scabies n : a contagious skin infection caused by the itch mite; characterized by persistent itching and skin irritation; "he has a bad case of the itch" [syn: itch]

English

Pronunciation

• IPA: /ˈskei.biz/
• Other 1: (skāʹbēz)
• Other 2: SKAY-beez
• Rhymes: -eɪbiz

Noun

scabies

1. An infestation of parasitic mites, Sarcoptes scabiei, causing intense itching caused by the mites burrowing into the skin of humans and other animals. It is easily transmissible from human to human; secondary skin infection may occur.

Related terms

• scab

Translations

• Catalan: sarna
• CJKV Characters: 疥
• Chinese: 筥筮 (jǔshì)
• Danish: fnat
• Dutch: schurft
• Finnish: syyhy
• French: gale ; mal de Sainte-Marie
• German: Krätze
• Hebrew: גרדת (garedet)
• Indonesian: kudis
• Italian: (acaro della) scabbia
• Korean: 옴 (om)
• Latin: scabiēs
• Luxembourgish: Krätz
• Norwegian: reveskabb
• Polish: świerzb
• Portuguese: sarna
• Russian: чесотка (česótka)
• Spanish: sarna
• Swedish: skabb
• Vietnamese: bệnh ghẻ

See also

mange

Scabies is a transmissible ectoparasite skin infection characterized by superficial burrows, intense pruritus (itching) and secondary infection. The word scabies comes from the Latin word for "scratch" (scabere).

Etiology

Scabies is caused by the mite Sarcoptes scabiei, variety hominis, as shown by the Italian biologist Diacinto Cestoni in the 18th century. It produces intense, itchy skin rashes when the impregnated female tunnels into the stratum corneum of the skin and deposits eggs in the burrow. The larvae, which hatch in 3-10 days, move about on the skin, molt into a "nymphal" stage, and then mature into adult mites. The adult mites live 3-4 weeks in the host's skin.

The action of the mites moving within the skin and on the skin itself produces an intense itch which may resemble an allergic reaction in appearance. The presence of the eggs produces a massive allergic response which, in turn, produces more itching.

Scabies is transmitted readily, often throughout an entire household, by skin-to-skin contact with an infected person (e.g. bed partners, schoolmates, daycare), and thus is sometimes classed as a sexually transmitted disease. Spread by clothing, bedding, or towels is a less significant risk, and is almost impossible.

The symptoms are caused by an allergic reaction that the body develops over time to the mites and their by-products under the skin, thus the 8 week "incubation" period. There are usually relatively few mites on a normal, healthy person — about 11 females in burrows. Scabies are microscopic although sometimes they are visible as a pinpoint of white. The females burrow into the skin and lay eggs there. Males roam on top of the skin, although they can and do occasionally burrow. Both males and females surface at times, especially at night. They can be washed or scratched off (however scratching should be done with a washcloth to avoid cutting the skin as this can lead to infection), which, although not a cure, helps to keep the total population low. Also, humans create antibodies to the scabies mites which do kill some of them.

Signs, symptoms, and diagnosis

A tiny mite (0.3 to 0.9 mm) may sometimes be seen at the end of a burrow. Most burrows occur in the webs of fingers, flexing surfaces of the wrists and armpits, the areolae of the breasts in females and on genitals of males, along the belt line, and on the lower buttocks. The face usually does not become involved in adults.

The rash may become secondarily infected; scratching the rash may break the skin and make secondary infection more likely. In persons with severely reduced immunity, such as those with advanced HIV infection, or people being treated with immunosuppressive drugs like steroids, a widespread rash with thick scaling may result. This variety of scabies is called Norwegian scabies.

Scabies is frequently misdiagnosed as intense pruritus (itching of healthy skin) before papular eruptions form. Upon initial pruritus the burrows appear as small, barely noticeable bumps on the hands and may be slightly shiny and dark in color rather than red. Initially the itching may not exactly correlate to the location of these bumps.

Generally diagnosis is made by finding burrows, which often may be difficult because they are scarce, because they are obscured by scratch marks, If burrows are not found in the primary areas known to be affected, the entire skin surface of the body should be examined.

