Threadworm
Threadworm - Summary
Threadworm or pinworm (Enterobius vermicularis) is a parasitic worm which infests the intestines of humans.
Threadworm infestation occurs after swallowing eggs, usually by eating contaminated food or from contaminated hands.
Threadworm is the most common parasitic worm infestation in the UK and is more likely to affect school or pre-school children than adults, because of their inattention to good personal hygiene and close contact with other children. Threadworms often affect family groups or institutions, especially if conditions are crowded. It is not necessary to exclude children with threadworms from school.
The most common symptom is perianal itching, which is worse during the night. Infestation may be symptomless and only detected when threadworms are seen on the perianal skin or in the stools.There may be signs of scratching in the perianal area and sometimes localized secondary bacterial infection. It is unusual to see worms in the perianal area when the person is examined during the day.
If the diagnosis is uncertain, the adhesive tape test for eggs may be useful. Transparent tape is applied to the perianal area first thing in the morning and then examined under a microscope to detect threadworm eggs. Stool examination is not generally recommended.
Other causes of perineal itch include dermatitis, candidal infection, and haemorrhoids. Threadworms are rarely confused with other types of worm infestation because of their different appearance.
Treatment is recommended if threadworms have been seen or eggs detected treatment. All household members should be treated at the same time.
An anthelmintic combined with hygiene measures is recommended.
Mebendazole in a single dose is the drug of choice for adults and children aged over 6 months.
Piperazine (combined with senna) in a single dose, repeated after 14 days, can be used from 3 months.
For people who do not wish to take an anthelmintic, physical removal of the eggs, combined with hygiene measures is recommended.
Treatment with an anthelmintic is contraindicated in children aged less than 3 months and women in the first trimester of pregnancy.
For children less than 3 months old, hygiene methods alone are preferred.
During pregnancy, or for breastfeeding women, physical removal of eggs combined with hygiene methods is the preferred treatment.
If infestation persists after hygiene measures have been continued for the recommended duration, a further course of drug treatment is recommended. It is important that household members are treated and adhere to hygiene measures.
Have I got the right topic?
This CKS topic covers the treatment of threadworm (pinworm) infestation (Enterobius vermicularis).
This CKS topic does not cover the treatment of tapeworm, hookworm, or more unusual worm infestations.
There are separate CKS topics on Pruritus ani, Pruritus vulvae, and Roundworm.
The target audience for this CKS topic is healthcare professionals working within the NHS in the UK, and providing first contact or primary health care.
How up-to-date is this topic?
How up-to-date is this topic?
Changes
November 2011 — revised. A literature search was conducted in October 2011 to identify evidence-based guidelines, UK policy, systematic reviews, and key RCTs published since the last revision of the topic. No changes to clinical recommendations have been made. Issued in December 2011.
Previous changes
March 2011 — topic structure revised to ensure consistency across CKS topics — no changes to clinical recommendations have been made.
August 2007 — minor typographical update to the Clinical Summary. Issued in August 2007.
March to June 2007 — converted from CKS guidance to CKS topic structure. The evidence-base has been reviewed in detail, and recommendations are more clearly justified and transparently linked to the supporting evidence.
There are no major changes to the recommendations.
October 2005 — minor technical update. Issued in November 2005.
March 2004 — updated with additional information for nurse prescribers. Issued in March 2004.
August 2003 — reviewed. Validated in December 2003 year and issued in February 2004.
March 2001 — rewritten. Validated in March 2001 and issued in June 2001.
June 1998 — reviewed.
September 1997 — written.
Update
New evidence
Evidence-based guidelines
No new evidence-based guidelines since 1 October 2011.
HTAs (Health Technology Assessments)
No new HTAs since 1 October 2011.
Economic appraisals
No new economic appraisals relevant to England since 1 October 2011.
Systematic reviews and meta-analyses
No new systematic reviews or meta-analyses since 1 October 2011.
Primary evidence
No new randomized controlled trials published in the major journals since 1 October 2011.
New policies
No new national policies or guidelines since 1 October 2011.
New safety alerts
No new safety alerts since 1 October 2011.
Changes in product availability
No changes in product availability since 1 October 2011.
Goals and outcome measures
Goals
To eradicate threadworms
To prevent reinfestation
Background information
Definition
What is it?
Threadworm or pinworm (Enterobius vermicularis) is a parasitic worm which infests the intestines of humans.
Threadworms have a white, thread-like appearance (hence the name).
