Black Widow Spider

1. See Also
   1. Neurotoxin
   2. Insect Bite
2. Epidemiology
   1. Most commonly active in warmer months
   2. Occurs throughout the United States except for Alaska
3. Types: Widow Spider scientific names
   1. Latrodectus mactans
   2. Latrodectus hesperus
   3. Latrodectus bishopi
   4. Latrodectus geometricus
   5. Latrodectus variolus
4. Range
   1. Southeast
   2. Southwest
      1. Arizona
      2. New Mexico
      3. Nevada
      4. Utah
      5. Southern California
5. Identification
   1. Female (only female delivers venomous bite)
      1. Glossy ink-black spider
      2. Abdomen globular
      3. Red hourglass on underside
      4. More venomous than males
      5. Leg span : 3-4 cm leg span
   2. Male
      1. Grey coloration
      2. Stripes or spots
      3. Rarely transmit significant venom with bite
      4. Leg span: 1.6 to 2.0 cm (Half the female size)
   3. Spiderlings
      1. Orange, brown and white striped pattern (zebra-like)
      2. Change color with molting
   4. Web
      1. Irregular, chaotic-patterned heavy, strong web
      2. Adult female spider rarely leaves web
6. Image
   1. 
7. Habitat
   1. Indoors (Buildings)
      1. Dark garages
      2. Basements
      3. Stables
   2. Outdoors
      1. Rock crevices
      2. Wood piles
      3. Overhangs
      4. Abandoned rodent holes
8. Pathophysiology
   1. Highly venomous Neurotoxin: a-Latrotoxin
      1. Stimulates presynaptic neurotransmitter release
   2. Bite results in systemic toxicity (Latrodectism)
      1. Excessive adrenergic stimulation
      2. Excessive cholinergic stimulation
9. Symptoms
   1. Initial
      1. Bite felt but not immediately painful
   2. First 10 to 20 minutes
      1. Pain and throbbing at bite site
   3. Next 2 to 3 hours
      1. Musculoskeletal symptoms
         1. Diffuse, progressive myalgias in 100% of patients
         2. Generalized sweating
      2. Cardiopulmonary symptoms
         1. Chest Pain of chest tightness
         2. Dyspnea
      3. Gastrointestinal Symptoms: Abdominal cramping (64%)
         1. Board-like rigidity
         2. Nausea and Vomiting (36%)
      4. Facial Symptoms
         1. Flushed sweating face
         2. Contorted, Painful grimace
         3. Conjunctivitis
         4. Trismus of masseters
      5. Neurologic Symptoms
         1. Headache (27%)
         2. Restlessness
         3. Paresthesias
         4. Seizures
10. Differential Diagnosis
    1. Toxin Ingestion
    2. Angina
    3. Pneumonia
    4. Asthma
    5. Acute Abdomen (Peritonitis)
    6. Nephrolithiasis
11. Signs
    1. Bite wound
       1. Two small central red fang marks on blanched skin
       2. Surrounded by erythematous rings
       3. Localized diaphoresis
       4. Muscle fasciculations in the involved extremity
    2. Systemic signs
       1. Hypertension
       2. Diaphoresis
       3. Tachycardia
       4. Shock
       5. Abdominal Pain (with rigid Abdomen)
       6. Back pain
12. Course
    1. Symptoms resolve over 2-3 days
    2. Mortality approaches 1%
    3. Shock or death are more common in children and elderly
13. Labs: Used to differentiate from other conditions
    1. Complete Blood Count
       1. Distinguish from peritonitis
    2. Urinalysis
       1. Distinguish from Urinary Tract Infection
    3. Serum Creatine Phosphokinase or Lactate Dehydrogenase
       1. Distinguish from Rhabdomyolysis
14. Management
    1. General
       1. Cold compresses or ice pack (prevents toxin spread)
       2. Thorough Wound Cleansing
       3. Steroid ointment
       4. Tetanus prophylaxis as needed
    2. Muscle spasms, rigidity, pain
       1. Calcium Gluconate
          1. Adult dose: 10 ml of 10% solution) slow IV infuse
          2. Can be repeated every 4 hours
       2. Diazepam (Valium)
          1. Infants/Toddlers: 0.2-5 mg slow IV infusion
          2. Older children and Adults: 10 mg slow IV infusion
       3. Methocarbamol (Robaxin)
          1. Adult dose: 10-30 ml slow IV infuse
          2. Calcium is more effective
    3. Pain relief (Analgesics)
       1. Use care with Narcotics: respiratory depression risk
15. Management: Antivenin (horse serum)
    1. Indications (rarely indicated)
       1. Critical Envenomation
       2. Respiratory arrest
       3. Seizures
       4. Hypertensive heart disease
       5. Young Children or elderly
       6. Pregnant women
    2. Dosing
       1. Skin test first before dosing
          1. Evaluate for sensitivity to horse serum
       2. IV: 2.5 ml (1 vial) in 250 ml NS IV over 2 hours
       3. IM: 2.5 ml IM
    3. Adverse effects: Serum Sickness
       1. Risk may be greater than risk of death by Spider Bite
    4. Efficacy
       1. Relieves symptoms within 1-2 hours
       2. Efficacious up to 90 hours after bite
16. Precautions
    1. Hospitalize severe cases or significant comorbidity
    2. Cohorts to consider hospitalization
       1. Pregnancy
       2. Extremes of age (very young or old)
       3. Coronary Artery Disease
       4. Severe Hypertension
17. References
    1. Diaz (2007) Am Fam Physician 75(6):869-73
    2. Koh (1998) Postgrad Med 103(4): 235-50