Worms Dr Trisha Macnair There are a number of different types of worm infection in the UK, each with different sources and symptoms.

In this article

Threadworms Tapeworms

Toxocara Other worms

Worms use in research

The only common worm in the UK is the threadworm, also known as the pinworm, which mainly affects children. Infection is rarely so serious that it causes major health problems, but it can be very itchy.

For more information about threadworm infections, read Worms in children.

The tapeworm, or cestode, is a long ribbon-like worm that can be caught from undercooked meat and fish. Modern animal husbandry and food standards mean tapeworms are much less common than they used to be.

Usually, the infected person carries just one worm, although as many as ten worms have been reported in one person. One worm may be several metres long and often the only symptom is passing tiny worm segments from the back passage.

Tapeworms can be caught from pets and occasionally when children accidentally swallow a dog flea infected with the worm.

Another important, but rare, worm that can be picked up from pets is the toxocara. This is an infection caused by the larval stage of dog or cat roundworms. About 100 people every year, usually children, are diagnosed with the eye form of the disease, which often leads to irreversible damage and scarring.

Everyone should be scrupulous about dealing with dog and cat faeces

The majority of the population has been exposed to the toxocara infection, as many homes have dogs and cats, but only about three per cent of the population have antibodies to toxocara. Everyone should be scrupulous about dealing with dog and cat faeces.

Pregnant women and children should steer clear of litter trays and always wash their hands after contact with pets.

In tropical climates and poorer nations, illnesses caused by worms are a major health problem, affecting millions of people. Schistosomiasis (flukes), hydatid disease (a type of tapeworm), ancylostomiasis (hookworm)... the list is long and the damage enormous.

One type of worm infection alone - lymphatic filariasis (elephantiasis) - affects 120 million people in the tropics and sub-tropics. It's a major cause of long-term disability and is transmitted by mosquitoes.

Huge efforts are being made to reduce the problem. There are encouraging results in the development of vaccines against schistosomiasis, while attempts made by organisations such as Unicef and the World Health Organisation to eradicate dracunculiasis, caused by the Guinea worm, are paying off.

Worms could hold the key as to why some people develop asthma and allergic diseases

Worms aren't all bad news. They play an important part in some medical research. For example, worms could hold the key as to why some people develop asthma and allergic diseases. Some doctors believe these conditions are related to abnormal responses of the immune defence systems, which evolved in our ancestors to cope with the heavy worm and parasite infections that were then a general problem.

This article was last medically reviewed by Dr Rob Hicks in July 2006.