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VOLUME 18
NUMBER 4
Management of threadworms in primary
care
SUMMARY
Threadworm infestation is most common in pre-school children but the risk of transmission to
family members is high. Treatment should be offered to the individual if threadworms have
been seen or their eggs have been detected, but all members of the household should be
treated simultaneously, even if they have no symptoms. Hygiene measures are essential,
whether anthelmintic treatment is used or not. Mebendazole is generally the preferred agent,
but piperazine (combined with senna) is also an option. There is very little evidence for
anthelmintic treatments but it is generally accepted that cure rates with either agent are
90–100%. Adoption of strict hygiene measures for at least six weeks is the only alternative for
those who can not have or do not want anthelmintic treatment (e.g. pregnant women).
What are threadworms?
Threadworms, also known as pinworms, are
parasites (Enterobius vermicularis) that infest
human intestines. Threadworm eggs, which
are invisible to the naked eye, are ingested.
These hatch in the small intestine, reach
maturity in two to six weeks, then travel to the
large intestine where they have a lifespan of
around six weeks. After mating, the pregnant
female migrates to the perianal area, usually at
night time, to deposit her eggs. The mucous
used to stick the eggs to the skin irritates the
area, leading to intense itching and scratching.
This can lead to the eggs being transferred by
the hand to the mouth, and the cycle begins
again.1,2
Threadworm infestation is the most common
parasitic worm infestation in humans in the UK,
responsible for around 40 GP consultations in
a 10,000-patient practice each year. In
addition, many individuals seek treatment in
community pharmacy, rather than via their GP,
so the actual prevalence in the community is
unknown. Threadworm infestation is more
common in pre-school children than adults due
to poorer hygiene practices and closer contact,
but often affects family groups or those in
crowded institutions.1
How is threadworm transmitted?
Threadworm eggs can survive for up to two
weeks on clothing, bedding, or other objects.
Individuals can therefore become infected after
accidentally ingesting threadworm eggs from
any contaminated surfaces, such as inhaling
and swallowing the eggs when making the bed,
or from eating food that has been contaminated,
etc.1,2
Treatment should
be offered if
threadworms have
been seen or their
eggs have been
detected
As the adult worm lifespan is around six weeks,
ongoing infestation requires ingestion of fresh
eggs.1
How should threadworm infestation be
diagnosed?
The most typical symptom is perianal pruritus,
especially at night, which may result in
excoriation and secondary bacterial skin
infection. However, there are several other
possible causes of pruritus in this area (e.g.
haemorrhoids in adults). Other symptoms of
threadworm infestation may include loss of
appetite, weight loss, irritability, insomnia,
enuresis and abdominal pain if the infestation
is persistent or heavy.1,2
Many of those affected are asymptomatic and
infestation only comes to light after seeing the
threadworm on the perianal skin or in the
stools. Threadworms are small (up to 13mm
long for the female and up to 5mm long for the
male) and are often described as small threads
of slow-moving white cotton. Other types of
worm infestation are uncommon in the UK and
are unlikely to be confused with threadworm
(e.g. roundworms are 300mm long).1
If the diagnosis is uncertain, the adhesive tape
test for eggs may on rare occasions, be useful.
This involves the application of trans-parent
adhesive tape to the perianal skin first thing in
the morning, before wiping or bathing. The
tape is then carefully removed and stuck on to
a glass slide or placed in a specimen
container. Diagnosis is confirmed by the
presence of threadworm eggs upon
microscopic examination at the GP surgery or
local laboratory service.1
This publication was
correct at the time of
preparation:
March 2008
This MeReC Publication is produced by the NHS for the NHS
MeReC Bulletin Volume 18, Number 4
11
Management of threadworms in primary care
How should threadworm be managed?
Recommendations on the management of
threadworm are generally based on expert
opinion.
All members of the
household should
be treated at the
same time and
follow the hygiene
measures,
irrespective of
whether they have
symptoms or not
Following confirmation of the diagnosis, Clinical
Knowledge Summaries (CKS) guidance
recommends treatment with an anthelmintic
unless contraindicated. Strict hygiene measures
should also be followed as outlined in Panel 1.1,3
All members of the household should be treated
at the same time and follow the hygiene
measures, irrespective of whether they have
symptoms or not, as the risk of transmission in
families is high and this will help to prevent
reinfestation.1,4
How should anthelmintics be used?
There is no good quality clinical trial evidence
supporting the efficacy of anthelmintics in the
treatment of threadworm, and there are no
published trials of mebendazole against
piperazine. It is generally accepted that both
agents have comparable efficacy, with cure
rates of 90–100%. Recommendations are
based on expert opinion and what is known
about the safety profile of the agents.1
Mebendazole is the preferred anthelmintic
agent in adults and children over six months of
age,1,5 although it is not licensed for children
aged less than two years.6,7 Mebendazole is
licensed for use as a single dose, repeated
after 14 days if the infestation persists,6,7 and
there are mixed views on whether a second
dose should be given routinely.1 Piperazine
(combined with senna) can be used in adults
and children over three months, and should be
given as a single dose, repeated after 14 days.
