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
Patient Case
* A 35yo mother comes to the pharmacy counter and
states that her children have been scratching their
bums quite often. She mentions that her friend
thinks it may be pinworms and asks for your advice
on treatment options.
* What would you recommend?
Pyrantel pamoate Mebendazole
Efficacy 90-100% closer to 100%
Safety CNS (Dizziness)
GI (N/V/D)
GI (N/V/D)
Rare: dermatologic (SJS)
and blood dyscrasias
Adherence
More complicated
dosing (weight based
11mg/kg) orally
Same dose for all 100mg
orally
Cost ~ $1.00/125mg pill ~$4.00/100mg pill
Counseling:
– Proper administration/dosing instructions of
treatment
– Retreatment in 2 weeks
– Prevention of transmission
– When to visit the physician