The adult male worm is 2–5 mm in length and the adult female is 8–13 mm in length.
Threadworm eggs are not visible to the naked eye.
Humans are thought to be the only host.
How people get infected
How do people get infected?
Threadworm infestation occurs after swallowing eggs that are present in the environment.
Once a person is infested, the infestation is maintained by swallowing fresh eggs.
To better understand this, an explanation of the lifecycle of the threadworm is necessary:
Eggs are ingested, usually by eating contaminated food or following transfer of eggs to the mouth by contaminated hands. Occasionally, infestation may be acquired from inhaling and then swallowing eggs that have become airborne (for example after shaking contaminated bedding).
Following ingestion of eggs, the larvae hatch in the small intestine. They reach maturity within 2–6 weeks and then travel to the large intestine.
The adult males remain in the large intestine. However, at the end of the female threadworm's lifecycle the pregnant females travel to the perianal skin and deposit large numbers of eggs (in girls and women, eggs may also be deposited around the vagina and urethra). This usually occurs during the night when the infested person is asleep, as inactivity of the host encourages the female worm to migrate.
The worm secretes a sticky mucus to attach the eggs to the skin, which causes intense itching.
The hands and nails of the host become contaminated with eggs from scratching the perianal area, or after wiping when going to the toilet. Hand-to-mouth contact results in fresh eggs being ingested (autoinfestation), continuing the cycle of infestation.
Person-to-person infestation occurs through handling contaminated clothes or bedding, or from touching contaminated surfaces such as furniture and carpets. Eggs can survive on such surfaces for up to 2 weeks.
Adult threadworms survive for about 6 weeks, and fresh eggs need to be ingested by the host for infestation to continue.
Threadworms only infest humans and cannot be caught from animals, such as dogs and cats (but eggs can contaminate the hair or fur of pets, with transmission to humans following patting).
Prevalence
How common is it?
Threadworm is the most common parasitic worm infestation in the UK.
In a general practice of 10,000 patients, about 40 consultations a year are due to threadworm [McCormick et al, 1995]. However, it is likely that many more people seek over-the-counter treatment. In addition, asymptomatic infestation is common.
Threadworms are much more common in school or pre-school children than in adults, because of their inattention to good personal hygiene and close contact with other children. Threadworms often affect family groups or institutions, especially if conditions are crowded [Cook and Zumla, 2002; CDC, 2004].
Complications and prognosis
Complications
Scratching of the perianal skin may make it inflamed and broken, with a risk of secondary infection.
Threadworm infestation outside of the intestine is extremely rare. It has been reported to occur in the vagina, the uterus, the pelvic peritoneum, the abdominal cavity, the liver, and even the lungs [Huh and Lee, 2006].
Prognosis
Without treatment (medication and/or strict hygiene), infestation will persist indefinitely [HPA, 2003].
Reinfestation is common [Huh and Lee, 2006].
Diagnosis
Diagnosis of threadworm
Symptoms
What are the symptoms of threadworm infestation?
Threadworm infestation is often symptomless, and individuals may present only because threadworms have been seen on their perianal skin or, less commonly, on their stools.
Threadworms are often described as looking like 'small threads of slowly-moving white cotton'.
They are best seen at night or when the person is resting, as this is when the females usually emerge from the anus to lay their eggs.
Perianal itching is the most common symptom, and is worse during the night.
Perivaginal itching can also occur.
Persistent or heavy infestation can cause loss of appetite, weight loss, insomnia, enuresis, and irritability.
Basis for recommendation
Basis for recommendation
This information is based on guidance from the US Centers for Disease Control and Prevention [CDC, 2004], the Health Protection Agency [HPA North West, 2005], and expert opinion in a review article [Huh and Lee, 2006].
Examination
What should I look for on examination?
There may be signs of scratching (excoriation) in the perianal area, and there may be signs of localized secondary bacterial infection.
Worms may be seen in the perianal area, although it is unusual to see these when the person is examined during the day.
Basis for recommendation
Basis for recommendation
This information is based on guidance from the US Centers for Disease Control and Prevention [CDC, 2004].
Investigations
How should I investigate suspected threadworm infestation?
If the diagnosis is uncertain, the adhesive tape test for eggs may be useful.
Give the following instructions to the person (or parent, if the person being investigated is a child):
Apply transparent adhesive tape to the perianal skin first thing in the morning, before wiping or bathing.
Then remove the tape and either stick it to a glass slide or place it in a specimen container (whichever has been provided).
