Scabies

Basics

Scabies is a major global health problem in crowded, resource-poor communities and refugee populations
Animal scabies (Sarcoptic mange) is transmissible 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 result in severe renal and cardiac sequelae

Scabies may present differently in children:
- More inflammatory (vesicular or bullous)
- Broader distribution including face, scalp, palms, or soles
Highest prevalence is in children <2 yr old

Epidemiology:
- 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) skin-to-skin contact or, less commonly, from infested bedding or clothing:
- It is associated with overcrowding and poverty, rather than a reflection of poor hygiene
- Family members, sexual contacts, and settings such as military barracks, nursing homes, and correctional facilities are at higher risk
Symptoms result from delayed (2–6 wk from 1st exposure) type IV hypersensitivity reaction to mite, eggs, saliva, and feces. Those previously infested have a shorter onset to symptoms:
- Inflammatory reaction leads to intense nocturnal pruritus, which is a hallmark
- Crusted scabies (Norwegian) is characterized by massive infestation with up to millions of mites, is highly contagious and more common in immunocompromised patients
Mites subsist on a diet of dissolved human tissue (do not feed on blood) and can live up to 72 hr off a host’s body
On average, the number of mites on a host at any time is ∼5–15 unless crusted (massive infestation)

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