Pinworm infection

What is a pinworm?

• Pinworm infection (Enterobius vermicularis) is most common in children aged 3–10, but older children and adults can also become infected.
• Pinworms occur only in humans. They live in the human intestine.
• Pinworms occur worldwide. In Finland, they are the most common cause of worm infections.
• The pale pinworm, measuring 3–13 millimetres in length, can be seen with the naked eye. The eggs cannot be seen with the naked eye.

Transmission and symptoms of pinworms

• Pinworm infection is not related to poor hygiene or inadequate care.
• Pinworm eggs usually enter the mouth through the fingers.
• It takes about one month for the egg to develop into a worm in the intestine.

• The worms lay eggs in the anal area, especially at night.

  The movement of the worm and the secretion on the surface of the eggs can cause intense itching in the anal area.

• As a result of scratching, worm eggs get onto the fingers and under the nails and can easily end up in the person’s own mouth. From the hands, the sticky eggs can attach to toys, door handles, towels and bed linen and be transferred from these to other people’s hands.
• Pinworm eggs remain infectious on surfaces and bed linen for several days and even weeks.
• A large proportion of pinworm infections are asymptomatic.
• In some cases, pinworms may cause pain in the bottom or stomach in addition to itching.
• Symptoms usually begin 1–2 months after swallowing one or more eggs.

Detection

• To confirm the infection, it is sufficient to see pale, moving pinworms about 1 cm long around the child’s anus. The worms resemble small pieces of thread.
• In unclear cases, a laboratory sample can be taken. A referral for the test is issued by the health station. The sample is taken with a cotton swab from the skin around the anal opening, not from stool. If the sample is taken at home, follow the sampling instructions carefully.

Treatment

• A confirmed pinworm infection is treated with an antiparasitic medication in tablet form. Pyrvinium embonate (Pyrvin®) is available from pharmacies without a prescription. Follow the instructions on the package. A physician can prescribe mebendazole (Vermox®). Both are effective.
• Even asymptomatic persons living in the same household are treated.
• The treatment is repeated for all persons living in the same household after two weeks.
• Pregnant individuals can use pyrvinium.
• Pinworms are rare in infants. Pyrvinium can be used when the child approaches a weight of 10 kg.

Hygiene and cleaning measures

• Wash your hands with soap and dry them carefully, especially after using the toilet, before eating and preparing food, and after doing laundry and cleaning.
• Keep the nails short and clean.
• Clean and do the laundry on the day after taking the medication:
  • Change underwear, nightwear, towels and the bed linen that has been in use. Place the textiles directly in the washing machine, avoiding unnecessary shaking. Wash at 60°C and/or tumble dry.

  • Change underwear in the morning and in the evening for one week.

    Vacuum mattresses and mattress toppers. Wash duvets and pillows or remove them from use for about one week.

  • Do the usual weekly cleaning: vacuum and wipe floors and other household surfaces with a damp cleaning cloth.
  • Clean the contact surfaces in the toilet and bathroom carefully.
  • Clean toys with household cleaning products and wash soft toys. Keep toys that cannot be washed out of use for about one week.
  • Repeat the cleaning measures two weeks later when the treatment is repeated.
• Sometimes repeated courses of medication and cleaning are required to eliminate pinworms.

Pinworm infections in day care centres and schools

• Pinworm infection does not require absence from early childhood education or school.
• If a child in day care is found to have pinworms, it is advisable to inform the day care staff.
• Pinworms can cause outbreaks in families and in early childhood education. In the case of a widespread outbreak in a day care centre, the physician responsible for infectious diseases in Helsinki may recommend simultaneous treatment of the entire child group.

Prepared by: Epidemiological Operations