Papule, Pustule or wheal

IX. Differential Diagnosis: Spider Bite

  1. Other Arthropod Bite (Insect Bite)
    1. Mosquito Bite
    2. Tick Bite
    3. Flea Bite
    4. Bee sting
  2. Infection - common (U.S.)
    1. Dermatomycosis
    2. Erysipelas
    3. Furuncle or boil (e.g. MRSA)
    4. HSV Infection
    5. Shingles
    6. Impetigo
    7. Lyme Disease
  3. Infection - less common
    1. Chagas Disease
    2. Cutaneous Anthrax
    3. Pyoderma Gangrenosum
    4. Southern Tick-Associated Rash Illness
    5. Sporotrichosis
    6. Syphilis
  4. Miscellaneous conditions
    1. Contact Dermatitis (e.g. Allergic Contact Dermatitis, Rhus Dermatitis, Irritant Contact Dermatitis)
    2. Angioneurotic edema
    3. Autoimmune Vasculitis
    4. Diabetic Foot Ulcer
    5. Erythema Multiforme
    6. Venous Stasis Ulcer

X. Labs

  1. Based on suspected bite type
  2. See Black Widow Spider Bite (lactrodectism)
  3. See Brown Recluse Spider Bite (Loxoscelism)

XI. Prevention

  1. See Prevention of Vector-borne Infection
  2. Check clothes for Insects before donning
  3. Flick Spiders off skin instead of crushing against skin
  4. Avoid habitats
    1. Woodpiles
    2. Crawl spaces
    3. Corners of buildings
  5. Remove Spider webs regularly
    1. Use brooms or vacuums
    2. Apply safe indoor Insecticides (Pyrethrins)
  6. Dress for working outdoors
    1. Keep skin covered by clothing
      1. Wear gloves
      2. Shirt tucked into pants
      3. Pants tucked into socks
      4. Wear a hat and high collar
      5. Avoid loose clothing
    2. Avoid Insect attractants
      1. Bright colors
      2. Perfumes
  7. Insect Repellents
    1. DEET
      1. Mosquitoes
      2. Fleas
      3. Gnats
      4. Chiggers
    2. Permethrin (Elimite, Nix) on clothes
      1. Ticks

XII. References

  1. Diaz (2007) Am Fam Physician 75(6):869-73 [PubMed]
  2. Herness (2022) Am Fam Physician 106(2): 137-47 [PubMed]
  3. Juckett (2013) Am Fam Physician 88(12): 841-7 [PubMed]

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