3. Learning Objectives:
By the end of this session, students are expected to be
able to:
Explain the geographical distribution and habitat
Enterobius vermicularis.
Describe morphology of Enterobius vermicularis.
Describe the mode of transmission & life cycle of
Enterobius vermicularis.
Explain the diseases caused Enterobius vermicularis.
Explain the prevention and control of Enterobius
vermicularis.
Explain the laboratory diagnosis of Enterobius
vermicularis.
4. HISTORY AND DISTRIBUTION
Formerly “oxyuris vermicularis”
Enterobius vermicularis means tiny worm living in
intestine.
World most common parasite.
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6. Definition of terms
Buccal capsule= in nematodes is a structure
connecting the oral opening with the anterior portion
of the esophagus. It also called the stoma.
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7. Enterobiasis
Disease: Enterobiasis, Pinworm infection.
Infectious agent: Enterobius vermicularis an
intestinal nematode which causes
enterobiasis, an intestinal parasitic infestation
that occurs commonly in children.
Enterobius vermicularis is also known as the
thread worm, pin or seat worm
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8. Morphology
The adult worms are small cylindrical and
white
› Have three lips no buccal capsule and the
oesophagus has a posterior bulb characteristics
Female measure
› 8-13mm x 0.3-0.5mm long
› Paired uterine are filled with thousand of eggs
Male measure
› 2-5 x 20-30mm long
› Posteriorly curved
› Single spicule measuring 70µ long
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9. Morphology…
The eggs:
Measure 50-60 x 20-30µm
Oval in shape
Has a characteristic shape flattened on one site.
Eggs can be found in
specimens collected from perianal skin. Occasionally
eggs can also be found in faeces.
It is almost colorless with a bean –shaped double
contour shell containing a fully formed embryo
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10. Habitat
Adult inhabit large intestine and
they remain attached to the
mucosa of the caecum, vermiform
appendix and adjacent parts of the
large intestine.
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11. 11
Distribution/epidemiology:
Prevalent worldwide, in temperate and colder climates.
More common in children.
It occurs in family groups or institutions such as
schools especially under crowded conditions.
Infection is hand to mouth
Reservoir: Humans
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12. Mode of Transmission
There are four possible ways of transmission:-
1. The commonest is by direct transmission from
the anal and perianal region to the mouth by
finger nail contamination and by dirty night
clothes
2. By exposure to viable eggs on dirty bed linen
other contaminated objects in the environment
3. Via the mouth or nose from contaminated dust in
which embryonated eggs have been found.
4. By rectroinfection in which eggs hatch on the
anal mucosa and larva migrate up to the bowel.
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13. Life Cycle
Life cycle of E. vermicularis is simple and is
completed in a single host. Man is a natural host,
no intermediate host is required.
No multiplication inside the body.
Mature female has a duration of life of 37-93 days.
After mating, the fertilized gravid female migrates
to the rectum, pass out of the anus during the
night and deposit the eggs numbering between
5000-10,000, on the perianal and perineal skin.
The males dies immediately after fertilizing the
female & the female also dies after depositing the
eggs.
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14. Life Cycle…
Man acquires infection by ingestion of the
embryonated eggs through contaminated hands
with eggs lodged under the finger nails.
Eggs hatch in stomach and larvae emerge which
rapidly grow up to 140-150µm in length.
They pass through the intestine to the ceacum
and appendix where they invade the glandular
crypts and mature.
The whole cycle takes between two and four
weeks.
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15. Life Cycle…
The infective eggs may cause infection in the
same host(auto-infection) by hand to mouth
transfer or in other hosts through infective
linens and beddings.
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17. Pathology
The adult worm lives in the upper part of the
large intestine, especially the caecum and
lower ileum, where minute ulcerations may
develop at the site of attachment of the adult
worms to the caecal and appendiceal mucosa.
Sometimes haemorrhages occur and
secondary infection causes ulcers and
submucosal abscesses
Symptoms are caused when gravid females
migrate out of the anus into perianal skin to
deposit eggs, where they cause itching.
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18. Symptoms and signs
Most cases are asymptomatic.
Pruritus is the main symptom and varies from
a mild itching to acute pain which is mainly at
night.
Pruritus provokes scratching of the perianal
region resulting secondary infection.
Vulvitis may be caused by pinworm entering
the vulva causing mucoid discharge and
pruritus of vulva.
Vulvitis (inflammation of the vulva) is often
accompanied by intense itching.
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19. Symptoms and signs…
<10% anal pruritus; rarely vaginitis.
General symptoms are insomnia, and
restless, and considerable proportion of
children show loss of appetite, loss of
weight, irritability.
There is usually no eosinophilia or anaemia.
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20. Diagnosis
Microscopic identification of eggs in faeces
Eggs are present in the faeces of no more than 5% of
infected individuals
Perianal scrapings or swabs from finger nails
Finding adult worms around anus, usually at
night.
