What Are Pinworms (threadworms)? What Causes Pinworm Infection?

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Main Category: GastroIntestinal / Gastroenterology
Also Included In: Pediatrics / Children's Health;  Public Health
Article Date: 05 Jan 2010 - 6:00 PDT

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The pinworm, also known as threadworm, seatworm, and formally known as Enterobius vermicularis, is a very common intestinal parasite. Enterobiasis, or oaxyuriasis refers to the medical condition associated with pinworm infestation.

Pinworm is the most common type of roundworm found in the USA. They are parasites that use the human body to survive and reproduce. The pinworm's microscopic eggs hatch and grow into adults in the human body - adults measure from 0.2 to 0.4 inches (5 to 10 millimeters). The worms mature in the intestine and then move through the digestive system to lay eggs in the anal area. Adult worms, which are white and look like small pieces of thread, live for up to six weeks.

Pinworms do not always cause symptoms. Some patients may experience itchiness around their anus and females may experience itchiness in the vaginal area. The itchiness tends to be worse or more noticeable at night, and can sometimes wake up the patient.

According to Medilexicon's medical dictionary:

A Pinworm is "A member of the genus Enterobius or related genera of nematodes in the family Oxyuridae, abundant in a large variety of vertebrates, including such species as Oxyuris equi (the horse pinworm), Enterobius vermicularis (the human pinworm), Syphacia and Aspiculuris species (the mouse pinworm), Passalurus ambiguus (the rabbit pinworm), and Syphacia muris (the rat pinworm)."

What are the signs and symptoms of pinworm infection?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

If the patient has only a small number of adult worms the infection will be mild and there may be no symptoms at all. Symptoms tend only to be present with heavy or moderate infections.

A few weeks after ingesting pinworm eggs, the mature females make their way from the intestine to the anal area, where eggs are laid, usually at night. During the maturing and reproduction stages the patient may experience:

• Disturbed sleep
• Itching of the anal area, may sometimes be intense, especially at night when the female worms are laying eggs
• Itching of the vaginal area (females)
• Slight nausea
• Vague intermittent abdominal pain

Individuals with severe itching may experience:

• Loss of appetite
• Severe irritability
• Sleeping difficulties
• Weight loss

If somebody is found to have an infection, all other members of the household should be treated too, even if they have no symptoms.

What are the causes of pinworm infection?

The main reason for pinworm infection is poor hygiene. Eggs are transferred from the anus of an infected person to either their mouth (re-infecting themselves) or another surface. If somebody else touches that contaminated surface and then touches their mouth, they may have ingested the eggs and become infected.

The female pinworm lays eggs around the anus and vagina (of females). A pinworm can lay thousands of microscopic eggs.

The eggs can be transferred from the person's anus to:

• Bed sheets
• Carpets
• Hands
• Towels
• Underwear and clothes

The female pinworm releases an itchy mucus when laying her eggs, triggering an urge to scratch the affected area (anus/vagina). If the area is scratched the eggs will be transferred to the patient's hands. From the hands, the eggs may be transferred to anything that is touched, such as:

• Bathroom utensils (toothbrush, combs, etc)
• Directly to other people's hands (if the hands of an infected person touch the hands of another)
• Furniture
• Kitchen and bathroom worktop surfaces
• Kitchen utensils
• Toys

Swallowing the eggs - the eggs can survive for up to three weeks on surfaces. If they are touched they will be transferred onto the hands. If the hands then touch the person's mouth, there is a serious risk of ingesting (swallowing) the eggs and becoming infected.

Breathing in the eggs - the microscopic eggs may become airborne and be breathed in and then swallowed. This may happen if you shake a towel or bed sheets.

The eggs hatch in the intestines two weeks after being swallowed. Two weeks later the pinworm is able to reproduce.

Poor hygiene - small children are more likely to become infected because they tend to be less thorough about hand washing, compared to other people.

Children may also have long-lasting infections because they are swallowing fresh eggs continually - children are usually in close contact with each other and share items and hold hands while playing, making re-infection more likely.

Pinworms are more common in crowded conditions.

Pinworms that affect humans cannot infect animals or pets. However, some microscopic eggs may land on a pet's fur and then be transferred to human hands when stroking (petting). It is important to remember that the problem is not the pet, it is human hand washing and hygiene.

How is a pinworm infection diagnosed?

• Tape test - this is a cellophane tape test. The doctor places a piece of clear plastic tape against the skin around the patient's anus and then looks at the tape under a microscope. As the worm tends to lay her eggs at night, good samples are more likely early in the morning. Patients may themselves apply the tape before going to the toilet (before defecating, doing a poo) or bathing. The sample should then be taken to the doctor. Sometimes several tape samples are required.


• Moistened swab - a doctor or nurse may take a moistened swab from around the anal area.


• Sighting a worm - sometimes the worms may be seen in the anal area, underwear or in the toilet (in stools). In stools the worms look like small pieces of white cotton thread. Because of their size and color (white), pinworms are difficult to see. The male worm is rarely seen because it remains inside the intestine.
  
