Pinworm infection

Contents

What is pinworm infection

What is pinworm infection

Pinworm infection is caused by a small, thin, white roundworm called Enterobius vermicularis. Pinworms are also called threadworms, enterobiasis and oxyuriasis. Pinworms are thin and white, measuring about 1/4 to 1/2 inch (about 5 to 13 millimeters) in length. Although pinworm infection can affect all people, it most commonly occurs among children, institutionalized persons, and household members of persons with pinworm infection.

Pinworms are small parasites that can live in the colon and rectum of humans. You get them when you swallow their eggs. The eggs hatch inside your intestines. While you sleep, the female pinworms leave the intestines through your anus and lay eggs on nearby skin.

Pinworms spread easily. When people who are infected touch their anus, the eggs attach to their fingertips. They can spread the eggs to others directly through their hands, or through contaminated clothing, bedding, food, or other articles. The eggs can live on household surfaces for up to 2 weeks.

A person is infected with pinworms by ingesting pinworm eggs either directly or indirectly. These eggs are deposited around the anus by the worm and can be carried to common surfaces such as hands, toys, bedding, clothing, and toilet seats. By putting anyone’s contaminated hands (including one’s own) around the mouth area or putting one’s mouth on common contaminated surfaces, a person can ingest pinworm eggs and become infected with the pinworm parasite. Since pinworm eggs are so small, it is possible to ingest them while breathing.

Once someone has ingested pinworm eggs, there is an incubation period of 1 to 2 months or longer for the adult gravid female to mature in the small intestine. Once mature, the adult female worm migrates to the colon and lays eggs around the anus at night, when many of their hosts are asleep. People who are infected with pinworm can transfer the parasite to others for as long as there is a female pinworm depositing eggs on the perianal skin. A person can also re-infect themselves, or be re-infected by eggs from another person.

Pinworm infection (called enterobiasis or oxyuriasis) is more common in children. Many people have no symptoms at all. Some people feel itching around the anus or vagina. The itching may become intense, interfere with sleep, and make you irritable. Symptoms are caused by the female pinworm laying her eggs. Symptoms of pinworm infection usually are mild and some infected people have no symptoms.

Worldwide, with pinworm infections are more frequent in school- or preschool-children and in crowded conditions. Pinworm infection appears to be more common in temperate than tropical countries. Pinworm infection is the most common helminthic infection in the United States (an estimated 40 million persons infected).

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.

The people most likely to be infected with pinworm are children under 18, people who take care of infected children and people who are institutionalized. In these groups, the prevalence can reach 50%.

How is pinworm infection spread?

Pinworm infection is spread by the fecal-oral route when their eggs are swallowed. 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.

Pinworms lay eggs around your anus, which make it itchy. The eggs get stuck on your fingers when you scratch. They can then pass on to anything you touch, including:

clothes
toys
toothbrushes
kitchen or bathroom surfaces
bedding
food
pets

Eggs can then pass to other people when they touch these surfaces and touch their mouth. They take around 2 weeks to hatch.

Children can get worms again after they’ve been treated for them if they get the eggs in their mouth. This is why it’s important to encourage children to wash their hands regularly.

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.

My little kids like to co-bathe – could this be how they are becoming infected?

During this treatment time and two weeks after final treatment, it is a good idea to avoid co-bathing and the reuse or sharing of washcloths. 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.

Did my pets give me pinworms / can I give pinworms to my pets?

No. Humans are considered to be the only hosts of Enterobius vermicularis which is also known as the human pinworm.

Pinworm is the most common worm infection in the United States. Humans are the only species that can transfer this parasite. Household pets like dogs and cats cannot become infected with human pinworms. Pinworm eggs can survive in the indoor environment for 2 to 3 weeks.

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.

Your health care provider can also diagnose pinworm infection by finding the eggs. Mild infections may not need treatment. If you do need medicine, everyone in the household should take it.

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, but reinfection, which occurs easily, should be prevented.

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.

Should family and other close contacts of someone with pinworm also be treated for pinworm?

Yes. The infected person and all household contacts and caretakers of the infected person should be treated at the same time.

What should be done if the pinworm infection occurs again?

Reinfection occurs easily. Prevention always should be discussed at the time of treatment. Good hand hygiene is the most effective means of prevention. If pinworm infection occurs again, the infected person should be retreated with the same two-dose treatment. The infected person’s household contacts and caretakers also should be treated. If pinworm infection continues to occur, the source of the infection should be sought and treated. Playmates, schoolmates, close contacts outside the home, and household members should be considered possible sources of infection. Each infected person should receive the recommended two-dose treatment.

