Pediculosis

Epidemiology And Etiology
Etiology :
Lice

Three types of lice:
• Head lice: Pediculus humanus
capitis (2-3 mm long)
• Body lice: Pediculus humanus
humanus (2.3-3.6 mm long)
• Pubic lice (crabs): Phthirus
pubis (1.1-1.8 mm long)

Head Lice Body Lice Pubic Lice

Transmission
Direct contact between individuals.
Indirect contact with bedding, brushes, or
clothing, according to species.
 Pediculosis and scabies may coexist in
the same individual

Secondary Infections of Excoriated
Sites
Excoriation may become secondarily
infected with S. aureus , GAS.
Infection can extend, resulting in cellulitis,
lymphangitis, and/or bacteremia

Clinical Manifestation
• Pruritus occurs in a variable
proportion.
• Excoriations can become secondarily
infected.

Management
• Topically Applied Insecticides :
Ideally, should have 100% activity against louse and egg.
• Malathion kills all lice after 5 min of exposure, and
>95% of eggs fail to hatch after 10 min of exposure.
• Permethrin are synthetic pyrethoids widely
used as insecticide, araricide, and insect repellant.
• Lotion preparations are preferred; creams, foams, gels
are also available.

Management
Recommended Regimen :
1. Permethrin:
• Nix : Over-the-counter 1% product
• Elimite : 5% product by prescription.
• Product applied to infested area(s) and
washed off after 10 min. Incubation period
of louse eggs is 6–10 days; reapply in 7–
14 days.

Management
 2. Pyrethrin and piperonyl butoxide (PBO):
PBO is a synergist of pyrethrin. Kills mites
louse and egg.
• Preparations: liquid, gels, shampoos.

Management
3. Malathion:
 0.5% in 78% isopropyl alcohol(Ovide). Applied
to involved site for 8–12 h; binds to hair
providing residual protection.
 Indicated in lindane -resistant cases.
 Should not be used in children younger than 6
months.

Management
Alternative Regimen :
1. Pyrethrins with PBO :
Applied to scalp and washed off after
10 min.

Management
2. Lindane 1% shampoo :
• Applied for 4 min and then thoroughly
washed off.
• (Not recommended for pregnant or
lactating women.)

Management
3. Ivermectin :
0.8% lotion or shampoo.

Management
• Systemic Therapy:
Oral ivermectin : 200 μg/kg; repeat
on day 10 to kill emerging nymphs.
• oral ivermectin in cases of resistance
to both pyrethroids and malathion

Pediculosis may be divided into the
following types :
1)Pediculosis capitis
2)Pediculosis corporis
3)Pediculosis pubis
Pediculosis

• An infestation of the scalp by the head
louse.
• Feeds on scalp and neck and deposits its
eggs on hair.
Pediculosis Capitis

• Etiology :
The subspecies Pediculus humanus capitis

• Sex, Age of Onset:
Girls > boys. 3–11 years, but all ages.
• Race:
In United States, more common in whites
than blacks

Transmission
1) Head-to-head contact.
2) Shared hats, caps, brushes, combs;
theater seats; pillows.
3) Epidemics in schools; classrooms are the
main source of infestations.
4) Head lice can survive off the scalp for up
to 55 h.

Predisposing Factors
• School-age children and their mothers.
• More common in warmer months.

Sites of predilection
• Head lice nearly always confined to scalp,
especially occipital and postauricular
regions.
• Rarely, head lice infest beard or other
hairy sites. Although more common with
crab lice, head lice can also infest the
eyelashes ( pediculosis palpebrarum ).

Skin Symptoms:
 Pruritus of the back and sides of scalp.
 Scratching and secondary infection associated
with occipital and/or cervical lymphadenopathy.

Skin Lesions
Bite reactions : at site of louse bites apparent
on neck. Phases related to immune sensitivity/
tolerance:
Phase I: no clinical symptoms.
Phase II: papular urticaria with moderate
pruritus.
Phase III: wheals immediately following bite
with subsequent delayed papules/intense
itching.
Phase IV: smaller papules with mild pruritus.

Eczema , excoriation , lichen simplex
chronicus on occipital scalp and neck
secondary to chronic scratching/rubbing

• Secondary impetiginization with S. aureus of
eczema or excoriations; may extend onto neck,
forehead, face, ears.
• Confluent, purulent mass of matted hair, lice,
nits, crusts, and purulent exudation in extreme
cases.
• Pediculid is a hypersensitivity rash, resembling
a viral exanthem.
• Wood lamp : Live nits fluoresce with a pearly
fluorescence; dead nits do not.

