Neglected Diseases
Scabies is a parasitic infection of the skin caused by infestation with the microscopic mite Sarcoptes scabiei var. hominis. It is a highly contagious disease, transmitted through close skin-to-skin contact, with the highest rates of infestation occurring in resource-limited settings, particularly associated with tropical climates and overcrowded living conditions. The infestation triggers an immune response causing intense itching and rash, which can be severe enough to disrupt day-to-day activities. Secondary effects result from bacterial skin infection (impetigo), which can progress to severe skin and soft tissue infections and sepsis, or rheumatic fever and glomerulonephritis (leading in turn to rheumatic heart disease and chronic kidney disease).
Scabies is one of the most common illnesses globally, with 565 million incident cases and 4.8 million DALYs in 2019. Although prevalent in most of the world, Asia, including Oceania, accounted for three-quarters (76%) of all new cases in 2019. Due to the high prevalence and greater vulnerability among socio-economically marginalised populations, WHO declared scabies a neglected tropical disease in 2017.
Due to the cost and limited availability of the most efficacious scabicide (permethrin 5% cream), many LMICs rely on less effective and less well-tolerated alternatives, such as benzyl benzoate and sulphur ointments. Topical treatments often suffer from acceptability and compliance issues. Oral ivermectin, approved in many countries for the treatment of scabies, is highly effective but does not kill scabies eggs, necessitating repeat doses and increasing the difficulty of mass drug administration (MDA). Ivermectin is also contraindicated for children less than 15kg and for pregnant and breastfeeding women. Thus, new oral drugs exhibiting prolonged skin activity, effective against newly hatched eggs, and usable by children and pregnant women are urgently needed. Novel diagnostics, such as molecular tests are at an early stage of development. There is an urgent need to develop point–of–care tests as an alternative to existing clinical examination and as a tool to guide ivermectin-based MDA
There are just four candidates in the scabies pipeline, three diagnostics (two in late-stage development) and one drug, moxidectin, for which Medicines Development for Global Health initiated a Phase II efficacy study in late 2023 for treatment of scabies in an adult population. The current study follows a dose-ranging proof-of-concept trial that finished in early 2022.