How can pinworm infection and reinfection be prevented?

Strict observance of good hand hygiene is the most effective means of preventing pinworm infection. This includes washing hands with soap and warm water after using the toilet, changing diapers, and before handling food. Keep fingernails clean and short, avoid fingernail-biting, and avoid scratching the skin in the perianal area. Teach children the importance of washing hands to prevent infection.

Daily morning bathing and changing of underclothes helps remove a large proportion of pinworm eggs and can help prevent infection and reinfection. Showering may be preferred to avoid possible contamination of bath water. Careful handling (avoid shaking) and frequent laundering of underclothes, night clothes, towels, and bed sheets using hot water also helps reduce the chance of infection and reinfection by reducing environmental contamination with eggs.

Control can be difficult in child care centers and schools because the rate of reinfection is high. In institutions, mass and simultaneous treatment, repeated in 2 weeks, can be effective. Hand hygiene is the most effective method of prevention. Trimming and scrubbing the fingernails and bathing after treatment is important to help prevent reinfection and spread of pinworms.

To prevent becoming infected or reinfected with pinworms,

Bathe after waking up
Wash your pajamas and bed sheets often
Wash your hands regularly, especially after using the bathroom or changing diapers
Change your underwear every day
Avoid nail biting
Avoid scratching the anal area.

Figure 1. Pinworm infection anus (Enterobius vermicularis)

Enterobius vermicularis adult worms

Adult males of Enterobius vermicularis measure up to 2.5 mm long by 0.1-0.2 mm wide; adult females measure 8-13 mm long by 0.3-0.5 mm wide. Adult males have a blunt posterior end with a single spicule; females possess a long pointed tail. In both sexes, there are cephalic expansions.

Figure 2. Pinworms (Enterobius vermicularis pinworms are about the length of a staple)

Severe pinworm infection

The most common clinical manifestation of a pinworm infection is an itchy anal region. When the infection is heavy, there can be a secondary bacterial infection due to the irritation and scratching of the anal area. Often the patient will complain of teeth grinding, and insomnia due to disturbed sleep, or even abdominal pain or appendicitis. Infection of the female genital tract has been well reported.

Pinworm infection life cycle

The nematode (roundworm) Enterobius vermicularis also called human pinworm. (Adult females: 8 to 13 mm, adult male: 2 to 5 mm.) Humans are considered to be the only hosts of Enterobius vermicularis. A second species, Enterobius gregorii, has been described and reported from Europe, Africa, and Asia. For all practical purposes, the morphology, life cycle, clinical presentation, and treatment of Enterobius gregorii is identical to Enterobius vermicularis.

Eggs are deposited on perianal folds.
Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area. Person-to-person transmission can also occur through handling of contaminated clothes or bed linens. Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g., curtains, carpeting). Some small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs.
Following ingestion of infective eggs, the larvae hatch in the small intestine and
The adults establish themselves in the colon. The time interval from ingestion of infective eggs to oviposition by the adult females is about one month. The life span of the adults is about two months.
Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area. The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions. Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown.

Figure 3. Pinworm infection life cycle

Pinworm infection causes

Accidentally swallowing or breathing in pinworm eggs causes a pinworm infection. The microscopic eggs can be carried to your mouth by contaminated food, drink or your fingers. Once swallowed, the eggs hatch in the intestines and mature into adult worms within a few weeks.

Female pinworms move to the anal area to lay their eggs, which often results in anal itching. When you scratch the itchy area, the eggs cling to your fingers and get under your fingernails. The eggs then get transferred to other surfaces, such as toys, bed linens or toilet seats. The eggs can also be transferred from contaminated fingers to food, liquids, clothes or other people.

Pinworm eggs can survive for two to three weeks on surfaces.

Risk factors for pinworm infection

Risk factors for pinworm infection include:

Being young. Pinworm infections are most likely to occur in children younger than 18. The microscopic eggs are easily spread to family members, caregivers, or other children at school or child care centers.
Living in crowded spaces. People who live in institutions are at higher risk of developing pinworm infections.

