Scabies (Sarcoptes Scabiei)

Description

• Is in the arthropod class Arachnida, subclass Acari, family Sarcoptidae
• Animal scabies or mange (Sarcoptes scabiei) can burrow but cannot reproduce on human hosts
• Gravid females form burrows where they deposit up to 2–3 eggs per day into the stratum corneum along with feces, skin moults, and saliva
• Secondary infections can occur and are usually due to Staphylococcus aureus or β-hemolytic streptococci and may predispose to renal and cardiac sequelae
• Scabies is a major global health problem in crowded, resource-poor communities and refugee populations

• Scabies may present differently in children:
  • More inflammatory (vesicular or bullous)
  • Involvement of face, scalp, palms, or soles
• Highest prevalence is in children <2 yr old

Etiology

• Epidemiology:
  • Prevalence reports are wide ranging
  • WHO reports up to 130 million infected at any time
  • Burden of disease is highest in countries with hot, tropical climates, especially where overcrowding and poverty coexist
• Transmitted by (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
  • Family members, sexual contacts, and institutional settings are at high risk for transmission
• Symptoms result from delayed (2–4 wk in first exposures) type IV hypersensitivity reaction to mite, eggs, saliva, and feces:
  • Inflammatory reaction leads to intense nocturnal pruritus, which is a hallmark
  • Crusted scabies (Norwegian) is characterized by massive infestation with up to millions mites and is highly contagious and is more common in immunocompromised patients
• Mites subsist on a diet of dissolved human tissue (do not feed on blood) and can live up to 3 d off a host's body
• On average, the number of mites on a host at any time is ∼5–15 unless crusted which suggests massive infestation