Arthropod Bites and Stings

Arthropod Bites and Stings is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • Arthropods are the largest division of the animal kingdom. Two classes, insects and arachnids, have the greatest impact on human disease.
  • Arthropods affect humans by inoculating poison or irritative substances through a bite or sting, by invading tissue, or by contact allergy to their skin, hairs, or secretions.
  • Transmission of infectious microorganisms during feeding is of the greatest concern.
  • Sequelae of bites, stings, or contact may include:
    • Local redness with itch, pain, and swelling: common, usually immediate and transient
    • Large local reactions increasing over 24 to 48 hours
    • Systemic reactions with anaphylaxis, neurotoxicity, organ damage, or other systemic toxin effects
    • Tissue necrosis or secondary infection
    • Infectious disease transmission: Presentation may be delayed weeks to years.

Epidemiology

Incidence
  • ~40 deaths per year in the United States from fatal anaphylactic reaction to insects but likely underreported
  • Unrecognized anaphylactic reactions to Hymenoptera stings may be cause of 1/4 of sudden and unexpected deaths outdoors.

Prevalence
Widespread, with regional and seasonal variations

Etiology and Pathophysiology

  • Arthropods: four medically important classes
    • Insects: Hymenoptera (bees, wasps, hornets, fire ants), mosquitoes, bed bugs, flies, lice, fleas, beetles, caterpillars, and moths
    • Arachnids: spiders, scorpions, mites, and ticks
    • Chilopods (centipedes)
    • Diplopods (millipedes)
  • Four general categories of pathophysiologic effects: toxic, allergic, infectious, and traumatic
    • Toxic effects of venom: local (tissue inflammation or destruction) versus systemic (neurotoxic or organ damage)
    • Allergic: Antigens in saliva may cause local inflammation. Exaggerated immune responses may result in anaphylaxis or serum sickness.
    • Trauma: Mechanical injury from biting or stinging causes pain, swelling, and portal of entry for bacteria and secondary infection. Retention of arthropod parts can cause a granulomatous reaction.
    • Infection: Arthropods transmit bacterial, viral, and protozoal diseases.

Genetics
Family history of atopy may be a factor in the development of more severe allergic reactions.

Risk Factors

  • Previous sensitization
  • Although most arthropod contact is inadvertent, some activities, occupations, and travel increase risk.
  • Greater risk for adverse outcome in young, elderly, immunocompromised, and those with unstable cardiac or respiratory disease
  • Increased risk of anaphylaxis in patients with mastocytosis (1)

General Prevention

  • Avoid common arthropod habitats.
  • Insect repellents (not effective for bees, spiders, scorpions, caterpillars, bed bugs, fleas, ants)
    • N,N-diethyl-meta-toluamide (DEET)
      • Most effective broad-spectrum repellent against biting arthropods (2)
      • Formulations with higher concentrations (20–50%) are first-line choice in areas of endemic arthropod-borne diseases (2).
      • Concentrations >30% have longer duration of action.
      • Safe for children >6 months of age and pregnant and lactating women (2)
    • Icaridin (formerly known as picaridin)
      • Concentrations <20% require more frequent applications to maintain activity.
    • P-menthane-3,8-diol (PMD-lemon eucalyptus extract)
      • Recommended alternative repellent to DEET at concentrations >20% (2)
      • May be used in children >6 months of age (2)
    • IR3535: less effective in most studies
    • Other botanical oils (citronella, etc.): less effective than DEET; not for disease-endemic areas
  • Barrier methods: clothing, bed nets
    • Use of light-colored pants, long-sleeved shirts, and hats may reduce arthropod impact.
    • Permethrin: synthetic insecticide derived from chrysanthemum plant. Do not apply directly to skin. Permethrin-impregnated clothing provides good protection against arthropods.
    • Mosquito nets: Insecticide-treated nets are advised for all travelers to disease-endemic areas at risk from biting arthropods (2).
  • Desensitization 75–95% effective for Hymenoptera-specific venom
    • Skin tests to determine sensitivity
    • Refer to allergist/immunologist.
  • Fire ant control (but not elimination) possible
    • Baits; sprays, dusts, aerosols; biologic agents
  • Risk of tick-borne diseases decreased by prompt removal of ticks within 24 hours of attachment.

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Citation

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TY - ELEC T1 - Arthropod Bites and Stings ID - 117544 Y1 - 2019 PB - 5-Minute Clinical Consult, Updating UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/117544/all/Arthropod_Bites_and_Stings ER -