Pinworm infection prevention

Pinworm eggs can cling to surfaces, including toys, faucets, bedding and toilet seats, for two weeks. So besides regular cleaning of surfaces, methods to help prevent the spread of pinworm eggs or to prevent reinfection include:

Wash in the morning. Because pinworms lay their eggs at night, washing the anal area in the morning can help reduce the number of pinworm eggs on your body. Showering may help avoid possible recontamination in bath water.
Change underwear and bed linen daily. This helps remove eggs.
Launder in hot water. Wash bedsheets, nightclothes, underwear, washcloths and towels in hot water to help kill pinworm eggs. Dry on high heat.
Don’t scratch. Avoid scratching the anal area. Trim your child’s fingernails so there’s less space for eggs to collect. Discourage nail biting.
Wash your hands. To reduce your risk of getting or spreading an infection, wash your hands thoroughly after having a bowel movement or changing a diaper and before eating.

Pinworm infection symptoms

Enterobiasis is frequently asymptomatic. The most typical symptom is perianal pruritus, especially at night, which may lead to excoriations and bacterial superinfection. Occasionally, invasion of the female genital tract with vulvovaginitis and pelvic or peritoneal granulomas can occur. Other symptoms include anorexia, irritability, and abdominal pain.

Symptoms of pinworm infection may include:

Itching of the anal or vaginal area
Insomnia, irritability and restlessness
Intermittent abdominal pain and nausea

Less common signs of pinworm infection include:

weight loss
wetting the bed
irritated skin around the anus

Pinworm infection diagnosis

Your doctor can confirm the presence of pinworms by identifying the worms or eggs.

To help your doctor make a diagnosis, you can perform the tape test. As soon as the person you suspect has pinworms wakes up and before he or she uses the toilet, washes or gets dressed, press the adhesive side of a piece of transparent tape to the skin around the anus. The eggs stick to the tape.

For best results, perform the tape test three days in a row, and then take the pieces of tape to your doctor. Your doctor can look at the tape under a microscope to see if there are any pinworm eggs.

Pinworm Tape Test

A pinworm test is a method used to identify a pinworm infection. Pinworms are small, thin worms that commonly infect young children, although anyone can be infected.

How the Pinworm Test is Performed

When a person has a pinworm infection, adult pinworms live in the intestine and colon. At night, the female adult worms deposit their eggs outside the rectum or anal area.

One way to detect pinworms is to shine a flashlight on the anal area. The worms are tiny, white, and threadlike. If none are seen, check for 2 or 3 additional nights.

The best way to diagnose this infection is to do a tape test. The best time to do this is in the morning before bathing, because pinworms lay their eggs at night.

Steps for the test are:

Firmly press the sticky side of a 1-inch (2.5 centimeters) strip of cellophane tape over the anal area for a few seconds. The eggs stick to the tape.
The tape is then transferred to a glass slide, sticky side down. Put the piece of tape in a plastic bag and seal the bag.
Wash your hands well.
Take the bag to your health care provider. The provider needs to check the tape to see if there are eggs.

The tape test may need to be done on 3 separate days to improve the chances of detecting the eggs.

You may be given a special pinworm test kit. If so, follow instructions on how to use it.

What Abnormal Results Mean

If adult pinworms or eggs are found, the person has a pinworm infection. Usually the whole family needs to be treated with medicine. This is because pinworms are easily passed back and forth between family members.

Laboratory Diagnosis

Microscopic identification of eggs collected in the perianal area is the method of choice for diagnosing enterobiasis. This must be done in the morning, before defecation and washing, by pressing transparent adhesive tape (“Scotch test”, cellulose-tape slide test) on the perianal skin and then examining the tape placed on a slide. Alternatively, anal swabs or “Swube tubes” (a paddle coated with adhesive material) can also be used. Eggs can also be found, but less frequently, in the stool, and occasionally are encountered in the urine or vaginal smears. Adult worms are also diagnostic, when found in the perianal area, or during ano-rectal or vaginal examinations.

Pinworm infection treatment

To treat pinworm infection, your doctor may recommend over-the-counter pyrantel pamoate (Reese’s Pinworm Medication, Pin-X) or prescribe medication to all members of your household to prevent infection and reinfection.

The medications used for the treatment of pinworm are either mebendazole, pyrantel pamoate, or albendazole. Any of these drugs are given in one dose initially, and then another single dose of the same drug two weeks later. Pyrantel pamoate is available without prescription. The second dose of medication is to eliminate possible re-infection since the first dose of medication. Health practitioners and parents should weigh the health risks and benefits of these drugs for patients under 2 years of age.

Repeated infections should be treated by the same method as the first infection. In households where more than one member is infected or where repeated, symptomatic infections occur, it is recommended that all household members be treated at the same time. In institutions, mass and simultaneous treatment, repeated in 2 weeks, can be effective.

