– A transmissible parasitic infestation of the skin characterized by burrows, intense itching, and excoriations.
Causes and Incidence
Scabies is caused by the Sarcoptes scabiei mite and is easily transmitted by skin-to-skin contact. The mite cannot live long off the human body and is rarely transmitted in any other fashion.
The impregnated female mite burrows under a superficial layer of skin, forming a tiny tunnel. She extends the tunnel daily as she deposits feces and two or three eggs to incubate and hatch. After 20 days, she dies. The eggs hatch and form adult mites within 10 days.
The individual is asymptomatic for 30 to 60 days after initial contact unless he or she has been previously sensitized. In those cases, symptoms appear within 48 hours. The first symptom is severe itching that is most intense at night. The burrows are seen as very fine, wavy dark lines that range from a few millimeters to 1 centimeter in length. They are seen primarily in finger webs, on the palms, on flexor wrist and elbow surfaces, in the axillary folds, around the areolae in girls and women and on the genitals in boys and men, on the buttocks, and around restrictive clothing lines. In infants they may be seen on the face. Scratching causes excoriation, papules, pustules, crusting, and secondary superimposed bacterial infections.
The individual may have a postscabies pruritus that is self-limiting.
The diagnosis is made from visualization of the lesions and scrapings that show the mite on microscopic examination.
Permethrin cream applied to entire body for 24 hours as a scabicide; corticosteroid cream for itching, which may take 1 or 2 weeks to subside; systemic antiinfective drugs for persistent secondary infections.
Examination of all close contacts for infestation; treatment of all members in the household, including pets; cool soaks or compresses to reduce itching.