When Frank Sinatra crooned ‘I’ve got you under my skin’, it’s unlikely he would have anticipated the song conjuring images of scabies infection. Yet for millions of people in developing countries, the skin condition caused by Sarcoptes scabiei var hominis is a substantial cause of morbidity due not only to potentially debilitating itchiness, but also secondary infectious and non-infectious complications from Streptococcus pyogenes or Staphylococcus aureus.
Effective oral and topical treatment is available for scabies infections, however in endemic areas, reinfection occurs frequently, even if household contacts are also treated. In NEJM this week, Romani et al present a comparative trial of Mass Drug Administration (MDA), to assess the effectiveness of different public health approaches to scabies infections.
The Skin Health Intervention Fiji Trial (SHIFT) compared oral ivermectin MDA, topical permethrim MDA, and standard care for scabies control. Endpoints were prevalence of scabies and impetigo at 12 months compared to baseline. Between 2012-2013, 3 comparable Fijian communities were randomly assigned to one intervention. All residents in the 3 communities were eligible and invited to participate; 2051 adult and pediatric participants were enrolled, 803 in the standard care arm, 532 in the permethrin arm, and 716 in the ivermectin arm. Participants were assessed at baseline and treated for scabies as per local guidelines, with permethrin, and second dose at Day 14 if symptoms persisted, and a single dose for contacts. In the Permethrin MDA arm, all participants were offered permethrin and a second dose 7-14 days later if scabies had been identified at baseline. Participants in the ivermectin MDA arm were offered a directly observed dose of oral ivermectin 200ug/kg; pregnant and breastfeeding women, children <15kg, participants with neurological disease, and those taking specific medications were offered topical permethrin instead of ivermectin. A second dose of the medication given at baseline (ivermectin or permethrin) was given to those with scabies at baseline at day 7-14.
At baseline, scabies prevalence was 36.6%, 41.7%, and 32.1% in the standard care, permethrin and ivermectin arms respectively. At 12 months, scabies prevalence decreased significantly in all 3 arms, most in the ivermectin MDA arm (relative reduction of 94% (95% CI 83-100), compared to 62% (95%CI 49-75) in the permethrin MDA arm, and 49% (95% CI 37-60) in the standard care arm. Impetigo prevalence at baseline was 21.6% in the standard care arm and 24.6% in both MDA arms; prevalence at 12 months decreased substantially, with a relative reduction in the ivermectin arm at 67% (95%CI 52-83) compared to 54% (95% CI 35-73) in the permethrin arm (p=0.26), and 32% (95%CI 14-50) in the standard care arm (p=0.05). Adverse events were more common with ivermectin, but no events were serious or persisted beyond 7 days.
In the accompanying editorial, Professor Bart Currie highlights the inclusion of scabies on the World Health Organization’s list of Neglected Tropical Diseases (NTDs) noting that any given time approximately 130 million people are affected globally by scabies infection. A cornerstone of addressing many NTDs has been the development of roadmaps that outline a multi-faceted approach to disease control, including epidemiology, availability of effective treatments, funding mechanisms and research priorities. MDA remains a frequent approach for many NTDs and the study by Romani et al underscores the effectiveness of such an approach in reducing the burden of disease associated with scabies.
Studies demonstrating the effectiveness of public health interventions to reduce disease burden, particularly in resource-limited settings, are an important tool to combat NTD and other diseases of poverty.