Lice
(Pediculosis)Introduction Infestation by lice or
"pediculosis", as is the medical term, has a double significance as
a medical disease. First, it is causing an itchy skin disease, which affects the
scalp, body or genitals depending on which type of louse it is. Secondly though
the lice are carriers of other diseases such as typhoid fever, trench fever and
relapsing fever. | |
Lice |
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Control
of infestation by lice has traditionally been one of the major Public Health concerns.
There are three types of lice in humans: 1. Head lice due to Pediculus
humanis capitis 2. Pubic lice due to Phthirus pubis. 3. Body lice
due to Pediculus humanis corporis. These different louse types have over the centuries
adjusted to specifically thrive in the areas to which they have adapted. This
table lists some of the characteristics of the various types of lice.
Head
lice: This is common among school children as the transmission in a classroom
with many school children is easy because of crowding. Transmission is by personal
touching, by sharing of combs or hats. Apart from being localized in the scalp
the head
louse can also live in eye brows and eyelashes as well as
beards. The lice deposit whitish oval shaped nits (each containing a louse egg)
around the hair. After several days to 2 weeks newly hatched lice invade the scalp
and then form new nits again. As the body is very sensitive to the foreign protein
from the lice, an irresistible itch (pruritus) develops in the scalp, which leads
to intensive scratching to the point where open scratch sores develop that can
get secondarily infected by skin bacteria. The diagnostic test for lice is the
finding of nits that are firmly attached to the hairs and cannot be dislodged
like dandruff flakes can. In children there is often a generalized nonspecific
skin dermatitis on the body, even though the lice are confined to the scalp. This
is called an "id"reaction and seems to be an allergic phenomenon.
Body
lice: With good hygiene body
lice (seen here in various stages of development) are rarely seen. However,
with poor hygiene lice can multiply in the seams of underwear that is worn close
to skin. Nits can be detected on body hair and in fabric of clothes that are not
washed. Common sites for developing itchy lesions are the abdomen, the buttocks,
and the shoulders. The physical findings can be mini
puncture wounds from direct louse bites, scratch marks (possibly with bacterial
superinfection such as impetigo or cellulitis), urticarial rash and furunculosis.
Pubic
lice: The pubic
louse is transmitted sexually through intimate genital contact. Like in the
other areas described above the louse tends to live in the skin
and hair of a confined area, in this case the anogenital region. In hairy people
some of the lice may also live in other
areas, but the highest concentration of lice will still be found in the hairs
of the anogenital areas. Nits can be found at the origin of the hairs close to
the skin. One sign to look for are tiny darkbrown spots of louse feces on underwear
where the anogenital region touches it. Skin breakdown from chronic itching and
scratching with subsequent bacterial or fungal superinfection is common. |
Treatment: Like in scabies the treatment
of choice is 5% permethrin cream (brand names: Kwellada cream, Kwellada lotion,
Nix Dermal Cream), which is applied and left in place for 6 to 12 hours before
it is washed off. In recent years some resistance to permethrin has been
observed. In these cases it is suggested to use the experimental drug ivermectin
as a single dose. In the past lindane was used, but this has neurotoxic side-effects,
which are not tolerable and this therapy has no place with a number of newer drugs
on the market that a dermatologist would have access to. If cases are difficult
to treat they should be referred to a dermatologist (=skin specialist).
Prevention: An
ounce of prevention is definitely worth more than a pound of cure with respect
to louse infestation. Children have to be taught to practice good hygiene, to
have a bath or shower daily, to not share combs, hats, clothes, brushes, make-up
etc. Responsible sexual behavior will prevent pubic lice transmission and also
other sexually transmitted diseases including venereal warts. Once there is a
case of louse infestation in a family member all of the remaining family members
should also be treated for prevention of further infestation. |
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Disclaimer This
outline is only a teaching aid to patients and should stimulate you to ask the
right questions when seeing your doctor. However, the responsibility of treatment
stays in the hands of your doctor and you. References 1.The
Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999.
Chapter 265. 2.James Chin et al., Editors: Control of Communicable Diseases
Manual, 17th edition, 2000, American Public Health Association 3.The Merck
Manual, 7th edition, by M. H. Beers et al., Whitehouse Station, N.J., 1999. Chapter
112. 4. The Merck Manual, 7th edition, by M. H. Beers et al., Whitehouse
Station, N.J., 1999. Chapter 115. 5. The Merck Manual, 7th edition, by M.
H. Beers et al., Whitehouse Station, N.J., 1999. Chapter 113. Last
Modified: April 20, 2012 | |
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