Scabies

Symptoms

• The absorption of mite excrement into the skin capillaries generates a hypersensitivity reaction.
• The main symptom, which may take 3 to 6 weeks to develop (1 to 3 days in cases of re-infection), is generalised itch – especially at night.

Signs

• Characteristic silvery lines may be seen in the skin where mites have burrowed.
• Classic sites include the interdigital folds, the wrists and elbows, and around breast nipples in women.
• Papules or nodules that may result from itching often affect the genital area.
• In HIV infection, crusted lesions that teem with mites (crusted scabies) pose a significant risk of scabies infection transmission.
• Scabies incognito: this refers to the altered clinical pictures seen following use of topical steroids, and consists of widespread atypical papular lesions that may mimic other generalised forms of eczema. Symptoms are masked but patient remains infectious

• Clinical - often confused with other itching conditions such as eczema.
• Itchy papules and nodules on the penis are almost certainly scabetic.
• Examine scrapings from burrows under light microscopy or use a magnifying glass to examine lesions.

• Offer a full STI testing including HIV.
• Avoid body contact until they and their partner(s) have completed treatment and follow up.
• May be able to help itch with antihistamines + crotamiton (Eurax) cream.
• Bedding, clothing and towels used by infested persons or the household, sexual and close contacts during the previous 4 days before treatment should be decontaminated by:
• washing at high temperature (greater than 60°C) and drying in a hot dryer, or
• by dry cleaning, or
• sealing in a plastic bag for at least 72 hours.
• Scabies mites generally do not survive more than 72 hours away from human skin.
• Patients should be given a detailed explanation of their condition, and clear and accurate written information on applying the treatment.
• Itch may persist for several weeks – retreatment too soon often results in the development of hypersensitivity to scabicide, thus compounding the itch.

First line treatment

Alternative treatments

Malathion 0.5% (Derbac-M, Prioderm, Quellada M): apply to whole body as above and wash off after 24 hours. If hands are washed within 24 hours of application, then re-apply. Repeat after 7 days.

Treatment of crusted scabies

Treatment should be discussed with a senior colleague familiar with the condition.

Complications

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

Partner notification

Trace and treat all sexual and household or institutional contacts over previous one months.

Follow up

• Re-treat if new burrows appear.
• Pruritus persisting more than 2 weeks after treatment may reflect treatment failure, reinfection, or drug allergy to anti-scabetics.

1. BASHH Guidelines [Internet]. SAGE Publications Ltd. 2016 UK National Guideline on the Management of Scabies: [2016; cited 2022 Nov 15]. Available from: https://bashhguidelines.org/media/1137/scabies-2016.pdf