Emergency Medicine Book


Black Widow Spider

Aka: Black Widow Spider, Latrodectus mactans, Widow Spider, Latrodectism, Widow Spider Bite, Poisoning due to Black Widow Spider Venom, Black Widow Spider Venom
  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. Most common in United States
      1. Latrodectus mactans
        1. South Eastern U.S.
      2. Latrodectus hesperus
        1. South Western U.S. - Arizona, New Mexico, Nevada, Utah, Southern California
      3. Latrodectus variolus
        1. Northern U.S.
    2. Less common in United States
      1. Latrodectus bishopi
      2. Latrodectus geometricus (Introduced brown Widow Spider)
        1. Southern United States
        2. Yellow-orange hour glass and milder venom
  4. Identification: Lactrodectus mactans (Southeastern black widow)
    1. Female (only female delivers venomous bite)
      1. Glossy ink-black Spider
      2. Abdomen globular
      3. Red hourglass on underside (ventral) Abdomen may be difficult to visualize
      4. More venomous than males
      5. Leg span : 3-4 cm
    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
    5. Images
      1. ErSpiderBlackWidow.jpg
  5. Habitat
    1. Indoors (Buildings)
      1. Dark garages
      2. Basements
      3. Stables
    2. Outdoors
      1. Yard debris
      2. Rock crevices
      3. Wood piles
      4. Overhangs
      5. Abandoned rodent holes
  6. Pathophysiology
    1. Highly venomous Neurotoxin: a-Latrotoxin
      1. Stimulates large presynaptic acetylcholine release
    2. Bite results in systemic toxicity (Latrodectism)
      1. Excessive adrenergic stimulation
      2. Excessive Cholinergic stimulation
  7. Symptoms
    1. Initial
      1. Bite felt as pinprick with minimal initial pain
    2. First 10 to 20 minutes
      1. Pain and throbbing at bite site
    3. Next 2 to 3 hours: Latrodectism
      1. Musculoskeletal symptoms
        1. Diffuse, progressive myalgias in 100% of patients
        2. Generalized sweating
      2. Cardiopulmonary symptoms (associated with upper extremity bites)
        1. Crampy Chest Pain or chest tightness
        2. Dyspnea
      3. Gastrointestinal Symptoms (associated with lower extremity bites)
        1. Abdominal cramping (64%)
        2. Board-like rigidity
        3. Nausea and Vomiting (36%)
      4. Facial Symptoms
        1. Flushed sweating face
        2. Contorted, Painful grimace
        3. Conjunctivitis
        4. Trismus of masseters
        5. Facial edema
      5. Neurologic Symptoms
        1. Headache (27%)
        2. Restlessness
        3. Paresthesias
        4. Seizures
        5. Weakness
  8. Signs
    1. Bite wound
      1. Two small central red fang marks on blanched skin
      2. Surrounded by erythematous rings (target appearance)
      3. Bite may also appear as wheal and flare pattern
      4. Localized diaphoresis
      5. 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
  9. Grading
    1. Grade 1
      1. Asymptomatic other than localized pain at Envenomation site
      2. Normal Vital Signs
    2. Grade 2
      1. Muscle pain in extremity with Envenomation
      2. Pain radiation into chest (arm bites) or Abdomen (leg bites)
      3. Local extremity diaphoresis
      4. Normal Vital Signs
    3. Grade 3
      1. Generalized Muscle pain in back, Abdomen and chest
      2. Generalized diaphoresis
      3. Abnormal Vital Signs (e.g. Hypertension, Tachycardia)
      4. Headache
      5. Nausea and Vomiting
    4. References
      1. Clark (1992) Ann Emerg Med 21(7): 782-7 [PubMed]
  10. Differential Diagnosis
    1. Toxin Ingestion
    2. Angina
    3. Pneumonia
    4. Asthma
    5. Acute Abdomen (Peritonitis)
    6. Nephrolithiasis
  11. Course
    1. Symptoms resolve over 2-3 days
    2. Mortality approaches 1%
    3. Shock or death are more common in children and elderly
  12. 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
  13. Management: General
    1. General
      1. Cold compresses or ice pack (prevents toxin spread)
      2. Thorough Wound Cleansing with soap and water
      3. Steroid ointment
      4. Tetanus Prophylaxis as needed
    2. Muscle spasms, rigidity, pain
      1. First-line therapy: Benzodiazepines
        1. Diazepam (Valium)
          1. Infants/Toddlers: 0.2-5 mg slow IV infusion
          2. Older children and Adults: 10 mg slow IV infusion
      2. Older regimens
        1. Calcium Gluconate
          1. Adult dose: 10 ml of 10% solution) slow IV infuse
          2. Can be repeated every 4 hours
        2. Methocarbamol (Robaxin)
          1. Adult dose: 10-30 ml slow IV infuse
          2. Calcium is more effective
    3. Opioid Analgesics
      1. Monitor for respiratory depression (especially in younger patients)
    4. Disposition
      1. Observe for 6 hours
      2. May discharge home if no concerning symptoms or signs
      3. Consider hospital observation for children and those with cardiovascular disease
  14. Management: Antivenin (horse serum)
    1. Indications (rarely indicated)
      1. Critical Envenomation (Grade 3 bites)
      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 100 to 250 ml NS IV over 2 hours
    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
  15. Complications
    1. Pulmonary Edema
    2. Cardiomyopathy
    3. Rhabdomyolysis
    4. Cardiovascular Collapse
  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. Cowling and Ferreri (2019) Crit Dec Emerg Med 33(2): 17-25
    2. Diaz (2007) Am Fam Physician 75(6):869-73 [PubMed]
    3. Juckett (2013) Am Fam Physician 88(12): 841-7 [PubMed]
    4. Koh (1998) Postgrad Med 103(4): 235-50 [PubMed]