Hand this back in at the surgery, so that it can be examined under a microscope either by the GP or the local laboratory.
If ovoid threadworm eggs are present, these are usually easily seen under a microscope.
Stool examination is much less reliable, and is generally not recommended.
Basis for recommendation
Basis for recommendation
This information is based on guidance from the US Centers for Disease Control and Prevention [CDC, 2004], the Health Protection Agency [HPA North West, 2005], and expert opinion in a review article [Huh and Lee, 2006].
Differential diagnosis
What else might it be?
Consider other causes of perianal itch, such as dermatitis, candidal infection, and haemorrhoids. For a detailed discussion, see the CKS topic on Pruritus ani.
Threadworms are rarely confused with other types of worm infestation:
Other worm infestations are much less common in the UK.
Human roundworm may occasionally be passed in the stool, but cannot be confused with threadworm as adult roundworms are approximately 30 cm long.
Tapeworm infestation may only become evident when segments are passed in the stool — these are called proglottids, and are either seen as single proglottids (like grains of rice) or as chains.
Management
Management
Scenario: Management: covers the management of threadworm and prevention of further episodes.
Scenario: Management
Scenario: Management of threadworm
Who to treat
Who should be treated?
Treat the person if threadworms have been seen, or their eggs have been detected.
Threadworms are best seen at night or when the person is resting, as this is when the females usually emerge from the anus to lay their eggs. The females are visible to the naked eye (8–13 mm long) and are often described as looking like 'small threads of slowly-moving white cotton' (see Diagnosis).
Treat all household members at the same time (unless contraindicated).
Basis for recommendation
Basis for recommendation
The recommendation to treat all members of the household is based on advice from the Health Protection Agency [HPA North West, 2005].
The risk of transmission in families is as high as 75%, and asymptomatic infestation is common [Richardson et al, 2001].
Managing threadworm
How should threadworm be managed?
Treatment with an anthelmintic is recommended, combined with hygiene measures.
Mebendazole is the drug of choice for adults and children aged over 6 months.
Give a single dose of mebendazole, repeat in 2 weeks if infestation persists.
Piperazine (combined with senna) can be used from 3 months.
Give a single dose, repeated after 14 days.
Treatment with an anthelmintic is contraindicated in children aged less than 3 months and women in the first trimester of pregnancy. Women in the second or third trimester and women who are breastfeeding may prefer not to take an anthelmintic (See Threadworm in pregnancy/breastfeeding).
For people who do not wish to take an anthelmintic, and those in whom an anthelmintic is not recommended, advise physical removal of the eggs, combined with hygiene measures.
Measures to physically remove the eggs include:
Washing the perianal area first thing in the morning.
Washing or wet-wiping at 3-hourly intervals during the day. (This may be impractical for some people, and twice a day is probably more realistic.)
Basis for recommendation
Basis for recommendation
These recommendations are based on expert opinion from the published literature, and the relative safety profiles of the two anthelmintics available in the UK.
CKS found no good trial evidence regarding the efficacy of anthelmintics in the treatment of threadworm. The limited data available are from relatively old, small studies comparing mebendazole with either placebo, or with drugs that are not available in the UK.
CKS found no published studies comparing the efficacy of mebendazole with piperazine. However, it is generally accepted that they have comparable efficacy (90–100% cure-rate) [Micromedex, 2007]:
Mebendazole is the drug of choice for threadworm in primary care, because there are few contraindications to its use, and the manufacturer reports that post-marketing surveillance has revealed no serious safety concerns [ABPI Medicines Compendium, 2005; BNF 53, 2007].
The BNF for Children recommends mebendazole as the drug of choice in for treating threadworm infection in children over 6 months, however it is not licensed for use in children less than 2 years of age [BNF for Children, 2006].
Piperazine (combined with senna) is licensed for use from 3 months old [BNF 53, 2007]. However, it is less preferred than mebendazole because there are more contraindications to its use, and it is systemically absorbed which increases the likelihood of adverse effects (see Prescribing information for further details).
Neither mebendazole nor piperazine kills eggs, therefore adequate personal and environmental hygiene is essential to prevent reinfestation from recently swallowed eggs, or eggs already in the environment.
The recommendation to treat people who cannot take or do not wish to take an anthelmintic with physical removal of the eggs combined with strict hygiene measures is based on expert opinion [Ibarra, 2001]. CKS found no published studies regarding the efficacy of these methods.