The suspicious area can be rubbed with ink from a fountain pen or alternately a topical tetracycline solution which will glow under a special light. The surface is then wiped off with an alcohol pad; if the person is infected with scabies, the characteristic zigzag or S pattern of the burrow across the skin will appear.

When a suspected burrow is found, diagnosis may be confirmed by microscopy of surface scrapings, which are placed on a slide in glycerol, mineral oil or immersion in oil and covered with a coverslip. Avoiding potassium hydroxide is necessary because it may dissolve fecal pellets. Positive diagnosis is made when the mite, ova, or fecal pellets are found.

Domestic animals

People with compromised immune systems may not develop antibodies to the mites and may develop crusted Norwegian scabies. In this case, many form scabs or develop very red skin especially in the elderly and the mentally handicapped where white or gray crusted areas develop with little itching and little or no red bumps and mite population numbers rise to thousands in AIDS patients . These cases require additional treatment options to ensure a complete kill. Ivermectin is a single oral treatment of choice in these patients combined with any other topical treatment.

Gallery of scabies infections

Evolution of infection

Treatment

Medications

Topical

• Permethrin: Another pesticide, lacks carcinogenic and teratogenic testing in humans although animal tests showed no signs of carcinogenic or teratogenic effects. Toxicity may resemble allergic reactions.
• Eurax (USP Crotamiton)
• Malathion Applied for 24 hours effective in killing adults and eggs.
• Lindane (Kwellada): For use with patients where permethrin has failed or is contraindicated.

Lindane is FDA approved as safe and effective when used as directed for the second-line treatment for both scabies and lice. Serious side effects are rare and have almost always resulted from product misuse. Lindane is registered for use in 50 countries, with restricted-use status in 33 of these countries. The latter includes the U.S. and Canada, which support public health uses of pharmaceutical lindane but no longer allow agricultural applications. Lindane should be washed off with warm, and not hot, water to avoid absorption through the skin. Five to –10% sulfur ointments are considered historical.

• 10% sulfur ointment: Can be used in pregnant women and infants under two months of age. It is available over-the-counter.

Oral

A single dose of ivermectin has been reported to cure scabies. In 1999, a small scale test comparing topically applied Lindane to orally administered ivermectin found no statistically-significant differences between the two treatments.

Preventing reinfection

All family and close contacts should be treated at the same time, even if asymptomatic. Cleaning of environment should occur simultaneously, as there is a risk of reinfection. Without a host, scabies mites can on average survive up to 48-72 hours away from human skin. (In cases of Crusted Scabies, mites can survive up to 7 days.) Therefore it is recommended to wash all material (such as clothes, bedding, and towels) that has been in contact with all infested persons in the last three days.

Cleaning the environment should include:

• Vacuuming floors, carpets, and rugs.
• Disinfecting floor and bathroom surfaces by mopping.
• Cleaning the shower/bath tub after each use.
• Daily washing of recently worn clothes, towels and bedding in hot water and drying in a hot dryer.
• Consistently rubbing antibacterial lotion on infected areas.
• Trying to keep infected areas covered by clothing or band aids.
• Hot drying pillows for 30 minutes.
• Overnight freezing, in a plastic bag: stuffed animals, brushes, combs, shoes, coats, gloves, hats, robes, wetsuits, etc.
• Quarantine in a plastic bag for two weeks: things that cannot be washed, hot dried, frozen or drycleaned.
• Drycleaning: things that cannot be washed, hot dried or frozen or quarantined.

Itchiness during treatment

Options to combat itchiness include antihistamines such as cetirizine. Prescription: Doxepin (Sinequan - oral or Zonalon - topical) or Hydroxine.

References

Notes

Resources

• The Merck Manual of Diagnosis and Therapy, 17th edition, 1999
• Clinician's Pocket Reference, 9th edition, 2002
• Taber's Cyclopedic Medical Dictionary, 17th edition, 1993
• United States Centers for Disease Control and Protection
• World Health Organization Essential Medicines Library
• American Social Health Association
• MedlinePlus Drug Information: Lindane
• Prevention and control of scabies in california long term care facilities

See also

• Lindane
• Crab louse
• Head louse

External links

• American Academy of Dermatology pamphlet on Scabies
• Scabies FAQ from the National Pediculosis Association

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