HEAD LICE

HOW DO I KNOW IF MY CHILD HAS HEAD LICE?

Many head lice infections cause no symptoms, and probably less than half cause itch. So you have to LOOK to find out if your child has head lice. Do not rely on itching and scratching.

Eggs are not difficult to see; use a strong light and look on the hair shafts. Newly laid eggs are usually within 1.5 cm of the scalp while older eggs are higher up the hair shafts. If you are not sure whether an object you find is a head louse egg, try sliding it up the hair shaft using your fingers. Eggs are usually quite difficult to move, whereas hair muffs and other items slide easily.

HEAD LICE EGGS

Head lice eggs occur in three states:
  1. Live egg
  2. Dead egg
  3. Hatched egg
Being able to identify the state of the egg is important. Hatched and dead eggs are historical evidence of infection, but are not an infection risk. If a child has hatched or dead eggs only, and no live eggs or no climbers, they do not have an active infection. No treatment is needed for inactive pediculosis.

How do I tell the state of the egg? Check the following:

  1. The shape in profile: Hatched eggs have no operculum and look like a boiled egg with the top cut off.
  2. The overall shape: Dead eggs collapse in on themselves and the sides are crumpled.
  3. The colour: Live eggs are brown; hatched eggs are pale; dead eggs are brown.
  4. The pressure inside the egg: Live eggs "pop" when squashed between the nails; dead eggs and hatched eggs don't.
The following photographs of head lice eggs have been made using a scanning electron microscope (SEM). The SEM is great for showing details of eggs, but the pictures are in black and white only.

However, finding live lice can be difficult since the climbers move away quickly from disturbances in the hair, and they are very difficult to see.

The complete egg consists of a tube which encircles the hair shaft with the egg attached to the end frtherest from the scalp. Note the operculum forming a lid on the top of the egg. To hatch the operculum opens. Live eggs have curved walls.

An unhatched egg has the operculum in place

Hatched eggs have lost the operculum, and have a flat top in profile.

Dead eggs have the operculum in place, but the sides of the egg have collapsed inwards. Probably a live embryo is needed to maintian pressure in the egg, and when the embryo dies, pressure falls and the atmosphereic pressure forces the walls in.

Remember:

  1. live eggs = active infection and an infection risk
  2. dead eggs only = inactive infection; no infection risk
  3. hatched eggs only = inactive infection; no infection risk
If you find lice, your child should be treated.

If your child has not been treated for head lice before, and you only find eggs, you should consider treating for head lice. However, another option if you do not want to use insecticidal treatments, is to check again the next day using the conditioner and comb technique.

If your child has been treated recently, and you find only hatched eggs, but no lice, you may not need to treat since the eggs could be from the old infection.

You should check your child every week using conditioner, a fine tooth comb, and paper tissue as described below.

HEAD LICE DETECTION KIT

Detecting head lice, even on yourself, can be a simple process by applying conditioner to dry hair, combing the hair with the usual plastic fine tooth comb, and looking for lice by wiping the combings on paper tissue.

A head lice detection kit therefore consists of 4 things:

  1. Conditioner - white conditioner is best since the lice and eggs are easier to see
  2. A fine tooth comb - to remove lice and eggs
  3. A normal comb - to remove tangles
  4. Paper tissue - white tissues are best since the lice and eggs are easier to see.
Conditioner and Fine Tooth Comb Technique
  1. Apply conditioner to dry hair aiming to cover each hair from root to tip with a layer of conditioner.
  2. Detangle the hair using an ordinary comb.
  3. Immediately comb the hair with a fine tooth comb. Plastic nit combs with conditioner are very effective for detecting and removing climbers, but far less effective for eggs. The Lice Meister comb removes about 10 times more eggs than plastic nit combs.
  4. Wipe the conditioner off the fine tooth comb onto a paper tissue and look for lice and eggs.
  5. Repeat the combing for every part of the head at least 5 times.
  6. Also examine the comb for lice and eggs.
Why the normal comb?

Using a fine tooth comb on tangled hair can be a painful experience for children, apart from being ineffective in detecting lice. By combing the hair with the normal comb while the conditioner is applied, you get rid of those tangles, and the fine tooth comb slides through easily. Makes the job so much easier!

Why use conditioner in a detection kit?

