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Of the many parasitic infestations involving worms, pinworms are the most prevalent form of worm infestation. They affect approximately 200 million people all over the world, one-third of which can be found in the United States.

Genus Enterobius or pinworm, is a parasitic roundworm belonging to the phylum Nematoda. It is also known as the threadworm, Enterobius vermicularis, and very recently, a new specie of pinworm - Enterobius gregorii - has been discovered.

Adult male pinworms can grow to as long as 1 to 4 millimeters, while adult female worms are 8 to 13 millimeters in length. Their size can be compared to that of a single staple wire. They are characterized by their long backsides which form the shape of a pin, hence the name.

Pinworms are an intestinal parasitic infection which commonly afflicts children, although other age groups can also catch it. These infestations are also known as “seatworm infection”, “threadworm infection,” and the clinical “enterobiasis,” or “oxyuriasis”.

While many intestinal parasites enter the body through the bloodstream or through other body organs, the pinworm makes an entrance via a person's digestive tract.


Pinworm infections are very contagious, and people can unconsciously get an infection by accidentally ingesting pinworm eggs that can be found on many surfaces like bed linens, towels, toilet seats, undergarments, food and utensils, drinking glasses, children's toys, kitchen counters, sandboxes, or school desks and lunch tables. Contrary to common belief, pinworms are not transmitted through animals.

These microscopic eggs pass into a person's digestive system and hatch within the small intestine. The pinworm larvae travel to the large intestine and upper part of the colon, and begin their lives as parasites by attaching their heads to the bowel's inside walls, using the human body as a host in order to live and reproduce.

Immediately after mating, the male pinworm dies. The pinworm female then travels to the anus and lays around 10,000 to 20,000 tiny eggs in the area surrounding the anus (perineum). This occurs approximately within 2 to 4 weeks after a person ingests the pinworm eggs.

After depositing her eggs, the female releases a substance that causes intense itching in the anal area. This invariably causes the host to scratch the affected region, thus transferring eggs to the fingers. The eggs in turn can be conveyed to clothing, toys, bathroom fixtures and other items. Sometimes the host reinfects himself by putting his fingers to his mouth and ingesting more eggs.

Outside the human body, pinworm eggs can survive on their own for up to 2 to 3 weeks. For eggs still left around the anus, they hatch in the perianal area, make their way back inside the anus and rectum, and migrate to the intestines where they begin the whole parasitic process all over again.

Children have the highest risk for contracting pinworm infections as they can be exposed to a lot of pinworm eggs from or near other children (e.g., in sandboxes, making mud pies, etc.), and they are prone to putting their fingers in their mouths, thereby unconsciously ingesting pinworm eggs.
Image: Pinworm


One of the risk factors for a pinworm infestation is poor hygiene. If an infected person scratches the area around the anus and fails to wash his hands, a pinworm infection is liable to spread. Pinworms also thrive better in milder and warmer climates, as evidenced by reports of pinworm infestations in the southern states of the U.S., and in countries with tropical climates. As pinworms commonly infect children, another risk factor includes having children in the household. A child with pinworms can easily spread the infestation to other members of the family.


Sometimes a person with a pinworm infection does not exhibit any symptoms, particularly when there are only a few adult worms within the body. With moderate or heavy infestations, the primary symptom of an infection is the intense and severe itching that the host experiences around the area of the anus. The itching from a pinworm infection usually begins between 1 to 2 months after the eggs are ingested.

As pinworms are most active during the night – the female pinworm lays her eggs at night – the uncontrollable itching starts at around this time. It is caused by the movement of the worms traveling around the rectal area to lay their eggs. It is also due in part to the substance released by the female pinworm right after she lays her eggs.

While scratching can momentarily relieve the itch, it can also cause eczema, an inflammation of the upper layers of the skin, and a bacterial infection. The itching that occurs only during nighttime may also cause insomnia, restlessness and irritability. Mild digestive problems like intermittent stomach pain and nausea will also be experienced.

When there is a heavy infestation in females, the scratching can also spread worms and their eggs towards the vagina, causing a peritoneal cavity infection. This happens when the worms travel to the vagina, the uterus, the fallopian tubes and other organs within the area, resulting in vaginitis or endometritis.

Females who are heavily infected are also likely get a urinary tract infection when the worms migrate to the bladder and cause cystitis. In some rare cases, a pinworm infestation increases the risk for appendicitis, and there have been some findings suggesting that enterobiasis is responsible for reducing the levels of zinc in the body.


If left untreated, pinworms will eventually cause diarrhea, weight loss, bedwetting, constant vaginal discharge and a genital rash. A pinworm infection in the female genital tract can also cause scars to form in the reproductive organs of the host.

Although pinworm eggs can only be detected under a microscope, the adult worms have a white and thread-like appearance and an elongated shape with one side that is convex and other side flat. They can often be seen after the infected person uses the toilet. They can also be found in the host’s underwear upon waking up in the morning.

To make an accurate pinworm diagnosis, the doctor will employ the tape test whereby a piece of clear cellophane test is pressed against the skin surrounding the perianal area. The tape is then removed and examined under a microscope to check for pinworm eggs. Since the female pinworms typically lay their eggs at night, the best time to do the tape test is early in the morning upon waking up.

As soon as a pinworm infection is diagnosed, the doctor will prescribe a round of anti-pinworm medication like albendazole (Albenza), mebendazole (Vermox), or pyrantel pamoate (Pin-X). These drugs remove up to 95% of adult pinworms only.

Patients with moderate to heavy infestations will need to return after two weeks for another round of treatment to eliminate the pinworms that have hatched from the remaining eggs. Patients with mild pinworm infections who do not exhibit any symptoms will not need any treatment as the infestation disappears on its own.

To ease the itch caused by pinworms, the doctor may prescribe a soothing cream or ointment to be applied to the perianal area. The doctor will also advise the patient to avoid scratching the affected area as much as possible to prevent the spread of the infestation and to keep the patient from reinfecting himself.

Proper hygiene is also recommended during treatment and to prevent further infestation, including keeping hands and fingernails clean, wiping toilet seats with disinfectant, and washing all items, like clothing or personal belongings that may have come into contact with the infected person.

Adults should remind susceptible children to shower everyday, avoid scratching their anal area, to wash their hands when needed, and change their underwear daily. Keeping the house clean is also advisable.
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Medication commonly used for these disease:

drugs Pinworm drugs