What is the pathophysiology of classic scabies infection?

Updated: Oct 13, 2020
  • Author: Megan Barry, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

In classic scabies infection, typically 10-15 mites (range, 3-50) live on the host. [9] Little evidence of infection exists during the first month (range, 2-6 wk), but after 4 weeks and with subsequent infections, a delayed type IV hypersensitivity reaction to the mites, eggs, and scybala (feces) occurs. The time required to induce immunity in primary infestations probably accounts for the 4-week asymptomatic latent period. With reinfestation, the sensitized individual may develop a rapid reaction (within hours). The resultant skin eruption and its associated intense pruritus are the hallmarks of classic scabies. (See the images below.)

Scabies. Courtesy of William D. James, MD. Scabies. Courtesy of William D. James, MD.
Scabies. Erythematous vesicles and papules are pre Scabies. Erythematous vesicles and papules are present on torso extremities, some with adjacent linear excoriations.

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