Headlice and worms are common parasites, but virtually all cases can be treated over the counter and you are ideally placed to offer parents the best advice
In this article you will learn:
• the lifecycle of two common parasites: headlice and threadworms
• how to spot a headlice or threadworm infection
• the different treatment options you can recommend
• advice on hygiene measures.
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Headlice and worms affect almost all children and, while an infestation can occur at any age, they're particularly common among those going to school. Fortunately, you are ideally placed to recommend the right products to treat any infection – and help prevent it spreading.
The life of lice
Headlice are insects that have been around since prehistoric times and are ideally adapted to living – and feeding – on humans. A parasite, headlice affect around one in three children in the UK each year, with around 8 to 10 per cent having headlice at any one time.
They're particularly common in children aged four to 11 years of age because of the way in which they spread, but they can also affect younger children and adults. Headlice are transferred by any human contact where two heads touch. They are incredibly fast and can crawl from hair to hair almost instantly. Once they have landed on a head, they will immediately start feeding by biting on the scalp and sucking blood through it. This happens about four times a day.
A female louse will then start laying eggs at an average of four a day – reaching up to 150. These eggs are coffee-coloured and in cooler climates are normally laid about one centimetre from the scalp, cemented onto hairs behind the ears and the back of the neck by glue released by the female.
After seven to 10 days the eggs will hatch, releasing a nymph the size of a pinhead. Unless removed with a comb, the egg shell can remain in the hair for months before starting to disintegrate. These discarded shells are white and will become more noticeable as the growing hair takes them further from the scalp.
Meanwhile, the nymph will continue to grow, shedding its shell in three stages over 20 days. Once it becomes a fully grown, sexually-mature louse it will measure about 3mm (see right). Females can start mating within hours of reaching their adult stage and begin laying their eggs within seven days.
An individual headlouse will normally die around 35 days after it has hatched, or within a day or so if away from hair. However its offspring will continue the infestation, soon leading to a population of many hundreds unless treated.
As mentioned above, a headlouse feeds by biting the patient's scalp and drinking blood. It has a small mouthpart, so the bite can't be felt, and injects a small amount of saliva to help prevent blood clots – this can cause patients to have an allergic reaction, resulting in itching. However, only around 30 per cent of people infested with headlice will have an itchy scalp, so a lack of itching doesn't mean that no headlice are present.
Headlice only affect the hair; lice in other parts of the body are likely to be a different type and these patients should be referred to the pharmacist.
Removing headlice
Although it's hard to prevent headlice, it's important to catch them early to help prevent spread and minimise symptoms. The best way to do this is to wet-comb children's hair on a weekly basis, using a 0.2 to 0.3mm fine-toothed comb.
This should be done in a well-lit environment and should be comfortable for the child. While most people look for discarded eggs (or nits), it's important to remember these are just empty eggs – actual eggs are very difficult to spot, while lice themselves have a natural camouflage as the blood breaks up their outline.
If headlice aren't found, then there's no need to take further action – just check again in a week's time. However, if there are signs of headlice, then the head needs to be treated.
Although wet combing can be used, it takes a long time to remove the lice completely, and the child will still be infectious, especially in families with several children.
For those wishing to use a product, several options are available, including insecticides and other medicated treatments. Two insecticides are used in the UK: malathion and permethrin. They both work by poisoning the lice and each product will have its own recommended method of use.
Generally, products will be left on the hair for a certain period of time before being washed out and should then be used again seven days later to kill any headlice that have hatched from eggs (preventing the infestation from continuing).
Insecticides have the disadvantage that they should not be used more than once a week for three weeks in a row. Headlice are also becoming increasingly resistant to insecticides, so these products may not be effective and an alternative may be required.
Alternative options include dimeticone and 1,2 octanediol. Dimeticone works by smothering the headlice, meaning they cannot breathe, and can also kill eggs to stop an infestation after one application. Alternatively, 1,2 octanediol removes the outer lipid (fatty) layer of the louse, causing them to dehydrate and die.
You should always refer a patient to the pharmacist if they are pregnant or aged under six months; not all products are suitable for young children aged under two years, so always read the product packaging.
