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Enterobiasis

Last updated Sept. 17, 2019

Approved by: Maulik P. Purohit MD, MPH

Enterobiasis, or Pinworm Infection, is caused by a small, thin, and white roundworm (pinworm or threadworm) that can survive in the colon and rectum of humans.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Pinworm Infection
  • Threadworm Infection
  • White Roundworm Infection

What is Enterobiasis? (Definition/Background Information)

  • Enterobiasis, or Pinworm Infection, is caused by a small, thin, and white roundworm (pinworm or threadworm) that can survive in the colon and rectum of humans
  • Any individual is susceptible to Pinworm Infection; but, individuals who reside in or travel to tropical climates, and young children, have an increased risk
  • Pinworms are transmitted through ingestion of pinworm eggs via the fecal-oral route. An oral ingestion is required for infection. The transmission is facilitated through interaction with contaminated food, water, clothing, and via unwashed hands
  • Many infected individuals remain asymptomatic. However, severe itching and/or rashes around the anus, bloody stools, and presence of pinworms in stool, are indicators of Enterobiasis
  • The treatment includes a schedule of oral medication to kill the worms in the digestive tract. Although, in many cases, Enterobiasis typically resolves on its own without medical intervention, and the condition rarely causes any health complications
  • Enterobiasis can be prevented by washing hands, washing laundry in hot water, and limiting contact with the infected individuals

Who gets Enterobiasis? (Age and Sex Distribution)

  • Enterobiasis has been reported from almost every continent of the world. Overall, the highest infection rates are observed in areas of warm, humid, and tropical climates
  • Enterobiasis is most endemic (common) in schools and daycare centers. Young children are at an increased risk of infection, because they generally have underdeveloped immune systems and lack proper hygiene (unless instructed adequately)
  • The highest prevalence of infection is among Indian children, where it is estimated up to 61% of children are infected with pinworms in some regions
  • It is estimated that there are between 20-40 million cases of Enterobiasis in the United States in a year, with the vast majority of cases being observed in young children between the ages of 5 and 10
  • Both male and female genders are affected without any bias
  • All racial groups and ethnicities are equally susceptible

It is important to note that there is no correlation between income levels and rates of infection. An individual from any income class is equally likely to contract Enterobiasis.

What are the Risk Factors for Enterobiasis? (Predisposing Factors)

The risk factors for Enterobiasis include the following:

  • Interaction with infected individuals and children (5-10 years old). Children, who have an extended stay in daycare centers and schools have a much higher risk
  • Failing to wash hands before eating
  • Failing to thoroughly cook food and purify water before consumption
    • Pinworm eggs can survive in water for up to two weeks. This includes bathing water and swimming pools
    • Although the eggs that cause Enterobiasis are not food-borne, handling food without washing hands can help promote infection

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Enterobiasis? (Etiology)

  • Enterobiasis is caused by ingestion of pinworm eggs. Pinworm eggs can survive digestion and attach themselves to the tissue surface of the human colon
    • Once in the colon, eggs develop into pinworms. Mature pinworms can survive and reproduce in the colon for about two months
    • Once fertile, female pinworms exit the colon through the rectum and deposit eggs around the surrounding tissue (in the anal area)
  • Pinworm eggs are incredibly small and impossible to notice. They require a microscope to be visualized. Additionally, microscopic pinworm eggs can survive in a moist environment for 1-2 weeks before host ingestion
  • Pinworm eggs must be repeatedly consumed for infection to become chronic. This is because pinworms can only survive for about 2 months and lay their eggs externally

There is no evidence of direct ingestion of mature pinworms causing a resultant infection. Only ingesting pinworm eggs leads to Enterobiasis.

What are the Signs and Symptoms of Enterobiasis?

In many cases, the infection is asymptomatic, meaning no symptoms are noticed. Many people with Enterobiasis do not even know they are infected. Frequently, individuals become infected and the condition self-resolves, without them ever noticing they were even infected.

The most common signs and symptoms of Enterobiasis include the following:

  • Severe itching and red rashes around the rectum
  • Evidence of blood or worms in stool
  • Lower abdominal pain, in rare cases

It is important to note that the presence of a sign or symptom does not confer infection. Additionally, infection could be experienced without any of the above signs or symptoms.

How is Enterobiasis Diagnosed?

