Spider Bites

Spider bites are a rare cause of morbidity and mortality. Almost all spiders are venomous, but the majority do not have the ability to penetrate skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin for envenomation. Brown recluse and black widow spiders are the most common causes of serious systemic reactions in the United States. The brown recluse spider contains a necrotizing venom that can lead to a painful, blistering, necrotic wound; fevers; myalgias; hemolysis; seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures; and renal failure. Black widow spiders have a neurotoxic venom that can cause muscle cramping and rigidity (often manifesting as severe abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain), vital sign instability, lacrimation and salivation, ptosis, and respiratory distress. The diagnosis is clinical. Management includes wound care, pain management Pain Management Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain is a subjective experience. Acute pain lasts < 3 months and typically has a specific, identifiable cause. Pain Management, supportive care for systemic symptoms, antivenom for black widow bites, and delayed debridement of necrotic tissue in brown recluse bites.

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Epidemiology and Species

Epidemiology

  • Spider bites are rarely a cause of serious morbidity or mortality.
  • < 3 deaths per year in the United States
  • Severe symptoms and death are more likely to occur in children.

Clinically relevant species

In the United States, the following spider bites can result in serious systemic symptoms: 

Brown recluse spider:

  • Found in central and southern United States
  • Occupy dry, secluded areas including: 
    • Basements
    • Attics
    • Wood piles
Brown recluse spider

The highly venomous brown recluse spider Loxosceles reclusa:
Note the characteristic violin-shaped marking visible on its dorsal cephalothorax.

Image: “1125” by Margaret Parsons. License: Public Domain

Black widow spider:

  • Found worldwide, including the southern and western United States
  • Prefers outdoor habitats:
    • Firewood piles
    • Garages
    • Gardening equipment
    • Trash
    • Outdoor furniture
Female black widow spider

A female black widow spider, Latrodectus mactans, in the process of spinning her web upon a tree branch:
Note the characteristic red hourglass located on her inferior abdominal surface, which can vary in coloration from yellowish to shades of orange and red. The female’s body is a shiny, jet-black color.

Image: “20260” by James Gathany. License: Public Domain

Pathophysiology

Brown recluse spider

  • Necrotizing venom
  • Cytotoxic and hemolytic
  • Components:
    • Sphingomyelinase D: 
      • Complement-mediated erythrocyte destruction
      • Tissue destruction
    • Proteases → degradation of:
      • Collagen
      • Fibronectin
      • Fibrinogen
      • Elastin

Black widow spider

  • Neurotoxic venom
  • Affects neuromuscular transmission and autonomic function
  • Alpha-latrotoxin is the primary toxin:
    • Binds irreversibly to receptors on presynaptic neurons
    • Causes an influx of calcium ions
    • Results in the release of:
      • Acetylcholine
      • Dopamine
      • Norepinephrine
      • Epinephrine
      • Glutamate

Clinical Presentation

Brown recluse spider

  • Bite site:
    • Erythema
    • 2 small puncture wounds may be noted.
    • Center of the bite will become paler.
    • Central blister with surrounding ecchymosis
    • Blister fills with blood and ruptures.
    • Ulceration and eschar formation
  • Localized symptoms:
    • May be painless initially
    • Severe pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain of the entire extremity develops 30‒60 minutes later.
    • Pruritis
  • Systemic symptoms:
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever and chills
    • Nausea and vomiting
    • Arthralgias and myalgias
    • Generalized, morbilliform rash
  • Complications:
    • Seizure
    • Hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
    • Disseminated intravascular coagulation Disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation
    • Thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia
    • Hemolysis
    • Renal failure

Black widow spider

  • Bite site:
    • 2 small puncture wounds may be seen.
    • Erythema and edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema around the bite
    • Central, pale clearing develops (target appearance).
  • Local symptoms:
    • Immediate, sharp, stinging pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
    • Piloerection
    • Isolated diaphoresis
  • Systemic symptoms:
    • Vital signs:
      • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
      • Tachycardia
      • Tachypnea
      • Hyperthermia
    • Severe cramping pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and rigidity of large muscle groups:
      • Abdomen
      • Back
      • Chest
      • Thighs
    • Headache
    • Nausea and vomiting
    • Salivation and lacrimation
    • Anxiety
    • Ptosis
    • Facial and extremity swelling
  • Complications:
    • Respiratory distress
    • Hypertensive emergency
    • Rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis
    • Myocarditis Myocarditis Myocarditis is an inflammatory disease of the myocardium, which may occur alone or in association with a systemic process. There are numerous etiologies of myocarditis, but all lead to inflammation and myocyte injury, most often leading to signs and symptoms of heart failure. Myocarditis
    • Ileus

Diagnosis

Diagnosis

Spider bites are a clinical diagnosis.

  • Spider bites are often falsely suspected by patients, especially in nonendemic regions.
  • Witnessing the bite or identification of the spider is required for confirmation.
  • MRSA skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin infections should be excluded.

