Geographical Distribution
O WorldwideO Most common worm infection in the
United States & Western Europe.O In the United States, a study by the
CDC reported incidence rate of 11.4% among all ages, 33% among children.
O Prevalence in children as high as 61% in India, 50% in England, 39% in Thailand, 37% in Sweden, and 29% in Denmark.
MorphologyO Egg has five membranesO Eggs are translucent and are covered in a
material that allows them to stick to environmental objectsO Membrane makes the eggs “itchy”O Eggs have a thick shell that is flattened on one
sideO The eggs small size (50-60 micrometers)O May contain an embryo or fully-developed
larvaO Larvae molt twice before hatching
Larvae Morphology
Larvae grow to 140-150 micrometers in length
Larvae are smaller and more coiled than the adults
Molt twice before becoming adults
Adult Morphology
White, small roundworm with
cylindrical body surrounded by 3 layered cuticle
The female has a sharply pointed posterior end
(8-13 mm long x 0.5 mm thick)
Have alae on anterior part of body wall
Can lay up to 15.000 eggs/day
Male has a curled posterior end
measuring 2 to 5 mm long x 0.2 mm thick
Both sexes have three lips
TransmissionHuman-to-human contact by
ingesting infectious eggs
Eggs remain viable in moist environment for up to three
weeks
Once eggs are deposited near anus they can contaminate other surfaces such as:
Fingernails
HandsClothing and bed linensThen onto food, water, furniture, toys, bathroom fixtures and pets.
PreventionO Wash hands after using the
bathroom and before preparing food. O Wash bedding and underclothing
frequently, especially those of any affected family members.
Life CycleEggs are ingested
Hatch in S.I.
Larvae emerge and migrate through small intestine to
colon
Molt twice to become adults
Gravid female attaches to intestinal mucosa in ileum,
cecum, appendix or ascending colon
Ingest colon contents until entire body is filled with
eggs
Life CycleGravid females migrate through the
colon towards the rectum at a rate of 12-14 cm/hour
Female emerges from anus and deposits eggs by
contracting and expelling,
dying and degrading,
or bodily rupture due to the host scratching.
The female comes out of the anus
so the eggs can be exposed to oxygen to mature
After laying eggs, the female becomes opaque and dies.
Under optimal conditions larvae
within the eggs will develop within
4-6 hrs. after being laid making them extremely infective
PathogenesisO Causes EnterobiasisO Retroinfection-larvae migrate back
up the bowel to the G.I. tractO Pinworms as seen in colonoscopy
SymptomsO Intense itching in the anal region,
especially at nightO Restless sleepO Infection can migrate to the vagina and
cause vaginal dischargeO Itching leads to secondary bacterial skin
infectionO Abdominal pain and nausea are
associated with high populationO Some are asymptomatic
DiagnosisO Itching around perianal region is
indicative of infectionO Worms are visible in the anal region,
especially 2 to 3 hours after sleep,O Look like tiny pieces of white thread
O Eggs are rarely seen in stool samples
“Scotch Tape Test”
Most reliable method to detect eggs
Piece of cellophane tape is placed sticky side down to the skin around the anus
Pinworm eggs will stick to the tape and then the tape can be viewed under a microscope
Test should be done immediately after the person wakes up in the morning before washing, going to the bathroom, or getting dressed since eggs may be removed during these processes.
TreatmentMebendazole or Albendazole commonly prescribed for entire family
OTC Pyrantel Pamoate
1 dose is given immediately, then wait two weeks for another dose. The second dose is to kill any adult worms that may have hatched in the meantime
ReviewO How many times do pinworms molt?
O What is the tell tale sign of a pinworm infection?
O What is one method of diagnosis?
O Where do females lay their eggs?
O How can you prevent pinworm infection?
Works CitedO http://www.ncbi.nlm.nih.gov/pubmed
health/PMH0002137/
O http://en.wikipedia.org/wiki/Enterobius
O http://animaldiversity.ummz.umich.edu/site/accounts/information/Enterobius_vermicularis.html