Pediculosis (Lice)

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Introduction

Pediculosis is a diseases due to blood sucking lice. Pediculosis can be divided into three conditions:

  1. Pediculosis capitis (head lice): Caused by Pediculus humanus var. capitis
  2. Pediculosis corporis (body lice): Caused by P. humanus var. corporis
  3. Phthiriasis pubis (pubic lice): Caused by Phthirus pubis

The arthropods are transmitted from human to human via:

  1. Direct contact
  2. Sharing of combs, brushes, towels (P. capitis)
  3. Sharing clothing (P. corporis)
  4. Shearing underwear
  5. Sexual intercourse or any intimate personal contact (P. pubis)

Symptoms and clinical features of pediculosis

1. Pediculosis capitis:

  1. Generally the only complaint is pruritus: Nits can easily be seen at the base of the hairs; careful inspection may reveal the adult louse Secondary impetiginization is common because of the itching
    • Cervical nodes may become enlarged
  2. Children and individuals with long hair are more likely to be affected.
  3. Homeless people and refugees are also vulnerable
  4. No age or economic stratum is immune
    • School children who share school caps, hair brushes and combs, pillow cases are particularly vulnerable

2. Pediculosiscorporis:

  1. Pruritus may be the only symptom in some patients
  2. Chronic scratching may result in characteristic hemorrhagic puncta and linear excoriations
  3. Patient eventually develops intensely pruritic papules and nodules, numerous excoriations, secondary infections and even lymphadenopathy
  4. The combination of excoriations,
    hyperpigmentation, healed scars and secondary impetiginization is quite typical and known as “vagabond’s skin”
  5. Overcrowding and poor personal hygiene promote infestation
  6. Refugees, destitutes and vagrants are particularly vulnerable

3. Pediculosis pubis:

  1. Most often found in the pubic and axillary hairs
  2. Occasionally may be found on abdominal trunk hairs
  3. On rare occasions may be seen on the scalp, eyebrows and even eyelashes
  4. Pruritus is also a symptom
  5. Classic clinical finding is the maculae cerulae
  6. Indistinct blue-grey or slate-coloured macules ranging in size from several millimetres to several centimeters
  7. They result from the bite of the louse causing small intracutaneous
    haemorrhages
  8. The colour is due to blood whose
    haemoglobin has been altered by the saliva

Differential diagnoses

1. P. capitis:

  1. Seborrhoeic dermatitis
  2. Pityriasis amiantacea
  3. Peripilar keratin
  4. Hair casts.
  5. Piedra

2. P. corporis:

  1. Scabies
  2. Atopic dermatitis
  3. All pruritic dermatoses
  1. P. pubis:
  1. Scabies
  2. Candidiasis
  3. In the axillae trichomycosis axillaris

Complications of pediculosis

  1. Secondary bacterial infections
  2. The body louse serves as a vector for diseases:
  3. Epidemic typhus (Rickettsia prowazekii)
  4. Trench fever (Bartonella quintana)
  5. Relapsing fever (Borrelia recurrentis)

Investigations

1. P. capitis and pubis:

  • Examine louse or the nits on epilated hair strands (especially from behind the ears) under the microscope

2. P. corporis:

  • Examine the seams of clothing for nits and lice

Treatment for pediculosis

Treatment objectives

  1. Eradicate the lice
  2. Prevent re-infection
  3. Treat complications

Drug treatment

1. P. capitis:

  • 1% permethrin cream rinse
  • The cream is lathered through the hair, left on for 10 minutes and thoroughly rinsed out. A fine-tooth comb should be used to remove adherent nits
  • Repeat treatment after a week

2. P. corporis:

  • Treat dermatitis with antipruritics or corticosteroids
  • Treat secondary infection with oral antibiotics.

Supportive measures

1. P. capitis:

  • All contact individuals should be examined and treated as necessary
  • Pillow cases should be disinfested as for clothing.

2. P. corporis:

  • Eradicate lice from clothing by laundering in hot water or machine-drying at a high
    temperature, followed by ironing the seams

3. P. pubis:

  • Treatment is the same as for pediculosis capitis, with the exception that pediculosis of
    the eyelashes should be treated with an occlusive ophthalmic ointment applied to the
    eyelid margins for 10 days
  • Affected persons’ sexual contact(s) should be treated simultaneously

Notable adverse drug reactions, caution

  • As stated under scabies

Prevention of pediculosis

  • Improve personal hygiene
  • Do not share hair combs, brushes, clothing, pants and pillows

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