Threadworm

Abstract

Threadworm or pinworm (Enterobius vermicularis) is a parasitic worm which infests the intestines of humans.Threadworm infestation occurs after swallowing eggs, usually by eating contaminated food or from contaminated hands.Threadworm is the most common parasitic worm infestation in the UK and is more likely to affect school or pre-school children than adults, because of their inattention to good personal hygiene and close contact with other children. Threadworms often affect family groups or institutions, especially if conditions are crowded. It is not necessary to exclude children with threadworms from school.The most common symptom is perianal itching, which is worse during the night. Infestation may be symptomless and only detected when threadworms are seen on the perianal skin or in the stools.There may be signs of scratching in the perianal area and sometimes localized secondary bacterial infection. It is unusual to see worms in the perianal area when the person is examined during the day.If the diagnosis is uncertain, the adhesive tape test for eggs may be useful. Transparent tape is applied to the perianal area first thing in the morning and then examined under a microscope to detect threadworm eggs. Stool examination is not generally recommended.Other causes of perineal itch include dermatitis, candidal infection, and haemorrhoids. Threadworms are rarely confused with other types of worm infestation because of their different appearance.Treatment is recommended if threadworms have been seen or eggs detected treatment. All household members should be treated at the same time.For adults and children aged over 6 months, an anthelmintic (mebendazole) combined with hygiene measures is recommended.For children aged 6 months and under, hygiene measures alone are recommended.For people who do not wish to take an anthelmintic, physical removal of the eggs, combined with hygiene measures is recommended.For pregnant or breastfeeding women, physical removal of eggs combined with hygiene methods is the preferred treatment. Treatment with mebendazole is contraindicated in the first trimester of pregnancy; however, it can be considered in the second or third trimester, or during breastfeeding if drug treatment is considered necessary (off-label use).If infestation persists after hygiene measures have been continued for the recommended duration, a further course of drug treatment is recommended. It is important that household members are treated and adhere to hygiene measures.