د.حنان

Lab -11-Intestinal Nematodes

Enterobius vermicularis

Introduction

Enterobius vermicularis, commonly known as pinworm or seatworm.
Disease: enterobiasis,pinworm infection.
Humans are the only host.
Adults worms reside in the colon.
World-wide distribution,particulary in temperate area, it is commonly found in kindergarten and primary school students.
The infective stage is the egg.

Morphology

Morphology -- Adult

Female -- fusiform body with a long, thin, tapering tail,7-14mm
Male -- “6” shape, curved tail, 2-4. Males die right after mating, thus are rarely seen
White in color

• Cephalic alae

The anterior end tapers and is flanked on each side by cuticular extensions of head
Pharyngeal bulb
The esophagus is slender, terminating in a prominent posterior bulb

Morphology -- Egg

Life cycle

Life cycle note

Ingestion of the infective eggs.
The eggs migrate through the digestive tract into the small intestine,where they hatch and release young larvae.
The larvae grow and mature into adult worms.
The adult worms reside in the colon.
Following copulation,the resulting pregnant(gravid) femal worm migrates outside the body to the perianal region where she may deposit up to 15,000 eggs.

Characteristics of life cycle

Humans are the only host in nature
No intermediate host (direct life cycle)
No larval migration between organs

Transmission

Ingestion of infective eggs.
Retroinfection.
Autoreinfection(hand to mouth contamination)

Clinical Symptoms

Asymptomatic .
The most common symptoms include intense itching and inflammation of the anal and vaginal areas.


Laboratory Diagnosis
Microscopic identification of eggs collected in the perianal area by cellophane (Graham Scotch) tape method or anal swabs. This must be done in the morning, before defecation and washing

• Detection of adult on anal skin

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