Conditioner stuns head lice! The stunning effect seems to last about 20 minutes. After this time most lice are active again.

Conditioner also makes it hard for the lice to grip the hair shafts. Lice hold onto hairs with their six claws and, when they are alive, they are usually not dislodged by the typical plastic fine tooth comb. However, if the hair is wet, or, better still, coated with conditioner, lice seem unable to hold on as strongly as on dry hair. Conditioner may also block up the spiracles, the opening to the tracheal system, and asphyxiate lice. Use conditioner on hair to increase the rate of detection. Applying conditioner to dry hair is best, but it will work on wet hair also.

Each of the six legs of a head louse ends in a claw. These are used to grasp the hair with such strength that head lice are diffiuclt to dislodge.

When moving through hair, they are trapeze artists, able to run quickly both forwards and backwards and transfere quickly from one hair to another. This makes them quite difficult to find since they run away from disturbances and will rapidly move away from searching fingers. Lice are very clumsy off the body since their claws are not made for walking.

People become infected by lice swinging from the hair on one head across to an adjacent hair from another head. For a brief instant, the head louse would have hairs from two heads within its grasp. Contact close enough so that hairs touch is required for transmission.

HOW DO I TREAT HEAD LICE?

Head lice live in the hair and come down to the scalp to feed by sucking blood.

So head lice formulations must be applied to all parts of the hair. A complete regime consists of two treatments 7 days apart, the first to kill the climbers, and the second to kill the juvenile lice hatched from the eggs over the intervening 6 days. No product currently available kills all eggs.

  1. Apply the product to all areas of the head and coat all hairs from roots to tips.
  2. If you are using lotions, apply the product to dry hair. For shampoos, wet the hair, but use the least amount of water possible.
  3. For long hair apply the treatment formulation near the scalp and then use an ordinary comb to carry the formulation down the hair shaft to the tip. If product is left on the comb after one sweep, it should be wiped onto the same or a new area of hair at the base and the process repeated. By repeating this process several times for hair all over the head, one can obtain an even coverage of all hairs from roots to tip. In addition the hair is tangle free and use of a fine tooth comb is subsequently simplified.
  4. Leave the preparation on the hair for at least 20 minutes.
  5. Cover the child's eyes while the treatment is being applied. Ask them to hold a towel against their eyes.

HOW CAN I TELL THAT THE TREATMENT HAS KILLED THE LICE?

If a head lice product works, lice will be dead within 20 minutes. You can test if the lice are killed by doing the following:

  1. After 20 minutes, use a fine tooth comb to comb the hair, and after each sweep from roots to tip, wipe the combings onto a tissue.
  2. Repeat this many times until the whole head has been combed at least twice and little treatment formulation is visible on the hair.
  3. Examine the tissues and see if lice are alive or dead. A magnifying lens is not needed to do this, but will help in the visually impaired. Grade each lice as dead (no movement at all), inactive but alive (louse is stationary, but is moving legs or antennae), or active (louse is crawling on the tissue).
  4. Assess success of treatment and possible insecticide resistance. • If all lice are dead, infestation is sensitive to product used. • If some lice are inactive but alive, infestation may be partly resistant to treatment, but regard the louse population as "sensitive" if no lice are active. • If some lice are active, infestation is resistant.
  5. For a sensitive population of head lice, the current treatment has been successful, but embryos in eggs will most likely survive. Retreat in 7 days using the same product.
  6. For resistant lice, the current treatment has been unsuccessful. See section "If lice aren't killed, what should I do?".
Lice breathe through 7 paired spiracles, 1 on the thorax and 6 on the abdomen. The SEM to the left shows a lateral view of the abdomen and the abdominal spiracles.

The spiracles are in the center of a raised circular structure set off from the body.

The spiracles open into a system of tubes called tracheae. Tracheae occur mainly inside the the thorax and abdomen. The wall of a trachea just below the spiracle consists of roughly hexagonal cells. In this view we can look through the spiracular opening into the trachea attached to it. Perhaps the hexagonal structures result in an increased surface area for gas exchange.

IS A SECOND TREATMENT NECESSARY?

