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Getting to the bottom of threadworm infection

Tina Green
RGN
Practice Nurse
Robin Hood Health Centre
Sutton, Surrey

Robert Short
Medical Writer

Threadworm (Enterobius vermicularis), sometimes referred to as "pinworm", is a very common infection - especially in children. Parents can be reassured that they need not keep their infected child away from school (although the school needs to be aware) and that the infection is generally harmless and easily treated.(1) Some parents need reassuring that threadworm infection does not reflect badly upon their standards of hygiene. It really is a very common infection in children that is easy to pick up.
Threadworms look like tiny wriggling pieces of white thread. They live in the rectum, usually without doing very much damage. They are common in school-age children but can spread to the whole family
Spread occurs easily within the household and at school. Eggs get stuck on the fingers and under the nails. Children suck their thumbs and are always putting their hands in their mouths, so it is a rapid journey for the eggs from hand to mouth. Thumbsucking is strongly associated with the prevalence of threadworms and may possibly be associated with persistent reinfection.(2) The sharing of bath towels is another route by which the eggs can be spread to the family. Eggs can live for about two weeks on clothes, bedding and carpets and within dust.
Once some eggs are swallowed, they will hatch out and the adult worms will swiftly develop from the larvae. The female adult worms become especially mobile when the infected person is still. So it is usually at night, while the host is sleeping, that they move to just outside the anal sphincter and deposit eggs. This causes irritation and scratching. This way eggs are collected on the fingers and under the nails, enabling the process of spread to go on.
Prevalence figures in the UK are over 20% in schoolchildren throughout the country, with perhaps higher rates in urban areas. Swedish studies have put the figure at about a quarter of children aged 8-11.(2) Infection rates are low in the summer, but start to rise in October and reach their highest in midwinter.(3)

Tickling symptoms and complications
About a fifth of children are entirely symptom-free carriers of the worm, and 90% will not even get the most common symptom - an itching, tickling feeling around the rectum.(2,4)
Generally there are no complications. However, in some children sleep will be disturbed, and some children develop sore bottoms due to scratching and secondary infection with bacteria.(5) If the infection is heavy or goes on for a long time it can cause loss of appetite, weight loss, insomnia and irritability.(1) Bedwetting may be another possible complication of threadworm infection.(5) In girls and women, the worms may, on rare occasions, migrate into the vagina, causing vulvovaginitis.(6)
 
Diagnosis
Quite often the worms are never seen.
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.

Treatment of the infection
It is always stressed that hygienic measures to prevent reinfection are an important part of treatment, even with drug treatment. UK guidance on the treatment of threadworm is given on the Prodigy website.(1) The whole family should receive both forms of treatment, unless there are medical or personal reasons for individuals not to receive the drug treatment.

Drug treatment
It is best to treat the whole family on the same day. Piperazine and mebendazole are the most commonly used drugs. Efficacy studies suggest that both products produce cure rates of about 90%.(7)
Piperazine (such as Pripsen Powder Sachets by Thornton & Ross) works by paralysing the adult worms, which are then expelled in the faeces. A second dose of piperazine is given at 14 days to ensure that any worms that hatched out after the first dose will be cleared from the system.
Mebendazole (Pripsen tablets by Thornton & Ross or Vermox by Janssen-Cilag) 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.
It is important to check that no one being treated in the household needs to see the GP first and that they are not allergic to any of the components of the treatment. Anyone who is pregnant or planning a pregnancy or who is breastfeeding a child should see a doctor. Children under two 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 two years of age. Piperazine should not be taken by those with  epilepsy, a gut blockage, liver disease or severely decreased kidney function. Those with a neurological disease should be seen by their doctor first.
Patients with complications should be seen by a doctor, as should patients in whom roundworm infection or other infestations are possibly also present. Patients who keep getting reinfected should also be seen by their doctor.

Hygienic measures
Hygiene controls for six weeks - the lifespan of the adult worms - if used by the entire household can break the cycle of infection by removing all eggs from the body, clothing, bedding and house. Every person in the house should:

  • Wear pyjamas or pants and change them daily.
  • Have a bath or shower and wash around the anus each morning.
  • Not share towels.
  • Change and wash underwear.
  • Keep nails short.
  • Wash hands and scrub under the nails, after using the toilet or changing nappies, and before eating or preparing food.
  • Avoid eating in the bedroom.
  • Damp dust and vacuum clean bedrooms daily.

More elaborate methods to remove eggs include those suggested by Ibarra:(8)

  • Cleaning the bottom of babies every three hours so that eggs do not hatch out and larvae migrate into the rectum.
  • Use tape or jelly at night around the mouth of the anus to trap worms, followed by washing the area around the anus after rising from bed and at three-hourly intervals during the day.

Hygiene methods may be the preferred way for people who want to avoid medication for medical or personal reasons.

Conclusions

Generally threadworm is a harmless infection. Drug treatment should be combined with hygiene measures. Drug treatment includes piperazine or mebendazole. This is usually combined with strict hygiene controls for the whole family for six weeks. This should break the cycle of infection by removing all eggs and letting the adult worms die naturally without being replaced by young worms.

References

  1. Prodigy. Guidance on the treatment of threadworm infection in the UK. Last update September 2004. Available from URL http://www.prodigy.nhs.uk/ guidance.asp?gt=Threadworm
  2. Herrström P, Friström A, Karlsson A, Högstedt B. Enterobius vermicularis and finger sucking in young Swedish children. Scand J Prim Health Care 1997;15:146-8.
  3. Tanowitz HB, Weiss LM, Wittner M. Diagnosis and treatment of common intestinal helminths. II: common intestinal nematodes. The Gastroenterologist 1994;2:39-49.
  4. Ibarra J.The ubiquitous threadworm, Enterobi vermicularis. Parasitology. Nurs Stand 1989;3:34-5.
  5. Cook GC. Tropical infection of the gastrointestinal tract and liver series. Enterobius vermicularis infection. Gut 1994:35:1159-62.
  6. Joishy M, Ashtekar CS, Jain A, Gonsalves R. Do we need to treat vulvovaginitis in prepubertal girls? BMJ 2005;330(7484):186-8.
  7. National Prescribing Centre. Prescribing Nurse Bull 1999;1(3):11-12.
  8. Ibarra J. Threadworms: a starting point for family hygiene. Br J Commun Nurs 2001;6(8):414-20.

Resource
The now annual "Fred Worm Campaign" with this year's Threadworm Action Month in September does much to raise awareness among parents and children of this infection and how it can be treated. Threadworm infection can be embarrassing for people, but the campaign's badges worn by nurses, GPs and pharmacists raise curiosity about the friendly "Fred Worm" pictured and encourages children and parents to "Ask about Fred". Everyone who asks gets information and receives a rubber wristband printed with "I know about Fred" to encourage their friends to enquire too
W:www.fredworm.co.uk