ENTEROBIUS VERMICULARIS Flashcards
Common name:
Pinworm, Oxyuris, seatworm
DISTRIBUTION
Cosmopolitan, more in temperate and cold climates
* Considered world’s most common parasite affecting children
Habitat:
- Caecum, appendix, ascending colon.
- attachement unknown.
Why is Enterobiasis known as a group infection?
Takes place in large families and in institutions including orphanages, boarding schools, mental homes and hospitals.
Male morphology
2-5mm curved tail ventrad,
Single copulatory spicule
Female morphology
8-13mm
Tail sharply pointed like a pin ,
Gravid uteri-greatly distended,
and Entire body filled with eggs.
Eggs morphology
elongate, ovoid
Compressed laterally
Resistant to disinfectant
Transmission
- Fingers - direct anus to mouth
- Bedclothes, underwear, fomites, airborne
Types of Infections
- Infection
- Re-infection (Self infection)
- Retro-infection
Infection
Occurs when healthy person ingest
the infective eggs from the environment
Re-infection (Self infection)
A person can re-infect themselves on their own ( by ingestion of infective eggs)
Retro-infection
This occur when eggs mature
and larvae hatch in anal area, this larva can migrate back to the large intestine through the anus, where they grow into mature worms
LIFE CYCLE
①Oviparous, meaning it lays eggs.
②It is monoxenous, completing its entire life cycle within a human host.
③Transmission; ingesting these eggs, with airborne also possible.
(Factors such as inadequate hygiene and nail biting can promote infection).
④The life cycle of the worm is completed within the intestines.
⑤After males fertilize the females, they die.
⑥Gravid females, carrying eggs, migrate from the colon to the perianal and perineal skin, where they lay approximately 10,000 to 11,000 eggs all at once before perishing.
⑦These eggs become embryonated and infective within 4 to 6 hours.
⑧Notably, no egg release occurs within the intestines.
⑨Adult worms may be found in feces after enemas.
Pathogenicity and Symptoms
①Sensations and Skin Reactions: Infected individuals may experience a crawling sensation due to migrating females.
＝This can lead to perianal pruritus (itching around the anus), which often results in scratching and scarification (scarring) of the anus.
②Immune and Digestive Responses: Enterobiasis can cause eosinophilia. It can also lead to appendicitis, inflammation of the appendix.
③Effects in Children: nervousness, insomnia, and nightmares. It can also lead to convulsions. Children may complain about being bitten at the anus, rectal discomfort, and “wandering worms.”
④Effects in Adolescent and Adult Females ages of 14 and 45； female worms can migrate to the vulva, vagina, and genitalia, and even up to the fallopian tubes. This can result in chronic salpingitis, inflammation of the fallopian tubes. The disease can also cause urinary and genital disturbances, including vaginal discharge.
DIAGNOSIS
①Patient History
②The presence of eggs or adult worms in the perineal skin (the area between the anus and the genitals) confirms the diagnosis.
③Tape Test: A common diagnostic method is the use of cellulose or Scotch tape. The tape is stuck to the skin around the anus, then transferred to a slide for microscopic examination. This test is used to detect the presence of eggs. 4-6 tape samples for a more accurate diagnosis.
④Anal Swab: An anal swab can also be used for diagnosis. Night samples are recommended as the female worms are more likely to lay eggs at night.
⑤Enemas: Adult worms may also be found in feces after enemas. This can further confirm the diagnosis.
