A16. Scabies, pediculosis

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Scabies

  • Sarcoptes scabiei var hominis
    • Obligate human parasite
  • Transmission by direct physical contact or contact with infected clothes
  • Highly contagious
  • Incubation period 3 – 6 weeks
  • Risk factors
    • Nursing homes
    • Childcare facilities
    • Prisons
  • Pathomechanism
    • Female mites burrow into stratum corneum, lays eggs and feces
    • Feces and dead mites trigger type IV hypersensitivity
  • Clinical features
    • Intense pruritus, especially at night
    • Skin lesions
      • Elongated erythematous papules
      • 2 – 10 mm burrows (elevations in the skin)
      • Vesicles
      • Excoriation due to itching
    • Predilection sites – warm areas with thin skin
      • Wrists
      • Fingers
      • Male genitalia
  • Diagnosis
    • Dermoscope
    • Clinical
  • Treatment
    • Permethrin 5% lotion
      • Applied to the whole body and left on the skin for 8 – 12 hours
      • The rest of the family should be treated too
    • Lindane 1% lotion
    • Oral ivermectin
    • Symptomatic treatment of pruritus
      • Oral antihistamines
      • Topical steroids

Pediculosis

  • Lice infection
  • Transmission by direct physical contact or indirect contact with infected clothes, etc.
  • Risk factors
    • Crowded places
    • School
    • Homeless
  • Pathomechanism
    • Delayed allergic reaction to lice saliva
    • May be asymptomatic for weeks while sensitization occurs
  • Pediculosis capitis
    • Pediculus humanus capitis (head louse)
    • Most common in children
    • Clinical features
      • Scalp/neck pruritus
      • Louse eczema on back of neck
    • Diagnosis
      • Detection of lice on the scalp or hair
    • Treatment
      • Permethrin shampoo
      • Lindane shampoo
      • Malathion shampoo
      • Then mechanical removal with a fine-toothed comb
      • Cleaning of all hair tools, bedding, clothes, etc.
  • Pediculosis corporis
    • Pediculus humanus corporis (body louse)
    • Most common in crowded, unsanitary living conditions
    • Clinical features
      • Pruritus
      • Bites on skin
      • Scratching lines
    • Diagnosis
      • Detection of lice in clothing
    • Treatment
      • Topical permethrin
      • Cleaning of all bedding, clothes, etc.
  • Pediculosis pubis
    • Pthirus pubis (crab louse)
    • Transmitted by sexual contact
    • Most common in teenagers and young adults
    • Pruritus in genital area
    • Blue-purple macules in patients with chronic infection
    • Diagnosis
      • Detection of lice in pubic hair
    • Treatment
      • Topical permethrin
      • Cleaning of all bedding, clothes, etc.