Help and Information > Worm Information > Pinworms and Threadworms

Pinworms and Threadworms

About threadworms, pinworms, and seatworms.

There are a number of types of worm (helminth) infestations that humans are susceptible to. Of these, the most common by far is the Enterobius vermicularis, also known as the threadworm, pinworm or seatworm. Do not confuse it with the Strongyloides stercoralis worm that is sometimes also referred to as "threadworm" but is a very different type of worm. Threadworms derive their name from their appearance, with the adult worms resembling fine pieces of white cotton.

The adult female threadworm is larger than its male counterpart and can grow up to 1.5cm in length. The threadworm is a nematode, which are distinguishable from other helminth by their unsegmented cylindrical bodies that taper at both ends. It has been estimated that hundreds of millions of people have experienced a threadworm infection at one time or another. Threadworms are the most commonly encountered human host specific nematode. They are parasitic because they obtain their food from the infected person.

Diagnosis and symptoms

There may not be many external symptoms to indicate that you have a threadworm infestation so it may go undetected. Common signs include an intense itchy feeling around the anus, usually at night or early in the morning. Such itching could, however, also be caused by haemorrhoids, a reaction to underclothes, perianal eczema, and pruritus ani. Other symptoms of a threadworm infestation include restless sleep, irritability, grinding your teeth in your sleep, or a loss of appetite.

In rare cases slight stomach pains associated with gastrointestinal upsets may be experienced. Threadworms do not cause illness but they can cause urinary tract infections. You may notice a child who previously did not have a problem starts wetting the bed. Remember that many people with threadworms do not have any symptoms at all.

More definitive proof of a threadworm infection requires some investigation. One method is to look to see if any worms are visible on the surface of faeces after a bowel motion. Any worms will resemble small, moving pieces of fine white cotton thread. This type of investigation may not be that successful and even a proper stool examination only has about a 20% detection rate.

Another method entails trying to observe the worms while they are moving around at night. If you suspect that your child has worms then you can use a torch and check for them. This is probably best done in the morning as soon as the child wakes up. The worms themselves will be visible to the naked eye. They will "glow" under the torchlight.

Another possible method of diagnosis is to look for the threadworm's eggs deposited around the anus on the perianal skin. They are best detected at night and look like small white specks. Alternatively, you could try to spot the eggs of the threadworm using the "adhesive tape test". This should take place in the morning before bathing or going to the toilet. Apply a piece of double-sided cellophane tape to a wooden stick.

If you use a piece of single-sided tape then ensure that the sticky side of the tape faces out. Your local chemist should be able to provide you with some hypo-allergenic tape if you require it. Press the tape against the anus and remove it. Any threadworm eggs will appear as tiny white marks on the tape. If you are unsure about this sort of test you could make an early morning appointment with your doctor and they can organise a laboratory-based test for you or they may be able to diagnose the infection based on the symptoms alone.

Related to these symptoms, scratching the perianal skin to relieve the itching can lead to a secondary bacterial infection of the region which worsens the condition if the skin becomes inflamed or broken. In rare cases girls and women may develop vulvovaginitis as the result of a threadworm infestation that is left untreated. This is where the "abnormal migration" of a threadworm takes it into the vagina causing inflammation of the vagina region, irritation, and vaginal discharge. This is actually a sign of the body's defences attacking the intruder. Other than the discomfort that this causes it is not much of a health risk as the threadworm will only be able to survive in this region for a limited time.

Threadworm, pinworms, and seatworm Infestion

Although commonly associated with young children because of their close social interaction and inattention to personal hygiene, threadworms are very contagious and adults are just as susceptible to a rapid transfer of the infection. Threadworm infestations can quickly be spread through family groups or any collection of people, including day-care centres, schools and camps. This is why it is a good idea to treat all the members of the family if one member becomes infected with threadworms.

Contrary to popular belief, the threadworm only infects humans. Animals are only vulnerable to a distantly related species of this worm, one that does not infect humans. Household pets like cats and dogs are not part of the threadworm life cycle but they can be carriers if the eggs of the threadworm are transferred into their fur and hair.

