Etiology
General Comments
- There are approximately 30 different widow spider species found worldwide
Latrodectus Mactans (Black Widow Spider, Show-Button Spider)
- Seasonal Prevalence: most black widow bites occur between April-October in the United States
- Geography
- Found in USA and Canada (Black Widow is Most Abundant in Southeastern United States)
- Spider Resides in Dark Spaces, Such as Wood Piles, Rock Piles, Sheds, Garages, and Basements
- Female Spider (Which are Responsible for Most Significant Human Bites)
- In Contrast, Male Widow spiders Have Smaller Fangs, Less Venom, and Weaker Biting Muscles
- Black with 1 cm Body, 5 cm Legspan, and Red Hourglass Mark on Ventral Abdomen
- Spider is Aggressive and Bites on Slight Provocation: typically when trapped or web is disturbed
Latrodectus Bishopi (Red-Legged Widow Spider)
- Geography
- Found in Florida
Other Latrodectus Species
- Geography
- Found in Other Temperate and Subtropical Parts of the World
False Black Widow Spiders
- Steatoda Species (see False Black Widow Spider Bite)
- May Produce a Similar (But Milder) Presentation (Called “Steatodism”) to that of Widow Spider Bite
Physiology
Alpha Latrotoxin (Neurotoxin) in Venom<
- Lack of Local Necrosis
- Binds Irreversibly to Nerves and Depletes Acetylcholine, Norepinephrine, Dopamine, Glutamate, and Enkephalin from Presynaptic Nerve Terminals
- Clinical Effects
- Autonomic Activation
- Diffuse Central and Peripheral Nervous System Excitation
- Neuropathy, Leading to Acute Hypoventilation
Diagnosis
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Clinical Manifestations (Latrodectism)
Widow Spider Bite Site
- General Comments
- History of Recent Activity (Within 8 hrs) Which May Have Led to Exposure to the Black Widow Spider: however, the time of onset of systemic symptoms is typically within 30-120 min after the bite
- Chopping Wood
- Cleaning Out an Area
- Gardening
- Using Outdoor Furniture
- Approximately 75% of All Bites Occur on the (Usually Lower) Extremities
- History of Recent Activity (Within 8 hrs) Which May Have Led to Exposure to the Black Widow Spider: however, the time of onset of systemic symptoms is typically within 30-120 min after the bite
- Asymptomatic Bite Site: occurs in many cases
- Symptomatic Bite Site
- Fang Puncture Sites at Bite Site: uncommon
- Momentary Sharp Pain at Bite Site: however, this is often not prominent on exam
Cardiovascular Manifestations
- Hypotension (see Hypotension)
- Epidemiology: rarely occurs
- Systolic Hypertension (see Hypertension)
- Physiology: due to vasoconstriction
- Tachycardia (see Sinus Tachycardia)
- Physiology: due to autonomic activation
Gastrointestinal Manifestations
- Abdominal Pain with Rigidity (see Abdominal Pain)
- Physiology: due to muscle spasms
- Clinical:
- Abdomen is Usually Not Tender on Exam
- May Be Mistaken for an Abdominal Surgical Emergency (Such as Appendicitis, etc)
- Nausea/Vomiting (see Nausea and Vomiting)
- Epidemiology: may occur
Hematologic Manifestations
- Leukocytosis (see Leukocytosis)
Neurologic Manifestations
- Anxiety (see Anxiety)
- Headache (see Headache)
- Hyperreflexia (see Hyperreflexia)
- Intracerebral Hemorrhage (Hemorrhagic Cerebrovascular Accident) (see Intracerebral Hemorrhage)
- Painful Muscle Cramps/Spasms of Extremities and Trunk
- Clinical: muscle cramping pain begins within 15-60 min after the bite
- Parasthesias of Hands/Feet (see Peripheral Neuropathy)
- Twitching/Tremor/Fasciculations (see Tremor)
- Weakness
Otolaryngologic Manifestations
- Sialorrhea (Hypersalivation) (see Sialorrhea)
Pulmonary Manifestations
- Labored Respirations: due to respiratory muscle weakness
- Acute Hypoventilation/Respiratory Failure (see Respiratory Failure)
Renal Manifestations
- Urinary Retention (see Urinary Retention)
- Rhabdomyolysis (see Rhabdomyolysis)
- Acute Kidney Injury (AKI) (see Acute Kidney Injury)
Other Manifestations
- Diaphoresis/Sweating (see Diaphoresis)
- Fever (see Fever)
- Uterine Contractions/Pre-Term Labor
Treatment
Treatment of Pain at Bite Site
- Spontaneous Resolution: pain at bite site usualy subsides within several hours (although recurrence over the next 2-3 days are common)
- Analgesics: may be required
- Hot Bath: prompt, but temporary relief of pain
- RICE Therapy
- Rest
- Ice
- Compression
- Elevation
Treatment of Muscle Spasms
- Spontaneous Resolution: painful spasms begin to subside within the first 12 hrs (but may recur for days-weeks before completely resolving)
- Calcium Gluconate (see Calcium Gluconate)
- Administration (10% Solution): 10 mL IV, given over 10-20 min
- Clinical Efficacy: transient cessation of muscle cramps
- Benzodiazepines: (see Benzodiazepines) useful for muscle spasms
- Methocarbamol (Robaxin) (see Methocarbamol)
- Administration: IV
- Clinical Efficacy: may relieve muscle spasms
Widow Spider Antivenom
- Administration: 1 vial in 50 mL of NS IV given over 15 min
- May Need to Test for Hypersensitivity Before Use
- Effective within a Few Hours: may repeat PRN
- Clinical Efficacy
- Controversial: indicated mainly for uncontrolled hypertension, pregnancy, seizures, or respiratory arrest
- Side Effects
- Anaphylaxis (see Anaphylaxis)
- Serum Sickness (see Serum Sickness): as antivenom is derived from horse serum
Tetanus Prophylaxis
- Indicated
Prognosis
- Deaths: have been reported (mostly in children, elderly, and debilitated)
References
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