Yes, in almost all cases a second treatment is needed since no head lice treatment kills 100% of the eggs. So if the first treatment killed all climbers, at the second treatment one would expect only juveniles, hatched from eggs during the 7 day period, and no adults. You must retreat on day 7 with the same product that worked on the first treatment, and evaluate efficacy using the same protocol. If lice are found at the second treatment, and they are killed by this treatment, there are two options:

  1. retreatment with same preparation a third time in 7 days to verify complete cure, or
  2. 7 days after the second treatment, put conditioner in the hair, comb with a fine tooth comb and check for lice.
The choice of option depends on your philosophy, option 1 being chosen if you want to make sure all lice are killed, and option 2 is chosen if you wish to minimise exposure to insecticides. If treatment has been as successful as possible, only juvenile lice should be found at the second treatment, and no lice should be found on the third treatment or the third examination.

If no lice are found at the second treatment, the case has been cured.

Head lice suck blood from skins capillaries. They do this painlessly. Unlike mosquitoes, their mouthparts are entirely hidden within the head. See the frontal portrait of a louse below.

The mouth opens onto the surface of a truncated, cone-shaped structrue best appreciated in the lateral view.

HOW DO I KNOW IF LICE ARE RESISTANT TO INSECTICIDES?

Insecticide resistance in head lice is common, but it can be detected by assessing the effect of treatments. If live lice are found in the combings after treatment that has been correctly applied, the head lice are resistant to the product used, and possibly to any other product using the same active compound.

Wash off the first product. Retreat as soon as possible using a product from a different active group than the one used. Although there are over 20 head lice products they fall into four groups based on the active compound:

  1. pyrethrins
  2. synthetic pyrethroids (permethrin and bioallethrin)
  3. organophosphates (malathion or maldison), and
  4. herbal.

WHAT ABOUT THE NYMPHS THAT HATCH BETWEEN TREATMENTS?

Between the treatments 7 days apart, embryos that were not killed by the head lice product in the egg will hatch and emerge to live on the head. They will be killed by the retreatment, but in the meantime the nymphs will feed and grow. Not an ideal situation!

A good strategy to manage this situation is to use the conditioner and fine tooth comb technique between treatments. If conditioner is applied and then immediately combed out, the nymphs that have hatched will be removed. Do this at least twice in the 7 days between treatment 1 and treatment 2.

NOTHING WORKS!

Some cases of pediculosis seem horribly persistent. To solve these you have to use a very systematic approach. Reasons for failure come down to one or several of the following:

  1. Inadequate application of the product
  2. Lice are resistant to insecticide
  3. Failure to retreat to kill nymphs emerged from eggs
  4. Reinfection.
The order of listing of these causes is very important. To determine why the pediculosis persists, you have to start at the top of the list and work to the bottom.

ARE HEAD LICE TREATMENTS SAFE?

All head lice products contain insecticides and most work by attacking the nervous system of the lice. All products licensed and registered with the Therapeutic Goods Administration in Australia have a Aust L or Aust R number. Check for this to see that the product is licensed for use in Australia. If the product does not have TGA listing, it may be marketed legally in Queensland under sole trader legislation, or it may be being sold as a head lice product without official approval. Be wary of head lice treatment products in Australia that are not officially approved.

The active ingredient of all Aust R products have low acute toxicities for humans. Please note that lindane and carbaryl are not licensed for use in Australia. Lindane as a treatment for pediculosis has been removed from many developed countries because of concerns about acute toxicity if used too frequently. Carbaryl is available in the UK only by prescription. The chronic toxicities of the active ingredients are less well recognised. The aim should be to keep exposure to insecticides to the minimum required to eradicate head lice.

WHAT IS DANGEROUS?

Some parents and guardians do risky things to get rid of head lice. Treatments that you should not use because they may harm your child include:
  1. Using insecticidal head lice products to prevent head lice.
  2. Using other insecticidal products on the head. Using pet flea or tick treatments, fly spray and insecticidal surface sprays is dangerous.
  3. Using keroscene.

Author:

Assoc. Professor Rick Speare
Dept. of Public Health and Tropical Medicine
James Cook University
Townsville AUSTRALIA 4811
Phone: 07-47225778 International: -61-7-47225778
Fax: 07-225788 International: -61-7-47225788
Email: richard.speare@jcu.edu.au
This information was recovered from the following web site: http://www.jcu.edu.au/school/phtm/PHTM/hlice/hlinfo1.htm

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