Scabies – A global health challenge

Scabies has endemic proportions among many refugees, homeless, and people in developing countries, but occur worldwide and may affect people of all social classes.

As Prof. Olivier Chosidow (Henri Mondor University Hospital, France) emphasised, for a long time, scabies has been a truly neglected disease [1]. Scabies in humans is caused by an infestation of the skin by mites (Sarcoptes scabiei var. hominis). The parasite burrows into the upper layer of the skin where it lays its eggs. The afflicted suffer from severe itching (especially in the evening and at night) and a rash, caused by hypersensitivity reactions to the faeces of the mites. Scabies usually starts between the fingers, wrists, or armpit while the face is usually spared in adults. Prof. Chosidow stressed the fact that major sleep disturbances, psychosocial stigma and complications might add to the burden of disease. Scratching triggers skin infections as the mites inhibit complement pathways, leading to Streptococcal and Staphylococcal infection of the skin. Impetigo in turn might lead to haematuria and may affect the kidneys (post-streptococcal glomerulonephritis) and trigger acute rheumatic fever or rheumatic heart disease [2]. Skin scrapings may reveal mites or eggs under the microscope and confirm any suspected diagnosis.

Scabies is more than a common parasitic skin disease. Thus, the speaker welcomed that -in response to the high burden of scabies and its complications- the World Health Organization (WHO) added scabies on the list of neglected tropical diseases in 2017. A study performed in the Netherlands in asylum seekers revealed that scabies prevention was feasible, he added. Risk of reinfection and development of scabies complications were effectively reduced [3]. Scabies has been added as an indication for ivermectin (the most commonly used derivative of avermectin) to the "WHO Model List of Essential Medicines". Ivermectin is able to significantly reduce the level of scabies and is highly effective in controlling scabies epidemics, although it is not able to kill eggs. Prof. Chosidow further mentioned moxidectin which, like avermectin and its derivatives, has activity against arthropods but has properties suited to long-acting formulations. In 2015, the Nobel Prize was granted for the discovery of avermectin; its derivatives have saved millions of lives.

1. 
   
   1. Chosidow O. Scabies, a global challenge. D1T04.4A, EADV 2020 Virtual Congress, 29-31 Oct.
   
   
   2. Chosidow O, Hay RJ. Lancet 2019;19:P454-6.
   
   
   3. Beeres DT, et al. PLoS Negl Trop Dis 2018;12:e0006401.