Scabies

Essentials

• Treatment given "just in case" may cause problems. Aim at diagnosis first.
• Examine in proper lighting, ask the patient to remove clothing covering the typical sites.
• Scabies is easily transmitted: it is important to treat all close contacts, not only those with symptoms.
• Clothes and bed clothes must be washed alongside treatment.

Epidemiology

• Scabies is not a sexually transmitted disease even though it may be transmitted during sexual intercourse.
• Scabies may be transmitted even during brief skin contact and in health care facilities or in day care, for example.

Symptoms and findings

• Itching, especially in the evening and during the night
  • The symptoms usually commence a few weeks after infection. In reinfections the latent period is shorter.
  • Most symptoms usually occur on the trunk and the limbs.
  • There is significant individual variation in the severity of the symptoms.
• Findings
  • There are extensive papules and signs of scratching on the skin (Images ). Pustules are also common (folliculitis).
  • Vesicles may occur (on palms and soles, particularly).
  • Secondary patchy eczema (on the trunk and/or limbs)
  • Nodules in the genital or flexural areas
  • A few itching, erythematous papules on male genitalia strongly suggest scabies (Images ).
  • Symptoms rarely occur on the face or the scalp.
  • Symptoms and findings may be atypical in, for instance, elderly people or people with intellectual disability or immunosuppression, who may have generalized scabies (Image ).
• Avoid attempts at determining the time of infection in individual patients.

Diagnosis

• Scabies is usually suspected based on a typical clinical picture or symptoms occurring in several close contacts.
• The diagnosis can be confirmed by finding scabies mite burrows or the mite; in most cases, this requires the use of tools (dermatoscope, magnifying glass, stereomicroscope or microscope).
• Mite burrows are seen nearly always in the wrist folds or between fingers (Images ), and in children, particularly, also on the palms and soles.
  • Other areas where mite burrows may be found include the antecubital fossae, armpits, feet and areolas.
• If there is a stereomicroscope available (even a magnifying glass is helpful), the mite can be seen as a dark spot and easily extracted from its burrow to be identified under an ordinary microscope.
• Also examine close contacts, as far as possible (such as examining the wrists and between the fingers of the parents of small children).
• In some cases, the diagnosis must be based on a typical clinical picture alone (no scabies mite or its burrows can be found).
  • If so, the differential diagnostic options should be considered, and targeted further investigations performed if there is no response to the treatment of scabies.

Differential diagnosis

• Insect bites Insect Stings and Bites (usually isolated itchy lesions)
• Eczematous diseases Seborrhoeic Dermatitis in the Adult Nummular Dermatitis Atopic Eczema (Atopic Dermatitis) in Adults
  • Note the typical location of eczematous diseases.
  • Scabies may involve secondary, patchy eczema.
• Folliculitis Skin Abscess and Folliculitis may sometimes resemble scabies.
  • The typical localization of the lesions and often similar symptoms in other persons living in the same household are essential features of scabies.
• Impetigo Impetigo and other Pyoderma
  • Usually less symptoms
  • Scabies may involve secondary skin infections, such as impetigo.
• See also Pruritus Pruritus

Treatment

• Two forms of treatment are available, with no difference observed in their efficacy for scabies: topical permethrin and oral ivermectin.
  • Depending on local availability, other, usually second-line treatments, may be available but not discussed here.
• The patient and all close contacts (family members, dating partners, etc.) should be treated.
• Topical Permethrin cream Treatments for Scabies
  • The cream should be applied all over the skin in the evening,
  • taking care to cover the scalp, inside the navel, the external genitals, the folds between fingers and toes, and underneath the nails.
  • The drug should be allowed to take effect overnight, for 8-12 hours, and then washed off.
  • This is the primary treatment for children.
• Oral ivermectin Treatments for Scabies
  • As a single weight-adjusted dose of 200 µg/kg body weight in patients weighing more than 15 kg
• For both forms of treatment, European guidelines suggest two treatments 7-14 days apart to prevent failure; the official recommendation by the pharmaceutical manufacturers is a single treatment.
• Alongside the treatment, bed clothes and clothes that have touched the skin should be washed.
• Infectiousness ends after the treatment, so the patient may return to day care or school, for instance, on the day after the treatment.
• After the treatment of scabies, itching papules may occur for even over a month. They should not be treated with anti-scabies drugs, unless scabies mites are genuinely found in the skin.
• Low and midpotency glucocorticoid ointments, or combination ointments containing a low to midpotency glucocorticoid and an antiseptic agent are suitable for treating itching and secondary eczema. The normal period of treatment is 1-3 weeks.
• Not uncommonly a false diagnosis or two coexistent skin diseases are the reason for a poor response to treatment. If the treatment fails, it often emerges that only symptomatic family members have been treated.
• If a patient needs recurrent treatment of scabies, it should be confirmed that the diagnosis is correct (could it still be some other itchy disease apart from scabies?) and that the patient's close contacts have been treated (recurring reinfestation).

Specialist consultation

• A dermatologist should be consulted in therapy-resistant cases or if there are diagnostic problems.

Pictures