Scabies diagnosis and management

Last updated: January 2017

Diagnosis

Microscopy

Scrapings taken from burrows may be examined under light microscopy to reveal mites, eggs, larvae or faeces collected from patient’s skin.

Clinical presentation

Observing typical lesions (characteristic silvery lines) in sites where mites have burrowed. Classic sites include wrists, finger web spaces, axillae, elbows, around breast/nipples in women. thighs, ankle, toe web spaces. Papules or nodules may be seen in the genital area.

Absorption of mite excrement into skin capillaries generate a hypersensitivity reaction which may take 4-6 weeks to develop

Main symptom is a generalised itch, with a classic pattern of pruritus at night, after a hot shower or bath.

If associated with exposure to an infected person, the index of suspicion should be high even in the context of non-specific symptoms.

Immunosuppressed patients (e.g. HIV patients) may present with Norwegian scabies – crusted lesions teeming with mites posing as a significant risk of transmission to others. This condition may not be pruritic.

Clinical appearance is typical but diagnostic confusion may occur with other itching dermatological conditions like eczema.

Secondary bacterial infection of skin lesions can occur following repeated scratching.

Treatment

Standard therapy

Permethrin 5% cream topical from neck downwards covering whole body, washed off after at least 12 hours overnight but not more than 24 hours (grade of recommendation A) (B2).

Note the following:

• Permethrin should be applied to clean and cool skin. The patient should not take a hot bath or shower prior to treatment.
• 1% creams and lotions are ineffective against scabies.
• Pay particular attention to the areas between the fingers and toes, under fingernails and toenails, wrists, armpits, genitals, buttocks and perianal area. It is usually helpful for a second person to assist with the application of cream to areas that are not easily accessible.
• Reapply cream to the hands if they are washed within 12 hours of treatment.
• Additional weekly treatments are warranted only if live mites can be demonstrated.

Adjunct therapy

• Topical steroids and oral antihistamines can be useful for control of itch
• Antihistamines may be required for several weeks for symptomatic relief of itch
• Oral antibiotics are sometimes required for secondary infection due to scratching.

Alternative therapy

Ivermectin 200mcg/kg orally, repeated in 2 weeks (B3).

Norwegian scabies is usually treated with oral Ivermectin.

Immunosuppressed and HIV co-infection

These patients may prove resistant to topical therapy. Review by a specialist may be necessary.

Pregnancy and Breast Feeding

Permethrin is safe during pregnancy and breastfeeding.

Patient education

The following points should be discussed:

• The nature of the infection
• Sex partners and household contacts should be treated concurrently
• Patients are advised to avoid close body contact until they and their partners have completed treatment
• Patients are advised to avoid close body contact until they and their partners have completed treatment
• Non-sexual transmission of scabies is possible, but requires direct and prolonged body contact
• Clothing and bed linen which may have been contaminated by the patient within the past 2 days should be machine washed and dried (hot cycle >50⁰ C if possible) or separated and dry cleaned
• Pruritus may persist for several weeks after adequate therapy due to sensitisation to mite antigens
• The presence of scabies indicates the need for a complete sexually transmitted infections (STI)/human immunodeficiency virus (HIV) screen.
• Arbitrary time span is for contacts from previous 2 months.

Follow up

Follow up is only indicated if symptoms have not resolved.

Appearance of new burrows at any stage post treatment is indicative of a need for further treatment.

In reinfections, symptoms of pruritis may recur before typical burrows have developed

Pruritus > 2 weeks after treatment may reflect treatment failure, reinfection or drug allergy to anti-scabetics.

Further information

For further information on the management and diagnosis of scabies, contact Adelaide Sexual Health Centre.

Disclaimer

These guidelines are based on review of current literature, current national and international guidelines and recommendations, and expert opinion.

They are written primarily for use by Adelaide Sexual Health Centre staff and some flexibility is required in applying them to certain private practice situations.