This document provides an introduction to roundworms of the class Nematoda. It describes their general morphology including elongated cylindrical shape, unsegmented body, separate sexes, and reproductive organs. It then focuses on Ascaris lumbricoides, the most common intestinal roundworm. It details its life cycle, symptoms, diagnosis, and treatment. Ascaris can grow over 20 cm long and infect over 1 billion people worldwide, often causing abdominal pain but also potentially blocking bile ducts or intestines. Diagnosis is via egg identification in stool and treatment involves anthelmintic drugs.

1. INTRUDUCTION
TO
Nematoda (round worms)
Dr. Souzan Eassa

2. The common name of class Nematoda is called Round
Worm
Differ in Size from few
mm. e.g. Enterobius to several
cm. e.g. Ascaris
Elongated or cylindrical in shape
The body is un-segmented
The sex is separates
i.e. (Bisexual, Male and Female)
Generally, female is larger than male and Male is
consists of copulatory bursa at posterior end
General Morphology

3. General Morphology
The male reproductive organs are
testis, seminal vesicle, copulatory
bursa and spicules.
Female reproductive organs (Ovary,
oviduct, uterus and vulvar opening.
It has longitudinal and transverse
muscle fibers.
 The body is covered by cuticle layer.
It has excretory system
(Longitudinal canal).

4. It has alimentary canal i.e. complete
digestive system, presence of body cavity
Head provided with buccal cavity
(Lips, teeth like, lancet, glands --- etc).
 Different types of esophagus (club, cylindrical,
rhabditiform, double bulbed and cellular).
It has nervous system (Esophageal
ganglion).
 Some nematodes are larviparous
(viviparous), oviparus and
oviviviparous.
General Morphology

5. Nematode
The intestinal nematodes
– Ascaris
– Hook worms
– Pin worm
– Whip worm
The blood- and tissue
dwelling nematodes
– The filarial
– Trichinella

6. Ascaris
Ascaris lumbricoides

7. Introduction
• The first representative and the most
common intestinal parasite
• Cosmopolitan in distribution
• Rural > urban
• Children > adults

8. Epidemiology
• Worldwide distribution, throughout
the temperate and tropical areas
• 1,000,000,000 people in the world
• 40% population in Africa and Asia
• 600,000,000 in China (1992)

9. Morphology
Adult
Looks like an earthworm
Female (20-35 cm); Male (12-30 cm)
3 lips which carry minute teeth

10. A pair of female and male worms of A. lumbricoides.
Notice the vulvar waist(arrow)of the female worm and the
coiled end of the male worm.

11. Ascaris female worm

12. A scanning electron micrograph of Ascaris showing the
three prominent “lips”

13. Egg
• Fertilized egg
• Unfertilized egg

14. Albuminous layer
Egg shell
Ovum
A. lumbricoides, fertilized egg (6050 micrometer)

15. A. lumbricoides, fertilized egg

16. A. lumbricoides unfertilized egg

17. The life cycle of A. lumbricoides

18. Living site
Adults in small
intestine
Diagnostic stage
Undeveloped
eggs in feces
Infective stage
Eggs embryonate in
soil by 2-3 wks
Method of infection
Infective eggs are
ingested
Migration
Larvae migrate
though the lungs
HOST
MAN

19. Symptomatology
Larva
Pneumonitis
Asthma attacks
Loeffler’s syndrome

20. Adult
•The presence of few worms may be
asymptomatic (85%)
•The most common symptoms are vague
abdominal pain
•Large numbers of worms may cause
malnutrition and present signs and
symptoms of obstruction

21. •Migration of adult worms may cause
signs and symptoms of perforation,
peritonitis, appendicitis or extrahepatic
biliary obstruction.

22. A.lumbricoides in common bile duct

23. Cross section of a liver specimen contains many adult
worms of A.lumbricoides obstructing the intrahepatic and
extrahepatic bile ducts.

24. Ascarid chronic pancreatitis

25. A large mass of Ascaris lumbricoides that was passed from
the intestinal tract. The ruler at the bottom of the image is 4
cm (about 1.5 inches) in length.

26. Peritonitis caused by intestinal
perforation due to Ascaris
Resected bowel and the adult
female from the peritoneal cavity

27. Diagnosis
• Microscopic identification eggs in the
stool, a direct wet mount examination of
the specimen (200,000 eggs/female/day).
• Macroscopic identification of adults passed
in stool or through the mouth or nose.

28. Prevention and Treatment
1.Treatment to ascariasis: Mebendazole,
Albendazole and Levamizole are effective.
2.Sanitary disposal of feces.
3.Hygienic habits such as cleaning of hands
before meals.
4.Health education.