Scabies

PDF

Scabies is an infestation of the skin by the burrowing mite Sarcoptes scabiei. Infestation is easily spread through direct skin-to-skin contact with sexual partners and household members, and may also occur by sharing clothing, towels and bedding. In adults, the areas most commonly affected are between the fingers and on the wrists, ankles and buttocks, although in the elderly, infection may manifest as a diffuse eruption. In infants and children, the face, scalp, palms and soles are also often affected. Scabies in adults is frequently sexually acquired, although in children usually is not. Symptoms appear about 4 weeks after initial infestation, or within 24 hours after a subsequent reinfestation.

The classic manifestation of scabies is generalized itching that is more intense at night, or after a hot bath or shower. Burrows may be seen in intertriginous areas such as web spaces, skin flexures and the natal cleft, and an associated pruritic rash. There may be papular or vesicular eruptions, or nodular genital lesions.

In HIV positive or immunocompromised patients, there is often an atypical presentation that may involve the face or scalp.

DIAGNOSIS

Diagnosis of a scabies usually is made based upon the typical appearance and distribution of skin lesions or rash and the presence of burrows. The diagnosis can be confirmed by identifying the mite, eggs or faecal matter (scybala). This is done by carefully removing the mite from the end of its burrow using the tip of a needle, by obtaining a skin scraping to examine debris under a microscope with KOH, or by identification of the Scabies mite under dermoscope examination.

TREATMENT
  • Recommended treatment is 5% permethrin cream (Lyclear,  ADEC Pregnancy Category B2), applied topically from the neck down, left on for 8 - 14 hours then thoroughly washed off. The application may be repeated in 1 – 2 weeks if still symptomatic.
  • Ivermectin (200 microgram/kg orally at days 1 and 14,) is an alternative for patients who cannot tolerate or comply with topical therapy, in crusted scabies, or in severe or complicated cases. It is contraindicated in children, and in pregnant or breast-feeding women.
  • Patients should be informed that the rash and pruritus of scabies might persist for up to 2 weeks after treatment, and can be relieved with antipruritic soothing lotions (Crotamiton (Eurax) 10% cream or lotion) or 1% hydrocortisone cream.
  • Pustular lesions may need antibiotic treatment.
  • Benzyl benzoate (Ascabiol – B2): can cause severe skin irritation, but may be a useful environmental spray in some circumstances.
  • Gamma benzene hexachloride (Lindane) should not be used, as it is associated with neurotoxicity and aplastic anaemia especially in infants, pregnant and lactating women, and in the elderly.
APPLICATION OF CREAMS AND LOTIONS
  • Easier if applied with sponge or pastry/paint brush, paying particular attention to the elbows, breasts, groin/genitals/natal cleft,  hands and soles of the feet including under the nails, but avoiding the eyes, nose and mouth.If one burrow is spared then the infestation will persist.
  • There is better absorption if the cream is applied after showering, and it should be left on for at least 8 hours before washing off. Cream should be reapplied to the hands if they are washed during this eight-hour period.
  • Fingernails should be closely trimmed to reduce injury from excessive scratching.
  • Application should be repeated in a week, although an infested person is not generally infectious 24 hours after adequately applied treatment.
  • All household and close physical contacts should receive treatment at the same time as the person with scabies, even if asymptomatic. Treatment  should be repeated in 7-10 days to maximise the chance of eradicating the infestation.
ENVIRONMENTAL MANAGEMENT
  • Mites die after 48 hours off the human host and are almost immobilized in temperatures <20°C. It is estimated that 20 minutes of contact is needed for transmission.
  • Bed linen and clothing should be hot machine-washed, machine-dried using the hot cycle, ironed or dry cleaned, but no special processing such as autoclaving or bleaching is required.
  • Shoes and other non-washable items should be placed in a tightly sealed plastic bag for at least 3 days to effectively eradicate mites.
FOLLOW UP

Treatment failure might be caused by resistance to medication or by faulty application of topical scabicides.Patients who do not respond to the recommended treatment should be re-treated with an alternative regimen.

Disclaimer
The content of these treatment guidelines is for information purposes only. The treatment guidelines are generic in character and should be applied to individuals only as deemed appropriate by the treating practitioner on a case by case basis. Alfred Health, through MSHC, does not accept liability to any person for the information or advice (or the use of such information or advice) which is provided through these treatment guidelines. The information contained within these treatment guidelines is provided on the basis that all persons accessing the treatment guidelines undertake responsibility for assessing the relevance and accuracy of the content and its suitability for a particular patient. Responsible use of these guidelines requires that the prescriber is familiar with contraindications and precautions relevant to the various pharmaceutical agents recommended herein.

Last Updated October 2014