Annals of Long Term Care

Scabies is a contagious parasitic disease (infestation) of the skin that can infect residents of long-term care facilities. By the time scabies is suspected, many residents and staff have been exposed, and, until properly treated, continued transmission is predictable. Facility outbreak control policies either do not exist or are outdated, resulting in the administration of ineffective scabicides or scabicides being improperly administered. To prevent outbreaks, facilities should develop a written scabies outbreak control plan; train healthcare workers to recognize, document, and report the condition of residents’ skin at the time of admission, and frequently thereafter; implement barrier precautions for residents with suspicious rashes or symptoms; perform diagnostic tests; and treat cases and their contacts with an effective scabicide. (Annals of Long-Term Care: Clinical Care and Aging 2009;17[4]:31-35)

What Is Scabies?

Whisper the word scabies in any long-term care facility, and there is immediate panic associated with psychosomatic itching and an image of microscopic bugs crawling on the skin. Scabies is a contagious parasitic disease (infestation) of the skin caused by the human itch mite, Sarcoptes scabiei var hominis. Scabies affects only humans and does not discriminate based on socioeconomic level, gender, ethnicity, age, race, sexual orientation, or personal hygiene habits.1

The life cycle2,3 of the scabies mite begins when one or several pregnant females are transferred from the skin of an infested person to the skin of an uninfested person. Following transfer, the pregnant mite wanders haphazardly around the skin surface before selecting a suitable burrow site. Once a site is selected, the mite(s) secretes a saliva-like substance and uses its four stubby legs to burrow through the outer layer of the host’s skin. A fertile female can lay about three eggs each day. The eggs hatch in 3-4 days, producing larvae that migrate to the surface of the skin, dig another burrow, and feed on intracellular fluids. Over the next 7-10 days, the larvae develop into sexually mature adult mites. This cycle is repeated many times during the 2-month lifespan of the female mite. The male mites have a very short lifespan (1-2 days) that is spent seeking out unmated females. In healthy persons, fewer than 10% of the eggs live long enough to reach adulthood. Most of the eggs are removed from the skin during bathing or other actions such as scratching. Once a female mite leaves the human skin, its life is terminated in about 3-4 days.

The severity of the infestation is related to the number of mites residing on the skin and the length of time between the initial infestation and subsequent treatment. If diagnosis and treatment are delayed, the number of mites multiplies daily, resulting in progression of the infestation from a typical or classic form (eg, fewer than 50 mites on the skin)3 to a heavier or atypical infestation. Keratotic or crusted scabies, sometimes referred to as Norwegian scabies, was first described in persons diagnosed with leprosy in Norway.4 This severe form of scabies is generally characterized by thick, crusty skin lesions. Embedded within these crusts are thousands to millions of live mites.5 There are several physiological and immunological conditions—including renal failure, insulin-dependent diabetes, severe mental retardation, malnutrition, acquired immunodeficiency syndrome (AIDS), T-cell leukemia,6 and the administration of topical and systemic corticosteroids1,3—that can hasten the progression of the infestation.

Recognizing Scabies

Healthy persons with no history of previous infestation will have no signs or symptoms immediately following an exposure and during the initial 3-6–week incubation period. Following the incubation period, the infested person will complain of pruritus, which intensifies at bedtime.