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The most prevalent type of human
worm infection in the United States and perhaps around the world is by that of
the pinworm.
The term worm in children is a
common lay term for pinworm. This frequently used reference to pinworms is
almost universal as a descriptive name for this parasite, which is an organism
of the genus and species Enterobius vermicularis.
E. vermicularis
is a nematode. Egg can also be found in specimens collected from perianal skins
and occasionally eggs can be found in faeces.
Transmission is by ingesting
infective eggs. The eggs are deposited on the anal skins usually during night
hours and within a few hours of being laid, they contain an infective larva. Autoinfection
by swallowing infected eggs is common in children because the egg causes
intense irritation and scratching of the infected area leads to the fingers
becoming contaminated with eggs and because many children put their dirty
fingers into their mouths, they are most susceptible to Enterobiasis
The life cycle of a pinworm is 4 to
6 weeks. Without treatment, infestation will continue as long as fresh eggs are
being swallowed, unless a person develops immunity to pinworms, which is
unusual before age 15
The condition is most often confirmed
by Microscopic examination of the characteristic eggs where one side of the egg
is flattened.
CHARACTERISTIC
ENTEROBIUS VERMICULARIS EGG
The egg of the species is oval but flattened
on one side. It has a thick and colorless shell
and measures 50 to 60 µm in length by 20 to 30µm in width. Larvae may be visible inside the egg due to the colorless shell of
the embryonated egg.
SIGNS
AND SYMPTOMS OF PINWORM INFECTIONS
Symptoms often range from being Asymptomatic to any or several of the
following signs and symptoms. An Itchy
anus due to inflammatory response of the adult worm, especially at night,
While be the most frequent symptom exhibited.
LABORATORY
DIAGNOSIS
The highest number of eggs can usually
be recovered in the morning soon after waking and before bathing. The eggs can
be collected from the skin around the anus or from clothing using clear adhesive tape or a saline swab.
Diagnosis is generally made by the
presence of eggs using the “SCOTCH TAPE TEST”.
Applying a piece of transparent cellophane tape over a tongue blade is into
the perianal folds late at night or before daylight affords the best
opportunity of recovering evidence of infection.
The slide is then examine
microscopically for the typical ova and four to six slide collected at
different times should be performed before ruling out the infection.
Occasionally the adult worm will also be found on the slide along with the
characteristic ova.
Note
: Egg ( from perianal skin) may also
be found in faeces and occasionally urine from females.
TREATMENT
Treatment with Mebendazole
The medications used for the
treatment of pinworm are either mebendazole, pyrantel pamoate, or albendazole.
Any of these drugs are given in one dose initially, and then another single
dose of the same drug two weeks later. Pyrantel pamoate is available without
prescription
PREVENTION
AND CONTROL
- Personal hygiene and sanitary living conditions are necessary to avoid becoming infected or re-infected.
- All family members should be treated when a single-family member is diagnosed with pinworm infection (Enterobiasis)
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Reference :
District Laboratory practice in
Tropical Countries (Monica CHEESBROUGH)
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