Schlossberg : Current Therapy of Infectious Disease - LICE, SCABIES, AND MYIASIS

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Current Therapy of Infectious Disease

David Schlossberg

PART 1:

CLINICAL PRESENTATION
Skin

22	LICE, SCABIES, AND MYIASIS William L. Krinsky

SCABIES

Scabies dermatitis is caused by the mite Sarcoptes scabiei and its secretions and excretions. The mites are microscopic; the adult female is the largest stage, 300 to 400 mm long. The female mites burrow into the skin and lay eggs. Skin lesions and intense pruritus are first noted 2 to 6 weeks after a person becomes infested. The most common lesions in order of frequency are papules, vesicles, crusted lesions, pustules, mite burrows, and wheals. The burrows, which have been observed in less than 25% of patients, are linear (5 to 15 mm long) or serpentine and gray, erythematous, slightly swollen, or scaly. Burrows are pathognomonic for scabies and occur most commonly in the interdigital areas, wrists, elbows, and lateral aspects of the hands, feet, and ankles. The burrows may be highlighted by applying mineral oil, ink, or tetracycline (which fluoresces under a UV lamp) and wiping off the excess that is not retained in the skin. Definitive diagnosis requires identification of the mite, which may be removed from a burrow by gently lifting the top off with a scalpel or needle and placing the debris from the burrow on a microscope slide. Observations of the material at 50´ to 100´ magnification can reveal living mites, ova, and mite feces. Mineral oil, immersion oil, or 10% potassium hydroxide placed on the burrow material on the slide may enhance identification of the mite.

Therapy

As in pediculosis, treatment of scabies involves use of any of various lotions or creams. The most commonly used preparations are lindane lotion, permethrin cream, and crotamiton lotion, or vanishing cream (Table 2). Permethrin, which is generally more effective than crotamiton and lacks the potential toxicity associated with lindane use, especially in infants, children, and pregnant or nursing women, is the treatment of choice for children and adults. Special effort should be made to coat the subungual areas and intertriginous spaces, such as the intergluteal cleft, with the scabieticide. Many patients, especially those with heavy mite burdens, as in crusted scabies, may continue to experience pruritus for several days after treatment. Repeat treatments should be given only if examination reveals the persistence of mites.

DRUG	TREATMENT	FOLLOW-UP
Table 2 Treatment for Scabies
Permethrin (Elimite or Acticin)—5% cream	Massage cream into skin from head to soles of feet (scalp, temples, and forehead to soles of children older than 2 months of age); wash off 8-14 hours later.	One treatment usually is curative.
Lindane (hexachlorocyclohexane) lotion 1%	Massage lotion into skin from neck down to soles of feet; wash off 8-12 hours later.	Repeat treatment may be needed 7 days later.
Crotamiton (Eurax)—10% lotion or cream	Massage into skin of whole body from chin down; may repeat application 24 hours later; bathe thoroughly 48 hours after last application.	May irritate raw or denuded skin, so close evaluation is necessary.

As in pediculosis, all close contacts should be treated. Laundering clothing and bedding in hot water or dry cleaning will destroy the mites. Suspect materials may be used safely after storage for 10 days in sealed plastic bags.