scabies /skā″bēz/ [L, scabere, to scratch] , a contagious disease caused by Sarcoptes scabiei, the human itch mite, characterized by intense itching of the skin and excoriation from scratching. The mite, transmitted by close contact with infected humans or domestic animals, burrows into outer layers of the skin, where the female lays eggs. Two to 4 months after the first infection, sensitization to the mites and their products begins, resulting in a pruritic papular rash most common on the webs of fingers, flexor surfaces of wrists, and thighs. Secondary bacterial infection may occur. Diagnosis may be made by microscopic identification of adult mites, larvae, or eggs in scrapings of the burrows. All contacts are treated simultaneously with topical application of permethrin, crotamiton, or another scabicide. Oral antihistamines and salicylates reduce itching. It is also recommended that clothes and bedding be washed in hot water and dried in a hot dryer. A more severe form of scabies is observed in immunocompromised patients and is characterized by vesicles and thick crusts over the skin. This form is known as Norwegian scabies and is treated with Ivermectin.
