Module 9 - Enterobius Vermicularis - Nematode

seatworm or pinworm

enterobiasis or oxyuriasis

They both mean the same. Oxy- pointed and uris, or tail. Vermicularis - worm like.

school or pre-school children and in crowded conditions

oval

it is clear, colorless and doubly refractive egg shell flattened on one side "D-shape"

• Adult worm has 2 anterior circular wing like expansion (alae)
• 2 lateral thickening along the length of the worm,
• three refratcile lips
• double bulbed esophagus

Female has a posterior end that is straight with long pointed tail and the male has a posterior end which is curved ventrally with one spicule.

Females are much larger than males

They need to obtain the oxygen necessary for maturation of the egg.

1. Infection occurs via self-inoculation (transferring eggs to the mouth with hands that have scratched the perianal area) or through exposure to eggs in the environment (e.g. contaminated surfaces, clothes, bed linens, etc.)

2.Following ingestion of infective eggs, the larvae hatch in the small intestine 

3.and the adults establish themselves in the colon, usually in the cecum 

4.The time interval from ingestion of infective eggs to oviposition by the adult females is about one month.

5.Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area 

6.The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions

When eggs are released or when female worm emerge in the perianal area.

When larvae are ingested by humans, could be from self- inoculation.

B.asymptomatic

perianal pruritus  or anal itching.

It is thought to be an allergic reaction to the presence of either the adult female of the egg. It is most notable during night.

• Weight loss
• Scratching predisposes to secondary bacterial infection.

scotch tape swab method..

• Mebendazole and albendazole, 1 dose at first, 2nd dose repeated after 2 weeks.
• Topical insecticides containing malathion can be applied on skin.

• 1.Wash hands with soap and water (after using toilet, before eating
• 2. Trimming nails regularly and avoid biting nails
• 3.Avoid scratching anal area
• 4.Showering every morning and washing the anal area to remove eggs
• 5.Do not co-path with infected people.
• 6. Cleaning bathroom and toilet