Washing or wiping at 3-hourly intervals is intended to prevent retroinfection [Ibarra, 2001]. However washing or wiping this frequently may be impractical, and the role that retroinfection plays in reinfestation is likely to be minimal. Therefore washing or wiping twice a day may be more realistic.
Advice about hygiene
What advice should I give about hygiene?
Environmental hygiene measures — undertake on the first day of treatment:
Wash sleepwear, bed linen, towels, cuddly toys at normal temperatures and rinse well.
Thoroughly vacuum and dust, paying particular attention to the bedrooms, including vacuuming mattresses.
Thoroughly clean the bathroom by 'damp-dusting' surfaces, washing the cloth frequently in hot water.
Strict personal hygiene measures — for 2 weeks if combined with drug treatment or for 6 weeks if used alone:
Wear close-fitting underpants or knickers at night. Change them every morning.
Cotton gloves may help prevent night-time scratching. Wash them daily.
Bath or shower immediately on rising each morning, washing around the anus to remove any eggs laid by the worms during the night.
General personal hygiene measures — encourage all the time for all household members:
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.
Discourage nail biting and finger sucking.
Avoid the use of 'communal' or shared towels or flannels.
Basis for recommendation
Basis for recommendation
Recommendations regarding hygiene measures are based on expert opinion from the published literature.
Environmental hygiene measures are designed to remove eggs from the home.
Personal hygiene measures are designed to prevent autoinfestation or person-to-person reinfestation.
Expert opinion varies regarding how long personal hygiene measures should continue. CKS suggests that personal hygiene measures should be continued for:
Two weeks in people who have taken an anthelmintic (as eggs can remain viable in the environment for up to 2 weeks).
Six weeks in people who are using hygiene measures alone (the approximate lifespan of a threadworm).
Threadworm in pregnancy/breastfeeding
How do I manage threadworm in a woman who is pregnant or breastfeeding?
Pregnancy
During pregnancy, physical removal of eggs combined with hygiene methods is the preferred treatment.
Neither mebendazole nor piperazine should be used in the first trimester of pregnancy.
If drug treatment is considered necessary in the second or third trimester of pregnancy, mebendazole is the anthelmintic of choice. This indication is off-licence.
For more details, contact the UK Teratology Information Service (UKTIS), formerly the National Teratology Information Service (NTIS), on 0844 892 0909.
Breastfeeding
If a woman is breastfeeding, physical removal of eggs combined with hygiene methods is generally preferred.
If drug treatment is required, mebendazole is the anthelmintic of choice. This indication is off-licence.
Some women who are pregnant or breastfeeding may be anxious to eradicate the worms as soon as possible (for example if it is proving difficult to prevent reinfection by hygiene methods alone). In this situation drug treatment may be preferred, provided the woman is not in the first trimester of pregnancy.
Basis for recommendation
Basis for recommendation
Pregnancy
Mebendazole has been reported to be teratogenic in some animal studies, however the clinical significance of this is unclear. There are no published studies in humans to suggest that mebendazole is associated with a significant increase in congenital malformations [NPIS, 2007]. In one study of over 400 women exposed to mebendazole during pregnancy, an increased risk of congenital malformations was not observed [Garbis et al, 2001]. A second prospective cohort study of 192 women exposed to mebendazole during pregnancy also found no significant increase in the rate of major malformations compared with women who were not exposed (1.7% vs. 3.3%; p = 0.478) [Diav-Citrin et al, 2003].
Piperazine has been reported to be teratogenic in rats [Micromedex, 2007]. However, there are few published reports of pregnancy outcome with piperazine in humans, so its safety during pregnancy is unknown. The BNF states that piperazine is not known to be harmful in pregnancy but the manufacturer advises avoid in the first trimester [Thornton & Ross Limited, 2004; BNF 53, 2007].
Breastfeeding
Although excretion of mebendazole into breast milk has not been studied, mebendazole is poorly absorbed from the gut, so the small amounts of mebendazole available for excretion into breast milk are unlikely to be harmful [NPIS, 2007]. As mebendazole is the anthelmintic of choice, CKS recommends mebendazole for a breastfeeding woman who requires drug treatment. This indication is off-licence.
Piperazine with senna is excreted into breast milk. As it is a single-dose product, the manufacturer advises that the dose should be given after a breastfeed, and that breastfeeding should then be avoided for 8 hours [Thornton & Ross Limited, 2004]. They also advise that milk should be expressed (and discarded) at the usual feeding times during this 8-hour period. However, this may not be practical if the woman cannot hand express or does not already own a breast pump, or the baby refuses to take a bottle.
