Scabies infection

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Epidemiology

Scabies is a common ectoparasitic infestation caused by Sarcoptes scabiei, a human-specific mite that is highly prevalent in some areas of the developing world, though the prevalence of infection in communities may be cyclical.[1][2][3]

Etiology and pathogenesis

It is mostly spread by close personal contact but can also be spread by clothing, sheets and towels. Secondary bacterial infection of scabies is common and might increase the risk for glomerulonephritis.[4][5]

Clinical findings

Typical sites of involvement are the interdigital spaces of the hands, the flexural parts of the wrists, the armpits, the feet and the genitals. One of the clinical signs, though not always present in warm climates, is the burrow (S- shaped ridge) caused by the excavation of the female mite for her eggs. Small erythematous papules can be present together with excoriations. Itching, especially at night, is the main complaint which often results in scratch marks and secondary infection.[6][7][8]

A quick diagnosis can be made with a KOH preparation see: direct Microscopy scabies

Differential diagnosis

Management

  • Treat all individuals living in same household at the same time.
  • Wash sheets and clothes or hang them outdoors for at least 24 hours.
  • Sulphur ointment 5-10% to apply twice daily for at least one week.
  • Benzyl benzoate emulsion (10 to 25%) is applied over the entire body and left on the skin for up to 24 hours before washing off. Treat during 3 nights and repeat after one week.
  • Epidemics in institutions like prisons and boarding schools may be treated with Ivermectin on day 1 and day 10 . Not suitable for children below 5 years of age. See for the dosages cutaneous larva migrans.
  • In case of secondary infection oral antibiotics like cloxacillin or erythromycin can be given. For the dosages see impetigo.
  • For severe itchiness sedating oral antihistamines like Piriton or promethazine can be used. For the dosages see urticaria.
  • After treatment complaints of itch may persist for weeks. This can be treated with mild topical steroids like hydrocortisone cream or ointment two times daily.

Photos

Literature

  1. Henderson CA. Skin disease in rural Tanzania. Int J Dermatol 1996; 35: 640-2.
  2. Hogewoning AA, et al. Skindiseases among schoolchildren in Ghana, Gabon and Rwanda. August 2012; accepted for publication in the International Journal of Dermatology.
  3. Terry BC, Kanjah F, Sahr F et al. Sarcoptes scabiei infestation among children in a displacement camp in Sierra Leone. Public Health 2001; 115: 208-11.
  4. Hoy WE, White AV, Dowling A et al. Post-streptococcal glomerulonephritis is a strong risk factor for chronic kidney disease in later life. Kidney Int 2012.
  5. Hay RJ. Scabies and pyodermas--diagnosis and treatment. Dermatol Ther 2009; 22: 466-74.
  6. Clarke P. Why am I so itchy? Aust Fam Physician 2004; 33: 489-94.
  7. Gilmore SJ. Control strategies for endemic childhood scabies. PLoS One 2011; 6: e15990.
  8. Shmidt E, Levitt J. Dermatologic infestations. Int J Dermatol 2012; 51: 131-41.
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