Threadworm

Introduction

Threadworm or pinworm (Enterobius vermicularis) is a parasitic worm that infects the intestines of human. It is very common in young children, and patients may seek advice from the pharmacist.

  • Eggs are transmitted to the human host primarily by the faecal-oral route (autoinfection) but also by retroinfection and inhalation.

Threadworm



Clinical Features

Most infections are asymptomatic.

Night-time perianal itching is the classic presentation (caused from the mucous produced by females when laying eggs). However, patients might experience symptoms ranging from a local tickling sensation to acute pain.

  • Itching can lead to sleep disturbances, resulting in irritability and tiredness the next day.
Diagnosis can be confirmed by observing threadworm on the stool, although they are not always visible.

  • Threadworms can survive outside the body for a short time and hence may be seen to be moving.



Conditions to Eliminate

Patients with roundworm and tapeworm infections experience non-specific abdominal symptoms such as loss of appetite, nausea and altered bowel habit.

Occasionally, dermatitis can cause perianal itching (especially in adults). If there is no recent family history of threadworm or there is no visible sign of threadworm on the faeces, dermatitis is possible.



Medications

Options for nonpregnant adults and children include albendazole, mebendazole and pyrantel pamoate. Reinfection is common and a second does should be given after 2 weeks.

  • Mebendazole 100 mg (child >6 months and 10 kg or less, 50 mg) orally, as a single dose.
    • The drug of choice for treating threadworm infection in patients of all ages over 6 months.
    • Avoid during first trimester of pregnancy.
  • Albendazole 400 mg (child >6 months and 10 kg or less, 200 mg) orally, as a single dose.
    • Albendazole is taken on an empty stomach to minimize absorption when used for intestinal infections and with food to increase absorption when used for systemic infections.
    • Use effective contraception during, and for 1 month after, albendazole treatment.
  • Pyrantel (adult and child >1 year) 10 mg/kg up to 1 g orally, as a single dose.
    • Pyrantel pamoate is favoured over mebendazole or albendazole for treatment of symptomatic enterobiasis in pregnant women.

Simultaneous treatment of the entire household is warranted given high transmission rates among families. In addition, all bedding and clothes should be washed.

NOTE: Treatment of enterobiasis in pregnant women should be reserved for patients with significant symptoms.



Hygienic Measures

Provide advice on hygiene measures to reduce the risk of reinfection and spread of infection.

  • A bath, or shower, with washing of the perianal area, immediately after rising will remove eggs laid during the night.
  • Getting the family to wash hands and scrubbing nails on getting up in the morning, before each meal and after each visit to the toilet is an essential part of management. This includes after changing nappies.
  • Discourage nail biting and finger sucking.
  • Some people advocate frequent washing of cuddly toys and bed linen as well.



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