Latrodectus mactans (C0005678)

Definition (MSH) A venomous New World spider with an hourglass-shaped red mark on the abdomen.
Concepts Eukaryote (T204)
MSH D001740
SnomedCT 70220001, 285590003, 285180000
English Black Widow Spider, Latrodectus mactans, Widow Spiders, Black, mactans, Latrodectus, Spiders, Black Widow, Widow Spider, Black, Latrodectus mactan, Black Widow Spiders, Spider, Black Widow, mactan, Latrodectus, black widow spider, black spider widow, black spiders widow, southern black widow, Latrodectus mactans Fabricius, 1775, Latrodectus mactans (living organism) (organism), Black widow spider, Latrodectus mactans mactans, Latrodectus mactans (organism), Latrodectus mactans mactans (organism), Latrodectus mactans (living organism) [Ambiguous], Lactrodectus schuchii
Swedish Svarta änkan
Czech černá vdova
Finnish Musta leski -hämähäkki
Japanese ゴケグモ, クロゴケグモ, 後家グモ, 黒後家グモ, 黒色後家グモ
Spanish Araña Viuda Negra, Latrodectus mactans (organismo vivo), Latrodectus mactans, Viuda Negra, Lactrodectus mactans (organismo), Lactrodectus mactans, Latrodectus mactans (concepto no activo), Latrodectus mactans mactans (organismo), araña viuda negra, Latrodectus mactans mactans
Italian Latrodectus mactans, Vedova nera
French Latrodectus mactans, Araignée veuve noire, Veuve noire
Polish Czarna wdowa
Norwegian Sort enke, Latrodectus mactans
Portuguese Viúva-Negra, Aranha Viúva Negra, Latrodectus mactans, Viúva Negra
German Latrodectus mactans, Schwarze Witwe
Dutch Latrodectus mactans, Zwarte weduwe
Derived from the NIH UMLS (Unified Medical Language System)

black widow spider venom (C0053838)

Concepts Amino Acid, Peptide, or Protein (T116) , Pharmacologic Substance (T121)
MSH C038599
SnomedCT 303319003
English black widow spider venom, LATRODECTUS MACTANS VENOM, Latrodectus mactans venom, Black widow spider venom, Black widow spider venom (substance)
Spanish veneno de araña viuda negra (sustancia), veneno de araña viuda negra
Derived from the NIH UMLS (Unified Medical Language System)

black widow spider bite (C0241811)

Concepts Injury or Poisoning (T037)
English spider bite black widow, bite black spider widow, bites black spider widow, black widow spider bite, Black Widow Spider Bites
Derived from the NIH UMLS (Unified Medical Language System)

Latrodectism (C0241969)

Concepts Disease or Syndrome (T047)
SnomedCT 217666004, 403150008
English Latrodectism, Latrodectism (disorder), Latrodectism (finding)
Spanish lactrodectismo (hallazgo), lactrodectismo (trastorno), lactrodectismo
Derived from the NIH UMLS (Unified Medical Language System)

Poisoning due to black widow spider venom (C1274555)

Concepts Injury or Poisoning (T037)
SnomedCT 80900001, 217666004
English Poison-black widow spider ven, Poisoning by Lactrodectus mactans bite, Poisoning by black widow spider bite, Poisoning by black widow spider bite (disorder), Poisoning due to black widow spider venom, black-widow-spider; syndrome, syndrome; black-widow-spider, Poisoning due to black widow spider venom (finding), Poisoning due to black widow spider venom (disorder)
Spanish envenenamiento por picadura de araña viuda negra (trastorno), envenenamiento por picadura de araña viuda negra (hallazgo), envenenamiento por picadura de Lactrodectus mactans, envenenamiento por la picadura de araña viuda negra, envenenamiento por la picadura de araña viuda negra (trastorno), envenenamiento por picadura de araña viuda negra
Dutch black-widow-spider; syndroom, syndroom; black-widow-spider
Derived from the NIH UMLS (Unified Medical Language System)

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