د.ياسين

Parasitology 12- Lab

Ascaris lumbricoides

Introduction

Common saying “round worm of man”
The largest of the intestinal nematodes parasitizing humans
The most common worm found in human
It is worldwide in distribution and most prevalent through out the tropics, sub-tropics and more prevalent in the countryside than in the city

Morphology

Adult:
Cylindrical in shape
Creamy-white or pinkish in color
The female averages 20-35cm in length, the largest 49cm
The male is smaller, averaging 15-31cm in length, has a typical curled tail with a pair sickle like copulatory spines
On the tip of the head there are three lips, arranged
Male has a single reproductive tubule
The female has two reproductive tubules and the vulva is ventrally located at the posterior part.

• Adult worm of A. lumbricoides

The lips of A. lumbricoides




• The three lips are seen at the anterior end. The margin of each lip is lined with minute teeth which are not visible at this magnification

Morphology

Egg
There are three kinds of the eggs
fertilized eggs
unfertilized eggs
decorticated eggs
We usually describe an egg in 5 aspects
size, color, shape, shell and content


Morphology
Fertilized egg:
an average size 60×45µm
broad oval in shape
brown in color
The shell is thick
Albuminous coat is thick and stained brown by bile
The content is a fertilized ovum
There is a new-moon (crescent) shaped clear space at each end inside the shell

Morphology

Unfertilized egg
Longer and slender than fertilized egg
The shell and albuminous coat are thinner
than those of the fertilized egg
The content is made of many refractable
granules various in size
Decorticated egg:
Both fertilized and unfertilized eggs sometimes may lack their outer albuminous coats and are colorless

Life Cycle

Life Cycle

Prevention and Control

The avoidance of using human feces as fertilizer,
as well as exercising proper sanitation and per-sonal hygiene practices, are critical measures for breaking the life cycle of A. lumbricoides.


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