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Pediculus
capitis (Head louse)
Life
> Eukaryotes >
Opisthokonta >
Metazoa (animals) > Bilateria > Ecdysozoa
> Panarthropoda > Tritocerebra > Phylum:
Arthopoda > Mandibulata >
Atelocerata > Panhexapoda >
Hexapoda
> Insecta (insects) > Dicondyla > Pterygota >
Metapterygota > Neoptera > Eumetabola > Paraneoptera >
Psocodea (booklice and lice) >
Phthiraptera (lice)
Head lice are usually found on the head but they can be
found amongst hairs in other parts of the body. They are a common problem in schools, causing consternation to teachers and parents
alike (see Treatment below). The closely related Body
louse Pediculus humanus is only found on the body or in the attached
clothing. Head lice like clean hair so infection by these insects is not
necessarily to do with poor hygiene. Body lice on the other hand tend to be
found on people who do not wash regularly. The third species of louse
commonly found on people is the crab louse Phthirus pubis which prefers
the pubic region but which can also be found in the armpits, beard, eyebrows and
eyelashes. The eggs (or 'nits') of head lice
are attached to hairs and the nymphs which hatch from them resemble the adults
except being smaller. Depending on temperature, it takes 2-4 weeks for the eggs
to hatch, the nymphs to pass through three moults and the adults to reach sexual
maturity.
There are three main approaches to treating head lice infestations.
- Insecticidal shampoo
. Two main types of shampoos are available in South Africa. The
cheaper (and most commonly used) of the two contains Gamma Benzine Hexachloride otherwise
known as lindane. There have been a number of horror reports of lindane causing
neurological problems and the National Pediculosis Association in the U.S.A. strongly
recommends that it should not be used. If you do use a lindane-based shampoo, follow the
instructions very carefully particularly with regard to how often you can apply it. The
other shampoo, which is more expensive, contains permethrin which has a much better safety
record than lindane.
- Combing.
Combing the hair with a louse comb is regarded as a very effective method
but it takes time and it is recommended that for children you keep them occupied with
something interesting such as watching a good video. Plastic louse combs (which sometimes
come with the shampoo you buy) are regarded as ineffective and a metal one should be used
instead.
- Application of oils.
There is good anecdotal evidence that application of certain
long-chain oils to the hair are effective in removing lice infestations. Coconut-oil or
olive-oil-based shampoo (or bar soap or pure oils) are recommended in combination with
combing: go to New
York Coalition for Alternatives to Pesticides for the best procedure for using this technique. Alternatively, you can make up the
following recipe: 30 ml olive oil, 20 drops of tea tree oil, 10 drops rosemary oil, 10
drops lavender oil and 10 drops lemon oil. With this recipe, first test that there is no
skin reaction by applying a little of this solution to the inside of the elbow and wait a
few hours to see if there is any adverse reaction. Apply this solution to the hair and
leave it there for an hour, then shampoo (the shampoo should not contain a conditioner
because the conditioner coats the hair and may protect the nits). It might be necessary to
repeat this process after a couple of days to eliminate the next batch of hatched lice and
maybe again after that.
In addition to direct control of the lice on the scalp, you also need to wash clothing
and linen that might be infected and dry it on high heat in a dryer. Vacuuming of carpets,
sofas and chairs is regarded as an effective way of removing loose lice and nits. Combs
and brushes need to be soaked in a hot ammonia solution (1 teaspoon amonia in two cups of
hot water). Head lice cannot survive for more than a couple of days at room temperature
without feeding on blood, and the nits (eggs) take about 8 days to develop. Isolating
items for about 10 days at warm temperatures is therefore an effective way of ridding them
of any stray lice or nits. Putting an item in a plastic bag in the sun would kill lice and
nits because of the high temperatures. Freezing the items for about four days would also
kill the lice and nits.
For more detailed information on control of head lice, go to:
Text by Hamish G. Robertson. |
