Scabies

Last updated: July 11, 2022

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Scabies is a parasitic skin infestation caused by the Sarcoptes scabiei var. hominis (S. scabiei) mite, which is primarily transmitted via direct human-to-human contact. The female scabies mite burrows into the superficial skin layer, causing severe pruritus, particularly at night. Primary lesions commonly include erythematous papules, vesicles, or burrows. Treatment involves topical medical therapy (e.g., permethrin) and decontamination of all clothing and textiles.

  • Pathogen: Sarcoptes scabiei var. hominis
  • Transmission
    • Highly contagious
    • Typically via direct physical (skin-to-skin or sexual) contact
    • Rarely indirect transmission (e.g., sharing textiles such as bedding, towels, or clothes)
    • Commonly affects children ; and individuals living closely with other people (e.g., in nursing homes or jails)
  • Risk factors: : crowded living conditions (e.g., institutions such as nursing homes, child care facilities, and prisons) [1]

References:[2][3]

References:[4]

References:[6]

Crusted scabies (Norwegian scabies)

  • Definition: a rare, severe, and highly contagious form of scabies that presents with a large number of scabies mites and eggs on the skin
  • Epidemiology: typically occurs in immunosuppressed (e.g., HIV), debilitated, or elderly patients
  • Clinical features
    • Slightly pronounced or absent pruritus
    • Lesions
      • Thick crusts or scales on an erythematous base with irregular borders
      • May have a wart-like appearance and fissures
      • Nail changes (i.e., dystrophic, thick)
    • Location
      • Typical areas include the scalp, hands, and feet
      • May involve the whole integument (especially if left untreated)
  • Treatment: rapid and aggressive medical therapy with a scabicidal agent to prevent an outbreak

Scabies may be mistaken for eczema, especially as the topical use of glucocorticoids initially alleviates symptoms.

Bed bugs

  • Definition: ectoparasitic arthropods of the Cimicidae family that feed on blood (typically at night, while individuals are asleep) and whose bite leaves a painless papule that typically becomes pruritic over time
  • Pathogen: Cimex lectularius
  • Transmission: direct contact with infested beds and other furniture and/or travelers who bring home bed bugs or their eggs (e.g., on clothes, in luggage) from stays in infested residences
  • Risk factors: crowded, unsanitary living conditions
  • Clinical features
    • Asymptomatic red punctum at the site of the bed-bug bite
    • Localized skin reactions on exposed skin
      • Painless, erythematous papules with hemorrhagic punctum in the middle
      • Size: 2–5 mm
      • Often appear in a linear pattern
      • Pruritus is common
      • Resolve spontaneously within 1–2 weeks
  • Diagnostics
    • Consult a pest control service
    • Detection of bed bugs in the patient's environment confirms the diagnosis
  • Treatment
  • Prognosis: bites usually resolve spontaneously within 7 days

The differential diagnoses listed here are not exhaustive.

  • Medical therapy: topical application of a scabicidal agent
  • General measures
    • Wash all textiles (e.g., clothing and bedding) (day 1 and day 8 post-treatment)
    • All contacts within the household should be treated for scabies infestation even if asymptomatic.

We list the most important complications. The selection is not exhaustive.

The local health care department should be notified of a suspected threat of community outbreak of scabies and the following measures implemented for:

  • Single noncrusted case
    • Following direct contact with the skin or a patient with scabies, hands should be thoroughly washed (also underneath the nails), then disinfected with an agent that is effective against scabies mites.
    • Appropriate identification and treatment of scabies in the affected individual, with adequate follow-up. All contacts (including within the hospital) should receive prophylactic treatment.
    • Avoid skin-to-skin contact for 8 hours after initial treatment.
    • Increased surveillance for new cases
  • Multiple noncrusted cases
    • In addition to the above, an institution-based awareness and education program
    • Adequate recording of epidemiological data
  • Crusted scabies case: same as above, but more rapid and aggressive approach

References:[7]

  1. Parasites - Scabies - Epidemiology & Risk Factors. https://www.cdc.gov/parasites/scabies/epi.html. Updated: November 2, 2010. Accessed: May 4, 2017.
  2. Management of Scabies. http://www.ifd.org/protocols/scabies. Updated: January 1, 2017. Accessed: May 4, 2017.
  3. Walton SF, Currie BJ. Problems in Diagnosing Scabies, a Global Disease in Human and Animal Populations. Clin Microbiol Rev. 2007; 20 (2): p.268-279. doi: 10.1128/CMR.00042-06 . | Open in Read by QxMD
  4. Bugs, Bites, and Stings. http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/dermatology/bugs-bites-and-stings/. Updated: April 1, 2012. Accessed: May 4, 2017.
  5. Euroform Healthcare » Skin Diseases - Sauer Notes. http://www.euroformhealthcare.biz/skin-diseases/sauer-notes-uvo.html. Updated: October 6, 2016. Accessed: May 5, 2017.
  6. Parasites - Scabies - Disease. https://www.cdc.gov/parasites/scabies/disease.html. Updated: November 2, 2010. Accessed: May 5, 2017.
  7. Parasites - Scabies - Control. https://www.cdc.gov/parasites/scabies/health_professionals/control.html. Updated: November 2, 2010. Accessed: May 5, 2017.

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