Spider Bite, Black Widow

Basics

Syndromes caused by envenomation by black widow spider bite
Mechanism of toxicity:
- Females are responsible for human envenomations
- Venom contains potent neurotoxin, α-latrotoxin:
  - Causes cation-channel opening presynaptically, resulting in increased neurotransmitter release into synapses and neuromuscular junctions
  - Increased neurotransmitter release causes increased neurologic, motor, and autonomic effects
Morbidity and mortality are dose dependent
Severity of envenomation depends on:
- Premorbid health of victim:
  - HTN or cardiovascular disease increase risk
- Size and age of victim:
  - Children (i.e., smaller size for a given dose of venom) are at greater risk of morbidity and mortality
- Number of bites
- Location of bite wounds
- Size and condition of spider
Rarely fatal

Black widow spider features:

Appearance:
- Glossy black with red markings shaped like an hourglass or a pair of spots on the ventral aspect of the globular abdomen
- Females have 25–50 mm leg spans and 15 mm long bodies
Found throughout North America, except the far north and Alaska
Prefer dark sheltered hideaways such as garages, barns, outhouses, woodpiles, and low-lying foliage
Most bites occur during the warmer months when spiders are defending their webs and egg clutches

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