Scabies

Scabies has been recognized as a contagious disease for centuries. Although large epidemics have been related to poverty, overcrowding, and social upheaval such as in wars, endemic scabies persists in most tropical regions. In addition to the discomfort of the often-intractable itch, secondary bacterial pyoderma is an important antecedent to systemic bacterial sepsis and poststreptococcal glomerulonephritis. Hyperinfestation (crusted or Norwegian scabies) is increasingly recognized in patients with acquired immunodeficiency syndrome (AIDS) and also in elderly individuals in nursing homes, who may be the focus of unexpected and initially unrecognized scabies out breaks. Molecular epidemiologic studies have shown scabies to be generally host restricted, with human-to-human infection cycles not overlapping with those of animal scabies. Although definitive diagnosis of scabies requires microscopic visualization of a mite retrieved from a skin burrow, empiric treatment based on clinical suspicion remains far more common. The skin rash of scabies can be very variable and hard to distinguish from many other dermatologic conditions. Furthermore, clinical care and availability of treatment are limited in many locations where scabies is endemic. Hence accurate global epidemiology is lacking and both over- and underdiagnosis frequently occur.