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Pinworms

Author: Daniel Jun Yi Wong, Medical Student, University of Melbourne, Australia, 2012. DermNet NZ Update September 2021


Pinworms — codes and concepts
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What are pinworms?

Pinworms (Enterobius vermicularis) are also called threadworms or seatworms, and the condition they cause is called enterobiasis or, the older term, oxyuriasis.

Who gets pinworms?

Infestationorinfection蛲虫是最常见的在t school-aged children, in some communities affecting up to two-thirds of children aged 5-10 years. Family members are at particular risk of acquiring pinworms.

Some studies report a male predominance.

The worldwide infestation rate is estimated to be 1 billion. It can affect all social classes, races, and countries.

What causes pinworm infestation?

Pinworms belong to the phylum Nematoda. They have a long thread-like appearance, are a white-beige colour, and round in shape (roundworm). They are visible to the naked eye - the female pinworm is 9-12 mm in length while the male is much shorter, 3-5 mm. Thetranslucenteggs are anasymmetricalelongated oval shape visible under amicroscope.

Why are pinworms so itchy at night?

At night, the female adult pinworm emerges from theanusto deposit eggs onto the skin around the anus. It is thought to be the movement of the female worms that causes the itch. The eggs are attached to the skin with an adhesive mix. After exposure to the air, themicroscopiceggs mature and are typically infectious within a few hours. They can survive for up to 2 weeks on the skin.

How do pinworms spread?

The main way that pinworms spread is through swallowing the eggs. When someone with pinworm scratches theirperianalskin, the eggs are lodged beneath their fingernails, and can be deposited on clothing, toys, and furniture.Infestedindividualsingestthe eggs (auto-infection) when biting theirnails, or putting fingers in their mouth.

Others can come in contact with pinworm eggs and ingest them unknowingly, although the eggs survive only a few days in the environment.

蛲虫感染可以spread during sexual intercourse.

What are the clinical features of pinworm infestation?

The most commonsymptomcaused by pinworms is itching around the anus. The itchiness tends to be worse at night when the female worms are active on the skin surface and can cause trouble sleeping.

The adult worms sometimes migrate to thevaginainstead of returning to the bowel. This may result in an itchyvaginitiswith amucousor blood-staineddischarge.

Severe infestations rarely result in abdominal pain, nausea, or vomiting.

However 40% of infested individuals have minimal symptoms or areasymptomatic

What are the complications of pinworm infestation?

  • Urinary tract infection particularly in children
  • Secondarybacterialinfection of the perianal skin
  • Perianalgranuloma
  • Rarely involvement of other organs such as the liver

How is pinworm infection confirmed?

The adult worms can be seen with the naked eye, as thin, white, wriggling threads: look at the anus at night or at the surface of bowel motions.

The ‘sticky tape’ test involves sticking a piece of clear adhesive tape to the crease of the anus, and is best carried out at night. The tape should catch any pinworm eggs, which can be confirmed by looking at the tape under the microscope.

Pinworms

How are pinworms treated?

It is important to prevent the spread of infection by maintaining good hygiene (hand washing with soap and water, keeping fingernails short, taking a shower or bath daily), washing linen and clothes in hot water (>40C), and trying not to scratch in order to prevent contact with the pinworm eggs.

Mildinfectionscan clear by themselves. However, pinworm infestation is usually treated with albendazole ormebendazole. A single dose has a high cure rate. A second dose two weeks later helps to preventrecurrenceof the infection. After each dose bed linen should be changed and the bedroom vacuumed.

Topicaltreatment of the itch may be required.

What is the outcome of pinworm infestation?

Because re-infection is common, the whole family should be treated at the same time to prevent recurrence and spread of infection to others.

See smartphone apps to check your skin.
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Bibliography:

  • Caldwell JP. Pinworms (enterobius vermicularis).Can Fam Physician. 1982;28:306-9.PubMed Central
  • Wendt S, Trawinski H, Schubert S, Rodloff AC, Mössner J, Lübbert C. The diagnosis and treatment of pinworm infection.Dtsch Arztebl Int. 2019;116(13):213-19. doi:10.3238/arztebl.2019.0213Journal

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