Tony Kiszewski and Richard Pollack of the Harvard School of
answered a few
questions for nationalgeographic.com.
ARE HEAD LICE FOUND PRETTY MUCH WHEREVER PEOPLE
LIVE? ARE THERE ANY GEOGRAPHIC PATTERNS?
They are found far and wide; in every possible climatic or
environmental situation from deserts to cities to rain forests.
In the United States we get reports from virtually every state.
Anecdotally we hear of higher infestations in warmer areas, but we
dont have any hard data to support this.
WHY DO LICE PROVOKE SUCH A REACTION IN PEOPLE?
DO THEY POSE ANY HEALTH THREAT?
Insects provoke anxiety in many people. Some people are
absolutely horrified when a moth invades their home or when
an ant walks across their picnic table. Can you imagine how
these people react when an insect invades their bodies? With some people, just talking about lice is enough
to make them scratch and squirm. Some think that they are
infested despite intensive examinations that reveal nothing.
There appears to be a primal fear associated with insects that
relates perhaps to their alienness. We cant say its because theyre
not warm-blooded, fuzzy creatures like us, because that doesnt
explain why people react so badly to mice. This seems to be a
cultural phenomenon. People from certain cultures, such as the
Yanomami of Venezuela, actually consider louse infestations to
be normal. Head lice and their eggs (nits) generally pose little
direct health threat in the United States. Mild itching from the
bites is the most frequent consequence. Greater harm may come
from indirect effects: Overzealous insecticidal use may cause
toxic reactions in patients.
WHAT ARE THE CHALLENGES INVOLVED IN GETTING
PARENTS, SCHOOLS, AND COMMUNITIES TO STOP SEEING
LICE AS A MORAL OR NEGLECT ISSUE?
One problem is the presumed association between head lice
infestations and hygiene. There is no association. Hygiene has
very little to do with the probability of acquiring infestations.
The neglect issue comes from the perception that all louse
infestations are readily treatable and that parents whose children
have lice are not providing proper care.
It has been our experience that children who have been
misdiagnosed or have insecticide-tolerant lice are being
overtreated. Its not the parents fault much of the time.
Sometimes the only recourse is daily combing and nit-picking,
and this may take some time to eliminate an infestation.
Another barrier is the lack of understanding about the modest
communicability of these infestations. Having an infested child
in a classroom does not necessarily mean that any of his or her
classmates are destined to become infested. People seem to think
that these things will crawl or even jump from one person to
another and will lie in wait on stuffed animals or sofas for their
victims to appear. It actually takes fairly close physical contact
for transmission to occurtouching heads or perhaps sharing
pillows, combs, or hats. Lice generally survive for
less than a day away from a human host.
Another problem is knowing when an infestation is real. Many
people have debris or dandruff that adheres to their hair shafts
and can be mistaken for nits. Others despair at their inability to
clear nits from their children when, in fact, the nits are but empty
husks from a prior infestation.
HOW CAN SCHOOLS AVOID EXTREME REACTIONS WHILE
STILL PROTECTING STUDENTS? WHAT SORT OF MESSAGE
SHOULD SCHOOLS SEND HOME?
This is a difficult one. How do you manage a communal
phobia? Schools should do only what is necessary to
remove the risk of transmission to other children. Anything
more, such as excluding from school children with dead nits in
their hair, is catering to hysteria.
Perhaps some sort of presentation to parents on the biology and
transmission of lice would help let them know that lice are not
superbugs. You will never be able to convince everybody,
though. Some parents wont be happy with such a policy, but
policies should be formed around reality, not illusion.
WHAT WOULD BE AN APPROPRIATE COMMUNITY
RESPONSE TO AN OUTBREAK OF LICE?
Lice and their eggs should be examined by a competent person to
confirm that an active infestation exists. The presence of old
(dead or hatched) eggs should not be cause for treatment or
exclusion from school. On the other hand, actively infested
children should be sent home where lice and eggs can be
removed manually. Parents may choose to augment (but not
replace) manual louse removal with over-the-counter
pediculicides. Children who have been treated pose little risk to
others, and may return to school.
A single follow-up treatment about two weeks later should be
conducted to target any newly hatched nits. Only those children
with active lice in their hair after one or both of these treatments
should be considered infested.
Active lice that are found after such treatments may suggest the
presence of insecticide resistance.
It is not necessary to treat other family members unless they too
have lice. Likewise no intensive campaigns of household
cleaning are necessary.
The Harvard School of Public Health has more information about
human lice and treatment options at
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