Enterobius vermicularis

Phylum: Nemathelminthes
Class: Nematoda
Order: Ascaroidea
Family: Ozyuridae
Genus: Enterobius  
Species: Enterobius vermicularis

Ascaris lumbricoides

Geographical Distribution

• This is one of few parasites which is more prevalent in the temperate regions of the world than the tropic.
• Children are more often involved.
• Groups living together like families, hostels, army camps etc.

Morphology

• Size of adults;
• Male : 5 mm long and 0.1 - 0.2 mm in diameter.
• Female : 13 mm long and 0.3 - 0.5 mm in diameter.
• Anterior end has 3 small lips without dentitions.
• The esophagus has a globular swelling at the posterior end.
• Gravid female has 2 distended uteri which almost fill the whole body.
• Male has curved tail and a spicule.
• The cuticle has a distinct cervical alae.
• The eggs appear flattened on one side.
• Egg has thick transparent shell. Unembrionated when passed out but become infective within a few hours.

Enterobius vermucularis egg

Enterobius vermucularis adults

Life Cycle

• The adults are mainly located in the caecal region.
• Female deposit eggs on the anus and perianal skin.
• Infection occurs by inhaling and swallowing the eggs.
• Autoinfection occurs by contamination of the fingers.
• There is no visceral migration.
• Larva matures into the adult in the lumen of the intestinal tract.
• Life cycle is completed in 6 weeks.

Life cycle