Pinworms

Question 1

Background

Answer 1

• 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.

Question 2

Prevalence

Answer 2

• 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

Question 3

Transmission

Answer 3

1. 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.

Question 4

Symptoms

Answer 4

• 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

Question 5

Complications

Answer 5

• 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.

Question 6

Diagnosis

Answer 6

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%

Question 7

Treatment

Answer 7

– 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.

Question 8

Treatment: Pharmacologic

Pyrantel pamoate (Combatrin)

Answer 8

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

Question 9

Treatment: Pharmacologic
* Mebendazole (Vermox)

Answer 9

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

Question 10

Treatment Considerations

Answer 10

• 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

Question 11

Treatment Considerations

Answer 11

– 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)

Question 12

Treatment: Non-Pharmacologic

Answer 12

• 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

Question 13

Treatment: Non-Pharmacologic

Answer 13

• 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

Question 14

Treatment: Monitoring

Answer 14

• 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

Question 15

Reinfection

Answer 15

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

Question 16

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?

Answer 16

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