Scabies, lice and infestations

Overview & Definition

A school-age child who cannot sleep because of an itch that burns worst at night, with burrows in the finger-webs and a sibling scratching just as badly, is the everyday face of scabies. Human ectoparasite infestations are infections of the skin by arthropods that have adapted to live on people: the scabies mite burrows into the stratum corneum, while lice cling to hair or clothing and feed on blood. Scabies alone affects more than 200 million people at any time, and in remote and overcrowded communities it is one of the commonest reasons a child presents to a clinician. [2]

The clinical thread that unites scabies and pediculosis is itch, but the mechanism differs. Scabies itch is a delayed allergy to mite antigens that takes weeks to develop, which is why a first infestation is silent at first and overwhelming by the time it is recognised. Louse itch is an immediate reaction to bites and saliva, together with the local damage caused by scratching. Both are contagious, both invite secondary bacterial infection, and both demand treatment of the child together with every household and close contact on the same day. [3]

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