Enterobius vermicularis

Chad ClarkKelli Rogers

Introduction

Kingdom: Animalia Phylum: Nematoda Family: Oxyuridae Known more commonly as the “Human

Pinworm” Enterobius gregorii is considered a “sister”

species and synonymy between E. gregorii and E. vermicularis has been proven via molecular biology

Infects at least 400 million people worldwide!!!

Geographic Area

Geographic distribution• Worldwide (mainly affects children)• Originated in Africa, but also thrives in

temperate zones• Greatest area of risk are

institutionalized areas such as an orphanage or a school.

Hosts

Definitive host • Humans Intermediate host• None (Direct Life Cycle)

Morphology

Both males and females have 3 lips surrounding their mouth

Males are 1-4 mm in length with a posterior end that strongly curves to the ventral side and have a single spicule which is 100-141 um in length

Females are 8-13 mm in length and have a posterior end that extends into a long, slender point and they contain 2 uteri that can store thousands of eggs

Eggs are elongated-oval and completely flat on one side and measure 50-60 um by 20-30 um

Eggs

Male Female

Cross Section

Epidemiology

Disease is transmitted from person to person

Fabric (IE clothing, bedding, towels, etc) is a perfect reservoir for eggs and spreads rapidly this way

Can also be found on curtains, walls carpet and even in dust

Another rapid mode of transmission is by placing soiled fingers or other objects in mouth

Life Cycle

Pathogenesis

Damage from the intestine is the result of adult attachment to the mucosa and can lead to mild inflammation and bacterial infection

Damage from eggs results in female movement out of the anus to deposit eggs causing a tickling sensation of the perianus causing a person to scratch (usually occurs while a person is sleeping)

Clinical Signs

About 1/3 of all infections are completely asymptomatic

If symptoms due arise, commonly perianal pruritus occurs

Other symptoms…• Anorexia• Irritability• Abdominal pain• Nightmares• Bed Wetting

Diagnosis

Ordinary fecal exams are unproductive In order to get accurate diagnosis the

area of the perianus must be reached• A short piece of cellophane (scotch) tape

is held against a flat wooden applicator or similar object sticky side out

• Tape is then pressed against the junction of the anal canal and the perianus

Treatment

Pyrantel pamoate How does it work?

• Pyrantel pamoate acts as a depolarizing neuromusclar blocking agent. It causes sudden contraction, followed by paralysis, of the helminths. This has the result of causing the worm to "lose its grip" on the intestinal wall and be passes out of the system by natural processes (defecation).

Control

Personal hygiene Laundering of beddingand other cloth materials

Public Health Concern

May cause….• Intestinal obstruction• Intestinal perforation• Granulomas and abcesses• Urinary tract infections

References

http://www.stanford.edu/group/parasites/ParaSites2006/Enterobius/Enterobius%20vermicularis.htm

http://www.dpd.cdc.gov/dpdx/HTML/Enterobiasis.htm

Foundations of Parasitology • Eighth Edition• Gerald D. Schmidt & Larry S. Roberts &

John Janovy, Jr

Egg Comparisons