The safety of drugs used to treat pinworm have not been studied for pregnant women. If the infection is compromising the pregnancy (i.e. weight loss, sleeplessness) then treatment can be considered, but should be withheld until the 3rd trimester when the risk, if any, to the fetus is likely to be reduced. Breastfeeding should not be withheld during mebendazole therapy. Only about 2%-10% of an oral dose is absorbed and as expected, the amounts of the drug excreted in milk are below the level of detection and appear to be clinically insignificant. Excretion in breast milk of the other drugs used to treat pinworm is not as well characterized.

Mebendazole is available in the United States only through compounding pharmacies.

Pyrantel pamoate is available for human use in the United States.

Oral albendazole is available for human use in the United States.

The most common prescription anti-parasite medications for pinworms are:

Mebendazole
Albendazole (Albenza)

You may have mild gastrointestinal side effects during the course of treatment, and you often need to take at least two doses to get rid of the pinworms completely.

Pyrantel Pamoate

Note on Treatment in Pregnancy

Pyrantel pamoate is in pregnancy category C. Data on the use of pyrantel pamoate in pregnant women are limited. In mass treatment programs for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of pyrantel pamoate in the 2nd and 3rd trimesters of pregnancy, acknowledging that the effects of pyrantel on birth outcome are not certain. The risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Pregnancy Category C: Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal, or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.

Note on Treatment During Lactation

It is not known whether pyrantel pamoate is excreted in breast milk. The WHO classifies pyrantel pamoate as compatible with breastfeeding, although data on the use of pyrantel pamoate during lactation are limited.

Note on Treatment in Pediatric Patients

The safety of pyrantel pamoate in children has not been established. According to WHO guidance on preventive chemotherapy, pyrantel may be used in children age 1 year and older during mass treatment programs without diagnosis. Pyrantel pamoate is listed as an intestinal antihelminthic medicine on the WHO Model List of Essential Medicines for Children, intended for the use of children up to 12 years of age.

Mebendazole

Note on Treatment in Pregnancy

Mebendazole is in pregnancy category C. Data on the use of mebendazole in pregnant women are limited. The available evidence suggests no difference in congenital anomalies in the children of women who were treated with mebendazole during mass treatment programs compared with those who were not. In mass treatment programs for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of mebendazole in the 2nd and 3rd trimesters of pregnancy. The risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Note on Treatment During Lactation

It is not known whether mebendazole is excreted in breast milk. The WHO classifies mebendazole as compatible with breastfeeding and allows the use of mebendazole in lactating women.

Note on Treatment in Pediatric Patients

The safety of mebendazole in children has not been established. There is limited data in children age 2 years and younger. Mebendazole is listed as an intestinal antihelminthic medicine on the WHO Model List of Essential Medicines for Children, intended for the use of children up to 12 years of age.

Albendazole

Note on Treatment in Pregnancy

Albendazole is pregnancy category C. Data on the use of albendazole in pregnant women are limited, though the available evidence suggests no difference in congenital abnormalities in the children of women who were accidentally treated with albendazole during mass prevention campaigns compared with those who were not. In mass prevention campaigns for which the World Health Organization (WHO) has determined that the benefit of treatment outweighs the risk, WHO allows use of albendazole in the 2nd and 3rd trimesters of pregnancy. However, the risk of treatment in pregnant women who are known to have an infection needs to be balanced with the risk of disease progression in the absence of treatment.

Note on Treatment During Lactation

It is not known whether albendazole is excreted in human milk. Albendazole should be used with caution in breastfeeding women.

Note on Treatment in Pediatric Patients

The safety of albendazole in children less than 6 years old is not certain. Studies of the use of albendazole in children as young as one year old suggest that its use is safe. According to WHO guidelines for mass prevention campaigns, albendazole can be used in children as young as 1 year old. Many children less than 6 years old have been treated in these campaigns with albendazole, albeit at a reduced dose.

Things you should do at home

Medicine kills the pinworms, but it doesn’t kill the eggs. Pinworm eggs can live for up to 2 weeks outside the body.

There are things you can do to stop becoming infected again.

wash hands and scrub under fingernails – particularly before eating, after using the toilet or changing nappies
encourage children to wash hands regularly
bathe or shower every morning
rinse toothbrushes before using them
keep fingernails short
wash sleepwear, sheets, towels and soft toys (at normal temperature)
disinfect kitchen and bathroom surfaces
vacuum and dust with a damp cloth
make sure children wear underwear at night – change it in the morning

DON’T