Scabies

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
• Male children from lower income quartiles were more likely to visit the ED in a retrospective analysis of nationally representative National Emergency Department Sample for 2013 to 2015, whereas older male patients, insured by Medicare, from the highest income quartile in the Midwest/West were most likely to be admitted to the hospital.

Prevalence
Prevalence varies substantially worldwide but is more common in resource-poor settings.

• More prevalent in areas of overcrowding and in developing countries, particularly tropical climates
• Added to World Health Organization’s list of neglected tropical diseases in 2017

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 (drug-induced), those with leukemia, lymphoma, or those with congenital immune deficiencies, including those with HIV/AIDS, are at increased risk of developing severe (crusted/Norwegian) scabies (1).

General Prevention

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