Threadworm infection

Question 1

Define threadworm infection.

Answer 1

AKA pinworm/Enterobius vermicularis is a common parasitic worm which infests the human gut

Question 2

What organisms cause threadworm infections?

Answer 2

Enterobius vermicularis, sometimes called pinworms

Question 3

How common is threadworm infection?

Answer 3

Commonest parasitic worm infestation in the UK
Mainly in children
Up to 40% have threadworm infestation at some point in their life - much is asymptomatic

Question 4

What type of infection is threadworm?

Answer 4

Helminth - Enterobius vermicularis

Question 5

Describe threadworms and their phases.

Answer 5

• Threadworms have a white, thread-like appearance — adult males are 2–5 mm in length and adult females 8–13 mm.
• Threadworm eggs are not visible to the naked eye and can survive for up to 2 weeks.
• Humans are thought to be the only host

Question 6

What symptoms are associated with threadworm infection in a child?

Answer 6

• Intense perianal itching (particularly at night)
• Some asymptomatic but may see moving worms in stools/on perianal skin
• Pruritus vulvae
• Secondary bacterial infection from itching

Question 7

How does threadworm infection occur?

Answer 7

• Faeco-oral - swallowing eggs from the environment. Eggs mature within 1-2months in the small intestine
• Adult threadworms survive for 6 weeks and infection is maintained by swallowing of fresh eggs

Question 8

How do you diagnose threadworm?

Answer 8

• History of itching
• Examining perianal area showing worms
• Arrange adhesive tape test for eggs - may need to examine over 3 consecutive mornings to confirm diagnosis

Question 9

What sample is sent to the lab for testing for threadworm?

Answer 9

Sellotape applied to the perianal area for microscopy

Question 10

What is the treatment for threadworm?

Answer 10

• Mebendazole (children >6 months) SINGLE DOSE and for the whole family . Second dose can be given 2 weeks later if required.
• Hygiene measures for 2 weeks - hand washing, cut fingernails, shower each morning, change bed linen daily for several days, dust and vacuum including mattress

Question 11

What are the complications and prognosis of threadworm?

Answer 11

• Lack of sleep due to itching
• Excoriation and secondary infection of perianal skin
• Disease due to migration e.g. genito-urinary tract pruritus vulvae, vaginitis, salpingitis or urethritis
• Colitis, abscess and granuloma formation within the intestines

Prognosis - lifecycle lasts 2months but re-infection is common and unlikely to resolve without treatment

Question 12

What are some differentials for threadworm?

Answer 12

Atopic/contact dermatitis
Psoriasis
Lichen planus
Infection - pubic lice, candida
IBD
Roundworm - these are much larger up to 30cm
Tapeworm - segments may be seen in stools as single proglottids (grains of rice)