Enterobius Vermicularis (round worm, seat worm)
It is commonly known as thread worm or pin worm or seatworm.
It is a nematode and a common intestinal parasite, or helminth, especially in humans.
It produce diseases called enterobiasis.
It is an intestinal nematode present in caecum and vermiform appendix of human being.
Morphology
Adult worm is small and white in colour.
It resemble short piece of thread.
Size and shape
Male measures 2 to 4 mm in length and 0.1 - 0.2 mm around middle.
Female is 8- 12 mm in length and 0.3-0.5 mm around middle.
Sources and mode of Transmission
It is transmitted by oro-fecal route (through infected fingers nail, infected soil, linen) and auto infection through infected fingers nail.
Pathogenesis and clinical significance
Children are usually affected
The first infection is due to contaminated food and drink.
Autoinfection may occur by carrying eggs on their fingers while scratching the affected Perianal area and cause itching area.
Symptoms
Stomach pain
Strong itching of anal area
Pain/ rash skin irritation around anus.
Presence of pinworm in stool
Presence of pinworm in area of child's anus.
The disease is spread between people by pinworm egg.
Cause irritation in urethra.
Life cycle
Man is definitive host and there is no intermediate host.
Life cycle of this worm is completed in single host.
Infection occurs by ingestion of egg which contain larvae, by fingers nail, infected host, linen etc.
Which scratching Perianal skin containing egg.
The eggs are swallowd when hands are not properly washed.
After that egg enter in gastrointestinal tract where egg's dissolve and larvae is released.
Larvae escape in small intestine and develop into male and female adult worms.
The male worm fertilize the female worm and dies.
Gravid (fertilized) female then migrate to caecum of large intestine and remain there until eggs develop.
At night, fertilized female comes out of anus to lay agg on Perianal skin.
Irritation occur on Perianal region due to worm egg what person scratch perianal skin containing egg and enter in finger nail and cycle is repeated.
1. Human ingest infective fertilized egg by contamination of finger during scratching from mouth egg mouth egg enter Gastrointestinal tract, where larva is released.
2. Adult in intestine male worm fertilize female worm and dies.
3. Fertilized female then move to caecum of large intestine and colon untill egg mature.
4. Migration of female worm from anus at night.
5. Deposition of eggs in Perianal areas.
Laboratory Diagnosis
Specimen collection
Perianal swab and stool specimen collected by NIH swab.
Microscopic examination
Examination of adult worms in stool specimen and Perianal areas are important for diagnosis.
Treatment
Thiabendazole, mebendazole are effective for treatment.
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