Scabies

BASICS

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

Global disease whose burden is highest in tropical areas, overcrowded regions, and in economically disadvantaged populations (1)
Most commonly affected: children, adolescents, and elderly.
In North America, case occurrence is more evenly distributed among all age groups.

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 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 list of neglected tropical diseases in 2017

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.

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.

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

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