A pinworm (“threadworm”) is a small, thin, white roundworm (nematode) called Enterobius vermicularis that sometimes lives in the colon and rectum of humans. Pinworms are about the length of a staple. While an infected person sleeps, female pinworms leave the intestine through the anus and deposit their eggs on the surrounding skin.
What are the symptoms of a pinworm infection?
Pinworm infection (called enterobiasis or oxyuriasis) causes itching around the anus which can lead to difficulty sleeping and restlessness. Symptoms are caused by the female pinworm laying her eggs.
Symptoms of pinworm infection usually are mild and some infected people have no symptoms.
Who is at risk for pinworm infection?
Pinworm infection occurs worldwide and affects persons of all ages and socioeconomic levels. It is the most common worm infection in the United States. Pinworm infection occurs most commonly among
- school-aged and preschool-aged children,
- institutionalized persons, and
- household members and caretakers of persons with pinworm infection.
- Pinworm infection often occurs in more than one person in household and institutional settings. Child care centers often are the site of cases of pinworm infection.
How is pinworm infection spread?
Pinworm infection is spread by the fecal-oral route, that is by the transfer of infective pinworm eggs from the anus to someone’s mouth, either directly by hand or indirectly through contaminated clothing, bedding, food, or other articles.
Pinworm eggs become infective within a few hours after being deposited on the skin around the anus and can survive for 2 to 3 weeks on clothing, bedding, or other objects.
People become infected, usually unknowingly, by swallowing (ingesting) infective pinworm eggs that are on fingers, under fingernails, or on clothing, bedding, and other contaminated objects and surfaces.
Because of their small size, pinworm eggs sometimes can become airborne and ingested while breathing.
Can my family become infected with pinworms from swimming pools?
Pinworm infections are rarely spread through the use of swimming pools. Pinworm infections occur when a person swallows pinworm eggs picked up from contaminated surfaces or fingers.
Although chlorine levels found in pools are not high enough to kill pinworm eggs, the presence of a small number of pinworm eggs in thousands of gallons of water (the amount typically found in pools) makes the chance of infection unlikely.
Risk Factors for Pinworm Infections
Pinworm infections affect people of all ages and geographical regions. Since the pinworm eggs are microscopic, it’s impossible to avoid infected individuals or areas.
While anyone can get a pinworm infection, the following groups are more susceptible:
- children who attend daycare, preschool, or elementary school
- family members or caregivers of infected children and adults
- individuals who live in institutions or other crowded accommodations
- children who don’t practice regular and careful hand washing prior to eating
- children who have a habit of sucking their thumbs
How is pinworm infection diagnosed?
Itching during the night in a child’s perianal area strongly suggests pinworm infection. Diagnosis is made by identifying the worm or its eggs. Worms can sometimes be seen on the skin near the anus or on underclothing, pajamas, or sheets about 2 to 3 hours after falling asleep.
Pinworm eggs can be collected and examined using the “tape test” as soon as the person wakes up. This “test” is done by firmly pressing the adhesive side of clear, transparent cellophane tape to the skin around the anus.
The eggs stick to the tape and the tape can be placed on a slide and looked at under a microscope. Because washing/bathing or having a bowel movement can remove eggs from the skin, this test should be done as soon as the person wakes up in the morning before they wash, bathe, go to the toilet, or get dressed.
The “tape test” should be done on three consecutive mornings to increase the chance of finding pinworm eggs.
Because itching and scratching of the anal area is common in pinworm infection, samples taken from under the fingernails may also contain eggs.
Pinworm eggs rarely are found in routine stool or urine samples.
Complications from Pinworm Infections
Most people don’t experience serious complications as a result of pinworm infections. Rarely, if the infestation is left untreated:
- In females, pinworm infections can sometimes cause a urinary tract infection.
- In females, pinworms can travel from the anus into the vagina, affecting the uterus, fallopian tubes, and other pelvic organs. Vaginitis, endometritis (an inflammation of the uterine lining), or other infections may result.T
The presence of a significant number of pinworms can cause abdominal pain.
Substantial pinworm populations can rob your body of essential nutrients, which can cause weight loss.
How is pinworm infection treated?
Pinworm can be treated with either prescription or over-the-counter medications. A health care provider should be consulted before treating a suspected case of pinworm infection.
Treatment involves two doses of medication with the second dose being given 2 weeks after the first dose. All household contacts and caretakers of the infected person should be treated at the same time.
Reinfection can occur easily so strict observance of good hand hygiene is essential (e.g. proper handwashing, maintaining clean short fingernails, avoiding nail biting, avoiding scratching the perianal area).
Daily morning bathing and daily changing of underwear helps removes a large proportion of eggs. Showering may be preferred to avoid possible contamination of bath water.
Careful handling and frequent changing of underclothing, night clothes, towels, and bedding can help reduce infection, reinfection, and environmental contamination with pinworm eggs.
These items should be laundered in hot water, especially after each treatment of the infected person and after each usage of washcloths until infection is cleared.
Outlook for Pinworm Infections
It’s possible to eradicate a pinworm infection with medication and the recommended cleaning regimen. However, because pinworm eggs are invisible to the naked eye and are highly contagious, reinfection can easily occur.
A person can reinfect themselves or become reinfected by eggs from another person. If you experience recurrent infections after you have treated your household, individuals and locations outside the household may be the primary source of the pinworm eggs.
Tips to Prevent Pinworm Infections
The best way to prevent pinworm infections and reinfections is to follow recommended hygiene routines and encourage other household members, especially children, to do the same.
You can work to prevent pinworm infections with the following practices:
- Wash your hands with warm water and soap after using the toilet. Be especially careful after bowel movements and changing diapers. Do the same before preparing food and eating.
- Keep your fingernails short and clean.
- Discourage children’s habits such as nail biting or scratching that could spread pinworm eggs.
- Shower daily in the morning to remove pinworm eggs that may have been deposited overnight.
- Change your underwear and clothing daily.
- Use hot water in the washing machine, followed by a hot dryer, to launder bedding, clothing, and towels that may contain pinworm eggs.
- Keep rooms well lit during the day because the eggs are sensitive to sunlight.