Other names for threadworms

Enterobius vermicularis
Formerly known as Occiyur vermicularis or oxyurides

Threadworm epidemiology

30% of children are infected with the parasite - most commonly 7-11 year olds
F:M = 3:1
Commonly seen in temperate climates and in areas with overcrowding and poor sanitation

Threadworm modes of transmission

Route of infection usually via human ingestion of ova i.e.faecal-oral transmission by contaminated fingers or fomites.
Airborne infection via through airborne eggs that are dislodged from bed linens/clothes/walls/carpets/curtains.
Retroinfection - in this

Lifecycle of threadworm

The eggs contain a partially developed juvenile that can develop to infectivity within 6 hours at body temperature, are swallowed and hatch in the duodenum. Once ingested the immature worms move slowly down the small intestine and are adults by the time o

Clinical features of threadworm infection

1/3 asymptomatic.
Pruritus ani, usually in bed at night.
May see worms - can appear as flakes of skin or tiny pieces of white cotton.

Complications of threadworms

Can mimic appendicitis or appendiceal "colic".
Most common extraintestinal site is female genital tract causing vaginitis, endometritis, tubo-ovarian abscess, PID, infertility. Should consider the diagnosis in pre-pubertal females with vaginal discharge,

Diagnosis of threadworm

Usually clinical.
In rare cases: early morning application of transparent sellotape or moistened swab to anus to collect eggs for microscopic identification - on 3 consecutive mornings after waking up and before wiping/washing - place tape in specimen pot

Threadworm treatment

>=2yo: 1 dose initially and then a further dose in 2 weeks of either mebendazole (most effective), pyrantel pamoate or albendazole.
The drugs do not harm threadworm eggs, which may remain viable for up to 2 weeks. To avoid re-infection it is important to

Threadworms and school/nursery

Do not need to be kept off school/nursery

Rare S/Es of mebendazole

Abdo pain, diarrhoea

Is mebendazole available from the pharmacy?


Threadworm hygiene measures

Thorough handwashing with soap and warm water and fingernail cleaning after using the toilet, changing diapers, and before handling food.
Discouragement of thumb sucking, cutting fingernails regularly, and avoiding biting the nails and scratching around t

Threadworm in pregnancy

No reported cases of causing harm to foetus.
Has not been linked to poor pregnancy outcome.

Treatment of threadworm in pregnancy and breastfeeding

Mebendazole therapy during pregnancy and breast-feeding does not appear to be associated with a significant increase in major congenital defects, but most advocate no treatment until after delivery unless the potential benefit greatly outweighs the risk t

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