Threadworm in a child under 3 months
How do I manage threadworm in a young child (< 3 months)?
For children less than 3 months old, hygiene methods alone are preferred.
Advise cleansing the bottom gently but thoroughly at each nappy change.
Advise parents to wash their hands thoroughly before and after each nappy change.
Basis for recommendation
Basis for recommendation
Neither of the drugs available for the treatment of threadworm in the UK is licensed for use in children less than 3 months old [BNF 53, 2007].
Action if treatment fails
What should I do if treatment does not work?
If infestation persists after hygiene measures have been continued for the recommended duration:
Offer a further course of drug treatment.
Ensure that all household members are treated.
Emphasize the importance of all household members adhering to strict hygiene measures.
If there are frequent recurrences consider seeking advice from a paediatrician or consultant in infectious diseases.
If an original diagnosis of threadworm was confirmed and the person is still experiencing symptoms such as intense itching in the perianal area at night, it is likely that reinfestation has occurred and a further course of treatment should be given.
If the person was originally treated empirically, confirm the diagnosis of threadworm (see Diagnosis).
Basis for recommendation
Basis for recommendation
These recommendations are a common-sense approach, based on the assumption that continued infestation is most likely to be due to reinfestation rather than failure of the anthelmintic.
Threadworm in children and school
Do children with threadworm need to be kept off school?
It is not necessary to exclude children with threadworms from school.
Schools and nurseries should be encouraged to promote hygiene measures.
Basis for recommendation
Basis for recommendation
The recommendation not to exclude children from school is based on advice from the Health Protection Agency [HPA, 2003].
Exclusion is not required because [DynaMed, 2006]:
The risk of transmission in schools is relatively low (less than 10%).
Asymptomatic infestation is often involved in transmission.
Threadworm is generally a mild illness in childhood.
Important aspects of prescribing information relevant to primary healthcare are covered in this section specifically for the drugs recommended in this CKS topic. For further information on contraindications, cautions, drug interactions, and adverse effects, see the electronic Medicines Compendium (eMC) (http://medicines.org.uk/emc), or the British National Formulary (BNF) (www.bnf.org).
Mebendazole
Mebendazole
Mebendazole acts by inhibiting the uptake of glucose by the worms, causing immobilization and death within a few days.
Mebendazole is largely unabsorbed and systemic adverse effects are minimal. Transient abdominal pain or diarrhoea occasionally occurs, especially in people with heavy infestations [ABPI Medicines Compendium, 2005].
There is some debate in the medical literature regarding whether a second dose of mebendazole should routinely be given 14 days after the initial dose. In line with the current Summary of Product Characteristics, CKS recommends that the dose is repeated if reinfestation occurs [ABPI Medicines Compendium, 2005].
Piperazine
Piperazine
Piperazine blocks the neurotransmitter acetylcholine in the worm, leading to paralysis. The addition of senna helps to expel the paralysed worms from the intestine by its laxative effect.
Gastrointestinal disturbances including abdominal pain, nausea, vomiting, colic, and diarrhoea are the most common adverse effects in people taking piperazine.
Piperazine should be avoided in people with epilepsy, renal impairment, or hepatic impairment, since neurotoxic reactions resulting in convulsions have been reported (rarely) in such cases.
Evidence
Evidence
Search strategy
Scope of search
A literature search was conducted for guidelines, systematic reviews and randomized controlled trials on primary care management of threadworm.
Search dates
2007 - October 2011.
Key search terms
Various combinations of searches were carried out. The terms listed below are the core search terms that were used for Medline and these were adapted for other databases. Further details are available on request.
exp Enterobius/, threadworm.tw., thread worm.tw., enterobius.tw., enterobius$.tw., enterobius vermicularis.tw., pin worm.tw., pinworm.tw.
