By Michael Head
Some diseases are more likely to enter public conversation than others. Covid-19 has dominated the public discourse in 2020, while cancer and Aids are high-profile diseases that attract significant scientific and media attention. You can safely discuss these diseases around the dinner table. Other diseases, such as scabies, not so much.
Scabies is classed as a neglected tropical disease. It’s out of sight and out of mind. But that doesn’t mean it isn’t there – there will be an infestation somewhere near you – take my word for it.
Scabies is caused by microscopic mites (Sarcoptes scabiei) that burrow under human skin and lay their eggs. The skin doesn’t take kindly to this infestation, which leads to an angry, itchy rash.
There are an estimated 455 million cases of scabies globally every year. That burden is unequally distributed, with poorer countries bearing the brunt of infestations. Yet even in wealthy countries, where most neglected tropical diseases are unheard of outside of travel clinics, scabies is present, often appearing as outbreaks in institutional settings, such as care homes for the elderly.
It gets everywhere. While treatable, it is also stigmatised, under-reported, often misdiagnosed, and the itch can be seriously unpleasant to bear.
My team and I recently carried out research on scabies in Ghana, describing how patients with scabies and other skin infections would travel further than necessary to report to a health centre. They bypassed their nearest centre, often heading for clinics several kilometres away, across difficult terrain.
The reasons for this are unclear. Colleagues in rural Ghana suggested that the day of the week that the patient reported to a clinic coincides with market day, and so the patient may combine a visit to the clinic and shopping in their nearest town during the one visit. Our statistical analysis did not bear this out, and we could not exclude the idea that patients would bypass their nearest health centre for reasons of stigma.
Scabies is sometimes perceived as an “unclean” condition, even in the published literature, and the idea that washing is a cure is widespread. Bathing will not rid a patient of scabies – but there are treatments that can clear it up.
In 2019, a huge outbreak of more than 6,000 cases of scabies occurred in the north-east region of Ghana. The media reported how there was locally widespread fear at the transmission of skin rashes between villagers. A combination of misdiagnosis and misinformation resulted in some infected people being temporarily banished from their homes.
Local journalists met some of the patients, describing them as having “bloody open sores all over their bodies due to the excessive scratchings”. The outbreak was later correctly diagnosed and treatment was provided. But transmission to thousands of people shows the potential for large outbreaks to occur. An Ethiopian outbreak covered 379,000 cases of confirmed scabies.
In developed countries, the true prevalence is often unknown, but the institutional outbreaks can have a major health, social and economic impact.
Our study in The Lancet showed how care home residents with dementia are more likely to end up with a scabies infection than those without dementia. Even in these settings of vulnerable populations, inequities still apply in terms of those most affected by infectious disease outbreaks.
Managing outbreaks in care homes is difficult and differs from how it is managed in other institutions, such as hospitals. A hospital ward is designed with infection control in mind, but care homes are quite literally that – people’s homes.
The Covid-19 pandemic has put these issues in a very harsh light with the thousands of excess deaths in care homes in countries such as the UK, Sweden and elsewhere. Managing scabies in the elderly is also not helped by ill-founded safety concerns about one of the main oral medicines, ivermectin.
A 1997 correspondence in The Lancet reported increased mortality in care home residents being treated for scabies. It was immediately criticised for inadequate consideration of confounders (other factors that might have influenced the death of the resident, such as severity of dementia), and other outbreak reports have failed to confirm this association.
The WHO has endorsed ivermectin as safe and an essential medicine, but it remains unlicensed for scabies treatment in the UK and is rarely used despite being safe and effective. And, as an oral medicine, it is easier to use than skin creams, such as permethrin.
Scabies doesn’t kill many people and it doesn’t attract headlines, but don’t underestimate the power of the itch. It makes life seriously unpleasant for those with the infection and can lead to stigma and poor quality of life. Multiply that one case you are thinking of by 455 million, and there you have the global annual picture.