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Threadworm infection







Threadworms (Enterobius vermicularis) or ‘pinworms’ look like wriggling pieces of white cotton thread. They are about 2-13 mm long. They live in the rectum and are generally harmless, although there can be some rare complications that the nurse should be aware of. They are especially common in children but can spread to all the family. It does not matter how financially well off or what social class the family is from (Gutierrez, 1990; Russell, 1991), everyone can get the infection. Note that the infection is not ‘got from the cat’, as some patients might believe. It is not transferred to or from animals (Prodigy, 2004).

Eggs stuck under the nails or on the fingers are transferred between children in schools and nurseries or to the family at home.  They easily get transferred to the mouth and some will be swallowed. The sharing of bath towels is another way in which they can be spread. They survive for up to a couple of weeks on clothing, bedding, in carpets and within household dust. The habit of thumb sucking and sucking other fingers is strongly associated with the prevalence of threadworms (Herrström et al 1997).

Once ingested, the eggs hatch out as threadworm larvae in the small intestine. The adult worms live in the colon. Adult worms live for about 6 weeks. A female threadworm can lay up to 16,000 eggs before dying.  The female adult worms, while the sufferer is inactive in sleep, move to the mouth of the anus and deposit eggs just outside it. This causes irritation around the anus and the sufferer will scratch the itching area, collect eggs on the fingers and under the nails, and this way the infection can spread to clothes and other members of the household.

A common infection

A decade ago in a general practice of 10,000 patients, there would be roughly 40 consultations a year for threadworm (McCormick et al, 1995), but a vast number of people will tend to treat themselves and their families by over-the-counter medications and never report the infection to their GP or practice nurse. With annual education campaigns aimed at parents and children (e.g. the Fredworm campaign  during Threadworm Action Month in September 2005), awareness of  threadworm infection is  increasing and parents are less embarrassed at approaching their pharmacist, GP or practice nurse to discuss ‘Fredworm’.

It is most common among school children aged 5-10 years old. Recent and referenced published figures in the UK appear rare in the scientific literature. NHS Direct have in the past on their website stated ‘at least 20% of all children are affected at any one time, but did not reference that statement nor is it there now.  Surveys in Canada in the 1960s show a prevalence of 40-60% in schoolchildren, and 30% in preschool children (Royer and Berdnikoff, 1962). Much more recent surveys in Swedish children have put the figure at about a quarter of children 8-11 (Herrström et al 1997). Infection rates start to rise in October and tend to reach a peak in midwinter (Tanowitz HB et al, 1994). Nearly half the parents who report threadworm infection in their child report that the infection returns in the same year (Ibarra, 1989a).

According to the Health Protection Agency’s advice to Prodigy, it is not necessary to exclude children with threadworm infection from school. (Prodigy, 2004)

Symptoms of infection

A tickling or itching sensation around the anal area at night is the most common symptom, but 9 out of ten sufferers will not feel this symptom (Ibarra, 1989b). Sleep may be disturbed and some children develop sore bottoms. Usually worms are only seen in the toilet, if at all. Many people will show no symptoms. In the Swedish study, 21% of children studied were symptom-free carriers of the worm (Herrström et al, 1997).


The nurse or GP may occasionally be able to make the diagnosis by seeing the worms in the area around the anus. Rarely, perhaps in only 5-15% of cases, worms might be detected in stools (Cook, 1994).

Tape testing which involves applying hypoallergenic tape around the anus to collect eggs/worms is no longer used as a diagnostic tool in general practice.  


Generally there are no complications, but it is worth the nurse being alert to the possibilities. The most common complication is a sore bottom, as the skin around the anus becomes broken, and secondary infection occurs (Cook, 1994).

Also if the infection is heavy or goes on for a long time it can cause loss of appetite, weight loss, insomnia and irritability (Prodigy, 2004). Enuresis may be another possible complication of threadworm infection (Cook, 1994)

In girls and women, the worms may migrate from the skin around the anus over the perineum to enter the vagina and cause vulvovaginitis (Joishy et al, 2005). Threadworms or eggs have been found in vaginal and cervical smears (Chung, Kong et al, 1997), and in peritoneal granulomas (Brooks et al 1962; Khan et al 1981; Saffos and Ratigan, 1977; Sun et al 1991). There have been very rarely granulomas of the liver, ovary, kidney, spleen and lung when the worms have got into the abdominal cavity (Cook and Zumla, 2002).There have been at least 11 cases of threadworm related granulomas of the perianal tissues that required surgery (Mattia, 1992); Simon and Walla, 1974; Kropp et al, 1978).

