Page 2
|
Page 2 |
The scabies mite is highly contagious and is spread by skin to skin contact such as hand holding. While scabies is not a notifiable disease, suspected outbreaks should be reported to the local public health team.
Spread of scabies can be rapid, requiring extensive tracing of all case contacts, including carers, friends and relatives. The mite cannot live for long away from the host, so there is very little chance of spread through bedclothes or clothing, which should be washed and laundered as normal.
Crusted or `Norwegian' scabies affects people with a poor
immune system. Crusts form which are full of mites and there is
little or no itching. This form of scabies is highly contagious
within institutional settings and requires specialist management advice.
| Figure 1. Typical distribution of the symmetrical scabies 'rash'. |
 |
| Note: These areas do not always correspond to the sites of the mite burrows. |
Scabies should be considered in the differential diagnosis of any itchy rash affecting the flexures. Diagnosis of scabies is usually made from the presentation and history of symptoms. A widespread rash develops two to six weeks after initial infection with the mite. This is usually accompanied by severe itching, which is often worse at night or after bathing when the skin is hot.
Typically, the rash is symmetrical and affects the areas marked in figure 1. The burrows produced by the scabies mite do not always correspond to the rash site and are often difficult to see. They are usually found on the hands, wrists, elbows, feet, genitals and armpits (see figure 2). Scabies usually only affects the face, neck, head and ears in immuno-compromised patients, children under two years and the elderly.
Diagnosis of scabies is only certain after the mite has been identified, as it may be mistaken for other skin conditions such as eczema. Identification of the mite can be helped by scraping the skin at the burrow sites to expose the mite and eggs. Although the mite can just be seen with the naked eye, examination with a magnifying glass or microscope may be necessary. Alternatively, skin scrapings may be sent for laboratory testing.
Two products are listed in the Nurse Prescribers' Formulary (NPF) for the treatment of scabies, malathion and permethrin. As skin may already be excoriated when treatment is initiated, use of the alcoholic lotions Prioderm and Suleo-M are not recommended. Choice is restricted to malathion 0.5% aqueous lotion (Derbac-M, Quellada M), or permethrin 5% cream (Lyclear Dermal Cream). These products are also available to buy over the counter from pharmacies.
Infected patients and their close contacts should be treated at the same time, regardless of whether they have symptoms or not. This includes all members of the household, as well as all skin to skin contacts within the last two months.3
An average sized adult will require 100ml of malathion for a single application.1 Two tubes of permethrin 5% cream may be required to treat a large adult.1
A Cochrane Collaboration review of the treatment of scabies was published in 1997.4 Nearly all of the studies included in this review took place in developing countries. Most studies also compared products that are either not available, or are not used as first-line treatment in the UK (e.g. lindane, crotamiton).
In the five studies of permethrin included in this review, about 90% of scabies cases were cured with this agent.4 In four of the studies, permethrin was shown to be significantly more effective in terms of clinical cure rate than the comparator agents (lindane and crotamiton). However, a larger study found no difference between permethrin and lindane in terms of clinical cure rate.
No studies of malathion were included in the Cochrane review due to their poor quality. However, a non-randomised study of 67 patients with scabies found that malathion cured about 90% of cases after a single application, compared with about 68% of those using benzyl benzoate (not listed in the NPF).5
The risk of neurotoxicity with permethrin and malathion is low when used according to instructions.6,7 For typical infections, scabicides should not be used more than once a week for more than three weeks at a time. In addition, both malathion and permethrin can cause skin irritation, even if the aqueous formulations are used.
Scabicides should be applied to cool, dry skin and NOT after a hot bath as this may decrease their effectiveness. The patient information leaflet gives further details of how to apply scabicides effectively.
| Figure 2: Common sites of the scabies mite burrows.2 |
 |
| Note: Feet can also be involved. |
 |
Download this document in PDF format for printing. |  |