Headlice
(pediculosis capitis)

Description
The head louse starts as a small egg about the size of a grain of salt which the female louse glues to the base of the hair shaft. Most often these eggs (nits) are found in the hair behind the ears, at the back of the neck, or around the crown and under the fringe. The eggs hatch in 7-10 days. They mature into an adult louse, which is a wingless insect 2-3 mm long with a flat body and six legs. The adult louse is capable of laying eggs after 10 days. Lice are very quick moving and very difficult to see in the hair. Headlice generally cause itching behind the ears and at the back of the neck. They are spread by direct contact with the scalp of an infested person, or by contact with personal items (such as combs, brushes, hats, scarves, jackets, sweaters, sheets, pillows and pillowcases, blankets, upholstered furniture etc). Lice are very host-specific. Those which live on animals will not live on humans and vice versa.


Incubation Period
The eggs usually hatch in 7-10 days. Once hatched, the lice are capable of laying eggs in 10 days.


Infectious Period
As long as the eggs or lice are alive. Lice do not survive more than two days away from a human host but their eggs may survive longer.


Controlling the Spread of Infection
Exclude a confirmed or suspected case from the centre. Re-admit the child the day after appropriate treatment has started. Dead eggs may still be present but the child is no longer infested and nits need not be removed. Inspect close contacts regularly for signs of infestation. Headlice move away quickly as the hair is parted. Eggs will be easier to see as they will be firmly attached to the hair. If the eggs are more than about 10-15mm from the scalp they have either hatched or died. A good light and a magnifying lens will help you find and identify lice. Discarded skins and black sandy excrement may be seen on pillows and collars. Educate the children, child care workers and parents about headlice and why personal items (like hats) should not be shared. The local health authority will help with this. Dry clean clothing and bedding or launder them in hot water for a minimum of 20 minutes. This should be done both at the centre and at home. Ironing clothes and drying clothes in a hot clothes dryer are also effective ways of killing lice. Place all items that cannot be washed or dry cleaned in a plastic bag for 3-4 days. Vacuum or gently iron carpet and furniture. Do not spray them with insecticide. Wash and clean combs and brushes with detergent and hot water.


Treatment
Use of pediculicides (insecticides that kill lice) Pregnant women, people with sensitive skin, and the parents of infants less than 12 months old should consult a doctor before applying pediculicides. To prevent unnecessary or repeated exposure to pediculicides, the person applying the chemical should wear protective gloves. Pediculicides are ideally applied twice, with the second application 7-10 days after the first. If the treatment is carried out correctly and still appears to be ineffective, then change the pediculicide to one that has a different insecticide base. Resistant headlice can be eradicated by switching to a different pediculicide. Over the years a large number of different products have been used to treat headlice. Three pediculicides stand out as being most effective. These are maldison, pyrethrins and lindane. The following guidelines give information on each product and how to use it. Maldison (CleenSheen, Ovanit Lotion, Head Lice Lotion, KP24) This is recommended by the NHMRC as the first line of treatment. Maldison blocks the action of an enzyme in the nervous system of headlice. Because of differences between insects and humans in the enzyme on which it acts, maldison is far more toxic to insects than it is to humans. In humans, maldison is rapidly broken down and excreted. Nevertheless, as with any insecticide, it should be used only in accordance with the manufacturer's recommendations. Care should be taken to avoid contact with the eyes, nose and throat. Never use garden strength maldison. Only use maldison preparations formulated for headlice control. There are several maldison formulations for headlice treatment which have either a kerosene or an alcohol (ethanol) base. It is easier to use an alcohol-based preparation. When the treatment is applied to the hair, the alcohol will evaporate rapidly, leaving only a residue of maldison in the hair. Do not use a hair dryer, as heat may inactivate the residue. Follow the manufacturer's instructions carefully. Pyrethrins (Lyban, Pyrifoam) Pyrethrins are naturally occurring insecticides derived from chrysanthemum flowers. Pyrethrins act on the louse's nervous system and as a stomach poison, killing headlice on contact. Despite their low toxicity to humans, some people are allergic to pyrethrins. Pyrethrins can also irritate the eyes, nose and throat. Contact with these parts of the body should be avoided. Pyrethrin shampoo is applied to the hair, left for 10 minutes, then rinsed out. Hair should be dried gently with a towel. Do not use a hair dryer as the heat may inactivate the pediculicide. Lindane (gammabenzene hexachloride) (Quellada) Lindane is an insecticide which paralyses the nervous system of the headlouse. Lindane is more toxic than either pyrethrin or maldison. Therefore it is very important to use it strictly according to the manufacturer's instructions. It should not be applied to the scalp following a hot bath or shower and it should not be scrubbed into the scalp. Avoid contact with the eyes, nose and throat. Small children, pregnant or breastfeeding women, and people with eczema or broken skin should not use lindane. However, lindane is safe and very effective if care is taken, and it is therefore a very useful pediculicide to have available alongside pyrethrin and maldison. Lindane is available as a lotion containing 1% lindane. This is gently rubbed into the hair, allowed to remain for four minutes, and then thoroughly rinsed out. Lindane can be purchased only from pharmacies, under the brand name Quellada.


Comments
Lice may infest people of any socioeconomic position, age or sex. In fact, they may prefer clean hair. The closeness of children in child care centres increases the potential for spread. Disclaimer Use of trade names in this document is for identification purposes only and does not constitute endorsement.

Disclaimer
The information contained in this website is intended as a guide only. Wollongong Medical Centre is not liable for any problems that may arise from incorrectly or otherwise applying information found in this website.


Further General Information

The following web site has information on infectious diseases: www.health.nsw.gov.au/infect/ or contact the Division of Population and Planning on 4255-2200.

For information on a large range of medical conditions and problems visit www.mayoclinic.com