Anal Itching Pinworm

Pinworm is a common intestinal parasitic infection that primarily affects children, while parents get infected by transmission through their children. Pinworms are small, about 1/4 to 1/2 inches long, round, white colored nematodes that live generally in the cecum, appendix, ascending colon and rectum in humans (often confused as cotton threads while seen in the anal area) causing severe perianal itching once the female worms moves out to the anus and lay eggs around the anus.

Synonyms

Seatworm, threadworm, Enterobius vermicularis.

Epidemiology

Worldwide, with infections more frequent in school- or preschool- children and in crowded conditions. This parasitic worm is found both in warm and cold climates but enterobiasis (infection with Enterobius vermicularis, the human pinworm) appears to be more common in temperate than tropical countries. Eggs can be found in crowded places such as daycare centres, schools, cinema halls and hospitals. It is the most common worm (helminthic) infection in the United States (an estimated 40 million persons infected).

Symptoms

Although pinworms are usually asymptomatic inhabitants of the intestine, when they do cause symptoms there can be a spectrum of complaints including perianal nocturnal itching, teeth grinding, poor appetite, whining, hyperactivity, nervousness, irritability, insomnia, bed-wetting, stomach aches, nausea and vomiting.

Diagnosis

Microscopic examination of perianal swab, butt paddle or butt tape (Sellotape slide/cellophane slide or Scotch tape) to confirm the presence of eggs/larvae. Eggs are not found in stools.

Spread

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 occurs through handling of contaminated food, clothes or bed linens. Enterobiasis can also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g., furniture, toys, curtains, carpeting). Small number of eggs may become airborne and inhaled. These would be swallowed and follow the same development as ingested eggs.

Life cycle

Pinworms in the anus seen as cotton threads.

Following the 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 anywhere from two to six weeks. 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 eggs become infective in four to six hours under optimal conditions. Retroinfection or the migration of newly hatched larvae from the anal skin back into the rectum is also possible.

Contagious?

Pinworms are an extremely contagious worm infection. The eggs can lay dormant up to two weeks if they are kept at room temperature and they can be found everywhere. The pinworm eggs cause your butt to itch, so you scratch at it, and the pinworm eggs get everywhere – under your nails, on your clothes, furniture, bedding, toilets, bathrooms, toys, food and even in the dust that hangs around your home. Once this happens, your entire family and their close contacts are almost guaranteed to get the same infection.

Prevention

• Clean everything the infected person has come into contact with, which includes mopping floors to avoid kicking up dust that may contain worm eggs apart from washing undergarments, sleeping clothes and bed spreads.
• Keep hands always clean. Trim nails. Wash hands after a toilet visit.
• Wash hands before preparation/consumption of food.
• Any anti-bacterial soap will usually insure a worm-free existence. Remember to wash hands after visiting public places like schools, gyms, public transport, cinema halls and any large institution. (Hope all these would make you aware of the importance of washing hands.)
• Discourage thumb sucking/nail biting of children.
• Keep hands away from butts on all other occasions.
• Deworm regularly or as directed by your primary physician.

Other possible infection

Pinworm vaginitis. This parasite also has been suspected as a cause of appendicitis as histologic findings of acute appendicitis demonstrated pinworms at the section.

Medications

Antiparasitic medications are available. Mebendazole and Pyrantel pamoate are the most commonly prescribed drugs which are usually taken by the whole family in two doses, two weeks apart. Talk to your doctor for the appropriate dosages and intervals.

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