The thread worm, or threadworm, is the most common of human parasites. Thread worms are scientifically known as Enterobius vermicularis, but are also commonly referred to as pinworms and seatworms. This species does not transmit to or from animals, although pets can harbor eggs in the fur. They get their names from a resemblance to cotton threads, which are visible to the naked eye.

Threadworms can affect any age but are most prevalent in children, who may inadvertently transfer the eggs after scratching. They thrive in dust and can be inhaled. These worms can be visibly identified in a bowel movement. They’re also easily spotted with a flashlight when the anal area is inspected at bedtime. Humans rarely become ill from threadworm but may suffer intense itching around the anal area, especially at night. This can lead to interrupted sleep. In worst cases, urinary tract infections can develop and females are susceptible to vaginitis. Secondary infections can occur, too, if a child or adult scratches the area. A child may suddenly begin bed-wetting as well. This can be due to threadworm irritation in the urethra.

While it is assumed that the spread among children is related to less concern for hygiene, thread worms can progress rapidly among adults. The entire family should be treated when one is infected. And lack of personal cleanliness is not the precise reason behind contracting threadworm. Contact with an infected person or touching a surface the person has come in contact with will cause a rapid spread. Thread worms can survive on toilet seats, in clothing, and even in swimming pools.

Once the egg is consumed or inhaled, it travels to the small intestine and hatches. As larvae, the threadworms navigate into the large intestine, grow into adults, and mate. The male then dies, while the female lives on for about eight weeks. When she is ready to lay eggs, the female threadworm moves to the outer anal area. One adult can produce about 10,000 eggs at one time. She dies and the eggs begin the cycle again. The itchiness comes from a sticky coating on the egg sac. When the coating dries, the eggs can become airborne. The eggs are light and float along with dust particles.

Reinfestation can also occur. If the eggs remain intact on their host until hatching, they will return to the large intestine to reach the adult stage.

Of course, handwashing is essential for everyone, but especially so for those with thread worm. Fingernails should be scrubbed underneath and kept short. Over the counter treatments are readily available and typically resolve the problem within ten days. However, young children should visit a physician for diagnosis. Other precautions include no sharing of belongings or food, daily morning showers, and a nightly change of underwear and sleepwear. Clean bedding regularly and dust daily, if possible. Vacuum carpets thoroughly and keep baseboards clear.

Thread worms remain the most common human parasitic infection, but one that is easily treated.