Enterobius vermicularis, or pinworm, is the most common childhood helminth infection in developed countries, with humans as the only host. The life cycle involves mature gravid females laying eggs on perianal skin, leading to symptoms such as anal itching, insomnia, and irritability. Diagnosis is made by detecting eggs in feces or perianal swabs, and treatment includes medications like albendazole and mebendazole.

1. Enterobius vermicularis
Pin worm

2. Enterobius vermicularis
• Intestinal nematode
• Most common childhood helminth infection in the developed world
• Humans are the only host
• No multiplication inside the body
• Natural habitat – caecum, appendix and adjacent ascending colon
• No soil development phase

3. Life Cycle

5. Life cycle
Mature gravid
female with eggs
in the ovary
Migrate to the
anus
Lay the eggs on
perianal skin
Ingestion of eggs
Eggs hatch in the
stomach
LarvaeRapid growth
Pass through
caecum,
appendix
Invade glandular
crypts and
mature
Again female
becomes gravid

6. Morphology
Adult worm
• Small white
• Double bulb
esophagus
• Mouth surrounded
by a cuticular
expansion
• Skin- transversely
striated
Adult male
• Posteriorly curved
• Blunt caudal
extremity
• Smaller (2.5 mm)
Adult female
• Long pointed tail
• Slit like vulva in
anterior ¼ of the
body

7. Morphology
Eggs
• Flattened on one side
• Plano-convex
• Colourless
• Double contour shell
• Fully formed embryo
inside

8. Transmission
Contaminated food and water
Autoinfection
• Scratching of perianal skin leads to deposition of eggs in finger
nails
Retroinfection
• Eggs laid on the perianal skin immediately hatch and larvae
migrate into the colon and develop into worms

9. In Majority
Enterobius lives out
its normal life span in
the caecum and
appendix
Migrate down to the
anus to lay eggs
Larvae re-establish in
the host causing few
/ no symptoms

10. Clinical features
• Pruritis anus (itchy anus)
• Vulvitis
• Insomnia
• Restlessness
• Loss of appetite
• Loss of weight
• Irritability
• No anaemia
• No eosinophilia

11. Diagnosis
• Eggs in faeces
• Perianal scrapings / swabs
• Usually at night

12. Treatment
• Albendazole
• Mebendazole
• Pyrantel pamoate
• Piperazine

13. Thank you