Enterobius Vermicularis( Pin Worm Infection)

Question 1

Aetiology of Enterobius vermicularis

Answer 1

Causes pinworm infection ( enterobiasis)

Question 2

Morphology and host

Answer 2

Small white worm
Blunt posterior end with a single spicule
Long pointed tail
adult female is 8-13mm adult male 2-5mm
Eggs are thin walled, ovoid and flattened on one side: assymetrical.
Host- humans only

Question 3

Epidemiology

Answer 3

Worldwide spread but most common in temperate regions
Person to person spread is greatest in crowded areas( day care institutions, schools)
Fecal oral mode of transmission
Retro infection/ autoinfection can occur when larvae migrate from anal skin back to the rectum
No animal reservoir

Question 4

D- fragilis

Answer 4

Thought to be transmitted in pinworm eggs shell

Question 5

Mode of transmission

Answer 5

Fecal oral
Autoinfection

Question 6

Life cycle of Enterobius vermicularis

Answer 6

Infective stage: embryonated egg
Diagnostic stage: eggs obtained from perianal folds.

Ingested embryonated egg(infection withing hours) >Eggs hatch in small intestine and differentiate into adults>migrate to the large intestine> mature into adults(2-6wks) adults and live in the lumen of the caecum where mating occurs> At night the female migrates to the anus to lay eggs into the environment ( perianal folds)

Question 7

Clinical features of enterobiasis

Answer 7

Perianal pruritis- especially at night
Vulvovaginitis- esp in children
Nocturnal enuresis
Insomnia
Irritability/ restlessness
Loss of appetite
Weight loss
Symptoms of intestinal infection: nausea vomiting and abdominal pain

Question 8

T/F: symptoms of enterobiasis in high worm burden may mimic appendicitis

Answer 8

True

Question 9

T/F: female Enterobius vermicularis lives after laying eggs

Answer 9

False. Female dies after laying eggs

Question 10

Lab diagnosis of Enterobius vermicularis

Answer 10

Microscopy of eggs collected in the perianal area - morning before defecation by pressing transparent adhesive tape for 3 consecutive mornings.
Detection of eggs on anal mucosa by
- scotch tape test
- swube tube

Eosinophilia
Incidental finding on endoscopy.

Question 11

T/F: Enterobius vermicularis eggs can be found in stool

Answer 11

False. Rarely.
The eggs are laid on the perianal skin and difficult to observe in stool

Question 12

Describe the structure of the egg of Enterobius vermicularis

Answer 12

Elongated asymmetrical with one side flattened and the other side convex
Colourless
Stage when passed- embryonated contain C shaped tadpole like embryo

Question 13

Treatment

Answer 13

Pyrantel pamoate
Mebendazole
albendazole
Dose should be repeated in 2 weeks as reinfection can occur with deposited eggs after therapy

Question 14

Prevention of pinworm infection

Answer 14

Good personal hygiene
Thorough washing of beddings and clothes
Clipping off fingernails
Prompt treatment of infected individuals
Dusting with damp mop to avoid inhalation of eggs