Spider bites

Background

• Standard abscess are not typically due to spider bites and should not be diagnosed as such

Clinically important spider genera by geographic region

• North America
  • Loxosceles (e.g. brown recluse)
  • Latrodectus (e.g. black widow)
  • Tegenaria
• South America
  • Loxosceles
  • Latrodectus
  • Phoneutria (e.g. armed spider)
• Africa
  • Loxosceles
  • Latrodectus
• Europe
  • Loxosceles
  • Latrodectus
• Australia
  • Atrax (e.g. funnel-web spider)
  • Hadronyche (e.g. funnel-web spider)
  • Latrodectus
• Asia
  • Latrodectus
• Other
  • Tarantula spider bite

Visual Spider Identification

• 

  Tarantula

• 

  Black widow spider

• 

  Brown recluse

• 

  Armed spider (phoneutria nigreventer)

• 

  Funnel-web spider (Hadronyche versuta)

Clinical Features

History

• Determine circumstances of bite to assess consistency with spider habitat and behavior
  • Indoors vs outdoors
  • Day vs night
  • Geographic location (recent travel)
• Appearance of the spider if seen
• Dead spiders can be preserved in 70% EtOH and later identified by arachnologists or entomologist

Physical Exam

• No pathognomonic signs proving lesion is a spider bite
• Assess both bite site and for systemic signs
• Bite Site
  • Location
    • Spider bites more common when clothing is tight against skin
  • Number of bites
    • Multiple bites suggest parasitic insect and not spider
  • Appearance of bite
    • Erythema, pallor, hemorrhage, induration, tenderness, paresthesia, vesicles
• Systemic findings
  • Abnormal vital signs (tachycardia possible with black widow)
  • Altered mental status
  • Abdominal pain
  • Diaphoresis
  • Generalized rash
  • Muscle fasciculations, spasm, or tenderness

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

Evaluation

Diagnosis

• Typically a clinical diagnosis

Management

• Clean area of bite
• Tetanus prophylaxis
• Analgesics
• Hydration
• Surgical follow up if indicated for debridement of necrotic area
• Antivenin is indicated only for specific envenomation
• No proven benefit for corticosteroids
• No indication for antibiotics unless concern for cellulitis

See Also

• Bites and Stings

References

• Boyer LV, Binford GJ, Degan JA. Spider Bites. In Auerbach PS, Cushing TA, Harris NS. Auerbach’s Wilderness Medicine. 7th ed. Philadelphia, PA: Elsevier; 2017: 993-1016.