Black widow spider bite

Background

Black widow spider

• Identification: red hourglass on otherwise black spider
• Genus: Latrodectus

Mechanism

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

Clinical Features

Grading System

• Grade 1: Range from no symptoms to local pain at the envenomation site with normal vital signs
• Grade 2: Involve muscular pain at the envenomation site to migration to the trunk, diaphoresis at bite site and normal vital signs
• Grade 3: Include grade 2 with abnormal vital signs; diaphoresis distant to envenomation site, generalized myalgias to back, chest and abdomen, nausea vomiting and headaches.

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

Diagnosis

• Typically clinical

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