Scabies Organism-Specific Therapy

The arthropod Sarcoptes scabiei var hominis causes an intensely pruritic and highly contagious skin infestation. Scabies in adults frequently is sexually acquired, although scabies in children usually is not. The first time a person is infested with S scabiei, sensitization can take several weeks to develop; however, pruritus may occur within 24 hours after a subsequent reinfestation.[1, 2, 3, 4]

Classic scabies should be treated primarily with topical treatments. Crusted scabies (Norwegian scabies) is a severe infestation with crusted lesions, typically in elderly and immunocompromised individuals; it is highly contagious, with individuals harboring millions of mites. Both oral and topical agents should be used together for crusted scabies.[5, 6]

Classic scabies - Treatment recommendations

First-line therapies[6]

Topical permethrin 5% (preferred therapy) is administered as follows:

• Cream thoroughly massaged into skin from the neck down; wash off after 8-14 hours
• One application is generally sufficient; can be done overnight, but a second application is recommended after 1 week
• Ensure application of cream under fingernails, toenails, soles of feet, and scalp for children

Oral ivermectin (recommended for more severe infestations) is administered as follows:

• 200 mcg/kg PO single treatment, repeated after 1-2 weeks
• Not recommended for pregnant or lactating patients or children who weigh less than 15 kg
• Low cost, easy administration, well tolerated, good for mass treatment in facilities

Benzyl benzoate 25% lotion is administered as follows:

• Low cost, recommended in resource limited countries
• Not available in United States

Other agents[2, 3, 6]

Crotamiton 10% lotion or cream is administered as follows:

• Treatment not standardized, considered less effective than permethrin
• Apply on two consecutive nights; thoroughly massage into skin of entire body from the chin down, paying particular attention to all folds and creases; second application is advisable 24 hours later; wash off 24 hours after second application

Topical sulfur, 6-33% cream, ointment, or lotion is administered as follows:

• 240 g of 8% or 10% precipitated sulfur in petrolatum for adults, applied to body overnight for three consecutive days
• Recommended for pregnant women, neonates

Malathion 0.05% lotion is administered as follows:

• Single application, applied overnight to skin and washed off 8-12 hours later

Crusted scabies (Norwegian scabies) - Treatment recommendations

Combination treatment is strongly recommended.

US Centers for Disease Control and Prevention's combination regimen for the treatment of crusted scabies is as follows:

• Topical 5% permethrin or topical 5% benzoyl benzoate applied for seven consecutive days, then twice weekly until cure AND
• Oral ivermectin (200 mcg/kg/dose) given on days 1, 2, 8, 9, and 15; doses on days 22 and 29 can be given for more severe infestations

The use of lindane is contraindicated for patients with Norwegian scabies, owing to the risk of toxicity.

Special considerations[1, 2, 5, 6]

Patients should be informed that the rash and pruritus of scabies may persist for up to 2 weeks after treatment.

Particular attention must be given to the fingernails of these patients, and recommendations include advising patients to trim fingernails. Mites may be found here.

Treatment of fellow household members and close contacts, as well as washing clothing, bedding, and towels in warm or hot water, is recommended.

Items that cannot be washed can alternatively be isolated from use for 3 days.

Infested individuals may be asymptomatic for up to 6 weeks but are able to transmit infestation; symptomatic individuals may harbor less than 15 mites, making the location of burrows difficult.

Symptomatic individuals in an institutional setting indicate an infestation lasting several months; surveillance among institutionalized persons and staff, as well as control (ie, handwashing, avoidance of skin-to-skin contact with cases), should be put in place.

Guidelines

US Centers for Disease Control and Prevention suggested guidelines for the treatment and prevention of scabies are summarized below.[5]

Treatment should be given to both the infested person and to household members and sexual contacts, particularly those who have had prolonged skin-to-skin contact with the infested person.

All persons should be treated at the same time to prevent reinfestation.

Bedding, clothing, and towels used by infested persons or close contacts anytime during the 3 days before treatment should be decontaminated by washing in hot water and drying in a hot dryer, by dry-cleaning, or by sealing in a plastic bag for at least 72 hours. Scabies mites generally do not survive more than 2-3 days away from human skin.

Use of insecticide sprays and fumigants is not recommended.

Scabicides are available only with a prescription. No over-the-counter (nonprescription) products have been tested and approved to treat scabies.