Itchy patient? Think scabies

After Rob’s blog about the rise of measles last week, this week we turn our attention to an outbreak of another age-old disease! Hands up if you’ve seen a patient with scabies recently? I can think of at least five cases, some of whom have had very nasty, persistent or widespread rashes. It therefore came as no surprise to me to see recent articles in the Guardian and Metro describing a surge in cases of scabies to at least double the seasonal average.

What’s going on? 

In the UK, scabies outbreaks do typically occur in the winter, when we’re all cuddled up together indoors, sharing our mites. Remember, the mites don’t jump but are easily spread through direct close contact, usually of 10 minutes or longer. Mites can also be spread through fomites, such as towels or clothing, though fortunately they only survive a matter of hours on inanimate objects so this route of transmission is less common. Symptoms may not develop for four to six weeks after transmission. 

However, it is thought that the outbreak has been particularly bad this year because of problems with the availability of the two main treatments, permethrin and malathion. Both of these should be available over the counter, but malathion in particular has been out of stock, with only limited supplies of permethrin. This has led to delays in people starting treatment, which offers a window of opportunity for the mites to spread from the host to new contacts. 

Just being aware of the increased prevalence of scabies at the moment can be helpful; as Dermnet.nz advise, ‘clinical suspicion is paramount’! We are all familiar with the itchy nodular rash that typically affects the hands and finger webs, skin creases or genitals, sometimes with characteristic burrow tracks. However, more atypical rashes can occur with a non-specific eczematous rash that can even spread to the head and neck or torso, particularly in children, the elderly or anyone immunocompromised. Think about scabies in any patient with a new itchy rash and remember to ask about possible contact history and travel. Dermoscopy or skin scrapings to assess for mite eggs or faeces may be helpful where there is diagnostic uncertainty. 

The best way of successfully treating scabies and preventing a recurrence is to make sure suspected cases and their close contacts are all treated correctly and at the same time. The BAD – British Association of Dermatologists (hats off for the acronym guys!), have produced a handy patient information leaflet summarising how to apply topical treatment, such as permethrin. Essentially, people need to get naked, wash before treatment and apply to ALL of the skin – only avoiding the area around the eyes. BAD recommend applying generously to the nipples and genitals (I suspect the erotic nature of all this will be diluted by the fact the treatment is only needed because you’re covered in biting mites and their faeces…), as well as under the nails, behind the ears and the soles of the feet. It’s best to apply the treatment overnight so it will stay on for 12 hours and if any areas are washed in this time, e.g. the hands, the treatment needs to be re-applied. Everyone should then re-apply the treatment after seven days. 

This advice is important to get right because there is also an increase in the number of people reporting a non-response to treatment. It is thought for many people this is due to poor treatment application or non-compliance, but there is a concern some mites may be growing resistant to permethrin. Limited mobility and previous topical steroid use have been reported as risk factors for treatment resistance. Ivermectin may now be considered in the UK for people with evidence of ongoing infestation despite topical treatment, or people with crusted scabies – a more severe reaction that is usually only seen in people who are immunocompromised. 

Finally, remember topical scabies treatment or the scabies themselves can cause a dermatitis and itching can continue for several weeks, even after successful treatment. If there is an ongoing rash that does not appear characteristic of scabies then consider treating with emollients, topical steroids or antihistamines, rather than repeated scabies treatment.