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View this article online at: patient.info/health/roundworms-leaflet
Roundworms
Roundworms (also called nematodes) are common in warm tropical countries. Children are more
often affected than adults. Treatment is usually very effective but wiping out (eradication of)
roundworm infections has proved to be very difficult.
What are roundworms?
Roundworms are worms with a long round body. They vary in
length from several millimetres to up to two metres. About 60
types (species) of roundworm can live in (are parasites of)
humans. They usually live in the human gut. However, some
species can travel from the gut to live in different parts of the
body.
Roundworm eggs and tiny young worms (larvae) live in the soil.
They most commonly get into the body when a person gets
them on his or her hands and then transfers them to the
mouth. Some can also get into the body through the skin.
Roundworms commonly parasitic on humans include:
Ascaris lumbricoides (also called human
roundworm), which is the most common
roundworm infection, and affects as many as one
billion people worldwide.
Hookworm infections.
Guinea worm disease (dracunculiasis).
Filariasis, which is caused by thread-like filarial nematodes (roundworms) in the family Filarioidea
(also known as filariae). There are eight known filarial nematodes which use humans as the host.
These are divided into three groups:
Lymphatic filariasis - caused by the worms Wuchereria bancrofti, Brugia malayi, and
Brugia timori.
Cutaneous filariasis - caused by Loa loa (the African eye worm), Mansonella streptocerca
and Onchocerca volvulus.
Body cavity filariasis - caused by the worms Mansonella perstans and Mansonella ozzardi.
Threadworm (pinworm) - see separate leaflet called Threadworms for more detail.
Trichuriasis (whipworm).
Trichinellosis.
Angiostrongyliasis.
Strongyloidiasis.
Toxocariasis.
Gnathostomiasis.
Anisakiasis.
Cutaneous larva migrans is a skin infection that causes a rash. It can be caused by the larvae of various
nematodes that get into the skin.
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The number of roundworm infections throughout the world is generally increasing but varies according to levels of
poverty, natural disasters and human conflicts. The spread of infection is also increasing in line with increased
travel and mobility. In areas where roundworms are common, children can be continuously infected. As some
worms die and are passed out in the stools (faeces), others may be growing to take their place.
The life of a roundworm
The life cycle of roundworms varies between types (species).
If you have worms in your gut, the female worm lays many tiny eggs. You pass these out with the stools (faeces).
Soil and water supplies may become contaminated with eggs in areas of poor sanitation. Many roundworms have
a complicated life cycle that includes both main hosts (large mammals such as humans or pigs) and
intermediate hosts (small animals such as snails). Therefore, some roundworm infections occur as a result of
eating uncooked contaminated food.
The eggs may survive for years in moist soil. In the soil the eggs develop into tiny young worms (larvae). Larvae
can get into the human gut if you eat them with contaminated food. They pass into the bloodstream and are
carried to other parts of the body - such as the lungs.
Larvae develop further and then often travel back to the gut, where the larvae then grow into adult worms. An adult
worm can lay many eggs, which are passed out with the stools.
What are the symptoms of roundworms?
The symptoms depend on the types (species) of roundworm causing the infection.
Many affected people have no symptoms.
Heavy roundworm infection in children can cause nutritional problems resulting in poor growth and
poor general well-being.
Some affected people may develop one or more of the following:
High temperature (fever).
Tiredness.
Allergic rash (urticaria).
Abdominal (tummy) pains.
Feeling sick (nausea), being sick (vomiting) and/or diarrhoea.
Nerve problems.
The larvae in the lungs can sometimes cause symptoms such as wheeze, cough, and other chest
problems.
Other symptoms are specific to the different species of roundworm. For example, onchocerciasis can
cause eye lesions, which may cause blindness.
Occasionally, roundworms cause a severe illness. For example, large numbers of worms can cause
a blockage in the gut. In some people, roundworms cause serious infections to the liver or pancreas,
or serious allergy symptoms.
What is the treatment for roundworms?
Control of roundworm infections is based on treatment with medication, improved sanitation and health
education. Treatments usually work well but wiping out (eradication of) roundworm infections from tropical
countries presents a major challenge. However, some eradication programmes (notably for guinea worm
disease) have been effective in reducing the burden of infection.
Mebendazole is the usual medicine used for children aged over 1 year, and for adults who are not
pregnant or breast-feeding. It comes as a tablet or drink. You take a dose twice a day for three days.
(Note: mebendazole is recommended in UK guidelines for treatment from the age of 1 year. However,
strictly speaking, it is not licensed for use in children younger than 2 years of age).
Other medicines such as albendazole, levamisole, and ivermectin are used in countries where
roundworms are common. They are not often used in the UK unless under the advice of a specialist.
Diethylcarbamazine or ivermectin is used for people with infection with filariasis.
For pregnant or breast-feeding women and newborn babies - your doctor will advise.
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Can roundworms be prevented?
Hygiene
In countries where roundworms are common, roundworms may be prevented by eating only cooked food and by
avoiding green vegetables and salads. It is best if children do not play in areas of poor sanitation, or where human
stool (faeces) is used as fertiliser. Always wash hands before eating or preparing food, and after going to the toilet
or changing nappies.
Medication
If there is a high risk of infection, taking preventative medicine may be advised. For example, if you stay in an area
known to be contaminated, or if you travel abroad to at-risk areas.
Further reading & references
Roundworm; NICE CKS, December 2011 (UK access only)
Bethony J, Brooker S, Albonico M, et al; Soil-transmitted helminth infections: ascariasis, trichuriasis, and hookworm.
Lancet. 2006 May 6;367(9521):1521-32.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical
conditions. EMIS has used all reasonable care in compiling the information but makes no warranty as to its
accuracy. Consult a doctor or other healthcare professional for diagnosis and treatment of medical conditions.
For details see our conditions.
Original Author:
Dr Tim Kenny
Current Version:
Dr Roger Henderson
Peer Reviewer:
Dr Adrian Bonsall
Document ID:
4385 (v40)
Last Checked:
11/11/2014
Next Review:
10/11/2017
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