  It is best to search for pinworms at night, when the female comes out to lay her eggs. If you are checking children it is best to inspect about two to three hours after they have fallen asleep.

The pinworm eggs are not visible to the naked eye.

If you are pregnant, breastfeeding, or have a baby less than three months of age, and you suspect you may have pinworms, you should see your doctor straight away.

Treatment for pinworm infection

Pinworm infection can be easily treated. It is important to remember that treatment also focuses on preventing reinfection. All members of the family need to be treated. Treatment may consist of either a six-week strict hygiene method, or medication followed by strict hygiene for two weeks.

Some medications are available OTC (over the counter, no prescription required) at your local pharmacy. It is important to follow the manufacturer's instructions. If you are pregnant, breastfeeding, or have a baby less than three months old you should be treated by your doctor.

Hygiene method - according to the National Health Service (NHS), UK, strict hygiene measures can clear up pinworm infection and significantly reduce the risk of reinfection. The worm has a life span of about six weeks; hence the hygiene method needs to last that long. Everyone in the household has to adhere to strict hygiene.

• Wash all bed linen, bedclothes (pajamas) and cuddly toys. Normal washing temperature is fine, but it needs to be well rinsed.
• Vacuum the home thoroughly, especially the bedrooms. Vacuuming needs to be regular and thorough throughout the six-week period.
• Damp-dust surfaces in the kitchen and bathroom, washing the cloth often in hot water. Do this regularly throughout the period.
• Do not shake things that may have eggs on them, such as clothing, pajamas, bed lined or towels.
• Do not eat in the bedroom. There is a risk of swallowing eggs that have shaken off the bedclothes.
• Make sure everybody's fingernails are cut short.
• Refrain from nail biting and finger sucking. This may not be easy if there are small children in the house.
• Wash your hands thoroughly and frequently, and scrub under your fingernails. Before eating, after going to the toilet, and after changing diapers (nappies) make sure you wash your hands.
• At night wear close-fitting underwear. Change your underwear every morning.
• Some people say that cotton gloves may help prevent scratching during sleep.
• Have a bath or shower regularly, thoroughly cleaning your body, paying particular attention to your anal and vaginal (females) areas.
• Do not share towels or face flannels.
• Toothbrushes should be kept in a closed cupboard and rinsed well before use.

When the infestation has gone, good hand washing practice and hygiene will help prevent reinfection. Good hygiene can prevent another outbreak even if children pick up another pinworm infection from friends at school.

Medication - if medication is used, it should be given to everybody in the household. There is a 75% risk of transmission between family members (people in the same household); so the chances of being infected if somebody has been diagnosed are high, even if no symptoms are present.

• Mebendazole - this medication blocks the worm's ability to absorb glucose, effectively killing it within a few days. It can be taken in chewable form or as a liquid. A single 100mg dose is usually enough. For reinfection, a repeated dose may be prescribed. Mebendazole is suitable for patients aged over two years. Side effects may include diarrhea or abdominal pain, especially if the patient has a severe infection.
• Piperazine - this medication paralyzes the worm so that it is rapidly expelled out of the bowel. Sometimes the patient is also given senna (a slight laxative). The two medications usually come in a sachet of powder; the powder is drunk with water. This medication is also suitable for patients aged 3 months to two years; in such cases they will need two doses of either 2.5ml or 5ml each, two weeks apart. Patients with kidney problems or epilepsy should not take this medication.
  
  Both mebendazole and piperazine are said to be from 90% to 100% effective at killing the pinworms. However, they do not kill the eggs. Hygiene measures should be followed for at least two weeks after treatment.

If the infection continues after medical treatment, you should see your doctor, who will probably recommend a second course of medication.

Pregnancy and breastfeeding - the hygiene method is recommended for pregnant or breastfeeding mothers, rather than medication. Neither mebendazole nor piperazine should be taken during the first 13 weeks of pregnancy. During the 2nd and 3rd trimesters of pregnancy and during breastfeeding, medication may be used if necessary. This decision should be made by a qualified health care professional.

Small babies - babies aged less than three months should not take medication; the hygiene method should be used. Every time the baby's diapers (nappies) are changed his/her bottom should be washed thoroughly and gently.

What are the possible complications of pinworm infection?

Complications rarely develop as a result of pinworm infection; when they do, they may include:

• Urinary tract infection - this is more common in females with a heavy pinworm infestation. The worm may also migrate to the bladder, causing cystitis.
• Peritoneal cavity infection - in females the worm may migrate from the anal area into the vagina and to the uterus, fallopian tubes and around the pelvic organs, causing vaginitis or endometritis.
• Weight loss - if the infection is severe the parasite may leech essential nutrients, resulting in weight loss.
• Skin infection - the itching may lead to intense scratching which may break the skin, raising the risk of infection.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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