Pinworms Flashcards
Background
- A pinworm infection is also known as enterobiasis.
- Intestinal infection with Enterobius vermicularis, a
parasitic helminth. - The only helminth that can be treated with nonprescription medications.
- The most common helminth infection in Canada
- The adult female is 8-13mm, long and spindleshaped. The adult male is about 2-5mm.
- One person may have from several to several
hundred worms.
Prevalence
- Most common in children, especially between 5-14
years of age (uncommon in children < 2 years) - Estimated that one-third of Canadian children will
develop pinworms during their childhood - Higher incidence in institutionalized settings
- Occurs often with crowded living conditions
Transmission
- Eggs are deposited on
perianal folds.
* 2. Infected individual
scratches around the anus
and touches another
person or an object.
* 3. Uninfected person puts
contaminated
hand/object into mouth
and swallows eggs.
* 4. Larvae hatch in small
intestine and adults reside
in colon.
* 5.At night, female worm
migrates to perianal
region to lay eggs.
Symptoms
- Most common symptom is pruritus ani or severe
peri-anal itching, especially at night
– Patients may be asymptomatic - This may disrupt sleep leading to restlessness and
irritability - May lead to loss of appetite
Complications
- Although pinworms are generally just a nuisance,
they may spread to other organs leading to infection,
appendicitis or other related complications. - Migration to vaginal area may lead to irritation,
discharge or urinary incontinence. - Severe peri-anal scratching may lead to bacterial
infections.
Diagnosis
Diagnosis
* Rarely seen in feces, but may see a thread-like worm at
night with a flashlight (flashlight test)
– Can place worms in alcohol or vinegar – bring to clinic or
physician for confirmation.
* Scotch tape test
– Perform at home in the morning before defecation or showering
– Piece of transparent adhesive tape pressed on perianal skin –
then stuck to a slide to be examined under microscope
– May have to repeat several times
* Single examination will confirm diagnosis in 50% of cases, 3 exams in
90% and 5 exams in 99%
Treatment
– Diagnosis recommended prior to initiating
pharmacologic treatment
* Education of parents:
– Reassure that pinworms are not caused by
uncleanliness
– Best to avoid prophylactic treatment
– Treat everyone in the household over the age of 2
years old
– Recommend a zinc oxide preparation to relieve itch.
Treatment: Pharmacologic
Pyrantel pamoate (Combatrin)
Pyrantel pamoate (Combatrin)
– 90-100% cure rate
– Single dose of 11mg/kg (max 1g)
* repeat in 2 weeks
– Paralyzes the adult worm, preventing it from attaching to
GI wall
– Little systemic absorption
– Caution with liver dysfunction
– May get GI side effects (N/V, diarrhea, cramping) and some
dizziness/drowsiness
– Schedule 2 drug in Alberta
Treatment: Pharmacologic
* Mebendazole (Vermox)
Mebendazole (Vermox)
– Cure rate is closer to 100%
– Single dose of 100mg in adults and children 2 years of age
and older
* repeat in 2 weeks
– Inhibits glucose absorption of worm
– Minimal systemic absorption (2-10%)
– GI (N/V/D), Rare: dermatologic (SJS) and blood dyscrasias
– Prescription therapy
Treatment Considerations
- Are all the ova killed?
– Pinworm medications only kill adult worms
– Eggs and larvae are unaffected
– Ova floating in the air can also cause reinfection for 2
weeks (their viability time)
– A routine 2nd treatment 2 weeks after the first is
mandatory
Treatment Considerations
– Pregnancy
– Due to lack of studies, avoid all in first trimester
– An asymptomatic pregnant woman can be treated after
delivery (no harmful effects of the worm to mother or
child)
– In the symptomatic mother, if natural cure through
meticulous personal hygiene unlikely, pyrantel pamoate or
mebendazole may be considered (delay until 2nd trimester
or later)
Treatment: Non-Pharmacologic
- Meticulous hand washing after defecation and
before eating - Keep fingernails cut short and discourage scratching
- Change underwear, pajamas and bed linens daily
- Wash underwear, pajamas and hand towels daily in
hot water for 2 weeks
Treatment: Non-Pharmacologic
- Shower in the morning so eggs laid the previous
night will be washed away - Frequent washing of the toilet seat
- Clean the floors and vacuum all areas of the
bedroom
Treatment: Monitoring
- Improvement in itching
– Should resolve within 7-14 days of starting treatment; if
not repeat treatment
– If itching does not resolve within 7 days of 2nd course, refer
to physician - Adverse effects of medication therapy
– GI, drowsiness/dizziness, etc
Reinfection
Very high likelihood of reinfection due to:
– Scratching
– Not properly washing of the hands after scratching or
using the washroom.
– Exposure to infected soils, dust, clothing, etc.
– Medications only kill the adult worms
