20. Scabies

OTHER NAMES
Sarcoptes scabiei
DEFINITION
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).

CAUSES, INCIDENCE, AND RISK FACTORS
Scabies is found worldwide among people of all groups and ages. It is spread by direct contact with infected individuals and less often by sharing clothing or bedding. Sometimes whole families are affected. The mites that cause scabies burrow into the skin and deposit their eggs forming a characteristic burrow that looks like a pencil mark. Eggs mature in 21 days. The itchy rash is an allergic response to the mite. Mites maybe more widespread on a babies skin causing pimples over the tnuik, or small blisters over the palms and soles. In young children, the head, neck, shoulders, palms and soles are involved. In older children, hands, wrists, and abdomen are involved.
PREVENTION
Avoid contact with infected persons, clothing bedding.
SYMPTOMS
- itching, especially at night
- thin, pencil-mark lines on the skin
- rashes
- Abrasions of the skin from scratching and digging
SIGNS AND TESTS
Examination of the skin shows characteristic signs of scabies.
Tests include microscopic examination of skin scrapings taken from a burrow.
Treatment & Prognosis

Treatment is aimed at killing scabies mites and controlling the dermatitis, which can persist for months after effective eradication of the mites. Bedding and clothing should be laundered or cleaned or set aside for 14 days in plastic bags. If secondary pyoderma is present, it is treated with systemic antibiotics (see photograph). Unless treatment is aimed at all infected persons in a family or institutionalized group, reinfestations will probably occur.

Permethrin 5% cream is highly effective and safe in the management of scabies. Treatment consists of a single application for 8–12 hours. It may be repeated in 1 week.

Pregnant patients should be treated only if they have documented scabies themselves. Permethrin 5% cream once for 12 hours—or 5% or 6% sulfur in petrolatum applied nightly for 3 nights from the collarbones down—may be used.

Patients will continue to itch for several weeks after treatment. Use of triamcinolone 0.1% cream will help resolve the dermatitis. Scabies in nursing home patients, institutionalized or mentally impaired (especially Down syndrome) patients, and AIDS patients may be much more difficult to treat.

Most failures in normal persons are related to incorrect use or incomplete treatment of the housing unit. In these cases, repeat treatment with permethrin once weekly for 2 weeks, with reeducation regarding the method and extent of application, is suggested. In immunocompetent individuals, ivermectin in a dose of 200 mcg/kg is effective in about 75% of cases with a single dose and 95% of cases with two doses 2 weeks apart. In immunosuppressed hosts and those with crusted (hyperkeratotic) scabies, multiple doses of ivermectin (every 2 weeks for two or three doses) plus topical therapy with permethrin once weekly may be effective when topical treatment and oral therapy alone fail.

Persistent pruritic postscabietic papules may be treated with mid- to high-potency corticosteroids or with intralesional triamcinolone acetonide (2.5–5 mg/mL).

Preventing Reinfection

All family and close contacts should be treated at the same time, even if asymptomatic. After treatment has been applied or taken, (or directly before treatment if you are careful and wear gloves) cleaning of environment should occur. A person can easily be reinfected with scabies.

Without a host, scabies mites can on average survive up to 48-72 hours away from human skin.  As in cases of Crusted Scabies, they can survive much longer, up to 7 days. Therefore it is recommended, after treatment, to wash all material (such as clothes, bedding, and towels) that has been in contact with all infested persons in the last three days.

All household members should be treated at the same time and cleaning must be thorough and simultaneous. Either isolate long enough for the mites to die in a plastic bag for at least 1 week, or clean or freeze overnight.

• Vacuuming floors, carpets, and rugs.
• Disinfecting floor and bathroom surfaces by mopping (this only needs to be done after the first treatment).
• Daily washing of recently worn clothes, towels and bedding in hot water and drying in a hot dryer.
• 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.

Treatment for Pets

Pets and humans get infected with different types of mites. The mites that we get can not survive and reproduce on pets.

Steroid Use During Treatment

Steroids or corticosteroids should not be used to combat itching. These can cause a weakened immune system creating various new diseases and the worst type of scabies. Options include antihistamines such as cetirizine. Prescription: Doxepin (Sinequan - oral or Zonalon - topical).

EXPECTATIONS (PROGNOSIS)
Scabies are annoying but not a serious disease.
COMPLICATIONS
A secondary skin infection can occur because of intense scratching.

Courtesy:

Compiled and Shared By: Habib Anwar 

habib.anwar@hotmail.com