ENTEROBIUS VERMICULARIS

Prof. Walter Jaoko

Department of Medical Microbiology University of Nairobi

Learning Objectives

At the end of this lesson, the learner should be able to:

• Classify the parasite Enterobius vermicularis

• Outline geographical distribution of E. vermicularis

• Describe morphology of key stages of E. vermicularis

• Describe the life cycle of E. vermicularis

• Describe clinical manifestations of E. vermicularis

• Describe the tests used to diagnose E. vermicularis

• Outline treatment of E. vermicularis

• Describe control of E. vermicularis

1.0 Introduction

• Intestinal nematode, found in the large intestines

• Also known as pinworm

• Worldwide distribution, more in temperate climates

• More common in overcrowding places

– Orphanages, boarding schools etc

• Children most affected – high prevalence & intensity

• Cause disease known as enterobiasis

2.0 Morphology

• Adults

– Females 9-12 mm, Males 2-3 mm

– Thick lips (cervical alae)

• Eggs

– Planocovex in shape

– Transparent wall

– Embryonated

Adult, Enterobius vermucularis

Egg in Iodine stained preparation Egg in wet saline preparation

3.0 Life cycle

• Adults mate in LI, females get out of anus, lay eggs

• Eggs passed embryonate within a few hours

• Itchiness of perineum, scratching, stick to fingers & nails, ingested accidentally (self or others), reach SI, hatch, larvae move to LI, attach to mucosa, adults

• May be transmitted through clothing, beddings, food etc contaminated with eggs, dustborne by inhalation, retroinfection

• Life cycle 4-6 weeks

4.0 Clinical presentation

• Light infection mostly asymptomatic

• Clinical presentation includes

– Pruritus ani (scratching the anus) usually at night

– Sleep disturbance

– Irritability & lack of concentration in school

– Poor class performance

– Loss of appetite

• Complications include

– Appendicitis

– Salpingitis in females (rare)

5.0 Laboratory Diagnosis

• Microscopic identification of eggs must be done in the morning, before defecation and washing by

– Adhesive scotch tape test - Press transparent adhesive tape on the perianal skin & then examining tape placed on a slide

– Anal swabs – Press a swab coated with adhesive material on the perianal skin

– Camel hair brush

• Eggs occasionally found in stool, urine, vaginal smears

• Adult worms may also be found in perianal area

Enterobius vermicularis eggs in a cellophane tape preparation

6.0 Treatment

• Mebendazole

• Albendazole

• Pyrantel Pamoate

* In institutional outbreaks treat all the household members

7.0 Prevention & Control

• Proper hygiene

– Daily bathing

– Frequent changing of clothes & beddings

– Keeping short nails etc,

• Avoiding overcrowding, opening of windows for ventilation etc

• Health education

– Washing of hands before eating of a meal

• Treatment of infected persons with antihelminthes