Mnemonic

NOT RECLUSE” can help exclude the diagnosis of a brown recluse spider bite:

  • N: Numerous lesions are not typical of a spider bite.
  • O: occurrence (bites tend to occur when disturbing a spider)
  • T: timing (most occur between April and October)
  • R: red center (recluse bites have a pale center)
  • E: Elevated lesions are not typical.
  • C: Chronic lesions are rare.
  • L: Large lesions are rare.
  • U: ulcerates too early
  • S: Swollen lesions usually occur only on the feet or face.
  • E: Exudative lesions do not occur.

Management

General measures

  • Wound cleansing
  • Elevation of the extremity
  • Ensure tetanus Tetanus Tetanus is a bacterial infection caused by Clostridium tetani, a gram-positive obligate anaerobic bacterium commonly found in soil that enters the body through a contaminated wound. C. tetani produces a neurotoxin that blocks the release of inhibitory neurotransmitters and causes prolonged tonic muscle contractions. Tetanus immunization is up to date.
  • Hospitalization and management for systemic manifestations

Additional measures for brown recluse spider bites

  • Cold compresses:
    • Sphingomyelinase D is temperature dependent.
    • Slows the necrosis process
  • Pain management:
    • NSAIDs
    • Opioids Opioids Opiates are drugs that are derived from the sap of the opium poppy. Opiates have been used since antiquity for the relief of acute severe pain. Opioids are synthetic opiates with properties that are substantially similar to those of opiates. Opioid Analgesics
  • Surgical excision of necrotic regions should be delayed until fully demarcated.

Additional measures for black widow spider bites

  • Pain management:
    • Opioids Opioids Opiates are drugs that are derived from the sap of the opium poppy. Opiates have been used since antiquity for the relief of acute severe pain. Opioids are synthetic opiates with properties that are substantially similar to those of opiates. Opioid Analgesics
    • Benzodiazepines Benzodiazepines Benzodiazepines work on the gamma-aminobutyric acid type A (GABAA) receptor to produce inhibitory effects on the CNS. Benzodiazepines do not mimic GABA, the main inhibitory neurotransmitter in humans, but instead potentiate GABA activity. Benzodiazepines for muscle relaxation
  • Black widow spider antivenom