Pediculosis capitis: multiple nits
on scalp hair

Diagnosis ?
1) Clinical Diagnosis (Skin lesion )
2) Laboratory Examinations :
• Microscopy : The louse or a nit
on a hair shaft
• Cultures :. If impetiginization is suspected
, bacterial cultures should be obtained.

Management
1. Fomite/Environmental Control :
 Avoid contact with possibly contaminated items such as
hats, headsets, clothing, towels, combs, hair brushes,
bedding, upholstery.
 The environment should be vacuumed.
 Bedding, clothing, and head gear should be washed
and dried on the hot cycle of a dryer.
 Combs and brushes should be soaked in rubbing
alcohol or Lysol 2% solution for 1 h.
 Families should look for lice routinely.

2.Pediculocide Therapy
• Topically Applied Insecticides :
Ideally, should have 100% activity against louse and egg.
• Malathion kills all lice after 5 min of exposure, and
>95% of eggs fail to hatch after 10 min of exposure.
• Permethrin are synthetic pyrethoids widely
used as insecticide, araricide, and insect repellant.
• Lotion preparations are preferred; creams, foams, gels
are also available.

Pediculosis Corporis
• In body louse infestations, lice reside and
lay eggs in clothing.
• Leave clothing to feed on human host .
• Body louse survive more than a few hours
away from the human host.
• Occurs in poor socioeconomic conditions.

Etiology :
Pediculus humanus humanus.

Risk Factors :
1. Poor socioeconomic conditions.
2. when clothing is not changed or washed
frequently: poverty, war, natural
disasters, indigence, homelessness,
refugee-camp populations.

Pediculosis corporis Severely malnourished, ill-kept, homeless
male with multiple excoriations, erosions and crusted papules, and
nodules and eczematized lesions. Lice and nits are seen in the
seams of clothing (inset).

Diagnosis :
Lice and eggs are found in clothing
seams.

Management
• Bedding and clothing must be
systematically decontaminated.
• Hygiene Measures : Basic sanitation
measures, and hygiene measures to
assure changes of clean clothing, body
washing, and sometimes shaving.

Management
• Delousing:
 Pyrethrins / pyrethroids or malathion for 8–24 h
is recommended in some cases.
 Outbreaks necessitate delousing of individuals
with 1% permethrin dusting powder .
• Louse-Borne Infections: Antibiotics are
indicated if louse-borne infectious disease
(trench fever, epidemic typhus) exists.

Pediculosis Pubis (Pthiriasis)
Crabs
 Sexually transmitted disease.
 Pediculosis pubis is an infestation of hair-bearing
regions:
▪ Most commonly the pubic area
▪ Hairy parts of the chest and axillae
▪ Upper eyelashes.
 Manifested clinically by mild to moderate
pruritus, papular urticaria, and excoriations.

• Age :Most common in young adults;
range, from childhood to senescence.
• Sex: More extensive infestation in males.
• Etiology :
Pthirius pubis

Transmission
1) Close physical contact: sharing bed;
possibly exchange of towels.
2) Sexual exposure. May coexist with
another sexually transmitted infection
(STI).
3) Nonsexual transmission: homeless
persons who have pubic lice in hair on
head and back.

 Often asymptomatic.
 Mild to moderate pruritus for months.
 Patient may detect a nodularity to hairs (nits or
eggs) while scratching.
 With excoriation and secondary infection, lesions
may become tender and be associated with
enlarged regional, e.g., inguinal, lymph node.

Skin Lesions
• Papular urticaria (small erythematous papules) at
sites of feeding, especially periumbilical ; blisters.
.

• Secondary infection: detected in patients
with significant pruritus.
• Maculae ceruleae ( taches bleues ): are
slate-gray or bluish-gray macules 0.5–1 cm in
diameter, irregular in shape, nonblanching.
Pigment thought to be breakdown product of
heme affected by louse saliva.

• Eyelash infestation :
Serous crusts may be present along with
lice and nits , occasionally, edema of eyelids
with severe infestation.

Laboratory Examinations
• Microscopy Lice (Fig.) and nits may be identified
and differentiated from head/body louse with hand lens
or microscope.
• Cultures Bacterial cultures if excoriation
impetiginized.
• Serology Sexually transmitted. Testing for other STIs
may be indicated in some individuals.

Management
1. Prevention:
Patient and sexual partners should be
treated.
2. Pediculocides :
see before

• SOURCE: From FITZPATRICK’S COLOR ATLAS
AND SYNOPSIS OF CLINICAL DERMATOLOGY
SIXTH EDITION

Pediculosis

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