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

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Basics

Description

  • Mites mate on skin surface and gravid female burrows into stratum corneum to lay eggs:
    • Animal scabies can burrow but cannot reproduce on human hosts
  • Symptoms result from delayed type IV hypersensitivity reaction to mite, eggs, saliva, and feces:
    • Inflammatory reaction leads to intense pruritus, which is the hallmark of the disease
    • Crusted Norwegian scabies is characterized by large numbers of mites and is seen in the immunocompromised, disabled, and institutionalized:
      • More infectious than ordinary scabies due to high mite count
  • Despite >2,500-yr existence, an effective way to prevent scabies is still not known
  • Secondary infection is common and, as such, the morbidity associated with scabies may be underestimated
  • Scabies is a major global health problem in many crowded, resource-poor communities
  • Infestations become secondarily infected and epidemic acute poststreptococcal glomerulonephritis and rheumatic heart disease are often associated with endemic scabies

Pediatric Considerations
  • Scabies manifests itself in various forms in children and differs from that in adults:
    • More inflammatory (vesicular or bullous)
    • Involvement of face, scalp, palms, or soles
  • Highest prevalence is in children <2 yr old

Etiology

  • Epidemiology:
    • Over the past 2 decades, the number of patients with scabies is increasing
    • Up to 300 million cases yearly
    • Burden of disease is highest in tropical countries
  • Produced by the human scabies mite, Sarcoptes scabiei var. hominis, or from animal mites
  • Transmitted by prolonged (15–20 min) direct skin-to-skin contact or, less commonly, by infested bedding or clothing:
    • It is a disease of overcrowding and poverty, rather than a reflection of poor hygiene
    • Probability of being infected is related to number of mites on infected person and length of contact
    • Family members, sexual contacts, and institutional settings are at high risk for transmission
    • Schools do not ordinarily provide the level of contact necessary for transmission
  • Mites subsist on a diet of dissolved human tissue (do not feed on blood) and can live up to 3 days off a host's body
  • On average, the number of mites on a host at any time is ∼5–15:
    • Main difference between crusted Norwegian scabies and ordinary scabies is the number of mites present on the host
    • Patients with crusted Norwegian scabies are infected with thousands or up to a million mites

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Citation

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TY - ELEC T1 - Scabies ID - 307616 Y1 - 2016 PB - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307616/all/Scabies ER -