Five headlice myths
1 They only affect clean hair Headlice don't really care if your hair is clean or dirty – as long as they can access the scalp any hair will do.
2 You only need to check for headlice during term time Headlice infestation can occur at any time hair comes into contact with someone else's.
3 Headlice can be spread without hair-to-hair contact This is true, although rare; it's possible to spread headlice on a comb, but it's unlikely.
4 Headlice can also infest hair extensions While theoretically possible, headlice mainly occupy hair near their food source – the scalp. They are unlikely to venture into hair extensions.
5 You need to fumigate bedding Headlice don't survive long off hair, and there is no need to wash or treat bedding.
War on worms
Threadworms are a very common childhood infection and will affect half of all children by the age of 10 years. Unlike headlice, threadworm spread can be controlled as they are linked to poor hygiene: eggs are transferred from the anus, usually to the fingernails or clothes, and deposited on anything the person touches. The infestation is passed on by touching the mouth after being in contact with an infected surface, or can be inhaled when infected sheets are shaken.
Threadworm eggs are quite hardy and can survive in moist environments for up to three weeks before entering a body. Household pets can often carry the eggs in their fur without being infected themselves (threadworms only affect humans). A threadworm infection usually means other household members will be infected, with the NHS suggesting rates of cross-infection among family members can be as high as 75 per cent.
Once taken in by the host, the eggs hatch in the duodenum of the small intestine, and the emerging larvae soon grows to 140 micrometres. They then migrate from the intestine to the colon, during which they moult twice and grow into adults. Adult males can reach 5mm in length, while the female can grow to between 8 to 13mm (see above).
Male and females mate in the ileum (the last part of the small intestine), where the male then dies. The females will attach themselves to the wall of either the ileum, appendix or ascending colon, feeding on the contents.
The body of the female will become filled with as many as 16,000 eggs. Around five weeks after entering the body, it will move towards the rectum where it will lay its eggs before dying. These eggs are translucent and invisible to the naked eye. They are also sticky and attach easily to fingernails and from there to other surfaces, helping to spread the infection.
While laying the egg, the female excretes a mucus, which causes intense itching; this usually occurs at night. Other signs of a threadworm infection include worms in stools, while severe infections can cause loss of appetite, weight loss or a secondary bacterial infection caused by the person scratching the anus.
Worm free
There are two stages to stopping a threadworm infection: OTC treatment and good hygiene. Treatment options for threadworms include mebendazole, which prevents the worms absorbing glucose, and piperazine, which paralyses them until they pass out of the bowel. Mebendazole is available as a tablet and suspension, and can be used in adults and children aged two years or older, while piperazine is available as a flavoured powder that also contains the laxative senna, and can be used in children as young as three months. Both treatments are around 90 per cent effective.
All members of a household should be treated at the same time, and a second dose taken after two weeks if re-infection is suspected. If a patient is still showing symptoms, they should be referred to their GP. Patients who are more than three months pregnant or breastfeeding should not use threadworm medication.
The second pillar of threadworm treatment is good hygiene, as medication will only kill the worms, not the eggs. When a patient is first diagnosed with threadworm, all nightclothes, bed linen, towels and soft toys should be washed to remove eggs (this only needs to be done at a normal washing temperature). Houses should be vacuumed and dusted, in particular the bedrooms, and kitchens and bathrooms should be cleaned regularly with hot water. Other tips include keeping fingernails short, discouraging children from sucking their fingers, regular bathing, and using separate towels.
Children with threadworms do not need to be kept off school. However, schools or nurseries should be informed so they can clean toys and equipment.
Remember… refer to the pharmacist if
● A patient with headlice is under six months of age or pregnant.
● A patient reports having lice anywhere other than the hair.
● A patient still has threadworm symptoms after two treatment attempts, or is pregnant.
Your next steps
● It's back to school time, so why not put up a stand in your pharmacy offering parents tips on checking for headlice and preventing threadworms.
● Headlice and threadworms aren't the only parasites you may encounter. Find out more about the signs of scabies and body lice.
● Read Category Focus in the August 18 issue of C+D for the latest market data on headlice and worming.
