Pinworm Infection

Pinworm infection is an infestation of the large intestine and anal area by a small, white parasite that resembles a "worm." The medical name for the parasite is Enterobius vermicularis, but it is commonly termed a pinworm in both the lay and medical literature. These parasites are also termed seatworms or threadworms, and the infections are medically termed enterobiasis, oxyuriasis, or helminthiasis.

• Pinworms and other helminthic parasitic worms (which, as a group, are termed helminths) feed off of the host animal by absorbing nutrients from the host animal.
• Pinworm infections are the most common helminth infection that occurs in the US. Pinworms only infect humans.
• Children are most commonly affected by pinworm infection.
• Dogs, cats, or other animals cannot become infected.

Pinworm infection is spread from person to person mostly in crowded places or in places where people live in institutions. Pinworm infection symptoms are caused by the female pinworm moving and laying her eggs, and this usually occurs at night. Within a few hours of being deposited on the skin around the anus, pinworm eggs become infective (capable of infecting another person).

Pinworm eggs can survive up to two weeks on night clothes, bed linen, or other objects. Pinworm infection is acquired when these eggs are accidentally swallowed, usually due to inadequate handwashing by the parents and children. However, eggs on bedding or other objects that are touched while the eggs are still viable can also cause infection or reinfection of people.

Pinworm is the most common parasitic worm infection in the United States, and the majority of pinworm infections worldwide occur in children, in temperate climates. Pinworm infection affects approximately 40 million people in the U.S. and 1 billion people worldwide. Pinworm infections are contagious.

Pinworms in children

The highest rates of pinworm infection occur in school-age children. This is followed by preschoolers. Institutional settings, including day care facilities, often harbor multiple individuals (adults and children) with pinworm infections. Sometimes, nearly half of the children may be infected in a day care facility.

Pinworms in adults

Pinworm infection often occurs in more than one family member. Adults are less likely to have pinworm infection, except for mothers of infected children. However, adult sexual partners can transfer the eggs to each other. Pinworms also may infect the vagina and urethra.

Symptoms of pinworms in adults include:

• Itching and irritation around the anus or vagina
• Difficulty sleeping or restlessness at night
• Abdominal pain

Some adults may have no symptoms associated with pinworm infection.

Figure 2: Picture of the life cycle of a pinworm

If symptoms are present, they are similar in both children and adults.

The signs and symptoms may include one or more of the following:

• Intense itching (pruritus) around the anus and/or vagina
• Discomfort in the anal and/or vaginal area
• Rash or skin irritation around the anus or vagina
• Insomnia or difficulty sleeping and/or restlessness due to irritation of the skin
• Pinworms often can be seen on the anal skin or in the stools, sometimes detected in the vagina, and may produce some vaginal discharge

Less common symptoms include:

• Abdominal pain
• Secondary bacterial infections from intense skin scratching
• Infrequent infection of the ureters and/or bladder may cause dysuria or bladder discomfort

Many infected children and adults have few or no symptoms, but if the pinworm infection is heavy, the symptoms can be correspondingly more severe.

The pinworms are white, can be seen with the naked eye (no magnification), and are about the length of a staple (about 8-13 mm for females and 2-5mm for male worms). The eggs that are laid by the female worms are not visible as they are about 55 micrometers in diameter and are translucent (see Figure 1). Pinworm infection mainly occurs when a child swallows these eggs.

The male and female worms live for the most part within the rectum of humans but have a life cycle in humans that involves rectal/oral transmission (see Figure 2).

While an infected person is asleep, female pinworms leave the intestines through the anus and deposit eggs on the skin around the anus. This causes itching and irritation of the surrounding area; children especially will scratch the rectal/anal area, get eggs on their fingers or underneath their fingernails and transport the infective eggs to bedding, toys, other humans, or back to themselves. The eggs hatch into larval forms in the small intestines and then progress to the large intestine where they mature and mate, and then progress to the rectal/anal area where females deposit about 10,000-15,000 eggs.

Figure 1: Picture of pinworm and pinworm eggs (magnified); image courtesy of CDC.gov

Yes, pinworms can infect the vagina (occurs in about 20% of infected girls). Infrequently, the pinworms can go on to infect the Fallopian tubes and other structures.

The majority of pinworm-infected patients can be treated by the patient's primary care or pediatric physician. Rarely, an infectious disease specialist, parasitologist, OB/GYN, gastroenterologist, or dermatologist is consulted.

