Threadworms

Threadworms are small intestinal worm parasites. The threadworm (sometimes called a pinworm), Enterobius vermicularis, is the commonest worm parasite of children in non-tropical areas such as northern Europe.

The mature female worm can be from 2mm to 13mm long, white, and with a blunt head and a fine, hair-like, pointed tail. The male is shorter and is rarely seen, as it remains in the intestine. Adult worms live for up to 6 weeks.

The female worm lays many tiny eggs around the anus, and around the vagina and urethra in girls. This usually happens at night, when the infested person is asleep. When laying the eggs, the female worm also secretes irritant mucus, which causes the person to scratch the itchy area. Eggs then stick under fingernails and on fingertips, and can be transferred to the mouth to cause re-infestation.

The eggs can survive for three weeks and sometimes hatch on the skin and re-enter the bowel. Swallowed eggs hatch in the intestine, and after a couple of weeks the worms reach adult size and begin to reproduce.

Threadworms are usually passed on by poor hygiene. When a person has threadworms, the eggs are laid around their anus, along with an itchy mucus. The person scratches the itchy area and eggs are transferred on to their hands. The eggs can then rub off onto other surfaces that can come into contact with peopleā€™s mouths such as childrenā€™s toys, kitchen utensils or toothbrushes. The eggs are swallowed and the infestation cycle begins again.

Threadworm is most common in small children because they are not fully aware of the importance of hygiene and easily forget to wash their hands. They are also in particularly close contact with one another, and sharing toys or holding hands while playing means that re-infestation is easy. It is also commonly found in family groups, especially those living in crowded conditions.

Animals cannot catch or pass on human threadworms.

Threadworms cause intense itching around the anus and, in girls, around the vagina. The itching is particularly intense at night, when the worms are active laying eggs. This may cause loss of sleep and irritability.

In cases of very heavy infestation, threadworms may cause loss of appetite, weight loss or insomnia.

Threadworms do not always produce symptoms, which is why all members of a household must be treated when one develops threadworms, even if the others are experiencing no symptoms.

Threadworms are difficult to see because of their size and colour. The best time to try to see them is at night, when the females come out to lay their eggs.

Sometimes worms and eggs can be found in stools. The worms look like little pieces of white cotton thread.

A sample can be taken by applying a wide piece of hypo-allergenic sticky tape to the skin around the anus. If done first thing in the morning, before bathing or wiping, this will pick up eggs, which can then be identified under the microscope.

Alternatively, your GP or nurse may take a moistened swab

If re-infestation is avoided, the problem will disappear spontaneously within six weeks, providing that strict hygiene measures are taken for this period. These include:

The life span of the worms is about six weeks, so re-infestation can be prevented if sensible hygiene measures are taken for this period. These include:

- Keep finger nails short;
- Wash hands and scrub under the finger nails frequently, especially before eating and after visiting the toilet.
- Wear pants at night and wash them daily;
- Wash or shower around the anal area first thing every morning;
- Discourage children from sucking their thumbs;
- Make sure everyone has their own face flannel and towel;
- Do not eat food in the bedroom (eggs can be shaken off bedclothes and survive in dust).
- Vacuum regularly;


Medicine treatments can also be used to remove threadworms. The most commonly used are mebendazole and piperazine. Mebendazole kills the worms, usually with only one dose, and is the preferred treatment for anyone over 2 years old. Piperazine only paralyses the worms until they are pushed naturally out of the bowel. Piperazine can be used in children from 3 months but needs to be taken in 2 doses, 2 weeks apart. Drug treatments are not usually suitable during pregnancy and breastfeeding, or in infants under 3 months, so hygiene measures alone are usually advised.

All members of the family or household need to be treated at the same time, to avoid re-infestation, even if they do not show symptoms. When using drug treatments, strict hygiene measures should still be followed for 2 weeks after treatment, because eggs can survive for this period outside the body.

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It is not possible to prevent threadworm but the chances of infestation can be limited by ensuring that standards of hygiene are high. Children should be taught to wash their hands regularly, particularly after going to the toilet and before meals. Kitchen and bathroom surfaces should be cleaned regularly.

Children with threadworm do not need to stay away from school but schools and nurseries should be encouraged to take hygiene measures.

Encouraging children not to scratch the area around their anus will help prevent re-infestations and will avoid any secondary infections as a result of scratching. However, because the itching most frequently occurs at night, it is quite possible to scratch the area while asleep without realising. NHSDEC07