Clinical Evidence Handbook

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Scabies



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Am Fam Physician. 2009 Jun 15;79(12):1089-1090.

This clinical content conforms to AAFP criteria for evidence-based continuing medical education (EB CME). See CME Quiz on page 1045.

Scabies is an infestation of the skin by the mite Sarcoptes scabiei. In adults, the most common sites of infestation are the fingers and the wrists, although infection may manifest in older persons as a diffuse truncal eruption.

  • The estimated prevalence is 300 million cases worldwide, with most instances occurring in resource-poor countries.

Topical permethrin is highly effective at increasing clinical and parasitic cure of scabies within 28 days.

  • Topical lindane is also an effective treatment for scabies, although it has been withdrawn from the market in the United Kingdom.

  • Lindane and permethrin may be more likely to be related to rare severe adverse effects, such as death or convulsions, compared with other treatments, such as benzyl benzoate, crotamiton, or malathion.

Topical crotamiton successfully produces clinical or parasitic cure after 28 days, although it is less effective than permethrin.

We did not find sufficient evidence to judge the effectiveness of topical benzyl benzoate, topical malathion, or topical sulfur compounds for treating scabies.

Oral ivermectin seems effective at increasing clinical cure rates compared with placebo.

  • Observational data suggest that oral ivermectin may be effective when included in the treatment of hyperkeratotic crusted scabies, and in persons with concomitant human immunodeficiency virus (HIV).

Clinical Questions

What are the effects of topical treatments for scabies?

Beneficial

Crotamiton (topical; as effective as topical lindane, but less effective than topical permethrin)

Permethrin (topical)

Trade-off between benefits and harms

Lindane (topical)

Unknown effectiveness

Benzyl benzoate (topical)

Malathion (topical)

Sulfur compounds (topical)

What are the effects of systemic treatments for scabies?

Likely to be beneficial

Ivermectin (oral)

Clinical Questions

View Table

Clinical Questions

What are the effects of topical treatments for scabies?

Beneficial

Crotamiton (topical; as effective as topical lindane, but less effective than topical permethrin)

Permethrin (topical)

Trade-off between benefits and harms

Lindane (topical)

Unknown effectiveness

Benzyl benzoate (topical)

Malathion (topical)

Sulfur compounds (topical)

What are the effects of systemic treatments for scabies?

Likely to be beneficial

Ivermectin (oral)

Definition

Scabies is an infestation of the skin by the mite Sarcoptes scabiei. Typical sites of infestation are skin folds and flexor surfaces. In adults, the most common sites are between the fingers and on the wrists, although infection may manifest in older persons as a diffuse truncal eruption. In infants and children, the face, scalp, palms, and soles are also often affected. Infection with the scabies mite causes discomfort and intense itching, particularly at night, with irritating papular or vesicular eruptions. The discomfort and itching can be especially debilitating among immunocompromised persons, such as those with HIV or acquired immunodeficiency syndrome (AIDS).

Prevalence

Scabies is a common public health problem, with an estimated prevalence of 300 million cases worldwide. It mostly affects persons in resource-poor countries, where prevalence can exceed 50 percent. In industrialized countries, it is most common in institutionalized communities. Case studies suggest that epidemic cycles occur every seven to 15 years, and that these partly reflect the population's immune status.

Etiology

Scabies is particularly common in areas where there is social disruption, overcrowding with close body contact, and limited access to water. Young children, immobilized older persons, persons with HIV or AIDS, and other medically and immunologically compromised persons are predisposed to scabies infestation and have particularly high mite counts.

Prognosis

Scabies is not life threatening, but the severe, persistent itching and secondary infections may be debilitating. Occasionally, crusted scabies develops. This form of the disease is resistant to routine treatment, can be a source of continued reinfestation, and may spread to other persons.

Author disclosure: Nothing to disclose.

editor's note: Benzyl benzoate is not available in the United States.

 

search date: October 2007

Adapted with permission from Johnstone P, Strong M. Scabies. Clin Evid Handbook. Dec 2008:571–572. Please visit http://www.clinicalevidence.bmj.com for full text and references.

This is one in a series of chapters excerpted from the Clinical Evidence Handbook, published by the BMJ Publishing Group, London, U.K. The medical information contained herein is the most accurate available at the date of publication. More updated and comprehensive information on this topic may be available in future print editions of the Clinical Evidence Handbook, as well as online at http://www.clinicalevidence.bmj.com (subscription required). Those who receive a complimentary print copy of the Clinical Evidence Handbook from United Health Foundation can gain complimentary online access by registering on the Web site using the ISBN number of their book.


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