Treatment of the infection

UK guidance on the treatment of threadworm is available on the Prodigy website (Prodigy, 2004). Note that this received its last update (adding in information for nurse prescribes, in March 2004), although there was some minor technical updating of the article in September 2004. Nurses are advised to check with the current BNF at www.bnf.org for updates of drug treatment. The BNF used for the current article was BNF 49 edition, March, 2005.

Treatment without drugs

Treatment without drugs is possible through hygiene controls for 6 weeks, breaking the cycle of infection by removing all eggs and allowing the adult worms to die. It is important that the whole family take these hygienic measures. For some people this may be the preferred option if they do not want to take medication or if it is not recommended. For example, it is usually inadvisable to give drug treatment during pregnancy.

Measures to remove eggs include: the use of tape or jelly at night around the anus, followed by washing or wet-wiping the perianal area after rising from bed and at 3-hourly intervals during the day; changing the nappies of babies and cleaning the bottom every 3 hours (eggs can hatch in 4-6 hours and some larvae could migrate back into the rectum).

Prodigy guidance, designed for nurses, nurse prescribers, GPs and other health professionals, advises that every person in the house:

  • wear close-fitting underpants or knickers at night;
  • have a bath or shower, wash around the anus each morning, immediately on rising;
  • change and wash underwear, and (if possible) bed linen each day (avoid shaking them as this also spreads eggs);
  • keep fingernails short;
  • Wash hands and scrub under the nails first thing in the morning, after using the toilet or changing nappies, and before eating or preparing food.

Eggs can be removed by daily damp dusting of surfaces and washing the cloth frequently in hot water or using disposable clothes. Good ventilation and reduced humidity both help to kill off the eggs. Daily vacuuming of carpets is another piece of advice that is commonly given. The eggs can survive for 2 weeks on clothing, bedding, or other objects.

Drug treatment

It is always stressed that the above hygienic measures to prevent re-infection are an important part of treatment, even if drug treatment is to be given.

With drug treatment, it is best to treat the entire family at the same time. The most commonly used drug treatments for threadworm include piperazine and mebendazole. 

The only Piperazine treatment available is Pripsen Powder Sachets which is Piperazine combined with a mild laxative (senna).  Piperazine works by paralysing the worms which are then evacuated by the laxative action of the senna. A second dose of piperazine is given after 14 days to ensure that any worms that were unhatched at the time of the first dose will be cleared from the system. Pripsen Powders are the only drug treatment for threadworms which can be given to children under the age of two years old (from 3 months of age).

Mebendazole (Pripsen tablets) is given as a single dose, but if reinfection occurs a second dose is given after two weeks. Mebendazole prevents sugar absorption by the worms and they die a few days later.  Efficacy studies are rare and old (and mostly against old products not used in the UK ) but mebendazole and piperazine apparently produce comparable cure rates of about 90% (National Prescribing Centre, 1999).

People who must see a doctor

As the parent or adult being treated may be treating the rest of the family, it is important to check that no one they are treating needs to see the GP first. 

Anyone who is pregnant or planning a pregnancy or who is breast feeding a child should see a doctor. Similarly, children under 2 years of age will need to be seen by a doctor before they are treated with drugs. Mebendazole is not to be used in children under 2 years of age. People should not be treated with piperazine if they have epilepsy, a gut blockage, liver disease or severely decreased kidney function. People with a neurological disease should be seen by their GP first. Check also that no one is allergic to any of the components of the treatment.

The potential complications of the infection have been mentioned and are rare. Patients with such complications should be seen by a doctor, as should a patient who you suspect of roundworm infection or other secondary infestations.  Also patients who persistently relapse should be seen by the GP and possibly referred to a parasitologist.


Threadworm infection is very common in school children and even when treated, reinfection is frequent. Strict hygiene controls for the whole family for six weeks is one way of treating the disease, especially for people who cannot or are willing to take medication. This should break the cycle of infection by removing all eggs and letting the adult worms die naturally without being replaced by young worms. Drug treatment should be combined with hygiene measures. Drug treatment includes piperazine and/or mebendazole. Generally, threadworm is a harmless infection.

Useful  patient website



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Cook C, Zumla A. 2002. Manson’s tropical diseases. 21st edition, London . WB Sanders 2002

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