If pinworms are suspected, transparent adhesive tape or a pinworm paddle (supplied by your health care professional) are applied to the anal region. The eggs (and sometimes the parasites themselves) adhere to the sticky tape or paddle and are identified by examination under a microscope. The test is sometimes referred to as "the Tape Test."

The test should be done as soon as the affected individual wakes up in the morning (because bathing or having a bowel movement may remove most eggs and parasites). The exam may require several samples for diagnosis. Samples taken from under the fingernails may also contain eggs (since scratching of the anal area is common by affected individuals).

At night, the adult worms can sometimes be seen directly in bedclothes or around the anal area: this is another good time to detect the parasites with the transparent adhesive tape method.

How to get rid of pinworms

Medications to get rid of pinworms include:

• Usually, a single tablet of mebendazole (Vermox) is used as pinworm medicine. This can sometimes be repeated a week later or, if the infection persists, the medication is given again three weeks later. Some clinicians recommend a treatment protocol of a drug dose every three weeks, three times so that the person has effective drug treatment for about nine weeks total. Vermox has been discontinued in the U.S., but stocks are still available in some pharmacies.
• Another effective medication is albendazole (Albenza), but it may require other medications to reduce the inflammation of the central nervous system, a side effect of the drug. Albendazole is well tolerated with minimal side effects due to minimal systemic absorption.
• Pyrantel pamoate (Pin-Rid, Pin-X) is available over the counter for pinworms after confirmation of the diagnosis by a licensed health care practitioner. Drugs available over the counter vary from country to country. Pyrantel is the treatment of choice for pregnant women.
• To treat pinworms affecting urinary and genital organs, combination therapy with oral mebendazole (Vermox) and ivermectin (Stromectol) for the worms as well as topical therapy for the eggs may be required.

Most pinworm infections are treated at home with the above medications. However, reinfection is fairly common. To both reduce the chances for reinfection and to help prevent others from getting pinworms, see the prevention section.

Pinworm infections can be cured, usually by three doses of medication, each three weeks apart. Individuals are encouraged to follow up with their doctor to be sure pinworm infection treatment has been effective.

There are many natural and/or home remedies for pinworms although there is a lack of data to support any claims.

Some of the many suggested remedies include the following:

• Garlic
• Coconut (grated)
• Grapefruit seed extract and paste
• Grated carrots daily
• Onion juice three times per day for two days
• Pumpkin seeds
• Wormwood extract

The above are just a few of the remedies. Check with your doctor before using these remedies.

Untreated pinworms may cause or have a role in causing:

• Diarrhea
• Significant malabsorption of food
• Weight loss
• Genital itching
• Bedwetting (enuresis)
• Pain during urination (dysuria)
• Vaginal discharge can be associated with genital skin irritation and rash

Most of the time, pinworm infections do not cause any serious issues. Complications arise if the pinworm infection is severe. Some of the complications may include:

• Endometriosis
• Salpingitis
• Urethritis
• Urinary tract infection (UTI)
• Vulvovaginitis
• Possibly appendicitis

Good hygiene will help reduce the spread of the parasites.

• Handwashing after handling bedding, diapers, underwear, and other items like child toilet seats, toys, changing tables, and other surfaces that may contain the infective pinworm eggs will also help prevent the spread of the parasite.
• Cleaning under the fingernails and not biting the fingernails will also help reduce the chance of contracting the parasites.
• Change and wash clothes in hot water daily, especially underwear, to help prevent the spreading of the disease.
• Treating everyone infected in a household at the same time may help prevent recurrence and spread to others.
• Because the eggs remain infective for up to three weeks in a moist environment, prevention of spread and reinfection is difficult but possible.

• What is the fastest way to get rid of pinworms? The fastest way to eliminate pinworms is for all infected family members to take over-the-counter oral medications, such as pyrantel pamoate. It is essential for everyone in the household to be treated to prevent reinfection.
• Do pinworms go away on their own? No, pinworms do not go away on their own. Untreated pinworm infections can lead to the spread of the infection, resulting in serious complications.
• Can I self-treat pinworms? No, you cannot self-treat pinworms. Although there are many home remedies to treat pinworms, the effectiveness of these remedies remains unproven.
• Can you visually see pinworms? Yes, you can sometimes see pinworms. They are small, white, thread-like worms, approximately half an inch long, usually located around the anus.
• What does pinworm poop look like? Pinworm feces typically appear as brown-colored stools, often containing small white, thread-like worms mixed in.