Resource Packages: Scabies

Historical Overview

Scabies, or body louse as it was called, is a worldwide disease that has been prevalent for centuries.  History books referred to the “seven year itch” which was probably scabies.  The scabie mite was isolated in 1687 and the cause of the itch finally diagnosed.  Lice were responsible for the spread of many diseases such as typhus, relapsing fever, and trench fever.

In 1937 Dr Robert A. Lyster wrote that to “combat the infection it may be necessary for every person in the family to receive a bath whilst the clothing and bedding are at the same time disinfected by the application of steam”.  Also recommended to be most effective was dusting with D.D.T powder. (Just where was not explained).

Scabies, Sarcoptic itch, or Acariasisis is a parasitic disease of the skin caused by a mite, whose penetration is visible as papules, vesicles or tiny linear burrows containing the mites and their eggs.

Although not a notifiable disease, the prevalence of scabies has increased not only in Australia but also worldwide.  Outbreaks have generally occurred in association with conditions of crowding, poor hygiene and malnutrition.  The current nationwide resurgence has affected persons from all socioeconomic levels without regard to sex, age or cleanliness.

Recent Developments

Scabies is frequently misdiagnosed because it may mimic several other cutaneous disorders such as eczema, insect bites, contact dermatitis or impetigo.

Scabies is transmitted by intimate personal contact, often sexual in nature, but casual contact including that of nursing, may be adequate for transmission.  Minimum contact with a patient with Norwegian scabies (or crusted scabies) can result in transmission because of the large number of mites in the exfoliating scales. Scabies can be transmitted as long as the patient remains untreated, including the interval before symptoms develop. 

Lesions are prominent around finger webs, anterior surfaces of wrists and elbows, anterior axillary folds, belt line, thighs and external genitalia in men, while nipples, abdomen, and the lower portion of the buttocks are frequently affected in women.  In infants, the head, neck, palms and soles may be involved, these areas are often spared in older individuals.  Itching is intense, especially at night.

Diagnosis is confirmed by identification of the scabie mite, the mites egg or scybala (faeces) from skin scrapings of intact burrows on the skin.  Prior application of mineral oil facilitates collecting the scrapings with a #15 scalpel, then transferring them to a glass slide, applying a coverslip and examining the specimen under low power microscope.

Alternatively, the burrow ink test may be performed by applying a felt-tipped ink pen to the burrow and wiping off the excess ink with alcohol, thereby allowing the ink to penetrate the burrow and become visible.

Other supporting features of infestation include burrows or suggestive skin lesions in the characteristic distribution, or a history of contact with a case.

Incubation period in persons without previous exposure is usually 4 to 6 weeks. Persons who were previously infected develop symptoms 1 to 4 days after repeat exposure to the mite, but these re-infections are usually milder.

Standard precautions should be practiced at all times.

Contact precautions should be considered for patients for 24 hours after start of effective treatment. Contact Precautions require a single room, gowns/aprons. Linen bedding and clothing used before treatment should be laundered in a washing machine with hot water and a hot drying cycle. The mites do not survive more than 3 to 4 days without contact with skin. Clothing that cannot be laundered should be removed from the patient and stored for several days in plastic bags.

Treatment

The agents available for treatment of scabies include lindane 1% (Kwell), crotamiton 10% (Eurax), permethrin 5% cream (Elimite), and sulphur 5% in petrolatum.

The agent that has been used most extensively is lindane, however lindane’s safety has been the subject of recent discussions.  When lindane is left on the skin too long, especially excoriated skin, percutaneous absorption can cause neurotoxity. Crotamiton 10% and sulphur 5% in petrolatum is a product that has been considered safe for infants and pregnant women, however definite data does not exist.  A single application of permethrin 5% cream has been shown to be more effective than crotamiton and lindane.

Patients should be bathed, then if using permethrin cream it should be massaged into the skin from the head including the scalp to the soles of the feet. Leave the cream on for 8 to 14 hours before bathing again.

If crotamiton is selected, it should be applied to the entire body including the scalp and left on for 24 hours after the initial bath.  A second 24-hour application is recommended before bathing again.

When using lindane, it should be applied to the entire body avoiding eyes and mucous membranes and the application left on the body for approximately 6 hours. After 6 hours, a second bath should be taken.

If after a week there is still evidence of active infestation (positive microscopic findings), a second treatment course may be initiated.  Patients should be informed that scratching (pruritus) might persist for more than 10 days since it usually results from retained parts of the scabietic mites.

Epidemics and localised outbreaks may require stringent and consistent measures to treat contacts.  Patients with Norwegian or crusted scabies and their close contacts must be treated promptly to avoid outbreaks.  It is important that not only the patient but also household members and close contacts are treated at the same time.

Children should be allowed to return to childcare or school after treatment has been completed.

References

Benenson AS. 16th ed,1995.  Control of Communicable Diseases Manual.  American Public Health Association, Washington, USA.

Committee on Infectious Diseases, 23rd ed, 1994.  American Academy of Pediatrics. Report of the Committee on Infectious Diseases, USA.

Failla D, Pankey GA. Apr 1995, vol 36, no 4. Treating Bacterial Skin Infections. Current Therapeutics, Australia’s Journal of Practical Drug Treatment, Australia.

Koda-Kimble, Mary Anne. Lloyd, Yee Young. 5th ed, 1992.  Applied Therapeutics, The Clinical Use Of Drugs.  Applied Therapeutics Inc, Vancouver, Canada.

Mandell LG, Douglas GR, Bennett JE. 1985, 3rd ed.  Principles and Practice of Infectious Diseases.  Churchill Livingstone, New York, USA.

Mayhall G, Glen. 1996.  Epidemiology and Infection Control.  Williams and Wilkins, Baltimore, USA.

NSW Health Department, 1999.  Infection Control Policy. 99/87, AIDS/Infectious Diseases Branch, Sydney.

Stein DH, 1991, pp 660 - 666. Scabies and pediculosis, Current Opinion in Pediatrics. USA.

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