The diagnosis of Enterobiasis is made by the following tools:

  • A physical examination and an assessment of symptoms
  • Evaluation of the affected individual’s medical and recent travel history
  • Visual presence of pinworms; this is the most common mode of diagnosis
  • Test using a transparent cellophane tape: The tape is placed on the perianal skin, the skin surrounding the rectum. This causes eggs on the skin surface to adhere to the cellophane tape. The tape can then be observed by a healthcare professional under a microscope, to check for the presence of pinworm eggs

Currently, serologic (blood or serum) tests are not available for diagnosing a Pinworm Infection.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Enterobiasis?

Complications from Enterobiasis are generally rare. But for gastrointestinal discomfort, these infections tend to be benign. There is no evidence of pinworms causing severe medical conditions in humans. Nevertheless, the following complications have been rarely reported:

  • In some women, pinworm eggs laid on the perianal skin near the rectum may enter the genital tract. This may lead to vaginal inflammation and spotted bleeding
  • Itching, and consequently rupturing, of the perianal skin near the rectum also increases the chance of a bacterial superinfection (secondary infection)
  • Severe and prolonged cases of pinworm infections may cause appendicitis, intestinal obstruction, intestinal perforation, and Crohn’s disease (an inflammatory bowel disease)

How is Enterobiasis Treated?

Enterobiasis is typically treated with a medication that kills pinworms in the colon. This treatment is typically performed by a healthcare professional and may require a prescription. The 3 drugs that may be prescribed include mebendazole, albendazole, and pyrantel pamoate.

  • Mebendazole works by inhibiting the synthesis of parasitic microtubules and degrading its structure. This medication can be used for several parasitic worm infections
  • Albendazole also works by inhibiting the synthesis of and degrading the structure of parasitic microtubules. This medication can be used for a very broad range of parasitic worm infections
  • Pyrantel pamoate is the only drug (of the 3 mentioned) that does not require a prescription. This drug works by killing the parasite through paralysis, which is then passed out through defecation

Appropriate precautions and directions of the healthcare provider should be acknowledged before beginning medication. Additionally, it is recommended that family members be treated as well, as the parasitic infection is highly-contagious and can easily spread from one individual to another.

How can Enterobiasis be Prevented?

  • Since Enterobiasis can spread through contaminated hands, the easiest preventive method is to wash hands thoroughly before eating, after a bowel movement, or changing a diaper 
  • If an infection is suspected, seeking immediate medical attention. A prompt treatment can lessen the duration of infection and prevent the spread of infection to others
  • Washing laundry in hot water can help kill pinworm eggs on clothes and bedding
  • Cook food and purify water thoroughly
    • Even though the parasite only originates from a human host, food and water may still be contaminated with parasitic eggs
    • Cooking food thoroughly and purifying water kills any parasites that may be present via contamination from other sources
  • Since pinworm eggs are laid on the perianal skin, avoid scratching the anal area
  • Pinworm eggs can accumulate under one’s fingernails. Trimming fingernails and avoiding nail biting can also prevent transmission of Enterobiasis
  • Ensure that any contact with infected individuals is kept to a minimum, or is limited

What is the Prognosis of Enterobiasis? (Outcomes/Resolutions)

  • The prognosis of Enterobiasis is typically good, since the infection is asymptomatic in most cases. It resolves in its own without the need for any treatment
  • Rarely, in severe and chronic cases, complications, such as vaginal infection, superinfection, appendicitis, Crohn’s disease, intestinal obstruction and perforation, can occur, if Enterobiasis is left untreated

Additional and Relevant Useful Information for Enterobiasis:

  • Pinworm infections are one of the most common infections in the United States, it is estimated that up to 40 million people can be infected with pinworms in one year 
  • There is ongoing research on acquiring immunity to pinworms. It is suspected that individuals over the age of 15 have an increased ability to fight Pinworm Infections and have a lower likelihood of becoming infected
  • Humans are the only known host to these infections. This means that the only way for the parasite to be transmissible is through direct or indirect contact with another infected human being
  • Mature and fertile female pinworms leave the intestine through the anus and deposit their eggs on surrounding skin
  • Once ingested, pinworm eggs travel through the digestive tract, where eventual incubation in the colon leads to the succeeding life cycle
  • In optimal conditions, pinworm eggs can hatch in 4-6 hours
  • Pinworms have been known to survive in bodies of water for up to two weeks. This includes swimming pools, bathtubs, sewage and sewage runoffs
  • A typical mature pinworm is quarter of an inch in size (about 6 mm), large enough to be visible to the naked eye

Pinworm Infection is the most common helminthic (parasitic worm) infection in the United States, the most common intestinal parasitic infection in the United States, and the fifth most common parasitic infection in the United States.

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Aug. 11, 2017
Last updated: Sept. 17, 2019