Applying transparent adhesive tape (scotch-tape)
swab to perianal region & examine the tape
microscopically for eggs (material obtained early in
the morning before bathing or defecation) 20
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23. Treatment
Pyrantel pomoate, Mebendazole
(vermox), Albendazole (zentel).
Treatment should be repeated after 2
weeks, concurrent treatment of the
whole family may be advisable if
several members are infected.
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24. Prevention
Educate the public in person hygiene,
particularly the need to wash hands before
eating or preparing food.
Removes source of infection by treatment of
cases
Daily morning baths
Frequent change to clean under clothing, night
clothes and bed sheets preferably after bathing.
Reduce overcrowding in living accommodations
Provide adequate sanitary facilities.
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26. Trichuris trichiura
Disease – whipworm disease, Trichuriasis
(whipworm infection).
Infectious agent: Trichuris trichiura
Habitat: large intestine; caecum, appendix &
rectum.
Occurrence: Worldwide, especially in warm and
moist regions.
Reservoir: humans.
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27. 2
7
Introduction
•Trichuris trichiura or Trichocephalus
trichiuris
•Inhabit a human large intestine (ceacum)
•Causing the disease known as
trichiuriasis.
•It is soil transmitted infection (eggs are
infective stage found in soil).
•Is commonly known as the whipworm
because it
looks like the whip.
29. Morphology
Common name –whipworm.
Adult - Small, pink-whitish, whip-like in
shape on anterior region.
Coiled and narrow at the anterior end and
wide at the tail end.
Male measure 4cm, posterior end curved
Female measure 5cm long.
The hair like tail anterior portion comprise
of 3/5 of the entire length of the parasite.
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30. • The worms has thin anterior and thick posterior part
• They attach to intestinal mucosa by embedding their
anterior part.
• They feed on tissue fluid (not blood).
3
0
31. Morphology…
• Both worms have an attenuated anterior
three-fifths traversed by a narrow
esophagus resembling a string of beads.
• And the robust posterior two-fifths
contain the intestine and a single set of
reproductive organs.
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33. Morphology…
Eggs;
Are lemon shaped with plug like
transculent polar prominences, barrel-
shaped with clear “ polar plugs”
Appear yellow in colour and measure
approximately 50µm x 25µm
Fertilized eggs are unsegmented.
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35. MODE OF TRANSMISSION
Transmission is direct from mature eggs to
the mouth via fingers, vegetables, water,
contaminated from infected soil, not
transmissible from person to person.
Eggs appear in the feces 70-90 days after
ingestion of the embryonated eggs;
symptoms may appear much earlier.
Children are more susceptible to infection
than adults due to their nature of playing
with faecally contaminated soil.
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36. LIFE CYCLE
Egg is laid unsegmented, required a minimum
of 10-14 days in warm moist soil to become
infective (embryonation).
Can withstand low temperatures.
The infection is direct from the infested faeces.
Egg when swallowed hatch in intestine, larvae
emerge in the small intestine, penetrates the
villi and develop for a week until it re-emerge
and passes to the ceacum and large intestine,
where it attaches itself to the mucosa and
become adults.
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37. When fertilized the female lay.
Un embryonated eggs and are excreted in
feces.
At warm damp soil the eggs embryonate.
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39. Clinical feature & Pathology
Few worms have little damage, in heavy infections
the worms spread throughout the large bowel to the
rectum causing;
Haemorrhages
Mucopurulent stools
Symptoms of dysentery with rectal prolapse
especially in children
Weight loss and weakness
Abdominal pain or tenderness
Nausea, vomiting & anemia
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40. Rectal Prolapse
Is the protrusion of a few or all layers of the
rectal mucous membrane through the anus.
Rectal prolapse has many cause;
Prolonged straining during bowel
movements due to constipation or diarrhea
Pregnancy and the stresses of childbirth
Advancing age.
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41. Progressive weakening of rectal muscles
and ligaments weaken the muscles causing
the rectum to slide downwards with gravity
leading to fecal incontinence.
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44. Diagnosis
Clinical manifestations are not specific
Microscopic demonstration of barrel-
shaped with clear “ polar plugs” eggs in
stool.
Eggs are distinctive –easily seen in fecal
specimens
Adults can be seen in heavy infections
Prevalent warm humid climates
Commonly, double infections occur with
ascaris
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47. Trichuris trichiura: a macroscopic view of a tangled mass
of adults (male and female) in pure glycerin.
The adult female measures about 35-50 mm in length, and
the male about 30-45 mm.
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49. Preventive measures
Educate all the members of the family,
particularly children, in the use of toilet
facilities
Provide adequate facilities for faces disposal
Encourage satisfactory hygiene habits,
especially hand washing before food handling
Avoid ingestion of soil likely to be
contaminated.
Food hygiene (washing of vegetables and
fruits thoroughly before eating).
Early diagnosis & treatment of infected
individuals.
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