Treatment of crusted scabies (Norwegian scabies)
In crusted scabies, the mite population on the patient is very high; this is more likely in patients with inadequate immune response (eg immunocompromised patients), who are physically incapacitated, or in remote Aboriginal and Torres Strait Islander communities. Crusted scabies is highly transmissibleWorld Health Organization (WHO), 2020. It is a notifiable disease in some states and territories in Australia. To prevent transmission of crusted scabies, empirically treat all members of the patient’s family and close contacts. Also see General measures for scabies for other recommendations to prevent transmission (eg washing clothes).
Treatment of crusted scabies is difficult, and discussion with an infectious diseases physician or a dermatologist is recommended. A combination of 3 treatments is required:
- oral ivermectin
- frequent application of a topical scabicide (permethrin, benzyl benzoate [sometimes in combination with tea tree oilDavis, 2013], sulfur or crotamiton)
- frequent application of a topical keratolytic agent (eg salicylic acid 5 to 10% in sorbolene cream, lactic acid 5%+urea 10% in sorbolene cream).
Apply the topical scabicide every second day for the first week, then twice a week until clinically cleared. For topical scabicide preparations and doses, see Treatment of scabies in adults and children older than 6 months or Treatment of scabies in infants younger than 6 months. Topical keratolytics reduce scaling—apply daily after washing, on days when the topical scabicide is not applied.
For crusted scabies, in addition to a topical scabicide and keratolytic, use:
ivermectin (adult and child 15 kg or more) 200 micrograms/kg orally with fatty food, for 3, 5 or 7 doses depending on severity and clinical response—seek specialist advice1 ivermectin ivermectin ivermectin
for a 3-dose regimen, give on days 1, 2 and 8
for a 5-dose regimen, give on days 1, 2, 8, 9 and 15
for a 7-dose regimen, give on days 1, 2, 8, 9, 15, 22 and 29.
Patients with crusted scabies are at risk of superimposed bacterial skin and soft tissue infection (eg skin sores, impetigo, pyoderma), and bacteraemiaHasan, 2020. For patients with crusted scabies in endemic settings (eg remote communities), empirical therapy is usually indicated because of secondary bacterial infection:
- For patients with sepsis and/or extensive skin sores, use empirical intravenous antibiotics initially to cover polymicrobial infection until results of blood cultures and cultures of skin sores can direct therapy. See Principles of managing sepsis and septic shock.
- For patients without sepsis but with some skin sores, use empirical therapy as for impetigo; see Management of impetigo.
For patients with crusted scabies in nonendemic settings, there is a low threshold for considering empirical therapy—see Management of impetigo.