Roundworms infest the small intestine and cause ascariasis.

Travel health

A simple guide to health precautions when travelling abroad, including vaccinations, taking condoms and a first aid kit, and being careful about drinking water.

Media last reviewed: 02/10/2013

Next review due: 02/10/2015

Roundworms are worms that can infest the human digestive tract, specifically the small intestine.

A roundworm infection is also sometimes known as ascariasis or acaris.

Roundworms are parasites. This means that they use the human body to stay alive, feed and reproduce.

In most people, a roundworm infection does not cause any noticeable symptoms. People most commonly see their GP because they have seen a worm in their faeces (stools).

Roundworms are the only worms found in human faeces that are roughly the size of an earth worm.

Less commonly symptoms can include a high temperature and dry cough 4-16 days after swallowing the eggs. If a large number of eggs have been ingested, or if the worms move from the small intestine to other parts of the body, they can cause serious complications such as a bowel obstruction.

In England these types of complications are rare.

See symptoms of roundworm for more information.

How infection occurs

A roundworm infection can occur if someone swallows the microscopic ascaris eggs in contaminated food or water.

It is also possible for someone to transfer eggs from their hands to their mouth if they touch contaminated soil. 

After the eggs mature into adult worms, the worms produce more eggs. The eggs are released from the body through the bowel and can then infect other humans.

The more roundworms inside your body, the worse your symptoms are likely to be.

See causes of roundworm infection for more information.

Who is affected?

Roundworm infections are one of the most common health conditions in the world - around a quarter of the world’s population currently has a roundworm infection.

Roundworm infections are most widespread in tropical and sub-tropical areas, particularly in parts of the world that are overcrowded and have poor sanitation.

Most cases recorded in England were contracted abroad, either by travellers or migrants coming here from parts of the world where roundworm is present. 

In England, Wales and Northern Ireland, an average of 80 cases of roundworm infection are reported every year.

If you notice a roundworm in your faeces or have unexplained asthma-like symptoms shortly after you have visited a tropical or sub-tropical country, see your GP.

Roundworm can be diagnosed by examining a stool sample under a microscope, to see if there are any eggs in the sample.

Learn more in diagnosis of roundworm infection.


Roundworm infections can usually be successfully treated with medication. Learn more in treatment of roundworm infection.


Regular hand washing can help prevent the spread of roundworm infection.

If you are travelling to a part of the world where roundworm is common, you should take additional precautions, such as drinking only bottled water and avoiding raw fruits and vegetables. These are the same precautions that help prevent many other infections  associated with poor sanitation.

Learn more in preventing roundworm infections.

Page last reviewed: 13/08/2012

Next review due: 13/08/2014


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The 1 comments posted are personal views. Any information they give has not been checked and may not be accurate.

User439841 said on 12 March 2010

I may have got dog faeces in my eye or mouth recently, have I got anything to worry about? The faeces were from a dog which I don't know.

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