Scabies: Mite Infestation, Transmission, and Treatment

Scabies is an intensely itchy skin infestation caused by the mite Sarcoptes scabiei var. hominis.

Transmission

• Prolonged skin-to-skin contact (sexual, household, caregiving).
• Less commonly: shared clothing, bedding, towels (mites survive 48–72 hours off host).
• Not transmitted by brief contact (handshake, hug) or pets (different mite species).

Symptoms

• Intense itching, worse at night.
• Burrows: thin, grayish, serpiginous lines (finger webs, wrists, elbows, axillae, beltline, genitalia).
• Papules, vesicles, nodules; secondary excoriation, impetigo.
• Incubation: 2–6 weeks (first infestation); 1–4 days (reinfestation).

Diagnosis

Clinical + microscopic identification of mites, eggs, or feces (scybala) from skin scrapings. Dermoscopy aids visualization.

Treatment

• First-line: Permethrin 5% cream (full body, neck down, 8–14 hrs). Repeat in 7 days.
• Alternative: Ivermectin 200 μg/kg oral (two doses 1–2 weeks apart). Preferred for crusted scabies, institutions.
• Environmental: Wash/dry bedding/clothing at 60°C; seal non-washables 72 hrs.
• Contacts: Treat all household/sexual contacts simultaneously, even if asymptomatic.

Special Populations

Infants/young children: treat scalp/face. Pregnancy: permethrin preferred. Crusted (Norwegian) scabies: aggressive combo therapy, isolation.