Differential Diagnosis

  • Insect sting: bee, wasp, and ant stings can cause envenomation with localized swelling. Some patients will develop a severe allergic reaction, including anaphylaxis. Neurologic manifestations and tissue necrosis are not usually present. The diagnosis is clinical. Management includes removing the stinger (if present), antihistamines Antihistamines Antihistamines are drugs that target histamine receptors, particularly H1 and H2 receptors. H1 antagonists are competitive and reversible inhibitors of H1 receptors. First-generation antihistamines cross the blood-brain barrier and can cause sedation. Antihistamines, pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain control, and emergency care for anaphylaxis.
  • Scorpion sting: most scorpion stings Scorpion stings Insect and scorpion stings are a rare cause of mortality. Hymenoptera insects and Centruroides scorpions can potentially lead to serious symptoms due to envenomation. Pain, swelling, erythema, and warmth are common at the site of a sting. Insect and Scorpion Stings are harmless; however, the bark scorpion is venomous. Patients will have pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and swelling at the site of the sting. Systemic manifestations can include muscle spasms, diaphoresis, abnormal neck and head movements, tachycardia, hypertension, and respiratory distress. The diagnosis is clinical. Management includes supportive care, pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain control, benzodiazepines for muscle spasms, and antivenom.
  • Cellulitis Cellulitis Cellulitis is a common infection caused by bacteria that affects the dermis and subcutaneous tissue of the skin. It is frequently caused by Staphylococcus aureus and Streptococcus pyogenes. The skin infection presents as an erythematous and edematous area with warmth and tenderness. Cellulitis: a common bacterial skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin infection that affects the deeper layers of the dermis and subcutaneous tissue. This condition is most commonly caused by Staphylococcus Staphylococcus Staphylococcus is a medically important genera of Gram-positive, aerobic cocci. These bacteria form clusters resembling grapes on culture plates. Staphylococci are ubiquitous for humans, and many strains compose the normal skin flora. Staphylococcus aureus and Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus pyogenes. Cellulitis Cellulitis Cellulitis is a common infection caused by bacteria that affects the dermis and subcutaneous tissue of the skin. It is frequently caused by Staphylococcus aureus and Streptococcus pyogenes. The skin infection presents as an erythematous and edematous area with warmth and tenderness. Cellulitis presents as an erythematous, edematous area that is warm and tender to the touch. Bullae, necrosis, and systemic toxicity are not usually present. The diagnosis is clinical, and management involves antibiotics tailored to the suspected organism.
  • Necrotizing fasciitis Necrotizing fasciitis Necrotizing fasciitis is a life-threatening infection that causes rapid destruction and necrosis of the fascia and subcutaneous tissues. Patients may present with significant pain out of proportion to the presenting symptoms and rapidly progressive erythema of the affected area. Necrotizing Fasciitis: a life-threatening infection that causes rapid destruction and necrosis of the fascia and subcutaneous tissues. Patients may have significant pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain and rapidly progressive erythema of the affected area. Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, hypotension, altered mental status, and multisystem organ failure may also be present. The diagnosis is primarily clinical. This type of infection is a surgical emergency and requires emergent surgical debridement, parenteral antibiotics, and close hemodynamic monitoring.
  • Anthrax Anthrax Anthrax is an infection caused by the bacterium Bacillus anthracis, which usually targets the skin, lungs, or intestines. Anthrax is a zoonotic disease and is usually transmitted to humans from animals or through animal products. Symptoms depend on which organ system is affected. Anthrax: an infection caused by Bacillus Bacillus Bacillus are aerobic, spore-forming, gram-positive bacilli. Two pathogenic species are Bacillus anthracis (B. anthracis) and B. cereus. Bacillus anthracis. Cutaneous infection presents with a painless, pruritic papule that enlarges to form an ulcer with a black eschar. Systemic symptoms such as fever, lymphadenopathy Lymphadenopathy Lymphadenopathy is lymph node enlargement (> 1 cm) and is benign and self-limited in most patients. Etiologies include malignancy, infection, and autoimmune disorders, as well as iatrogenic causes such as the use of certain medications. Generalized lymphadenopathy often indicates underlying systemic disease. Lymphadenopathy, myalgia, and nausea are common. Hematologic, neurologic, and renal complications are not seen. The diagnosis requires identification of the organism on culture, direct fluorescent antibody testing, or PCR. Antibiotics are used for treatment.
  • Mesenteric ischemia Mesenteric Ischemia Mesenteric ischemia is a rare, life-threatening condition caused by inadequate blood flow through the mesenteric vessels, which results in ischemia and necrosis of the intestinal wall. Mesenteric ischemia can be either acute or chronic. Mesenteric Ischemia: interruption in blood flow through the mesenteric arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries resulting in ischemia of the bowel. Patients present with abdominal pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain out of proportion to the clinical exam. Peritonitis, hematochezia, and shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock occur with bowel infarction. No skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin lesion will be seen. Computed tomography with angiography is the diagnostic modality of choice. Management is often surgical and focuses on re-establishing blood flow to the intestines.
  • Hypocalcemia Hypocalcemia Hypocalcemia, a serum calcium < 8.5 mg/dL, can result from various conditions. The causes may include hypoparathyroidism, drugs, disorders leading to vitamin D deficiency, and more. Calcium levels are regulated and affected by different elements such as dietary intake, parathyroid hormone (PTH), vitamin D, pH, and albumin. Presentation can range from an asymptomatic (mild deficiency) to a life-threatening condition (acute, significant deficiency). Hypocalcemia: a low plasma calcium concentration that may be due to hypoparathyroidism Hypoparathyroidism Hypoparathyroidism is defined as reduced parathyroid hormone (PTH) levels due to poor function of the parathyroid glands. The cause of hypoparathyroidism is most commonly iatrogenic following neck surgery, but it can also be associated with genetic or autoimmune disorders as well as infiltrative diseases causing destruction of the normal parathyroid tissue. Hypoparathyroidism, vitamin D deficiency, or renal disease. Patients with severe hypocalcemia may present with paresthesias, muscle cramping, tetany, hyperreflexia, and seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures. The skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin lesion and other systemic symptoms of a black widow spider bite will not be seen. Low serum calcium levels provide the diagnosis, and management requires calcium supplementation and correction of the underlying etiology.

References

  1. Centers for Disease Control and Prevention. Venomous spiders. National Institute for Occupational Safety and Health (NIOSH). Reviewed May 31, 2018. https://www.cdc.gov/niosh/topics/spiders/
  2. Bush, S.P., Cohen, J.P., Green, S. (2020). Widow spider envenomation. In Alcock, J. (Ed.). Medscape. Retrieved March 24, 2021, from https://emedicine.medscape.com/article/772196-overview
  3. Arnold, T.C. (2018). Brown recluse spider envenomation. In Alcock, J. (Ed.). Medscape. Retrieved March 24, 2021, from https://emedicine.medscape.com/article/772295-overview
  4. Anoka, I.A., Robb, E.L., Baker, M.B. (2020). Brown recluse spider toxicity. StatPearls. Retrieved March 24, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK537045/
  5. Williams, M., Anderson, J., Nappe, T. (2020). Black widow spider toxicity. StatPearls. Retrieved March 24, 2021, from https://www.statpearls.com/ArticleLibrary/viewarticle/29298
  6. Barish, R.A., Arnold, T. (2020). Spider bites. MSD Manual Professional Version. Retrieved March 24, 2021, from https://www.msdmanuals.com/professional/injuries-poisoning/bites-and-stings/spider-bites

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