Lice are wingless, flattened, blood-sucking
insects that are survive as surface parasites on birds and mammals.
Pediculosis
is a term used to denote infestation by Pediculus
capitis (head louse), Pediculus
humans (body louse), or Phthirus
pubis (pubic louse). The bites of lice are painless and difficult to
detect. The clinical signs and symptoms are the result of the patient’s
reaction to the saliva and anticoagulant injected into the dermis by the louse
at the time of feeding. Depending on the degree of sensitivity and previous
exposure, the feeding sites produce reddish rash hours to days after feeding.
Itching
(Pruritus) is the most common symptom of any type of pediculosis.
Lice
cannot jump or fly. Pets are not vectors (carriers of insect). Diagnosis is
made by seeing the lice or their eggs.
Lice
feed approximately five times each day by piercing the skin with their claws,
injecting irritating saliva, and sucking blood.
Lice
are active and can travel very fast. That is why they can be transmitted so
easily. The life cycle from egg to hatching of the insect, and then laying new
egg is approximately 1 month.
NITS/LICE EGGS
The
female lays approximately six eggs, or nits, each day for up to 1 month, and
then dies. The louse incubates, hatches in 8 to 10 days, and reaches maturity
in approximately 18 days. Nits are 0.8 mm long and are firmly cemented to the
bases of hair shafts to close to the skin to acquire adequate for incubation.
Nits are very difficult to remove from the hair shaft.
Clinical manifestations
Lice
infestation of the scalp is most common in children. An average patient carries
less than 20 adult lice. A small minority of patients can have more than 100
lice in the scalp. Scratching causes inflammation and secondary bacterial
infection, with boils (pustules), crusting, and lumps in the neck (cervical lymphadenopathy).
The
eyelashes may be involved, causing redness and swelling. Examination of the
back of scalp shows few adult organisms but many nits. Nits are cemented to the
hair, whereas dandruff scale can be easily moved along the hair shaft. Head
lice can survive away from the human host for about 3 days, and nits can survive
for up to 10 days.
Transmission
The main
source of transmission is direct skin to skin contact. Other sources like hats,
brushes, combs, earphones, bedding, furniture is common. Head lice do not carry
or transmit any contagious infection.
Diagnosis
Lice
are suspected when a patient complains of itching in a localized area without
an apparent rash. The itching tends to very severe sometimes. Scalp and public
lice will be apparent to those who carefully examine individual hairs. They are
not apparent with only a cursory examination.
Finding
nits does not indicate active infestation. Nits may persist for months after
successful treatment. Live eggs reside within a quarter inch of the scalp.
COMBING
Combing
the hair with a fine-toothed “nit,” or detection, comb is effective for
detecting and removing live lice. The comb is inserted near the crown until it
touches the scalp, and then drawn firmly down. The teeth of the comb should be
0.2 to 0.3 mm apart to trap lice. The entire head of hair should be examined
for lice after each stroke. It usually takes 1 minute to find the first louse.
Lice and nits can be seen easily under a microscope and a hand lens.
Wood lamp examination
Live
nits fluoresce and can be detected easily by Wood’s light examination, a
technique that is especially useful for rapid examination of a large group of
children. Nits that contain an unborn louse fluoresce white. Nits that are
empty fluoresce gray.
MANAGEMENT STRATEGY
Infestation
is most common among children 3-12 years of age and their parents.
Identification of live lice is the gold standard of diagnosis; however, finding
nits alone in a patient who has not been treated also warrants treatment. Nits are easier to spot, especially at the
nape of the neck and behind the ears. Hatched nits are white; unhatched nits
are brown. Detection combing of wet hair with a fine-toothed nit comb allows for efficient recovery of
lice and nits for diagnosis.
Examination
for nits and lice via nit combing
Nit
combing is four times more efficient than and twice as fast as direct visual
inspection.
FIRST-LINE THERAPIES
·
Malathion 0.5%
lotion
·
Permethrin 1%
cream rinse
·
Carbaryl
0.5% lotion
OTHER
THERAPIES
Ø
Topical crotamiton
10%
Ø
Nit picking
-
Bug Busting (wet combing)
Ø
Lindane 1%
Ø
Oral Ivermection
Ø
Topical lvermection
Ø
Trimethoprim /Sulfamethoxazole
Ø
Levamisole
Ø
Fomite control
Ø
Head shaving
Launderable
items (worn clothing and used bedding, towels, scarves, and hats) should be
placed in a dryer at 60°C for 10 minutes. Brushes, combs, and hair ornaments
can be placed in hot water (60°C or more) for 10 minutes. Non-launderable items (i.e, certain stuffed animals) should
be placed in a bag for 3 days (not 15 days, as eggs laid off a host will
probably not hatch close enough to a host to obtain their first blood meals).
Cloth
furniture and rugs should be vacuumed. Fumigation of the home is not required.
Contacts
of all detected cases, including classmates, should be screened. Empiric
therapy for close household contacts is also recommended. Those likely to have
had head-to head contact with the index case in the previous 4-6 weeks should
be identified and screened. Children should not be excluded from school for
head lice as the infestation often has been around for month prior to its
detection. Hair grows 1cm per month, and lice lay eggs close to the scalp where
it is moist and warm. Nits detected 2 cm from the scalp represent a 2 months old
infestation. Therapy within a week of the detected infestation is more reasonable.
Dr Arika Sethi
Dr Pradeep Sethi
http://www.directhairtransplantation.com
