Armed spider bite


Phoneutria nigreventer, The Brazilian Wandering Spider
  • Identification: Brown gray with white spots forming a longitudinal band on the dorsal abdomen and a red-brown brush of hair on the chelicerae. Large in size (4.5-6cm) with 4-5mm fangs.
    • They do not form webs, but rather are mobile nocturnal hunters
    • among the largest and most aggressive spiders in South AmericaHabitat restricted to South America, largely Brazil, Argentina, and Uruguay.
  • Genus: Phoneutria
  • The best-known representative is P. nigriventer, the Brazilian Wandering Spider


  • A complex mixture of polypeptide components. Neurotoxicity is the most clinically relevant.
  • Histamine and other components potentiate localized swelling and vascular permeability
  • Several neurotoxic components that activate sodium channels, potentiating action potentials and causing uncontrolled muscle contractions.

Clinical Features

Differential Diagnosis

Envenomations, bites and stings


  • Generally a clinical diagnosis


  • Largely Supportive Care
    • Pain Control
      • Local anesthetic infiltration at site of the bite is effective in 95% of cases
      • Opioids are discouraged as they may potentiate respiratory depression in severe envenomation
  • Antivenom
    • Polyvalent and Monovalent formulations available
      • Skin testing and antihistamine prophylaxis recommended prior to use
      • 1-5 vials given IV or IM
    • Clinical response judged by relief of pain or resolution of priapism


  • May discharge those with no systemic symptoms after period of ED observation
  • Admit patients with signs or symptoms of systemic toxicity

See Also


  1. Leslie V. Boyer, Greta J. Binford, Janice A. Degan. Spider Bites. Paul S. Auerbach. In: Auerbach’s Wilderness Medicine. 7th Ed. 2017: 1010-1011.