Table 1. Key to search terms.| Search commands | Explanation |
|---|---|
| / | indicates a MeSh subject heading with all subheadings selected |
| .tw | indicates a search for a term in the title or abstract |
| exp | indicates that the MeSH subject heading was exploded to include the narrower, more specific terms beneath it in the MeSH tree |
| $ | indicates that the search term was truncated (e.g. wart$ searches for wart and warts) |
Sources of guidelines
National Institute for Health and Clinical Excellence (NICE)
Scottish Intercollegiate Guidelines Network (SIGN)
National Guidelines Clearinghouse
British Columbia Medical Association
Institute for Clinical Systems Improvement
Guidelines International Network
National Library of Guidelines
National Health and Medical Research Council (Australia)
University of Michigan Medical School
Michigan Quality Improvement Consortium
Royal Australian College of General Practitioners
National Resource for Infection Control
NHS Scotland National Patient Pathways
Agency for Healthcare Research and Quality
UK Ambulance Service Clinical Practice Guidelines
RefHELP NHS Lothian Referral Guidelines
Medline (with guideline filter)
Driver and Vehicle Licensing Agency
NHS Plus (occupational health practice)
Sources of systematic reviews and meta-analyses
Systematic reviews
Protocols
Database of Abstracts of Reviews of Effects
Medline (with systematic review filter)
EMBASE (with systematic review filter)
Sources of health technology assessments and economic appraisals
NIHR Health Technology Assessment programme
NHS Economic Evaluations
Health Technology Assessments
Canadian Agency for Drugs and Technologies in Health
International Network of Agencies for Health Technology Assessment
Sources of randomized controlled trials
Central Register of Controlled Trials
Medline (with randomized controlled trial filter)
EMBASE (with randomized controlled trial filter)
Sources of evidence based reviews and evidence summaries
DynaMed
Central Services Agency COMPASS Therapeutic Notes
Sources of national policy
Health Management Information Consortium (HMIC)
Sources of medicines information
The following sources are used by CKS pharmacists and are not necessarily searched by CKS information specialists for all topics. Some of these resources are not freely available and require subscriptions to access content.
British National Formulary (BNF)
electronic Medicines Compendium (eMC)
European Medicines Agency (EMEA)
References
ABPI Medicines Compendium (2005) Summary of product characteristics for Vermox tablets. ABPI Medicines Compendium..Datapharm Communications Ltd.www.medicines.org.uk [Free Full-text]
BNF 53 (2007) British National Formulary. 53rd edn. London: British Medical Association and Royal Pharmaceutical Society of Great Britain.
BNF for Children (2006) British National Formulary for children. London: British Medical Association and the Royal Pharmaceutical Society of Great Britain.
CDC (1999) Pinworm infection - fact sheet. Centers for Disease Control and Prevention...www.cdc.gov
CDC (2004) Enterobiasis. DPDx - Laboratory Identification of Parasites of Public Health Concern..Centers for Disease Control and Prevention.www.dpd.cdc.gov [Free Full-text]
Cook, G.C. and Zumla, A. (Eds.) (2002) Manson's tropical diseases. 21st edn. London: W.B. Saunders.
Diav-Citrin, O., Shechtman, S., Arnon, J. et al. (2003) Pregnancy outcome after gestational exposure to mebendazole: a prospective controlled cohort study. American Journal of Obstetrics and Gynecology 188(1), 282-285. [Abstract]
DynaMed (2006) Enterobiasis. DynaMed..EBSCO Publishing.www.dynamicmedical.com
Garbis, H., Reuvers, M. and Rost van Tonningen, M. (2001)
HPA (2003) Guidelines on the management of communicable diseases in schools and nurseries: threadworms (enterobiasis, oxyuriasis, pinworms). ..Health Protection Agency.www.hpa.org.uk
HPA North West (2005) Threadworms. ..Health Protection Agency.www.hpa.org.uk [Free Full-text]
Huh, S. and Lee, S. (2006) Pinworm. eMedicine..WebMD.www.emedicine.com [Free Full-text]
Ibarra, J. (2001) Threadworms: a starting point for family hygiene. British Journal of Community Nursing 6(8), 414-420. [Abstract]
McCormick, A., Fleming, D. and Charlton, J. (1995) Morbidity statistics from general practice. Fourth national study 1991-1992. ..Office of Population Censuses and Surveys.www.statistics.gov.uk
Micromedex (2007) MICROMEDEX [CD-ROM].(Vol 131, 1st quarter 2007).Thomson Healthcare.
NPIS (2007) TOXBASE. ..National Poisons Information Service.www.spib.axl.co.uk
Prescribing Nurse Bulletin (1999) Threadworms. Prescribing Nurse Bulletin 1(3), 11-12.
Richardson, M., Elliman, D., Maguire, H. et al. (2001) Evidence base of incubation periods, periods of infectiousness and exclusion policies for the control of communicable diseases in schools and preschools. Pediatric Infectious Diseases Journal 20(4), 380-391. [Abstract]
Thornton & Ross Limited (2004) Summary of product characteristics for Pripsen (piperazine citrate powder). Huddersfield: Thornton & Ross Limited.