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Roundworm - Symptoms of a roundworm infection

NHS Choices Medical Reference

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In most people, a roundworm infection does not cause any noticeable symptoms.

When symptoms occur, they usually follow a two-stage course:

  • Early-phase symptoms are caused by the larvae (newly hatched worms) moving from the small intestine to the lungs. It is unclear why some people develop these symptoms while others do not. 
  • Late-phase symptoms are caused by adult worms living in the intestine. They cannot reproduce inside you. There will only be as many as the eggs you first ingested (see causes of roundworm infection  for more information about the life cycle of the roundworm).

Early-phase symptoms

The early-phase symptoms of a roundworm infection affect only a small proportion of those affected and are rare in the UK. They usually begin four to 16 days after swallowing the eggs and last up to 3 weeks. They include:

  • high temperature (fever) of 38C (100.4F) or above
  • a dry cough
  • shortness of breath
  • wheezing

Late-phase symptoms

The late-phase symptoms are even more rare in the UK, especially in adults.  If there are a lot of mature worms in the intestine they can cause blockages.  This will not occur before six weeks after the eggs have been swallowed.

Signs and symptoms associated with mature worms include:

  • passing a worm in your faeces
  • mild abdominal (tummy) pain
  • nausea
  • vomiting
  • diarrhoea (you may also notice blood in your stools)

(Most people have no symptoms).

Signs and symptoms associated with an intestinal blockage due to a large number of worms include:

  • severe abdominal pain
  • vomiting
Medical Review: August 11, 2012
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