Black widow spider bite

Background

• Identification: red hourglass on otherwise black spider

Mechanism

Envenomation causes release of acetylcholine and norepinephrine from the nerve terminals causing muscle cramps, tachycardia and hypertension

Clinical Features

• Local
  • Pinprick sensation; then increasing local pain that may spread to entire extremity
  • Erythema appears 20-60 min after the bite
  • Pain begins to abate after several hours and disappears by 2-3d
• Systemic
  • Muscle cramp-like spasms in large muscle groups (although exam rarely reveals rigidity)
  • Pain becomes generalized
    • Severe abdominal wall musculature pain and cramping
  • HA, n/v, diaphoresis, photophobia, dyspnea
  • A-fib, myocarditis, priapism, and death are rare

Differential Diagnosis

Envenomations, bites and stings

• Hymenoptera stings (bees, wasps, ants)
• Mammalian bites
  • Closed fist infection (Fight bite)
  • Dog bite
• Marine toxins and envenomations
  • Toxins (ciguatera, neurotoxic shellfish poisoning, paralytic shellfish poisoning, scombroid, tetrodotoxin
  • Stingers (stingray injury)
  • Venomous fish (catfish, zebrafish, scorpion fish, stonefish, cone shells, lionfish, sea urchins)
  • Nematocysts (coral reef, fire coral, box jellyfish, sea wasp, portuguese man-of-war, sea anemones)
  • Phylum porifera (sponges)
  • Bites (alligator/crocodile, octopus, shark)
• Scorpion envenomation
• Reptile envenomation
  • Snake bites
    • Crotaline (Pit Vipers)
    • Elapidae (Coral Snakes)
  • Lizard bites
• Spider bites
  • Black widow
  • Brown recluse
  • Tarantula
  • Funnel-web spider bite
  • Armed spider bite

Management

• Pain and muscle spasms
  • Opiods and benzos
• Systemic illness
  • Antivenin
    • Consider for:
      • Children
      • Pregnant women
      • Elderly

Disposition

• Consider admission for:
  • Symptoms of moderate envenomation
  • Pregnant women
  • Children
  • Pts w/ preexisting cardiovascular disease or HTN

See Also

• Bites and Stings