There are two main ways that you can catch threadworm. The first is by direct contact with an infected person. The second is by coming into contact with an object or surface that has become contaminated through contact with an infected person. This could be anywhere, from a toilet seat, bedding, toys, kitchen bench, clothing, door handles, food or furniture. The eggs can even survive in swimming pools.

Contracting threadworm is not something that is connected with a lack of personal hygiene but is an everyday hazard of communal living. Once the eggs lose their stickiness, catching threadworm can be as easy as breathing in the airborne eggs contained in household dust. The eggs can survive in external environments for about two to three weeks. Poor hygiene, however, can contribute to the spread of threadworm once you have contracted it. Threadworm eggs become infective within hour of being laid. The small eggs are quite difficult to see with the naked eye and stick to anything that they come into contact with. Invariably, the infected person's hands become contaminated with the eggs and they become widely dispersed.

Humans become infected when they ingest the eggs and begin the life cycle of the threadworm. After they have swallowed the eggs they hatch inside the small intestine. The shells of the eggs are dissolved by stomach juices. The juvenile threadworm larvae then move to the large intestine to grow and mate. It takes about a month, the incubation period taking anywhere between 2 to 6 weeks, for the swallowed egg to turn into a sexually mature adult worm. An adult worm lives for approximately two months, although the male threadworm dies after copulation.

When the female is ready to lay eggs she emerges out of the human host's anus while they are asleep and inactive. The female then lays up to 10,000 eggs, depositing them on the perianal skin, before dying. At body temperature the eggs develop quickly and they become infective after about 6 hours. Typically this is associated with itching and discomfort around the anus, which is caused by the mucus, or "glue", that the female threadworm secretes in order to attach the eggs to the skin. These eggs are triangular in cross section and flat along one side. When the host scratches this area they transfer the eggs to their hands or under their fingernails, contaminating them and beginning the cycle once again. If the eggs remain on the perianal skin long enough to hatch then the juveniles will crawl back into the anus to the intestines to mature into adults. This process is known as retroinfection.

Treating threadworm, pinworms, and seatworm infestion

To treat threadworm you should use a treatment like Vermox or Combantrin-1, which contain mebendazole, or Combantrin, which contains pyrantel embonate as the active ingredient. Mebendazole is an anthelmintic that works by interfering with the proteins in either the worm's intestine or absorptive cells. This inhibits the threadworms' ability to absorb glucose (sugars) which depletes them of the energy that they need to survive. As a result the threadworm dies within several days.

Pyrantel embonate, a "neuro-muscular blocking agent", causes paralysis of the threadworm's nervous system. The paralysed worms are then expelled in the faeces by the normal actions of the bowel.

These treatments are not intended to be used by pregnant women or children under two years-of-age. If you want to use the worm treatments in these situations then you should consult your doctor or pharmacist first.

These worming treatments only work on the adult worms that are present in the intestine at the time the medicine is taken. The whole family or all the people living in the same household should be treated at the same time. You should give your home a thorough clean after treatment in order to kill any remaining eggs and to help prevent reinfestation. It is also a good idea to treat everyone again about two weeks after the initial treatment if you suspect that reinfection has occurred.

Here are some general hygiene measures that you can take in order to help you get rid of worms.

  • A morning shower or bath will remove any eggs laid during the night.
  • Make sure that everyone in the household using their own towel and facecloth.
  • During treatment change the nightclothes and underwear of the person with the infection daily.
  • Vacuum carpets as often as possible, especially bedrooms, to remove as much dust as possible.
  • Bed-sheets should be changed frequently, especially in the first 7 to 10 days after starting the treatment.
  • Use hot laundry wash cycles for a while in order to kill the remaining eggs.
  • Keep the nails of the infected people short to reduce the chances of eggs being stored there.
  • This will also discourage nail biting amongst children.
  • Wash your hands thoroughly after using the bathroom and before each meal.
  • Keep the toilet and the bathroom area clean. Eggs can be lifted off toilet seats and door handles with paper dampened with water.
  • If possible, you could make the children wear cotton gloves at night.
  • It is a good idea to avoid eating food in your bedroom.
  • Avoid food and drinks containing a lot of sugar because treatments containing mebendazole are trying to stave the worms of glucose.
  • If you are using a treatment containing Pyrantel embonate then eating high-fibre food will help to prevent constipation and will assist expelling the worms.