Infection of the intestine in human beings is a mild problem in Britain and other Westernized countries, but can be chronically debilitating in the tropics.

Roundworms (nematodes) and threadworms (pinworms)

These white worms can grow up to a centimetre long and are found specifically in children all over the world. They live in the colon and rectum and travel down to the anal margin to lay their eggs, usually at night. The result is an itchy anus, which is the principal symptom. Irritability and insomnia are other factors.

The eggs may be visible.



These are very common parasites, with the worms growing up to half a centimetre in length and tending to attach themselves to the first part of the large bowel. Symptoms are extremely uncommon unless a child is malnourished, when bloody diarrhoea or rectal prolapse may actually occur.


This is not to be confused with toxoplasmosis, which is a parasitic infection also contracted from cats and specifically dangerous in pregnancy.

This condition is an accidental infection from cat or dog faeces. The worms do not develop in humans but if the larvae are ingested they travel via the bloodstream into major organs, where they die causing obstruction of blood vessels.

Tapeworms (cestodes)

Tapeworms normally share two hosts: the worm living in the intestine of one organism and the larvae normally in the muscles of another. In human beings the most common tapeworms are Taenia saginata and Taenia solium. The former exists in beef and the latter in pork.

These worms may grow into a parasite up to 5 metres (26 feet) long over a three-month period. Symptoms are often absent but weight loss, disturbed appetite and vague abdominal pains may accompany the passage of segments of the worm noted in the stool.

Other worms

Any symptoms suggestive of worm infestation should be discussed with a physician who should check the anus and take samples via the stickytape method and stool samples.

Treatment with orthodox antihelminthic drugs is safe and recommended. Remember that the whole family group and possibly the school class should be treated as well.