However, it should be avoided in those with
epilepsy, or liver or renal problems due to the
risk of neurotoxic reactions.1
Neither anthelmintic is licensed for use in
pregnancy or breastfeeding, and the manufacturers advise avoidance.1,6–8 Strict hygiene
measures and physical removal of the eggs
for six weeks, in an attempt to break the
cycle of infestation, are preferred in these
circumstances. 1 CKS acknowledges that
some women who are pregnant or
breastfeeding may be anxious to eradicate
the worms as soon as possible (e.g. if it is
proving difficult to prevent reinfestation by
hygiene methods alone). In this situation,
drug treatment may be preferred, but CKS
advises that neither anthelmintic should be
used in the first trimester of pregnancy. If an
anthelmintic is to be used during the second
or third trimester of pregnancy, or while
breastfeeding, mebendazole is preferred on
the basis of the limited available data in
women exposed to the agent during
pregnancy.1 CKS recommends contacting
the National Teratology Information Service
for more details.1
What if treatment fails?
Reasons for treatment failure include nonadherence to the hygiene measures and reinfestation. It could also be that symptoms
persist because of misdiagnosis. Another
course of treatment can be offered for all
members of the household, and the importance
of adhering to strict hygiene measures should
be emphasised. If the patient was originally
treated empirically, the diagnosis should be
confirmed. If recurrences are frequent, the
advice of a paediatrician/consultant in infectious
diseases may be necessary.1
Panel 1: Patient counselling points for threadworm management1,3
Drug treatment is recommended only if threadworms have been seen or eggs have been detected.
If drug treatment is recommended, all members of the household should be treated at the same time and follow the strict hygiene
measures, even if they do not have symptoms.
Use drug treatment as follows:
1. If mebendazole is used it should be given as a single dose, repeated after 14 days if infestation persists.
2. If piperazine is used it should be given as a single dose, repeated after 14 days.
On the
•
•
•
first day of treatment undertake environmental hygiene measures:
Wash sleepwear, bed linen, towels and cuddly toys.
Vacuum and dust the whole house, and especially the bedroom including mattresses.
Thoroughly clean the bathroom by damp-dusting surfaces.
Strict personal hygiene measures should be followed for the two weeks of drug treatment, and for six weeks in those not using drug
treatment:
• Wash hands and scrub nails before each meal and after visiting the toilet.
• Keep nails short.
• Avoid nail biting and finger sucking.
• Take a bath or shower every morning to remove any eggs laid in the night.
• Wash/wet wipe the perianal area every three hours (although this may be impractical and twice daily may be more realistic).
• Avoid sharing towels and flannels.
• Wash nightwear every day.
• Wear pyjamas with underwear to discourage night-time scratching.
• Cotton gloves may also help.
• Change bed linen as often as possible, taking care not to shake as this may spread viable eggs.
• The whole family should be encouraged to follow these measures.
12
MeReC Bulletin Volume 18, Number 4
Management of threadworms in primary care
References
1. CKS. Threadworm (Topic Review). Clinical Knowledge Summaries
Service. June 2007. Accessed from www.cks.library.nhs.uk
/threadworm on 19/02/08
2. Centers for Disease Control and Prevention. Enterobiasis. DPDx
— Laboratory Identification of Parasites of Public Health
Concern. May 2004. Accessed from www.dpd.cdc.gov/dpdx
/HTML/Enterobiasis.htm on 19/02/08
3. National Prescribing Centre. The management of scabies and
threadworm. Prescribing Nurse Bulletin 1999;1:9–12. Accessed
from www.npc.co.uk/nurse_prescribing/bulletins/scabies3.1.htm
on 19/02/08
4. Health Protection Agency North West. Threadworms. September
2005. Accessed from www.hpa.org.uk/cumbriaandlancashire
/factsheets/THREADWORM.pdf on 19/02/08
5.
6.
7.
8.
British Medical Association/Royal Pharmaceutical Society of
Great Britain/Royal College of Paediatrics and Child
Health/Neonatal and Paediatric Pharmacists Group. British
National Formulary for Children 2007
Summary of Product Characteristics. Ovex suspension.
Accessed from http://emc.medicines.org.uk/ on 19/02/08
Summary of Product Characteristics. Vermox suspension.
Accessed from http://emc.medicines.org.uk/ on 22/02/08
British Medical Association/Royal Pharmaceutical Society of
Great Britain. British National Formulary No. 54. September
2007.
The National Institute for Health and Clinical Excellence (NICE) is associated with MeReC Publications published by the NPC through a funding contract. This
arrangement provides NICE with the ability to secure value for money in the use of NHS funds invested in its work and enables it to influence topic selection,
methodology and dissemination practice. NICE considers the work of this organisation to be of value to the NHS in England and Wales and recommends that it
be used to inform decisions on service organisation and delivery. This publication represents the views of the authors and not necessarily those of the Institute.
© The National Prescribing Centre, The Infirmary, 70 Pembroke Place, Liverpool, L69 3GF
Telephone: 0151 794 8146 Fax: 0151 794 8139 www.npc.co.uk www.npc.nhs.uk
MeReC Bulletin Volume 18, Number 2
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