Scabies and pediculosis.

Scabies and pediculosis are ubiquitous, contagious, and debilitating parasitic dermatoses. They have been known since antiquity and are distributed worldwide. Clusters of infestation occur-for example, scabies affecting immunocompromised individuals or patients and staff in hospitals and nursing homes for the elderly, and pediculosis affecting schoolchildren or homeless people. Associations with other disorders are common: infections with human T-cell leukaemia/lymphoma virus I (HTLV-I) and HIV are associated with scabies, and trench fever and exanthematous typhus with pediculosis. Specific forms of scabies, including bullous scabies or localised crusted scabies, may be misdiagnosed. Moreover, definitive parasitic diagnosis can be difficult to obtain, and the value of new techniques remains to be confirmed. Difficulties in management have returned scabies and pediculosis to the limelight.