Scabies

Contact Precautions

Scabies is a highly transmissible skin infection that is characterized by burrows, pruritus, and excoriations with secondary bacterial infection. It occurs worldwide, is associated with overcrowding and poor hygiene, and can be endemic. The mites that cause this disorder can live their entire life cycle in human skin, causing chronic infection. The female mite burrows into the skin to lay eggs, from which larvae emerge to copulate and then re-burrow under the skin.

Causes

Infestation with Sarcoptes scabiei var. hominis (itch mite) causes scabies. (See Scabies: cause and effect.) Transmission is via direct, prolonged skin contact. It is most often seen in nursing home residents, school-age children and their families, and the intimate contacts of those with scabies. The adult mite can live for 2 to 3 days without a human host; therefore, inanimate objects can’t be ruled out as a means of transmission.

Complications

Persistent pruritus caused by secondary mite sensitization is a complication of scabies. Intense scratching can lead to excoriation, tissue trauma, and secondary bacterial infection.

Assessment Findings

The patient history may uncover predisposing factors. The patient may first present with asymptomatic lesions. The patient who has been infected for several weeks will complain of intense itching that becomes more severe at night.

Inspection may reveal characteristic gray-brown burrows, which may appear as erythematous nodules when excoriated. These threadlike lesions, about 1 cm long, occur between the fingers, on the flexor surfaces of the wrists, on the elbows, in axillary folds, at the waistline, on the nipples in females, and on the genitalia in males. In infants, the burrows (lesions) may appear on the head and neck. Secondary infection may develop, resulting in the formation of papules and vesicles as well as crusting.

Diagnostic Tests