SCABIES

 

Etiology:

  1. 0.3 mm mite with 4 pairs of legs. Female burrows into corneal layer and deposits eggs that produce larva in 4 days, mite in 2 weeks.
     
  2. Generally transmitted by skin-to-skin contact , sheets (mites can remain alive x 48 hrs.).
     
  3. After infection, incubation takes 1 month during which time the pt becomes sensitized to the mite and its secretions. If the patient has been sensitized in the past, the second infection will occur almost instantly.

S & S:

  1. Intense pruritus, sometimes worse at night.
     
  2. Burrows (0.5-1.0 cm long) with brownish-red papule at the end may be seen in finger webs, aroeola, penile shaft  or scrotum (thin skin is commonly affected). Eczematous patches occur from repeated scratching and red-brown hyperkeratotic nodules may be seen.  Excoriations, crusts and suprainfections occur.
     
  3. Common sites are hands (web spaces and sides of palms), flexor surfaces of wrists, axilla, ankles, back, abdomen, buttocks, knees, penis/vulva,  but in infants lesions may be distributed on all body parts.

DX :

  1. Mite can be isolated by scraping the end of burrow with a blade.  The material collected should be placed on slide with KOH or mineral oil. (Immunocompetent patients usually only harbor 10 – 25 mites.  Thus, a negative prep should not dissuade you from treating if your clinical suspicion is high.)

Treatment:

  1. Both the patient and their personal contacts should be treated.
     
  2. Permethrin 5% to body ( from neck to toes) x 8-12hrs. Repeat application in 1 week.
     
  3. Lindane is also effective but has adverse reactions if misused. It is neurotoxic if left on body for  more then 12 hrs. and toxicity usually takes the form of seizures. It is contraindicated in pregnant women, infants and those with a history of seizures.
  4. Antihistamines may help with pruritus.
     
  5. Patients should be instructed to launder sheets, clothing and personal articles using hot water cycle.
     
  6. It should be explained to patients that they may continue to experience pruritus for weeks after successful treatment due to a hypersensitivity to mite products. A second application of  Permethrin may be necessary if pt did not apply properly or failed to repeat the process 1 week later.

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