Threadworm

Also called pinworms

Having threadworms is common in childhood, but anyone of any age can be affected. Threadworms are not harmful, you may not notice you have them, but they can be itchy and annoying.

On this page, you will find the following information:

What are threadworms?

Threadworms are small, thin, white worms between 2mm and 13mm long. They look like cotton threads and live in your bowel (gut). Strict hygiene measures (washing and cleaning) can help clear up a threadworm infection and reduce the likelihood of reinfection. To treat threadworms successfully, all household members must be treated, even if they don't have any symptoms.

How do you get threadworms?

Threadworms are spread from human to human. They are not carried by animals so you can't get them from your pets. Threadworms are spread easily within families/whānau, early childhood centres, schools and camps. If one person in your family/whānau has threadworms, others probably do too.

  • Most people get threadworms by swallowing the worm's eggs.
  • Threadworms leave your gut at night and lay eggs on the skin around your anus (bottom). The eggs can get onto your hands or under your fingernails through scratching the itchy area or because of poor handwashing after using the toilet/whare paku.
  • You can pass the eggs on to an uninfected person, eg, through food/kai handling.
  • Threadworm eggs can also get onto carpets, bed linen, towels, flannels and into household dust and, in this way, they are passed from person to person.
  • It may be between 2 and 6 weeks after contact with a source of infection before the life-cycle is complete and eggs are laid in the newly infected person.

Can humans get threadworms from pets?

Threadworms are spread from human to human. They are host-specific, which means that animals do not infect humans, so you cannot get threadworms from your pets.

What are the signs of threadworms?

The most common sign of threadworms is itching around your anus (bottom), which is worse at night. This is because the worms are most active at night. In some instances, the worms can be seen in your stool (poo) or on toilet paper. Other signs include bedwetting, restless sleep, loss of appetite and irritability. Many people with a threadworm infection have no symptoms.

How is a threadworm infection diagnosed?

The most obvious way an infection is diagnosed is if the threadworms can be seen in your stool (poo) or on toilet paper. But, if this is not the case, your doctor may ask you to do a sticky tape test.

To do this you press some see-through tape on to the skin around your anus (bottom) first thing in the morning, before wiping or bathing. You then place the tape on a glass slide or put it in a specimen container. The tape is then sent to the laboratory to be looked at under a microscope to see if any threadworm eggs are stuck to it.

How is a threadworm infection treated?

In most cases, a threadworm infection can be treated with strict hygiene measures (washing and cleaning). The hygiene measures also reduce prevent threadworms from spreading and reduce the likelihood of reinfection. Medicine to treat a threadworm infection can be bought over the counter from your local pharmacy or prescribed by your healthcare provider (doctor/GP or nurse).

Hygiene measures

Follow good hygiene practice to prevent threadworms or stop spreading them to others:

  • wash your hands carefully and often
  • avoid scratching around your bottom
  • keep your fingernails short
  • wash your clothes and bedding regularly
  • bathe and change your underwear every day
  • avoid sharing a bathtub or face cloths
  • vacuum your carpets often.

Medicine

You can buy worm medicine such as mebendazole from your pharmacy. This medicine will kill the worms in your gut but will not kill the eggs that have been laid around your bottom. Eggs can survive for up to 2 weeks outside your body on underwear or bedding, and in dust, so proper hygiene measures are important.

  • All household members, including adults and those without symptoms, should be treated with worm medicine at the same time.
  • It is recommended you take 2 doses of mebendazole – one dose initially and another dose 2 weeks later.
  • After you take each dose, wash your underwear and bed linen, and vacuum your carpets.
  • Read more about mebendazole.

Do I need to take worm medicine regularly to prevent threadworms?

You don't need to take worm medicine to prevent threadworm. Worm medicine should only be used if someone in your home has threadworm. All household members should be treated at the same time. Follow the good hygiene steps above to help prevent threadworm infection.

When to see your GP

In most cases, you won’t need to see your GP. However, if you are pregnant or breastfeeding and have threadworms, or if your child is under 2 years old and has threadworms, you should see your GP. This is because the recommended treatment in these circumstances is usually different from that recommended for most other people.

Learn more

Threadworms Regional Public Health, Greater Wellington Region, NZ

Reference

  1. Pinworms DermNet, NZ

Reviewed by

Dr Alice Miller trained as a GP in the UK and has been working in New Zealand since 2013. She has undertaken extra study in diabetes, sexual and reproductive healthcare, and skin cancer medicine. Alice has a special interest in preventative health and self-care, which she is building on by studying for the Diploma of Public Health with the University of Otago in Wellington.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Alice Miller, FRNZCGP Last reviewed: 23 Nov 2021