Scabies

Scabies is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • A contagious parasitic infection of the skin caused by the mite Sarcoptes scabiei, var. hominis
  • Typically, a clinical diagnosis based on history and physical exam
  • System(s) affected: skin/exocrine

Epidemiology

Incidence
Predominant age: children, sexually active young adults, and the elderly

Prevalence

Prevalence varies substantially worldwide but is more common in resource-poor settings (1):

  • More prevalent in areas of overcrowding and in developing countries, particularly tropical climates
  • Added to World Health Organization list of neglected tropical diseases in 2013

Etiology and Pathophysiology

  • S. scabiei, var. hominis
    • An obligate human parasite
    • Primarily transmitted by prolonged human-to-human direct skin contact
    • Infrequently transmitted via fomites (e.g., bedding, clothing, or furnishings)
  • Female mite lays eggs in burrows in the stratum corneum and epidermis.
  • Itching is caused by a delayed type IV hypersensitivity reaction to the mite saliva, eggs, or excrement.

Risk Factors

  • Prolonged skin-to-skin contact (e.g., sexual, overcrowding, nosocomial infection)
  • Poor nutritional status, poverty, and homelessness
  • Hot, tropical climates
  • Seasonal variation: Incidence may be higher in the winter than in the summer (due to overcrowding).
  • Immunocompromised patients, including those with HIV/AIDS, are at increased risk of developing severe (crusted/Norwegian) scabies.

General Prevention

Prevent outbreaks by prompt treatment and cleansing of fomites (see “General Measures”).

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