Research Laboratory: Pinworms

(Enterobius vermicularis, Oxyuris spp.)

Pinworms generally live in the large intestine and cecum. It is found worldwide, and causes the most common infection enterobiasis in humans. Unlike many other intestinal parasites, the pinworm does not usually enter the bloodstream or any other organs besides the intestines. Only in rare cases are pinworms found in the vagina, and even more rarely in the uterus, fallopian tubes, liver, and peritoneum, but the worms cannot survive long in these places.

Over 200 million people worldwide are thought to be infested by pinworms with 30 to 40 million living in the United States. This worm is found in both warm and cold climates and no socioeconomic group is immune to infection. It is commonly found in crowded institutions such as day-care centers, schools, hospitals and orphanages. It is most prevalent in children. They are tiny, 2-13 millimeters, and ivory or pearly-white in color. Up to eighty percent of the children between 2 and 10 years of age contract pinworms at some time. Children are more likely than adults to acquire the infestation because they are more likely to play with soil and mud and insert their fingers in their mouths without washing them first.

Adult pinworms inhabit the cecum and other portions of the large and small intestines. Female worms crawl down the intestines and pass out of the anus to lay their eggs around the anal region at night. Occasionally, they can be found on the first stool in the morning. One female can deposit over 15,000 eggs that become infective immediately or within a few hours.

This common occuring worm is acquired through contaminated food, water, and house dust, as well as human-to-human contact. The crawling of the female worm on the skin around the anal area often produces intense itching causing a person to scratch there, getting the eggs on the hands. Without washing, the hands touch the mouth. Now the eggs are swallowed and hatch in the lower colon where the pinworms mate, and cycle continues.

The eggs are usually found on the infected person's pajamas and bed linen. Children can easily infect the entire family through the bathtub, toilet seat, and bedclothes. The eggs are easily transported by air currents making it common to find them in every room of the house; on sheets, clothes, walls and carpets. They can easily stay viable for weeks. Infections and reinfections continue by wearing clothes or sleeping in the bed of an infected person, as well as handling infected pets. It can be passed from an infected person that handles the food in the household. If one person in the family has pinworms, it is common to find others infected as well. This is a very contagious organism.

Complications are much more common in women than in men. This stems from the fact that the female worm, after depositing her eggs, loses her way while trying to return to the colon. She enters the vagina instead, traveling up the uterus and fallopian tubes.

Itching around the anal or vaginal areas are the most common pinworm symptoms. Suspect a pinworm infection if your child shows night time itching in these areas. Symptoms also include poor appetite, teeth grinding, hyperactivity, nervousness, irritability, insomnia, bed wetting, stomach aches, nausea and vomiting. Sometimes the anal area becomes infected with bacteria because of the constant scratching. Pinworms are also often found within the appendix and have been associated with acute and chronic inflammation.

Eggs are seldom found in the feces. A parent needs to inspect the child's rectal area at night when the child is sleeping for evidence of the organism. One way is to perform a Scotch tape test. The first thing in the morning pat the sticky side of the Scotch tape around the child's anal opening. Fold the tape together with the smooth side out, the pinworm eggs will be viewable under a microscope.

While doing a pinworm cleanse, it is also good to try to prevent infection and re-infection from pinworms. Bathe daily, but use one washcloth and towel for the face and hands, and another for the rest of the body. Don't reuse the towels before washing them. It is important to scrub hands after bathroom use and before eating. Keep toothbrushes in containers so they will not be contaminated. If there is someone infected in the household, they need to wear close-fitting underpants at all times, even when sleeping, and not share the bed with others. Bed linens and personal clothing must be washed daily. Scrub toilet seats, and clean and vacuum daily to remove eggs. Keep all rooms well aired out.

If you are consistent with the cleanse program and keep the dwelling place clean using the above mentioned tips; the pinworm infestation will soon be neutralized and the reinfection factor will be diminished.

Life Cycle Diagram (Courtesy of the DPD)

Eggs are deposited on perineal folds

Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perineal 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 pinworm adult is about two months. Gravid females migrate nocturnally outside the anus and deposit while crawling on the skin of the perineal 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.