1. Enterobius vermicularis
Presented by Sandra Thorbus & Samantha Todd

2. Hosts
Definitive Host: Humans
Not associated with socioeconomic status

3. Geographical Distribution
Worldwide
Most common worm infection in the United States & Western Europe.
In the United States, a study by the CDC reported incidence rate of 11.4% among all ages, 33% among children.
Prevalence in children as high as 61% in India, 50% in England, 39% in Thailand, 37% in Sweden, and 29% in Denmark.

4. Morphology Egg has five membranes
Eggs are translucent and are covered in a material that allows them to stick to environmental objects
Membrane makes the eggs “itchy”
Eggs have a thick shell that is flattened on one side
The eggs small size (50-60 micrometers)
May contain an embryo or fully-developed larva
Larvae molt twice before hatching

5. Enterobius vermicularis eggs

6. Larvae Morphology Larvae grow to 140-150 micrometers in length
Larvae are smaller and more coiled than the adults
Molt twice before becoming adults

7. 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 eggs/day
Male has a curled posterior end measuring 2 to 5 mm long x 0.2 mm thick
Both sexes have three lips

8. Alae on Female

9. Transmission Human-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
Hands
Clothing and bed linens
Then onto food, water, furniture, toys, bathroom fixtures and pets.

10. Prevention
Wash hands after using the bathroom and before preparing food.
Wash bedding and underclothing frequently, especially those of any affected family members.

11. Life Cycle Eggs 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

12. Life Cycle
Gravid females migrate through the colon towards the rectum at a rate of 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

13. Pathogenesis Causes Enterobiasis
Retroinfection-larvae migrate back up the bowel to the G.I. tract
Pinworms as seen in colonoscopy

14. Symptoms Intense itching in the anal region, especially at night
Restless sleep
Infection can migrate to the vagina and cause vaginal discharge
Itching leads to secondary bacterial skin infection
Abdominal pain and nausea are associated with high population
Some are asymptomatic

15. Diagnosis Itching around perianal region is indicative of infection
Worms are visible in the anal region, especially 2 to 3 hours after sleep,
Look like tiny pieces of white thread
Eggs are rarely seen in stool samples

16. Most reliable method to detect eggs
“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.

17. Treatment
Mebendazole 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

18. Review How many times do pinworms molt?
What is the tell tale sign of a pinworm infection?
What is one method of diagnosis?
Where do females lay their eggs?
How can you prevent pinworm infection?

19. Works Cited http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002137/